Transdermal delivery of nalbuphine and nalbuphine pivalate from hydrogels by passive diffusion and iontophoresis

The objective of this study was to evaluate the in vitro transdermal permeation of nalbuphine hydrochloride (CAS 23277-43-2) (NA) and nalbuphine pivalate (NAP), a novel prodrug of NA, from different hydrogel formulations under passive diffusion as well as iontophoresis. Various concentrations of polymers, including polyvinylpyrrolidone (PVP) and hydroxypropyl cellulose (HPC) were used in the hydrogel formulations. The passive permeation rate of NA was affected by the polymer concentrations, which can be attributed to different viscosities of the hydrated formulations; whereas the passive permeation rate of NAP was not influenced by the various polymer concentrations. Iontophoresis significantly increased the permeation rates of NA and NAP from various hydrogel formulations through skin; the enhancement ratios were higher for NA in all the formulations studied. The iontophoretic permeation rates of NA were slightly decreased by the incorporation of polymers; however, the transdermal flux and membrane potential were independent of polymer concentrations for both NA and NAP, demonstrating that the polymer concentrations in the hydrogel formulations did not have significant effects on the iontophoretic permeation of NA and NAP.

Antibiotic use in public hospitals in Taiwan after the implementation of National Health Insurance

BACKGROUND AND PURPOSE

Only limited data is available on the patterns of antibiotic use in hospitals in Taiwan before and after the implementation of national health insurance. This study aimed to determine the patterns of use of antibiotics in public hospitals in Taiwan after the implementation of the National Health Insurance program and to compare these with patterns prior to the implementation.

METHODS

Data on the annual use of all antibiotics in public hospitals in Taiwan during the period from fiscal year (FY) 1994-1995 to 1997-1998 were collected and analyzed. Hospitals included seven medical centers, 19 regional hospitals, 53 district hospitals, and eight specialty service hospitals.

RESULTS

The annual cost of antibiotics made up 17.4% of the annual cost of all medication used in these hospitals in FY 1994-1995, and decreased year by year to 12.6% in FY 1997-1998. During the study period, 57.4% of the total cost of antibiotics were incurred by medical centers, 24.6% by regional hospitals, 16.2% by district hospitals, and 1.8% by specialty service hospitals. The most commonly used class of antibiotic was cephalosporins, accounting for 48.0% to 54.3% of total antibiotic costs. The second most commonly used class of antibiotic was penicillins, accounting for 15.9% to 17.4% of total antibiotic costs. In FY 1994-1995, the next most commonly used classes of antibiotics were aminoglycosides, fluoroquinolones, and other beta-lactams, respectively, but by FY 1997-1998 these had changed to fluoroquinolones, glycopeptides, and aminoglycosides, respectively. Among the various cephalosporins used, first-generation cephalosporins accounted for 76.1% of all cephalosporins used in FY 1994-1995, which increased year by year to 84.0% in FY 1997-1998. Second-generation cephalosporins accounted for 20.7% of all cephalosporins used in FY 1994-1995, decreasing to 13.2% in FY 1997-1998.

CONCLUSION

The introduction of the National Health Insurance program in Taiwan brought about a major change in antibiotic use patterns in public hospitals.

High-performance liquid chromatographic method for the simultaneous determination of nalbuphine and its prodrug, sebacoyl dinalbuphine ester, in dog plasma and application to pharmacokinetic studies in dogs

For the determination of nalbuphine and its long acting prodrug, sebacoyl dinalbuphine ester (SDN), in biological samples, a reversed-phase high-performance liquid chromatographic method using dual detectors was established. Ultraviolet and fluorescence detectors were connected in series for determining SDN and nalbuphine, respectively. The two analytes and internal standard were extracted from plasma by alkaline liquid-liquid extraction using n-hexane-isoamyl alcohol (9:1, v/v). The calibration curve for nalbuphine was linear over the range from 10 to 2,500 ng/ml, while the range was 25 to 2,500 ng/ml for SDN. The within- and between-day precision and accuracy were all within 10% for both nalbuphine and SDN over these concentrations. The method was applied successfully to a pharmacokinetic study of SDN administered at 20 mg/kg to two beagle dogs. Pharmacokinetic analysis revealed that SDN followed a linear one-compartment model with an elimination half-life of 74.7 min. Formation of nalbuphine after intravenous administration of SDN was observed in the first time point sample (5 min). These results indicate that SDN is rapidly metabolized to its active moiety, nalbuphine, in dogs and no other metabolites are detected in plasma.

Delivery of nalbuphine and its prodrugs across skin by passive diffusion and iontophoresis

The in vitro transport of nalbuphine (NA) and its prodrugs across various skins was investigated in order to assess the effects of prodrug lipophilicity on passive as well as iontophoretic permeation. The passive diffusion of NA and its prodrugs increased with the drug lipophilicity. Iontophoresis significantly increased the transport of NA and its prodrugs; the enhancement ratio was highest for NA and decreased as the drug lipophilicity increased. Measurements using intact and stratum corneum (SC)-stripped skins showed that the SC was the major skin diffusion barrier for the passive permeation of NA and nalbuphine pivalate (NAP). The iontophoretic permeation of NA and NAP across intact and SC-stripped skins indicated that the SC layer was not rate-limiting for the permeation of NA, but remained the rate-limiting barrier for transdermal permeation of NAP. Permeation studies using SC-stripped and delipidized skins suggested that the intercellular pathway was the predominant route for the passive permeation of NA and NAP as well as the iontophoretic permeation of NAP across the SC. The relative rates of passive and iontophoretic permeation across Wistar rat skins demonstrated that a significant amount of NA may permeate skin via the appendageal routes, whereas NAP permeated predominantly through the lipid matrix.

Does Chinese ethnicity affect the pharmacokinetics and pharmacodynamics of angiotensin-converting enzyme inhibitors?

Information from clinical and pharmacokinetic studies of angiotensin-converting enzyme inhibitors (ACEIs) has come from subjects who are mostly male and Caucasian, but the use of ACEIs extends to populations worldwide. Significant differences between Chinese in general and male Caucasians have been demonstrated in the pharmacokinetics/dynamics of other drug classes that could have implications for the use of ACEIs in the Chinese population. These include: significant Chinese/Caucasian genetic variation in the renin-angiotensin system based on an insertion/deletion (O/D) polymorphism of the ACE gene; the genetic determination of plasma ACE activity in the Chinese population; and genetic factors involving the disease substrate which may also influence the response to treatment. Oral and IV pharmacokinetic data from various studies of Chinese and Caucasian subjects are available for cilazapril, fosinopril, and perindopril, and pharmacodynamic data are available for eight different ACEIs. Based on these data, there are few differences among the pharmacokinetics of ACEIs between Chinese and Caucasians. Most ACEIs showed good blood pressure lowering efficacy in Chinese (benazepril, enalapril, fosinopril and spirapril), with perhaps less blood pressure lowering with cilazapril or a relatively shorter-term effect with cilazapril or perindopril compared to Caucasions. Chinese experience more cough from ACEIs (captopril and enalapril) than Caucasians. Data suggest that fosinopril may not induce cough in as many subjects as other ACEIs, and this seems to be true of Chinese as well. The mechanism, currently unknown, could involve fosinopril's dual elimination pathway (hepatic and renal). Pharmacokinetic data also support the use of fosinopril in congestive heart failure where elimination pathways may be impaired. In conclusion, ethnic differences between Chinese and Caucasians with respect to ACE and AGT gene polymorphism, which might be expected to differentially affect the action of ACEIs in these two ethnic groups, do not, in fact, have such an effect. Rather, differences among the ACEIs appear to be more important. Journal of Human Hypertension (2000) 14, 163-170.

Cardiovascular effect and simultaneous pharmacokinetic and pharmacodynamic modeling of pimobendan in healthy normal subjects

Pimobendan is a new inotropic agent with vasodilator properties. We have reported the pharmacokinetics of enantiomers of pimobendan in healthy humans. The present report focuses on the pharmacodynamic effect of pimobendan and a simultaneous pharmacokinetic-pharmacodynamic modeling. Eight normal healthy volunteers were studied with oral administration of 7.5 mg and i.v. administration of 5 mg of racemic pimobendan. Concentrations of enantiomers of pimobendan were determined by high performance liquid chromatography. Cardiovascular effects of pimobendan were evaluated by echocardiography. Oral pimobendan significantly reduced 29.0% and 16.5% of the left ventricle end-systolic dimension (LVESD) and end-diastolic dimension, respectively. The mean velocity of circumferential fiber shortening, ejection fraction, and fractional shortening significantly increased 105.9%, 29.8%, and 46% from their baseline values, respectively. The cardiovascular effects of i.v. pimobendan were similar but to a lesser extent. Plots of effect versus plasma concentration (Cp) showed counterclockwise hysteresis loops. A hypothetical effect compartment was established and incorporated into a sigmoid Emax model to describe the time courses of Cps of pimobendan and effects on LVESD. The maximal changes (Emax) in LVESD would be 2.60 +/- 0.51 cm and 2.30 +/- 0.13 cm as estimated from plasma data of (+)- and (-)-pimobendan, respectively. The estimated effect-site concentrations corresponding with 50% of the maximal effect (Ce50) were 6.54 +/- 1.35 and 6.64 +/- 1.35 ng/ml for (+)- and (-)-pimobendan, respectively. A simultaneous pharmacokinetic-pharmacodynamic model could be established to suppress the hysteresis loop and to predict the pharmacological effect based on Cp.

Fosinopril: pharmacokinetics and pharmacodynamics in Chinese subjects

This study examined thepharmacokinetics and pharmacodynamics of fosinopril (IVand oral) in Chinese subjects to determine whether they were different from a group of somewhat heavier and older Western control subjects previously published using the same methods. It was an open-label, randomized, balanced, two-way crossover study comparing oral and IV pharmacokinetics in 12 healthy Chinese subjects in a clinic in Taiwan. Each subject received 10 mg of oral fosinopril or 7.5 mg of IV fosinoprilatin a randomized sequence with sampling for fosinoprilat concentrations over 48 hours. Standard pharmacokinetics, including AUC, Cmax Tmax, T 1/2, Vss, bioavailability, total clearance, and renal and nonrenal clearance, were determined as well as pharmacodynamic effects on angiotensin-converting enzyme (ACE) activity. Following oral administration of 10 mg fosinopril, AUC0-T and AUCinf were 1,556 +/- 586 ng x hr/mL and 1,636 +/- 620 ng x hr/mL, respectively; T 1/2 was 17.4 +/- 11.4 hr; Cmax was 183.4 +/- 59.4 ng/mL; and median Tmax was 4.0 hr, with > 99% protein binding. Following IV administration of 7.5 mg fosinoprilat, AUC0-T and AUCinf were 7,727 +/- 2,638 ng x hr/mL and 7,816 +/- 2,693 ng x hr/mL, respectively; T 1/2 was 13.0 +/- 5.2 hr; and median Tmax was 4.0 hr, with 99.5% +/- 0.22% protein binding and a Vss of 5,850 +/- 2,780 mL. Bioavailability was 22.3% +/- 7.9%. Percent urinary excretion was 7.6% +/- 2.6% after oral dosing and 42.6% +/- 6.1% after IV dosing. After IV, dosing total clearance was 1,088 +/- 439 mL/hr, renal clearance was 472 +/- 213 mL/hr, and nonrenal clearance was 617 +/- 246 mL/hr. ACE inhibition was essentially complete through 12 hours and markedly reduced through 24 hours. Compared to a somewhat heavier and older previously reported control group, pharmacokinetic values were similar except for a slightly lower AUC and total clearance in Chinese and a statistically significantly lower nonrenal clearance. Pharmacodynamic effects on ACE activity were essentially identical. There is no reason to expect significant differences in fosinopril dosing or effect in a Chinese population compared to a Western population.

Mucoadhesive buccal disks for novel nalbuphine prodrug controlled delivery: effect of formulation variables on drug release and mucoadhesive performance

The objective of this work was to assess the effects of drug solubility and loading percent, as well as Carbopol 934/hydroxypropylcellulose (CP/HPC) ratio, on drug release and mucoadhesive performance of the nalbuphine prodrug loaded buccal disks. Drug release rates for the disks were found to be a function of drug solubility, with higher drug release rates for disks loaded with more hydrophilic prodrugs and an increased amount of beta-cyclodextrin. The drug release rates increased with loading percents for nalbuphine hydrochloride, whereas an opposite drug release trend was observed for disks loaded with nalbuphine enanthate, which can be explained by the diffusional drug release mechanism. The CP/HPC ratio affected release rates of nalbuphine enanthate, whereas the ratio had no impact on the release of nalbuphine hydrochloride. Within the 2 days of experiment time, all formulations attached well to the porcine buccal tissues, indicating those formulation variables had no influence on the mucoadhesive performance of CP/HPC-based buccal disks.

Determination of morphine by high-performance liquid chromatography with electrochemical detection: application to human and rabbit pharmacokinetic studies

A rapid, sensitive, precise and accurate high-performance liquid chromatographic assay with coulometric electrochemical detection was developed for the determination of morphine in human, rabbit, pig and dog plasma. It includes a one-step extraction procedure with hexane-isoamyl alcohol (1:1, v/v) at pH 8.9 (adjusted with phosphoric acid) and reversed-phase liquid chromatography on a microPorasil column. The mobile phase was composed of 5 mM sodium acetate buffer (pH 3.75)-acetonitrile (25:75, v/v). A flow-rate of 1.2 ml/min at 20 degrees C was used. The working potentials for the electrochemical detector were +0.20 V for detector cell 1, +0.55 V for detector cell 2 and +0.75 V for the guard cell. The limit of detection of morphine was 100 pg/ml of plasma. Repeatability, precision and accuracy were also determined concomitantly. The calibration graphs were linear in the concentration range 0.25-250 ng/ml with correlation coefficients of 0.998+/-0.01 and with a minimum intercept of 0.05+/-0.08. The precision in plasma was acceptable, with coefficients of variation less than 11%. The absolute recoveries of morphine and nalbuphine (internal standard) were between 86 and 89% and independent of morphine concentration. Pharmacokinetics after oral morphine [MST Continus (morphine sulphate tablets) 30 mg, Bard Pharmaceutical, Cambridge, UK] in humans revealed a one-compartment first-order absorption model with one absorption phase and one elimination phase. The absorption and elimination half-lives were 2.46 and 1.80 h, respectively. Pharmacokinetics after intravenous morphine (3 mg/kg) in rabbits showed a linear two-compartment open model with one distribution phase and one elimination phase. The distribution and elimination half-lives were 0.5 and 33.8 h, respectively.

Phase II and pharmacokinetic study of paclitaxel therapy for unresectable hepatocellular carcinoma patients

Hepatocellular carcinoma (HCC) is a common lethal disease in Asia and there is no effective chemotherapy. Identification of new effective drugs in the treatment of inoperable HCC is urgently need. This is a phase II clinical study to investigate the efficacy, toxicity and pharmacokinetics of paclitaxel in HCC patients. Twenty patients with measurable, unresectable HCC, normal serum bilirubin, normal bone marrow and renal functions were studied. Paclitaxel 175 mg m(-2) was given intravenously over 3 h every 3 weeks. No complete or partial responses were observed. Five patients had stable disease. Major treatment toxicities (grade 3-4) were neutropenia (25%), thrombocytopenia (15%), infection (10%) and allergy (10%). Treatment-related deaths occurred in two patients. The median survival was 12 weeks (range 1-36). Paclitaxel is metabolized by the liver and the pharmacokinetics of paclitaxel in cancer patients with liver involvement or impairment may be important clinically. Pharmacokinetic study was completed in 13 HCC patients. The paclitaxel area under the curve was significantly increased (P < 0.02), clearance decreased (P < 0.02) and treatment-related deaths increased (P = 0.03) in patients with hepatic impairment. In conclusion, paclitaxel in this dose and schedule has no significant anti-cancer effect in HCC patients. Paclitaxel should be used with caution in cancer patients with liver impairment.

Novel single-point plasma or saliva dextromethorphan method for determining CYP2D6 activity

O-Demethylation of dextromethorphan co-segregates with 4-hydroxylation of debrisoquin and is used for CYP2D6 phenotyping. In most previous studies, 8-h urinary samples were collected for determining the dextromethorphan metabolic ratio (dextromethorphan/dextrorphan molar ratio). In addition, a salivary sampling at 3 h had been suggested for the phenotyping. To evaluate the repeatability and validity of previously reported and other potential phenotyping methods, we determined the metabolic ratios from urine samples (for various intervals), or from plasma or saliva (at varying time points) after repetitive single doses of immediate-release or repetitive multiple doses of controlled-release dextromethorphan preparations. For the single-dose study, each of 12 subjects received 15 mg of immediate-release dextromethorphan in period I and period II, respectively, with a 1-week washout period. For the multiple-dose study, each of 16 subjects received 60 mg controlled-release dextromethorphan twice daily for 5 days in period I and period II, respectively, with a 2-week washout period. Dextromethorphan and dextrorphan were assayed by high-performance liquid chromatography. In the single-dose study, most metabolic ratios revealed good repeatabilities for the two periods (paired t test). The metabolic ratio from urine collected for 4 h, 6 h, 8 h or 12 h from plasma at any time between 1 h and 5 h or at 8 h, or from saliva at 2 h or 6 h, could reflect that from 0- to 24-h urine or AUCinfinity. In the multiple-dose study, all metabolic ratios revealed good repeatabilities. The plasma metabolic ratio at any time between 0.5 h and 10 h or the saliva metabolic ratio at any time between 3 h and 12 h, but not the urine metabolic ratio from any interval, could predict the metabolic ratio from ACUSStau. The 2 h, 3 h, 4 h or 5 h plasma metabolic ratio and 6 h saliva metabolic ratios after a single dose correlated significantly with their corresponding multiple-dose metabolic ratio (r > 0.8, P < .05). In conclusion, the plasma sample at 2 h, 3 h, 4 h or 5 h or the saliva sample at 6 h in either the single immediate-release (15 mg) or the multiple controlled-release dose (60 mg) procedure could be used for determining the dextromethorphan metabolic ratio.

Comparison of PCA nalbuphine and morphine in Chinese gynecologic patients

BACKGROUND

The aim of this study was to evaluate the efficacy and side effects of PCA nalbuphine (intravenous) versus morphine on postoperative pain in Chinese gynecologic patients.

METHODS

Sixty women undergoing abdominal hysterectomy or myomectomy under spinal anesthesia were enrolled into the investigation. Patients were randomly divided into 2 groups (n = 30 each). Group 1 received intravenous nalbuphine using PCA device for the management of postoperative pain, whereas group 2 received PCA morphine for the same purpose. During the first 48 hours postoperatively, we collected the following data: analgesic doses, pain scores, vital signs, nausea, vomiting, pruritus and dizziness.

RESULTS

The results showed that despite different treatments, pain scores on day 1 and day 2 postoperatively were low and were not significantly different between groups. Meanwhile, the cumulative consumption of PCA nalbuphine (32 +/- 10 mg) and PCA morphine (30 +/- 9 mg) was similar. Both treatments showed only minor side effects and the incidence of each side effect was not significant between groups.

CONCLUSIONS

Both PCA nalbuphine and morphine are effective in the treatment of postoperative pain in Chinese gynecologic patients undergoing hysterectomy or myomectomy after spinal anesthesia and the potency of nalbuphine is similar to that of morphine.

Single dose pharmacokinetic study of lithium in Taiwanese/Chinese bipolar patients

OBJECTIVE

The purpose of this study is to investigate the single dose pharmacokinetics of lithium in Taiwanese/Chinese bipolar patients for future interracial comparisons.

METHOD

Eight bipolar patients took 900 mg of lithium carbonate after overnight fasting. Blood samples of 5 mL were taken after 15 min, 30 min, 45 min, 1 h, 2 h, 3 h, 4 h, 7 h, 9 h, 15 h, 25 h and 31 h after dosing. The computer programs CSTRIP and PCNONLIN were used for pharmacokinetic analysis.

RESULTS

The pharmacokinetic parameters obtained were as follows: Cmax, 0.970 +/- 0.170 (SD) mmol/L; Tmax, 1.59 +/- 0.78 h; AUC31 h = 548.9 +/- 135.4 mmol x m/L; AUC to infinity = 722.6 +/- 262.7 mmol x m/L; beta-half-life = 16.3 +/- 7.18 h; kappa-half-life = 0.613 +/- 0.442 h; Cl(oral) = 1.13 +/- 0.39 mL/min/kg; Vd/F = 1.43 +/- 0.387 L/kg. Most of the pharmacokinetic parameters were within the ranges reported in investigations of Caucasian subjects.

CONCLUSIONS

This study showed that racial differences in lithium pharmacokinetics might not exist. We suggest that methodological designs, including method of blood sampling, measurement of lithium, and pharmacokinetic and statistical calculations, be standardised if future cross-ethnic comparisons are to be conducted.

Dose-dependent reduced haloperidol/haloperidol ratios: influence of patient-related variables

Plasma reduced haloperidol (RH) concentrations or RH to haloperidol (HL) ratios have been suggested to be important in determining the clinical efficacy and extrapyramidal side effects of HL. In this study, we measured the steady-state plasma HL and RH levels by high performance liquid chromatography and analyzed the effects of various variables (dose, gender, age, and body weight) on RH/HL ratios in four dose groups of Chinese schizophrenic inpatients: 10 mg/day (n = 84), 20 (n = 111), 30 (n = 29), and 60 (n = 55). In addition, the polymorphic distribution of RH/HL ratios, suggested by previous investigators, was further tested in each dosage group (for controlling the potential dosage effect on RH/HL ratios). As a result, both age and body weight could influence RH/HL ratios. Each year increase in age (after adjusting the effects of gender, body weight, and dosage) would elevate the RH/HL ratio by 0.0067 (P < 0.0001). On the other hand, after adjusting gender, age, and dosage effects, each kg increment in body weight would decrease the RH/HL ratio by 0.0044 (P < 0.01). Gender did not influence the ratio. Furthermore, the high dosage groups had higher RH/HL ratios (even with other variables being controlled). In comparison with the 10 mg group, the 60 mg group exhibited a higher mean RH/HL ratio by 0.84 (P < 0.0001) and the 30 mg group did by 0.31 (P < 0.0001). The 20 mg group was almost equal to the 10 mg group in RH/HL ratios. Besides, at each dosage group, the frequency distribution of RH/HL ratios seemed to be predominantly unimodal with a small proportion of extreme outliers. The results of this study clearly indicate that aging or a high dose (> or = 30 mg/day) of HL could raise the plasma RH/HL ratio, while an increasing body weight would reduce that. In contrast, gender does not affect the ratios.

Pharmacokinetics of fosinoprilat in Chinese and whites after intravenous administration

The pharmacokinetics of fosinoprilat was studied in 12 healthy Chinese men after a 7.5 mg intravenous dose of fosinoprilat. The data were compared with those from an earlier study using the same protocol in nine healthy white men. Blood and urine samples were obtained before and at various time intervals after fosinoprilat administration up to 24 hours and 48 hours, respectively. Pharmacokinetic parameters were calculated by fitting the plasma or serum concentrations to a three-compartment model. The total clearance (Clt), renal clearance (ClT), and nonrenal clearance (ClNR) were significantly lower in Chinese (16.29 +/- 6.92, 6.85 +/- 2.97, and 9.44 +/- 5.08 mL.hr-1.kg-1) than those obtained in whites (29.88 +/- 6.36, 13.55 +/- 3.45, and 16.33 +/- 5.07 mL.hr-1.kg-1). The Chinese subjects had a significantly lower volume of distribution (Vc [volume of distribution of central compartment] and Vdss [volume of distribution at steady state]) (29.38 +/- 21.12 and 73.67 +/- 40.20 mL/kg) than white men (58.14 +/- 15.01 and 152.49 +/- 24.89 mL/kg). The Chinese men also had a shorter elimination half-life than whites, although not statistically significant. The respective half-lives in Chinese and whites were 5.51 +/- 1.53 and 8.24 +/- 1.99 hours. The significant differences in ClNR and ClR may be related to lower liver elimination function and lower kidney excretory function, respectively. Plasma protein binding may contribute to part of the difference in the volume of distribution. Chinese men have smaller volume of distribution and clearances of fosinoprilat after intravenous administration compared with white men. The cumulative urine excretion of fosinoprilat was not different between Chinese and whites. Chinese may require a lower fosinoprilat dosage to obtain plasma concentrations similar to whites after intravenous administration. However, since a relatively high variation was found in fosinopril oral absorption, the oral dosage of fosinopril for Chinese and whites may not be different. Further study is obviously needed to elucidate whether the pharmacodynamic effect may be different between Chinese and whites.

Dextromethorphan phenotyping and haloperidol disposition in schizophrenic patients

This study examined the relationship between the metabolic ratios of dextromethorphan/dextrorphan, haloperidol disposition, and the incidence of extrapyramidal side effects in schizophrenic patients. Eighteen schizophrenic patients were phenotyped with a test dose of dextromethorphan prior to the initiation of haloperidol treatment. The metabolic ratio of dextromethorphan/dextrorphan was determined in each patient. Patients were treated with oral haloperidol 10 mg/day for 2 weeks. Blood samples for haloperidol and reduced haloperidol were obtained at week 2 of haloperidol treatment. Haloperidol and reduced haloperidol plasma concentrations were assayed by HPLC with electrochemical detection. Significant correlations of dextromethorphan/dextrorphan metabolic ratios vs. plasma haloperidol concentrations, reduced haloperidol concentrations, and reduced haloperidol/haloperidol ratios were found (r = 0.726, P = 0.0007; r = 0.782, P = 0.0001; and r = 0.619, P = 0.006, respectively). Ten patients who experienced extrapyramidal side effects had higher reduced haloperidol concentrations and reduced haloperidol/haloperidol ratios than the other patients (2.49 +/- 1.42 [S.D.] ng/ml vs. 1.10 +/- 0.46 ng/ml, P = 0.014 and 0.287 +/- 0.102 vs. 0.192 +/- 0.065, P = 0.030). The former also had a trend to have higher haloperidol concentrations and dextromethorphan/dextrorphan ratios than the latter (8.04 +/- 2.91 ng/ml vs. 5.83 +/- 1.79 ng/ml, P = 0.066 and 0.023 +/- 0.017 vs. 0.011 +/- 0.010, P = 0.077). Phenotyping patients has the potential to assist clinicians in predicting plasma drug concentrations during the subsequent neuroleptic drug treatment. Further research with phenotyping and psychotropic drug metabolism in psychiatric patients is needed.

Blood levels of reduced haloperidol versus clinical efficacy and extrapyramidal side effects of haloperidol

1. The studies of relationships between blood levels of reduced haloperidol HL (RH) and clinical efficacy in haloperidol (HL)-treated patients have yielded variable results. On the other hand, the contribution of RH upon HL's extrapyramidal side effects (EPS) had been suggested in animal models as well as in preliminary clinical studies with limited subjects. 2. This study explored the relationships between blood drug levels and clinical effects and EPS of HL in 48 Chinese acutely exacerbated schizophrenic inpatients. After a single-blind placebo period of one week, the patients were treated with a fixed dose 10 mg of HL for two weeks. Steady-state levels of HL and RH in plasma (n = 48) and in red blood cells (RBC) (n = 37) were measured by high performance liquid chromatography. 3. The mean RH/HL ratio in RBC in the Chinese (0.55) is lower than that in non-Chinese patients as reported in the literature (> 2), so is the RH/HL ratios in plasma. 4. No significant relationship emerged between percent improvement in BPRS total score and any of drug indices (HL, RH, sum of two compounds (HL+RH), and RH/HL ratio) in plasma and in RBC. Furthermore, the responders did not differ significantly from the nonresponders in each drug index. 5. Plasma RH levels were significantly higher in 30 patients experiencing EPS compared with the other 18 patients (mean 2.14 +/- 1.71 (S.D.) ng/ml vs. 1.38 +/- 0.37 ng/ml, p < 0.05). No significant differences in other drug indices were noted between subjects with or without EPS.

A pharmacokinetic study with the high-dose anticancer agent menadione in rabbits

The aim of this investigation was to assess the pharmacokinetic properties of high-dose menadione (VK3), as an anticancer agent, in plasma and red blood cells (RBCs) in rabbits. An extremely high dose of 75 mg menadiol sodium diphosphate (Synkayvite) was intravenously injected. HPLC analysis was applied to measure the major metabolite, menadione, VK3. The kinetic properties of VK3 in both plasma and red blood cells showed a short elimination half-life, high clearance, and large volume of distribution in plasma and RBCs. The mean elimination t1/2 values of menadione in plasma and in RBCs were 27.17 +/- 10.49 min and 35.22 +/- 11.82 min, respectively. The plasma clearance (CL/F) of VK3 was 0.822 +/- 0.254 L min-1. The systemic clearance in RBCs was 0.407 +/- 0.152 L min-1. The apparent volume of distribution (Vd/F) in plasma was 30.833 +/- 12.835 L and that in RBCs 20.488 +/- 9.401 L. The plasma AUC was 32.453 +/- 9.785 micrograms min mL-1 and that of RBCs 67.219 +/- 24.449 micrograms min mL-1. Menadiol was rapidly biotransformed to menadione in blood. The formation rate constant (kf) of menadione in plasma was 0.589 +/- 0.246 min-1, and that of RBCs 1.520 +/- 1.345 min-1. Through this study the estimated menadione dosage needed to maintain a plasma level of 1 microgram mL-1 for anticancer purposes was 19.7 mg kg-1 every hour.

Comparison of intravenous nalbuphine infusion versus saline as an adjuvant for epidural morphine

BACKGROUND AND OBJECTIVES

Radical (three-quadrant) hemorrhoidectomy is a major anorectal surgery that may necessitate aggressive pain management. This study was undertaken to determine whether intravenous nalbuphine infusion as an adjuvant to epidural morphine could offer not only a good quality of pain relief but also a lower incidence of side effects.

METHODS

Sixty patients requiring epidural anesthesia for radical hemorrhoidectomy were enrolled in a randomized, double-blind study. At the end of the surgery, all patients received epidural morphine 4 mg for relief of postoperative pain. Thereafter, 2 mg and 3 mg of morphine were administered via the epidural route at 8 p.m. and 8 a.m., respectively, for a 48-hour observation period. Patients in group 1 received an adjuvant intravenous infusion of nalbuphine 15 micrograms/kg/h, whereas patients in group 2 received intravenous saline only. A rescue analgesic of intramuscular meperidine 40 mg (every 4 hours) was available for each patient.

RESULTS

All patients had adequate postoperative pain relief. Cumulative (48-hour) analgesic requirements were similar. During the 48-hour observation period, one patient in group 1 and six in group 2 demonstrated a PaCO2 above 45 mm Hg. No patient had an SaO2 below 90%. The incidence of nausea and/or vomiting was 13% in group 1 and 62% in group 2. The incidence of pruritus was 7% in group 1 and 62% in group 2.

CONCLUSIONS

The results suggest that intravenous nalbuphine infusion as an adjuvant for epidural morphine reduces the incidence of side effects without decreasing the quality of pain relief.

Determination of nalbuphine by high-performance liquid chromatography with ultraviolet detection: application to human and rabbit pharmacokinetic studies

A rapid, sensitive, precise and accurate high-performance liquid chromatographic assay with ultraviolet detection was developed for the determination of nalbuphine in human, rabbit, pig and dog plasma. It is comprised of only a one-step extraction procedure with hexane-isoamyl alcohol at pH 9.25 and reversed-phase chromatography on a micro Porasil column. The recoveries of nalbuphine and ethylmorphine (internal standard) were greater than 86%. Calibration graphs were linear over the concentration range 0.75-150 ng/ml with a coefficient of variation, both within-day and between-day, of less than 10% at any level. The limit of quantitation was 0.75 ng/ml of plasma based on a signal-to-noise ratio of 3. Seven other clinically used analgesics were investigated to check for potential interferences and their analytical conditions. The specificity of this assay was checked with a metabolite of nalbuphine (noroxymorphine). Nalbuphine in plasma did not decompose significantly at -20 degrees C for six weeks. Pharmacokinetic application in three surgical patients and four rabbits revealed that nalbuphine followed a linear three-compartment model with two distribution phases. The two distribution and one elimination half-lives and the plasma clearance of nalbuphine were 0.9, 5.8 and 157 min and 370 ml/min in human, and 3.5, 28 and 117 min and 21 166 ml/min in rabbits.

Paw pressure test in the rabbit: a new animal model for the study of pain

BACKGROUND

In order to develop an animal model which is suitable for the pharmacokinetic (PK) and pharmacodynamic (PD) studies of analgesics in the field of pain assessment, we examined a new animal model, the paw pressure test (PPT), in rabbits for the study of pain.

METHODS

The sensitivity of the model was tested with a broad range of drugs, including mu-opioid agonist (morphine), kappa-opioid agonist (nalbuphine), three non-opioid analgesics (acetaminophen, ketorprofen and indomethacin) and two non-analgesics (droperidol and diazepam). Furthermore, PK and PD studies of nalbuphine (chosen as an example of analgesics) were performed.

RESULTS

The authors found that the PPT in rabbits recognized the antinociceptive activities of both opioid and non-opioid analgesics with no positive response to non-analgesics. AD50s determined by the PPT in rabbits for morphine and nalbuphine were 3.1 and 8.4 mg/kg, respectively. In the PK and PD studies, the plasma concentration time profiles of nalbuphine were well fitted to a linear two-compartment open model, and the correlation between pharmacokinetics and pharmacodynamics was significant (p < 0.05).

CONCLUSIONS

These results suggest that the PPT in rabbits can be used extensively to explore the analgesic effects (PD) of a broad range of analgesics. Also, with this model, PK and PD studies of analgesics can be easily performed.

The effect of aging on the pharmacokinetics of nalbuphine in rabbits

For the purpose of selecting an animal model for the study of the aging effect on the pharmacokinetics of nalbuphine, the pharmacokinetic properties in young and in aged rabbits were reported. Thirty-one healthy New Zealand white rabbits ranging in ages (mean) from three months to 43 months (six three months old, group I; nine eight months old, group II; nine 18 months old, group III; and seven 43 months old, group IV) were included in the study. After intravenous bolus injection of nalbuphine (10 mg kg-1) to each rabbit, plasma samples were collected and analysed for nalbuphine by a high-performance liquid chromatography method. The plasma concentration-time data regarding nalbuphine were successfully fitted to a linear two-compartment open model. The elimination half-life of nalbuphine in rabbits increased significantly with age. Consequently, clearance decreased significantly with age. The parameter AUCO-affinity, which is derived from dose/clearance, increased significantly with age. The effect of aging on the pharmacokinetics of nalbuphine in rabbits is quite similar to that in humans. From the present study, it is concluded that rabbits may be suitable for the study of aging effects on the pharmacokinetics of nalbuphine.

Pharmacokinetics and pharmacodynamics of enantiomers of pimobendan in patients with dilated cardiomyopathy and congestive heart failure after single and repeated oral dosing

Pharmacokinetics and pharmacodynamics of pimobendan were studied in eight patients with dilated cardiomyopathy and chronic congestive heart failure after single dosing and after 2-week repeated dosing of 5 mg racemic pimobendan. Enantiomers of pimobendan and its demethylated metabolite in plasma and in red blood cells were measured. In the single-dose study, the peak plasma levels of 16.3 +/- 4.0 and 17.0 +/- 3.1 ng/ml of (+)- and (-)-pimobendan were observed at 0.9 hour after dosing. The concentration-time curves followed a two-compartment model, with terminal half-lives of 2.56 +/- 0.35 and 2.93 +/- 0.33 hours for (+)- and (-)-pimobendan (p > 0.05), respectively. The oral volumes of distribution after equilibrium were 3.26 +/- 0.74 and 3.13 +/- 0.75 L/kg, and oral clearances were 28.6 +/- 7.0 and 21.9 +/- 4.1 ml/min/kg for (+)- and (-)-pimobendan (p > 0.05), respectively. In red blood cells, the respective (+)- and (-)-pimobendan concentrations were 5.8 and 8.4 times higher than those in plasma, indicating a stereoselective partitioning of drugs between plasma and red blood cells. The pharmacodynamic effect of pimobendan was evaluated by echocardiography. The ejection fraction, mean velocity of circumferential fiber shortening, aortic flow peak velocity, cardiac index, and stroke volume index significantly increased 50% to 60%. The left ventricular end-systolic dimension, systolic blood pressure, and diastolic blood pressure significantly decreased 8% to 11%. These effects lasted for more than 8 hours. In a 2-week repeated-dose study, there was no significant dose accumulation in plasma and red blood cells. The pharmacokinetic parameters were similar to those in the single-dose study, except for significantly shorter absorption half-lives. The baseline levels of cardiac index and stroke volume index were significantly higher than the baseline levels in the single-dose study. This suggests an accumulation of pharmacodynamic effects despite a relatively short elimination half-life.

Determination of anticancer drug vitamin K3 in plasma by high-performance liquid chromatography

Synthetic vitamin K3 (VK3, 2-methyl-1,4-naphthoquinone, or menadione) has been found to exhibit antitumor activity against various human cancer cells at relative high dose. Parallel to our study on the mechanism of VK3 action and for future clinical trials in Taiwan, we developed a simple, sensitive and accurate high-performance liquid chromatographic method for the determination of VK3 in biological fluids. VK3 was extracted from the plasma samples with n-hexane. The chromatographic separation employed an ODS analytical column (5 microns, 250 x 4.6 mm I.D.) with a mobile phase of methanol-water (70:30, v/v) and UV detection at 265 nm. On completely drying of the extraction solution, n-hexane, by a stream of nitrogen, menadione was lost to a great extent. Methanol (70%, 200 microliters) was added to the extraction solvent after extraction and centrifugation to prevent the loss of menadione. The absolute recovery was 82.4 +/- 7.69% (n = 7). The within-day and between-day calibration curves of VK3 in plasma in the ranges of interest (0.01-10.00 micrograms/ml; 0.01-5.00 micrograms/ml) showed good linearity (r > 0.999) and acceptable precision. The limit of quantitation of VK3 was 10 ng/ml in plasma. This method has been successfully applied to a pilot pharmacokinetic study of VK3 in rabbits receiving an intravenous high-dose bolus injection of 75 mg menadiol sodium diphosphate (Synkayvite). The pharmacokinetic properties of menadione could be described adequately by an open two-compartment model. The mean half-life of menadiol (transformation to menadione) was 2.60 +/- 0.12 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel galactose single point method as a measure of residual liver function: example of cefoperazone kinetics in patients with liver cirrhosis

A novel, simple, clinically useful quantitative liver function test, called the galactose single point (GSP) method, was developed to assess residual liver function by measuring galactose blood concentration 1 hour after galactose was administered (0.5 g/kg). This method was applied to the study of cefoperazone kinetics in patients with hepatic cirrhosis. To study the influence of hepatic cirrhosis on the residual liver function and the correlation between the residual liver function and the pharmacokinetics of cefoperazone, a dose of 1 g of cefoperazone was administered to 11 healthy volunteers and 12 patients with liver cirrhosis. The GSP method, the galactose elimination capacity (GEC) test, and the modified galactose elimination capacity (MGEC) test were done for each volunteer and patient to measure residual liver function. The galactose concentrations were determined enzymatically. Cefoperazone was administered intravenously, and blood and urine samples were collected at appropriate intervals after drug administration. All blood and urine samples were stored at -30 degrees C until high-performance liquid chromatography analysis. Cefoperazone plasma concentrations were much higher in cirrhosis patients than in normal subjects at all times. The elimination half-life, hepatic clearance, mean residence time, and renal clearance of cirrhosis patients differed significantly from those of healthy volunteers. The plasma protein binding was unaltered in both groups. Urinary excretion of cefoperazone was significantly increased in cirrhosis patients (23.95 +/- 5.06% for normal men and 51.09 +/- 11.50% in cirrhosis patients). Hepatic clearance, fraction excreted in urine, and total clearance significantly correlated with GSP, GEC, and MGEC (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma and red blood cell pharmacokinetics of pimobendan enantiomers in healthy Chinese

The pharmacokinetics of enantiomers of pimobendan and their demethylated metabolites in plasma and red cells were studied in 8 normal healthy volunteers. After racemic pimobendan 5 mg IV, the plasma concentration-time curve followed a two-compartment open-model with elimination half-lives of 1.81 h and 1.86 h for (+)- and (-)-pimobendan, respectively. The clearances and volumes of distribution postequilibrium were 13.5 ml.min-1.kg-1, 14.4 ml.min-1.kg-1; 1.74 l.kg-1 and 2.34 l.kg-1 for (+)- and (-)-pimobendan, respectively. Plasma protein binding (n = 3) of (+)-, (-)-pimobendan, (+)- and (-)-demethylated metabolites was 97.6, 97.6, 92.2 and 92.5%, respectively. The plasma concentration-time curve also followed a two-compartment open model after oral administration of 7.5 mg racemic pimobendan. The absolute bioavailabilities of (+)- and (-)-pimobendan were 0.51 and 0.55. Peak levels of (+)- and (-)-pimobendan, both at 1.2 h, were 15.8 and 16.8 ng.ml-1, respectively. The (+)- and (-)-pimobendan concentrations in red cells were determined and their pharmacokinetics were estimated using red blood cell data. Interesting phenomena were observed: the peak concentrations of (+)- and (-)-pimobendan in red blood cells were about 5.5- and 9.2-times higher than in plasma, and the AUCs were correspondingly elevated. The volume of distribution of the central compartment of (-)-pimobendan in red cell was significantly smaller than that of (+)-pimobendan. (0.24 vs. 0.42 l.kg-1.) Similar phenomena were found after IV administration.

Determination of galactose in human blood by high-performance liquid chromatography: comparison with an enzymatic method and application to the pharmacokinetic study of galactose in patients with liver dysfunction

Galactose, the C-4 epimer of glucose, is an agent of choice for the quantitation of liver function. A simple, precise, and accurate high-performance liquid chromatographic (HPLC) assay with refractive index detection was developed for the determination of galactose in human whole blood. The method consists of organic solvent-heavy metal deproteinization procedures and reversed-phase chromatography on a cation-exchange column in the calcium form. Calibration graphs were linear over the concentration range 100-2500 microgram/mL, with correlation coefficients > 0.999. The within-day coefficient of variation (CV) ranged from 2.08 to 8.94%, and the between-day CV ranged from 1.61 to 10.9%. The limit of quantitation was 100 micrograms/mL in whole blood. However, the limit of detection was 75 micrograms/mL based on a signal-to-noise ratio of > or = 3. Eight structurally related sugars and polyols were investigated to check for potential interferences using the analytical condition of the assay. The possible metabolites of galactose present in the body were also checked to determine the specificity of this assay. The proposed HPLC assay was compared with an enzymatic assay and an excellent correlation was observed (HPLC = 1.0299Enz. - 12.907, r = 0.952, p < 0.001). This HPLC method has been successfully applied to the pharmacokinetic study of galactose in six patients with liver dysfunction. Following the intravenous administration of a dose of 0.5 g/kg body weight, galactose pharmacokinetics followed a nonlinear two-compartment model with Michaelis-Menten elimination from the central compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

An innovative cold tail-flick test: the cold ethanol tail-flick test

An innovative antinociceptive test, the cold ethanol tail-flick test (CET), was developed for evaluating the actions of opioid analgesics. To select an optimal operation temperature range for the CET, temperatures from -5 degrees C to -30 degrees C were screened. After screening, temperatures ranging between -20 degrees C and -30 degrees C were both strong and effective enough to act as a noxious cold stimulus. In the following study, -20 degrees C was selected as the cold stimulus for the CET. The sensitivity and specificity of this test were challenged by opioid analgesics: an agonist (morphine) and two agonist-antagonists (buprenorphine and nalbuphine), two tranquilizers (droperidol and diazepam), and four nonopioid analgesics (acetaminophen, aspirin, indomethacin, and ketoprofen). The sensitivity of the CET was also compared with the assays using heat (radiant heat and hot water). The AD50 values determined by the CET for morphine, buprenorphine, and nalbuphine were 0.16 mg/kg, 0.22 micrograms/kg, and 0.19 mg/kg, respectively. Naloxone, an opioid antagonist, blocked the antinociceptive effects of these opioids which were determined by the CET. Furthermore, the tranquilizers and nonopioid analgesics did not show any activity in the CET. Our results show that not only can the CET assess the antinociceptive activity of both opioid agonist and mixed agonist-antagonist, it also possess the characteristics of sensitivity, specificity, simplicity, and reproducibility.

Pharmacokinetics of promazine in patients with hepatic cirrhosis--correlation with a novel galactose single point method

We examined promazine pharmacokinetics in nine patients with hepatic cirrhosis and in six healthy subjects. A specific and sensitive HPLC method was used to measure promazine concentrations in plasma, plasma water (free drug), red blood cells, and urine after oral administration of promazine (2 x 50 mg tablet). There were highly significant reductions in total plasma clearance (p < 0.01), free drug total plasma clearance (p < 0.01), metabolic clearance (p < 0.01), metabolic clearance of free drug (p < 0.01), and fraction bound (p < 0.01) in the cirrhotic patients. The elimination half-life and the area under the plasma concentration-time curve were significantly increased (p < 0.001 and p < 0.05, respectively) in the cirrhotic patients. However, the overall excreted promazine in urine, time to the promazine peak concentration, distribution half-life, renal clearance, apparent volume of distribution, and the promazine concentration ratio between plasma and red blood cells were not different. Thus caution is needed in using promazine for patients with hepatic cirrhosis. A newly developed galactose single point (GSP) method was applied to quantitatively measure the residual liver function in cirrhosis patients and successfully correlated it with promazine elimination half-life (r = 0.770, p < 0.01), total plasma clearance of free drug (r = 0.899, p < 0.005), metabolic clearance of free drug (r = 0.902, p < 0.005), and plasma protein binding (r = 0.822, p < 0.005). GSP may be a convenient index for promazine routine dosage adjustment in patients with liver cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic properties of recombinant porcine growth hormone in pigs

The plasma pharmacokinetic profile of recombinant porcine growth hormone (rpGH) was studied in six healthy gilts after a rapid single i.v. injection of 250 micrograms/kg rpGH. The linear pharmacokinetic properties of rpGH were investigated by giving four different doses of the hormone at intervals of 2 days. The plasma rpGH concentration was determined by radioimmunoassay with a lowest detection limit of 50 pg/ml. Plasma levels of rpGH were fitted to a three-compartment open model; a triexponential decrease in plasma rpGH with a rather long mean terminal half-life of 40.22 +/- 5.623 min was obtained in these pigs. Linear pharmacokinetic properties of rpGH were confirmed in the additional pig that received doses between 25 and 250 micrograms/kg rpGH. The small volume of distribution, 0.029 +/- 0.003 l/kg, indicated that most of the injected rpGH was confined to the blood and probably lymph. The total plasma clearance of rpGH was 31.80 +/- 2.802 ml/h x kg. The results not only contribute significantly to our knowledge about rpGH pharmacokinetics, but also to future studies for the rational design of optimal dosage regimens and the development of a controlled-release device for rpGH.

A double-blind randomized controlled trial of colchicine in patients with hepatitis B virus-related postnecrotic cirrhosis

The preliminary results of a prospective double-blind controlled trial of colchicine in 100 patients with hepatitis B virus-related cirrhosis are reported. The patients, 94 males and 6 females, aged 32-80, were assigned to receive either 1 mg of colchicine or an identical placebo orally on a daily basis. The duration of the follow up ranged from 15 to 51 months (median 26 months). Seventy percent had histological proof of cirrhosis. On entry, 80 patients were in Child-Pugh class A, 19 were in class B, and one was in class C. Compared to the placebo group, there was no improvement in the colchicine group after a 24-month follow up in any of the biochemistry data, for example, serum albumin, alkaline phosphatase, alanine and aspartate aminotransferase, bilirubin, and prothrombin time. The difference in the cumulative survival rates at 51 months did not reach statistical significance (p = 0.8) in either group. There was no histological improvement in 30 patients who were willing to undergo repeated liver biopsies. No trend toward improvement of the hepatic pressure gradient was observed in these patients. The serum levels of aminopropeptide of type III procollagen increased significantly in patients in both groups after 24 months of therapy (1.07 +/- 0.06 vs. 1.36 +/- 0.06 U/ml in the colchicine group, 0.93 +/- 0.09 vs. 1.25 +/- 0.07 U/ml in the placebo group; p < 0.05). In addition, neither the clinical deterioration of cirrhosis nor death was prevented in patients receiving colchicine therapy. This report indicates that colchicine has no effect in the treatment of HBV-related postnecrotic cirrhosis.

The influence of chronic lobular hepatitis on pharmacokinetics of cefoperazone--a novel galactose single-point method as a measure of residual liver function

Cefoperazone is a semisynthetic cephalosporin antibiotic containing a piperazine side chain, which results in antipseudomonal activity. Unlike the other cephalosporins, it is mainly cleared by the liver (60-80%) and it may be more sensitive to changes in the liver function and/or plasma protein binding than other cephalosporins, which are not primarily cleared by the liver. In order to study the influence of chronic lobular hepatitis on the pharmacokinetics of cefoperazone, a dose of 1 g of cefoperazone was administered to 11 normal, healthy volunteers and 16 subjects with chronic lobular hepatitis. In each volunteer or patient, a novel galactose single-point (GSP) method, the galactose elimination capacity (GEC) test, and the modified galactose elimination capacity (MGEC) test were also performed as a measure of residual liver function. Cefoperazone was administered intravenously over a period of 3-5 min. Blood and urine samples were collected at appropriate intervals after drug administration and stored at -30 degrees C until high-pressure liquid chromatographic (HPLC) analysis. The cefoperazone hepatic clearance, mean residence time, and renal clearance in hepatitis patients were significantly different from those of normal healthy volunteers, whereas the plasma protein binding was unaltered between the two groups. Urinary excretion of cefoperazone showed a highly significant increase in patients, 23.95 +/- 5.06% and 37.54 +/- 13.61% for normal men and hepatitis patients respectively. Hepatic clearance and fraction excreted in urine significantly correlated with values of GSP and MGEC respectively (p < 0.05). These results suggest (i) cefoperazone kinetics was significantly altered in patients with chronic lobular hepatitis; (ii) GSP, a novel simple, clinically useful quantitative liver function test, can predict the cefoperazone hepatic clearance in patients with liver dysfunction.

Evaluation of gastric emptying in severe, burn-injured patients

OBJECTIVE

The aim of this study was to evaluate the possible effect of a severe burn on gastric emptying by determining the absorption kinetics of orally administered acetaminophen.

DESIGN

A prospective, controlled study.

SETTING

A ten-bed burn center in a 1,300-bed university hospital.

PATIENTS

Ten adult patients suffering from second-degree burn involving > 20% of total body surface area and 20 normal, healthy volunteers who acted as controls.

INTERVENTIONS

Patients received routine treatment such as nutritional support and cimetidine. However, opiates were stopped for at least 12 hrs before the start of the study, and nonsteroidal anti-inflammatory drugs as alternatives were used. After an 8-hr fast, the subjects ingested 0.5 g acetaminophen with 200 mL of water. The plasma concentrations of acetaminophen were determined by high-performance liquid chromatography, and the absorption kinetics was estimated from determination of time to reach the maximum plasma concentration, the maximum plasma concentration, and the area under the plasma concentration-time curve.

MEASUREMENTS AND MAIN RESULTS

The mean time for reaching the maximum plasma concentration was 33 +/- 24 (SD) mins in patients and 39 +/- 24 mins in the healthy volunteers. The mean area under the plasma concentration-time curve from time 0 to 120 mins and the mean maximum plasma concentration were 556 +/- 190 micrograms/mL/min and 9.5 +/- 3.5 micrograms/mL in patients, and 539 +/- 131 micrograms/mL/min and 7.8 +/- 2.8 micrograms/mL in volunteers, respectively. There was no statistical difference between groups in the time to reach the maximum plasma concentration, the area under the plasma concentration-time curve from time 0 to 120 mins, and the maximum plasma concentration. The time for reaching the maximum plasma concentration was not correlated with the severity of the burn (% area of burn) and the duration of healing (days) after burn.

CONCLUSIONS

We conclude that severe burn injury does not affect the kinetics of gastric emptying, and that 200 mL of water ingested 2 hrs before anesthesia is quite safe in severely burned patients. Also, the absorption kinetics of acetaminophen was not altered by burn injury.

Reinduction of the hypnotic effects of thiopental with NSAIDs by decreasing thiopental plasma protein binding in humans

The effects of 14 non-steroidal anti-inflammatory drugs (NSAIDs)--naproxen, ibuprofen, mefenamic acid, ketoprofen, indomethacin, fenoprofen, diclofenac sodium, aspirin, salicylic acid, piroxicam, sulindac, fenbufen, flurbiprofen and benzydamine, on the plasma protein binding of thiopental and the clinical consequences of such interactions were studied. Four of them, naproxen, ibuprofen, salicylic acid and aspirin, very significantly decreased the protein binding of thiopental in vitro in human plasma (P < 0.005). Structurally, they were salicylates and propionic acid derivatives among the six classes of NSAIDs studied. The aspirin study demonstrated that the protein-displacing phenomenon was temperature-dependent, and concentration-dependent. Clinically, aspirin administered intravenously resulted in a significant increase in the percentage of plasma free thiopental from 16.01 +/- 3.59% to 22.27 +/- 3.96% (P < 0.001, n = 10) in patients undergoing surgery, and resulted in three of seven patients sleeping again during recovery from thiopental-induced anesthesia. Although the effect of chronic use of NSAIDs before anesthesia is uncertain, studies should be carried out to find out if naproxen, ibuprofen, and aspirin influence the depth of anesthesia, time of recovery and duration of action of thiopental.

Pharmacokinetic and pharmacodynamic studies with mitoxantrone in the treatment of patients with nasopharyngeal carcinoma

The pharmacokinetics and pharmacodynamics of mitoxantrone were studied in 15 patients with advanced nasopharyngeal carcinoma (NPC) after single intravenous rapid infusion (12 to 14 mg/m2). Mitoxantrone plasma concentrations and urinary excretion were measured specifically with the use of a high-performance liquid chromatographic method with ultraviolet detection at 242 and 658 nm. The pharmacokinetic parameters are described adequately by a three-compartment model with a terminal half-life of 71.5 +/- 40.1 hours and a volume of distribution of 5037 +/- 2377 l. The total plasma clearance was 743 +/- 462 ml/minute, and the renal clearance was 18.8 +/- 8.49 ml/minute. Within 72 hours, 1.8 +/- 0.6% of the administration dose was excreted in urine as mitoxantrone parent compound. From the urinary excretion rate data, glomerular filtration and possible tubular reabsorption were the mechanisms involved in the urinary excretion of mitoxantrone. The values for unbound fraction (%) in plasma at time 0 and 5 minutes were 2.88 +/- 0.91% and 3.25 +/- 1.19%, with an average of 3.04 +/- 1.01%. The degree of protein binding of mitoxantrone was not affected by concentration (P greater than 0.05) in Chinese patients with NPC. The response rate for mitoxantrone was poor in this study. Clinical studies have demonstrated that mitoxantrone was generally well tolerated. Only very low incidences of nausea, vomiting, and alopecia were observed. The mild and rapidly reversible dose-limiting hematologic toxic effects have proven leukopenia. Although the toxicities reported here were tolerated for most patients, other combination regimens including mitoxantrone or other administration routes may be considered and need to be evaluated carefully.

Assessment of liver function using a novel galactose single point method

A novel, simple, clinically useful quantitative liver function test, called the galactose single point (GSP) method, was developed by measurement of galactose blood concentration 1 h after galactose was administered (0.5 g/kg). It was quickly infused intravenously in 55 normal healthy volunteers, 73 patients with chronic hepatitis (CH), 36 with cirrhosis and 41 with hepatocellular carcinoma (HCC). Patients with CH diagnosis were assessed by liver biopsy. Cirrhosis was diagnosed by histological examination or a chronic hepatitis history with esophageal varices or ascites, whereas HCC was diagnosed either histologically, or cytologically proved, or as implied in the 'one imagine study' being positive with AFP > 300 ng/dl. Highly significant galactose blood levels were observed between normal healthy volunteers and patients 50, 60 and 70 min after galactose was administered. Galactose elimination capacity (GEC), modified GEC (MGEC) and consecutive GSP tests were performed in 6 healthy volunteers for 2 days. 0.64-16.87% variation was observed for each subject. The significant differences (p < 0.001) in average GSP values were 247 +/- 18.1, 422 +/- 27.3, 629 +/- 42.8 and 579 +/- 43.6 micrograms/ml for normal healthy volunteers, CH, cirrhosis and HCC patients, respectively. Highly significant correlations (p < 0.001) were obtained among GSP, GEC and MGEC for all patients. Positive correlations were observed between GSP, GEC, MGEC and AST (serum aspartate aminotransferase), ALT (serum alanine aminotransferase), serum bilirubin, albumin, prothrombin time and r-globulin. According to results obtained from 202 normal healthy volunteers and patients, the GSP method may be a simple, clinically useful quantitative measurement of liver function for the determination of a patient's residual liver function, the prognosis of liver function for patients with cirrhosis, postoperational follow-up and, finally, the timing of a liver transplant.

Determination of fenoverine, a modulator of smooth muscle motility, in capsules and in human plasma: application to dosage form stability and a pilot study in humans

Fenoverine is a novel, potent, musculotropic, spasmolytic agent that affects primarily the gastrointestinal tract, bile duct, and female genital organs. A simple, specific, and accurate HPLC method was developed for the determination of fenoverine in capsules and plasma. This method has been successfully applied to stability studies of fenoverine capsules and to a pilot study in a normal, healthy volunteer following oral administration of fenoverine. For the determination of fenoverine in capsules, a Nucleosil 5-micron CN column, with acetonitrile:0.1 M ammonium acetate (60:40) as mobile phase and detection at 254 nm, was employed. The mean correlation coefficient of the calibration curve (n = 6) for the assay was 0.9999 over a concentration range of 24.6 to 147.6 micrograms/mL of fenoverine standard solutions. Fenoverine did not decompose significantly at 4, 45, 55, and 65 degrees C for 3 months. The mean correlation coefficients of within-day and between-day calibration curves were 0.9995 and 0.9999, respectively, over a range of 10 to 1000 ng/mL of fenoverine in plasma. The limit of detection was 10 ng in plasma.

Determination of buprenorphine by high-performance liquid chromatography with fluorescence detection: application to human and rabbit pharmacokinetic studies

A rapid, sensitive, precise and accurate high-performance liquid chromatographic assay with fluorescence detection was developed for the determination of buprenorphine in human, rabbit, pig and dog plasma. It is comprised of only a one-step extraction procedure with hexane-isoamyl alcohol at pH 9.25 and reversed-phase chromatography on a muPorasil column. The recoveries of buprenorphine and nalbuphine (internal standard) were greater than 90%. Calibration graphs were linear over the concentration range 3-300 ng/ml with a coefficient of variation, both within-day and between-day, of less than 9% at any level. The limit of detection was 1.0 ng/ml of plasma based on a signal-to-noise ratio of 3. Eight other clinically used narcotics were investigated to check for potential interferences and their analytical conditions. The possible decomposed compounds of buprenorphine were also checked for the specificity of this assay. The method has been successfully applied to the stability and pharmacokinetic studies of buprenorphine. Buprenorphine in plasma did not decompose significantly at -20 degrees C for four weeks. Pharmacokinetic application in six rabbits and a surgical patient revealed that buprenorphine followed a linear three-compartment model with two distribution phases. The two distribution and elimination half-lives and the clearance of buprenorphine were 1.32, 24.8 and 230 min and 224 ml/min in human plasma, and 0.94, 12.5 and 232 min and 30 ml/min in rabbit plasma.

Pharmacokinetic properties of ranitidine in Chinese people

The pharmacokinetics and relative bioavailability of two different formulated ranitidine tablets were examined in 12 healthy young Chinese males at one week intervals in a randomized crossover design. Both ranitidine plasma and urine concentrations were measured by a sensitive, accurate and specific High Performance Liquid Chromatography method. No bioavailability differences were found between Glaxo's and Veteran's ranitidine products. However, larger apparent volume of distribution, higher total oral clearance and higher non-renal clearance was observed in Chinese. Further studies are needed to elucidate a higher ranitidine dosage may be required for Chinese to achieve the desired plasma level.

Effect of physostigmine on the loss of consciousness induced by midazolam, etomidate and althesin

The effect of physostigmine, a cholinesterase inhibitor, on the loss of consciousness induced by three different intravenous induction anesthetics, namely midazolam, etomidate and althesin at ED50, was studied in three comparable groups of patients. Ten min before induction, the first and second groups received physostigmine 8 micrograms/kg and 16 micrograms/kg, respectively, and the third group received 2 ml of saline solution. Physostigmine 16 micrograms/kg resulted in a significant decrease in the percentage of unconscious patients with midazolam (from 50% to 10%), but it did not modify the incidence with etomidate or althesin. Physostigmine at doses of 8 micrograms/kg and 16 micrograms/kg could cause 6.7% and 10% nausea, respectively. Although the mechanism of the drug interaction of physostigmine and midazolam is unclear, physostigmine could be used clinically to reverse post-anesthetic somnolence induced by midazolam.

Determination of vecuronium in blood by HPLC with UV and electrochemical detection: a pilot study in man

Vecuronium bromide is a non-depolarizing neuromuscular blocking agent with a rather low therapeutic level. Rapid, sensitive, and selective determination of vecuronium bromide in human blood or plasma was essential for pharmacokinetic study. We developed such a method using HPLC with electrochemical detection. Samples were first acidified, followed by a one-step liquid-liquid extraction. Tubocurarine, which has a structure similar to that of vecuronium, was used as the internal standard. The electrochemical detector, Ag/AgCl electrodes, was operated by setting the working electrodes, W1 and W2, at +0.65 V and +1.05 V, respectively. When vecuronium blood concentration was plotted versus peak area ratios (PAR) of vecuronium over tubocurarine, a linear relationship was observed over the range of 25 ng/mL to 500 ng/mL with a correlation coefficient greater than 0.997. Clinically possible sources of interference, such as atropine, apresoline, droperidol, fentanyl, labetalol, thiopentone, atracurium, and valium, were examined and none showed interference in the assay of vecuronium and tubocurarine. This method has been successfully applied in a preliminary study of the pharmacokinetics of vecuronium in a patient undergoing surgery. The low detection limit of this method in the patient was 3 ng/mL.

Novel assay method for mitoxantrone in plasma, and its application in cancer patients

Mitoxantrone is an anthracene derivative that acts as a cytostatic in a variety of cancers. A quantitative analytical method has been established for the determination of mitoxantrone in plasma. The method employed C18 reversed-phase ion-pair chromatography with an isocratic mobile phase of 50.0% methanol in 10 mM phosphate buffer (pH 3.0) plus 0.09% 1-pentanesulphonic acid and ultraviolet detection. Sample preparation consisted of two extraction steps using same organic solvent system at different pH to remove plasma impurities efficiently. Potential adsorption of mitoxantrone onto glassware was considered. Silanization of all glassware with 5% dichlorodimethylsilane in chloroform increased the extraction recovery in plasma from 50 to 85% with high reproducibility. Mitoxantrone was unstable in human plasma. To maintain plasma sample integrity, each millilitre of sample should be fortified with 0.1 ml of 5% vitamin C (in citrate buffer) and kept frozen until analysis. Using this new method, the calibration curve of mitoxantrone in plasma in the range of interest (1-500 ng/ml) showed good linearity (r = 0.996) and precision (both between-day and within-day coefficients of variation less than 10%). The lower detection limit of this assay method was 1 ng. The application of this method allowed us to study the stability of mitoxantrone in plasma, and the pharmacokinetics of mitoxantrone in nasopharyngeal carcinoma patients receiving 12 mg/m2. The study revealed a prolonged terminal phase half-life for mitoxantrone.

Pharmacokinetics of promazine: I. Disposition in patients with acute viral hepatitis B

Concentrations of promazine in plasma, plasma water, red blood cells, and urine were measured after oral administration of the drug to six patients during and after apparent recovery from the acute phase of viral hepatitis B. None of the promazine pharmacokinetic parameters were significantly different during and after the acute phase; these parameters included clearance, free drug clearance, metabolic clearance, volume of distribution, distribution and elimination half-life values, plasma protein binding, and per cent excreted in the urine. During the acute period of the illness, SGOP, SGPT, alkaline phosphatase, and total bilirubin were increased in all patients; they returned to within or near the upper limits or normal after recovery. Despite the unchanged promazine disposition, four out of six patients had more severe promazine side-effects, such as sedation, postural hypotension, and dizziness during the acute phase of the illness. This study suggests that promazine disposition was not significantly altered as a consequence of viral hepatitis. However, the pharmacodynamic effects of promazine were changed significantly. Care must be taken with patients who are taking promazine during the acute phase of viral hepatitis B.

[The study of pretreatment with diphenylhydantoin or D-tubocurarine on succinylcholine-induced adverse effects]

Intravenous succinylcholine (SCh) is widely used as a muscle relaxant but it is often associated with adverse effects, including muscle fasciculations, postoperative myalgia, elevated serum potassium (K+) and creatine phosphokinase (CPK), etc. The present study was undertaken to evaluate the effects of pretreatment with Diphenylhydantoin (DPH) or d-Tubocurarine (d-TC) on SCh-induced adverse effects. 54 ASA I-II adult patients were randomly divided into 3 groups of 18 patients each. Four min before injection of SCh, group A received 1 ml of normal saline as a control group, group B DPH 2.5 mg kg-1 and group C d-TC 50 micrograms kg-1. Anesthesia was induced with thiopentone 3-4 mg kg-1 and then SCh was given to facilitate tracheal intubation. Anesthesia was maintained with isoflurane and nitrous oxide in oxygen. Muscle fasciculations, postoperative 24 hours myalgia, intubating conditions and levels of serum K+, CPK and DPH were recorded in every patient. All data were analyzed with Chi-Square and ANOVA tests. DPH and d-TC significantly decreased the incidence of fasciculations, whereas there were no differences regarding intubating condition, post-operative myalgia, and serum K+ among three groups. DPH concentration was 8.49 +/- 1.55 micrograms ml-1. Serum CPK was increased postoperatively in three groups. Pretreatment with DPH 2.5 mg kg-1 or d-TC 50 micrograms kg-1 effectively decreased SCh-induced fasciculations and did not affect intubating condition facilitated with SCh 1.5 mg kg-1. Nevertheless, these pretreatment did not improve postoperative myalgia and decrease serum CPK.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of abdominal motor blockade using surface integrated electromyography during bupivacaine spinal anesthesia]

The study was undertaken to investigate abdominal motor blockade and compare sensory-motor differential blockade in bupivacaine spinal anesthesia by surface integrated electromyography (SIEMG). Seventeen physical status I adult male patients underwent lower limb surgery under spinal anesthesia were divided into two groups: hyperbaric bupivacaine (HB) group (n = 8) receiving 3 mL of 0.5% bupivacaine (8% glucose) and isobaric bupivacaine (IB) group (n = 9), 3 mL of 0.5% bupivacaine (glucose-free). Each patient was monitored with a blood pressure cuff, an ECG and a precordial stethoscope. Spinal anesthesia was performed at L3-4 interspace on the lateral position. Immediately following injection of bupivacaine, the patients were turned to the supine position and then simultaneous measurements of sensory blockade using pinprick, abdominal motor blockade at T6, T8, T10, T12 level using SIEMG and lower limb motor blockade using Bromage scale were made for 4 hours. Between two groups, there were no significant differences in terms of age, body weight, height as maximum level and mean times to maximum level of sensory blockade, abdominal motor blockade and lower limb motor blockade. The times of 2-segment regression of sensory blockade were 66.3 +/- 11.1 min in HB group and 115.6 +/- 31.3 min in IB group. The sensory-motor differential blockades were 4.6 +/- 0.5 segments and 4.8 +/- 2.1 segments in HB and IB groups, respectively. According to the linear regression analysis, the correlation between sensory blockade and abdominal motor blockade was better than the lower limb motor blockade and abdominal motor blockade. (Correlation coefficient (r): 0.893 vs 0.580 in HB group; 0.773 vs 0.366 in IB group).(ABSTRACT TRUNCATED AT 250 WORDS)

Stability, human blood distribution and rat tissue localization of promazine and desmonomethylpromazine

The stability in human blood and urine, partitioning into red blood cells and plasma protein binding of promazine and desmonomethylpromazine were investigated. Tissue localization was investigated in rats. Promazine and desmonomethylpromazine were stable in human plasma and urine for at least 64 days at -20 degrees. The percentage of promazine not bound to protein in plasma was 10.4 +/- 2.43 as estimated by equilibrium dialysis with correction for volume shift, and 11.6 +/- 0.43 per cent as estimated by ultracentrifugation. Data for the mean plasma/red blood cell concentration ratio and the red blood cell/plasma distribution coefficient for promazine were 1.19 +/- 0.13 and 8.21 +/- 0.40, respectively. There was no evidence of time-dependence in plasma/red blood cell partitioning. Ten rat organs and tissues were examined. The concentrations of promazine and desmonemethylpromazine were highest in lung. For promazine, the rank order of tissue localization was lung greater than liver greater than kidney greater than intestine greater than brain greater than spleen greater than red blood cell greater than voluntary muscle greater than plasma greater than stomach greater than heart. For desmonomethylpromazine, the order was reversed in the cases of spleen and brain and interchanged in the cases of stomach and muscle. The brain/plasma concentration ratios for promazine and desmonomethylpromazine in rat were 4.69 and 3.87, respectively.

Pharmacokinetic and pharmacodynamic studies with 4'-epi-doxorubicin in nasopharyngeal carcinoma patients

The plasma pharmacokinetic profile of 4'-epidoxorubicin (epirubicin) was investigated in 28 patients with nasopharyngeal carcinoma (NPC) after single i.v. rapid infusions. All patients had normal liver and renal functions. Plasma concentrations of the parent compound were specifically determined by a high-performance liquid chromatographic (HPLC) method, with UV detection at 254 nm. Plasma levels of the compound were fitted to a three-compartment open model; a triexponential decrease in plasma concentrations with a long terminal plasma half-life (44.8 +/- 21.2 h) was observed in 27 patients. The respective mean (+/- SD) serum concentration at 72 h and the AUC, plasma clearance, and terminal elimination rate constant in complete responders were 7.67 +/- 1.98 ng/ml, 4,002 +/- 3,080 ng.h/ml, 26.6 +/- 12.9 l/h.m2, and 0.009 +/- 0.007 l/h, whereas those in nonresponders were 4.96 +/- 1.8 ng/ml, 1.88 +/- 652.8 ng.h/ml, 44.4 +/- 15 l/h.m2, and 0.017 +/- 0.006 l/h, respectively; these differences were significant (P less than 0.05). Epirubicin produced a 52% response rate, including 6 patients with a complete response, 8 with a partial response, 11 with no change, and 2 with progressive disease. No relationship could be found between the various pharmacokinetic parameters and either leukopenia, age, or sex. These observations strongly suggest that plasma clearance may be one of the determining factors affecting the response or nonresponse of NPC patients to epirubicin, and a dose adjustment according to plasma clearance would probably increase the response rate.

The mechanism of reducing thiopentone dose in elderly patients undergoing surgery

The dose of thiopentone required to induce anesthesia in adults decreasing with age is not due to pharmacodynamic change. The change of pharmacokinetic properties of thiopentone with age in undergoing surgery patient's arterial blood was investigated in seven elderly (67-82 yr) and six young (21-33 yr) patients of both sexes. Thiopentone (3 mg kg-1) was administered intravenously and arterial blood samples were obtained immediately after the injection to measure plasma and red blood cell thiopentone concentrations by an HPLC method. Plasma protein binding was studied using ultracentrifuge method. The disappearance of thiopentone from the arterial blood was described by a two-compartment open model. The distribution rate constant (alpha) was significantly larger in the young patients (p less than 0.001). The distribution half-life was longer in the elderly (p less than 0.05). Both the input microscopic rate constant, K21, and the exit microscopic rate constant, K12, with the central compartment were significantly larger in the young patients. (p less than 0.02 and p less than 0.001, respectively). The difference between the exit and input microscopic rate constant, K12-K21, was much larger in the young patients (p less than 0.001). The plasma protein binding was significantly reduced in the elderly (p less than 0.05). The apparent overall volume of distribution, Vd was not significantly different between young and elder patients. However, the volume of distribution of the central compartment was smaller in the young patients (p less than 0.05). This was probably due to the difficulty of estimation of initial thiopentone plasma concentration post-equilibrium in the central compartment after administration of thiopentone.(ABSTRACT TRUNCATED AT 250 WORDS)