Assessment of the analgesic effect of remifentanil using three pain models in healthy Korean volunteers: a randomized, controlled study

Quantitative pain assessment in human beings is useful for developing new analgesics. This study assessed the analgesic effect of remifentanil in 20 healthy Korean men using three pain models to investigate whether these models can be used in Asians. The study was a double-blind, placebo-controlled, two-way cross-over study. The subjects received intravenous remifentanil with doses starting at 0.01 μg/kg/min. and increasing by 0.01 μg/kg/min. up to 0.10 μg/kg/min. in one session; they received placebo in another session. Heat pain thresholds were assessed at dose levels of 0.02, 0.05, 0.08 and 0.10 μg/kg/min. Pressure pain threshold and tolerance and mechanical pain threshold were assessed at 0.08 μg/kg/min. Remifentanil dose-dependently increased the heat pain threshold. The differences (95% confidence interval) between remifentanil and placebo were 1.54°C (0.78, 2.31), 1.82°C (1.11, 2.54) and 2.47°C (1.55, 3.38) at 0.05, 0.08 and 0.10 μg/kg/min. remifentanil, respectively. Remifentanil conferred a significantly higher pressure pain threshold and tolerance than placebo (p = 0.0001). There was a trend of increasing mechanical pain threshold with remifentanil, although it was not statistically significant. The results suggest that heat pain and pressure pain models are valid in East Asians for assessing analgesic effects.

Efficacy, tolerability, and pharmacokinetics of oxcarbazepine oral loading in patients with epilepsy

The rapid achievement of effective levels of antiepileptic drugs (AEDs) is required in patients with epilepsy who have a higher risk of seizures, and oral loading of AEDs may be an important consideration in these patients. We performed the present study to investigate the efficacy and tolerability of oral loading of oxcarbazepine in patients with recurrent seizures, or after temporary discontinuation of AEDs for diagnostic or presurgical evaluation of epilepsy. Forty adult patients were studied and oxcarbazepine was administered orally at a single loading dosage of 30 mg/kg. The plasma levels of oxcarbazepine and its active metabolite, 10,11-dihydro-10-hydroxy-carbazepine (monohydroxy derivative, MHD), were measured, and clinical assessment of adverse events was performed at 2, 4, 6, 8, 10, 12, 16, and 24 h after oral loading of oxcarbazepine. Approximately two-thirds of patients reached effective levels of MHD 2 h after receiving the oral loading, and all patients reached effective levels 4 h after oxcarbazepine administration. Most patients maintained therapeutic MHD levels for at least 16 h. Almost half of the patients experienced adverse events, but all were mild to moderate in severity and resolved spontaneously within 24 h. Our study shows that oral loading of oxcarbazepine is an effective and well-tolerated method for rapidly achieving therapeutic levels of MHD in patients with epilepsy, and is a useful option in selected patients with recurrent seizures, or after temporary discontinuation of AEDs.

The potential inhibitory effect of revaprazan, an acid pump antagonist, on anticoagulation with warfarin

Revaprazan is the first acid pump antagonist with a function similar to that of proton pump inhibitors (PPIs). It has a dual action, active suppression of gastric acid secretion and gastric mucosa protection. While PPIs are known to enhance the prolongation of prothrombin time by warfarin, no research has been done on the drug interaction between revaprazan and warfarin. This study was conducted in order to verify the potential drug interaction between revaprazan and warfarin. Omeprazole, a representative PPI, was used as the control for revaprazan. We searched for patients who were given either revaprazan or omeprazole along with warfarin using the medical record database of Seoul National University Hospital between July 2007 and June 2010. Among the 15 patients who took revaprazan and warfarin together, 73.3% (11/15) showed more than 30% reduction of anticoagulation effect by warfarin after revaprazan was added. The revaprazan group showed a significant shortening of prothrombin time during revaprazan administration compared to pre- and post-revaprazan medication (P < 0.05) while the omeprazole group did not show such difference. Revaprazan seems to have cumulative dose-dependent anti-warfarin or anti-coagulation effect, as judged from the fact that the longer medication with revaprazan showed correlation with the shortening of prothrombin time (R = -0.632, P < 0.05). This study shows a possible interaction between revaprazan and warfarin and suggests that revaprazan can cause shortening of prothrombin time. Therefore, when revaprazan is prescribed to patients on warfarin therapy, prothrombin time should be frequently monitored.

Tolerability and pharmacokinetics of lobeglitazone (CKD-501), a peroxisome proliferator-activated receptor-γ agonist: a single- and multiple-dose, double-blind, randomized control study in healthy male Korean subjects

BACKGROUND

Lobeglitazone, a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist with partial PPAR-α affinity, was developed to treat type 2 diabetes mellitus.

OBJECTIVE

This study's aim was to evaluate the tolerability and pharmacokinetic (PK) properties of lobeglitazone to satisfy regulatory requirements for marketing approval in Korea.

METHODS

A block-randomized, double-blind, placebo-controlled, single- and multiple-dose study was conducted in healthy subjects. In the pilot study, 4 subjects were administered 0.5 mg, including 1 receiving a placebo. Then, the single-dose study was conducted with 1, 2, 4, and 8 mg doses (8 subjects in each group, including 2 receiving placebos), followed by the multiple-dose study with 1, 2, and 4 mg doses (once daily for 7 days; 8 subjects in each group, including 2 receiving placebos). Serial samples of blood and urine were collected and drug concentrations were determined by high turbulence liquid chromatography-LC/MS/MS. Tolerability assessments were performed throughout the study. Adverse events (AEs) were determined from general health-related questions and self-reports.

RESULTS

Thirty-six (mean [SD]; age, 23.6 [2.7] years; weight, 70.0 [6.9] kg) and 25 Korean male subjects (age, 23.5 [3.1] years; weight 69.4 [9.4] kg) were enrolled in the single- and multiple-dose studies, respectively. The data from subjects administered lobeglitazone who completed the study (27, single; 18, multiple) was included in the PK analyses. In the single-dose study, the AUC and C(max) of lobeglitazone increased with the dose. After repeated dosing for 7 days, the accumulation ratio ranged from 1.1 to 1.4. A total of 25 AEs were reported by 11 (30.6%) and 8 subjects (33.3%) in the single- and multiple-dose studies, respectively. All AEs were mild in intensity and not serious.

CONCLUSIONS

Lobeglitazone was well tolerated in this small, selected group of healthy male Korean volunteers. The AUC and C(max) of lobeglitazone increased in a dose-proportional manner from 1 to 4 mg.

Pharmacokinetic comparison of a new sustained-release formulation of glimepiride/metformin 1/500 mg combination tablet and a sustained-release formulation of glimepiride/metformin 2/500 mg combination tablet in healthy Korean male volunteers: a randomized, 2-sequence, 2-period, 2-treatment crossover study

BACKGROUND

The combination of glimepiride and metformin is used for glycemic control in patients with diabetes mellitus. A fixed-dose combination of glimepiride/metformin 2/500 mg slow-release (SR) formulation was developed to improve compliance in polymedicated patients. To accommodate the various dosing regimens of glimepiride, a glimepiride/metformin 1/500 mg SR tablet was also developed.

OBJECTIVE

The goal of this study was to compare the pharmacokinetic properties of SR fixed-dose combinations of glimepiride/metformin 2/500 mg and the newly developed glimepiride/metformin 1/500 mg formulation to meet the regulatory requirements for marketing in Korea.

METHODS

An open-label, randomized, 2-treatment, 2-period, 2-sequence crossover study was conducted with healthy male volunteers. Eligible subjects were randomly assigned to receive a single dose of glimepiride/metformin 1/500 mg SR (test) or glimepiride/metformin 2/500 mg SR (reference) followed by a 1-week washout period and then administration of the alternate treatment. Serial blood samples were collected immediately before and after dosing for 30 hours, and plasma concentrations were determined by using LC-MS/MS with validated methods. Adverse events were assessed by subjects' self-report and interviews addressing general health-related issues. Safety profiles were evaluated throughout the study.

RESULTS

Thirty-three subjects were enrolled (mean [SD] age: 27.9 [4.95] years [range, 21-40 years]). Safety profiles were assessed for all 32 subjects who were administered the study drugs, and pharmacokinetic characteristics were evaluated in the 30 subjects who completed the study. The geometric mean ratios (90% CIs) of test to reference for the dose-normalized C(max) and AUC(0-last) of glimepiride were 0.98 (0.90-1.07) and 1.06 (0.98-1.14), respectively. In the case of metformin, the geometric mean ratios (90% CIs) of test to reference for C(max) and AUC(0-last) were 1.06 (0.98-1.15) and 1.04 (0.97-1.12), respectively. Nine adverse events were reported. Among them, loose stool, abdominal pain, and headache were considered to be likely related to the study drug. All reported adverse events were mild in intensity.

CONCLUSIONS

Dose-proportional characteristics of glimepiride and comparable pharmacokinetic properties of metformin were observed between the SR fixed-dose combinations of glimepiride/metformin 1/500 mg and 2/500 mg. A single dose of either treatment was well tolerated, and the safety profiles of the 2 treatments were comparable in this small, selected all-male group of healthy Korean volunteers.

Long-term social outcome in children with moyamoya disease who have reached adulthood

OBJECT

Although the reported surgical outcome is favorable, there is little information regarding the long-term quality of life in pediatric patients with moyamoya disease (MMD) when they grow to adulthood. The authors conducted a survey to provide details of social adaptation and satisfaction in adults who underwent revascularization surgery for MMD during childhood.

METHODS

One hundred twenty-three patients with MMD who had undergone surgery during childhood and were older than 18 years of age were recruited for this study. The authors mailed self-administered questionnaires regarding each patient's education, employment, marriage, driver's license, physical condition, and satisfaction. Sixty-five patients (53%) responded.

RESULTS

Compared with the general population, the patients showed a similar rate of attaining a higher education. Forty-nine (80%) of 61 patients who were not currently high school students had entered college or university. However, the presence of neurological deficits on preoperative examination was a negative predictor of entrance into a college or university, as well as employment. Some patients had difficulty in planning marriage because of physical handicaps, and the rate of acquiring a driver's license and actual driving were relatively low. Approximately 80% of the responders were satisfied with their treatment outcomes, but more than one-half reported subjectively assessed neurological problems.

CONCLUSIONS

In this study, pediatric patients with MMD showed favorable social adaptation in adulthood. The findings also indicated that early diagnosis and intervention before the establishment of neurological deficits are essential to children with MMD in becoming better socially adapted. Further, more thorough clinical examinations are required during follow-up in patients with MMD.

Calculating occupancy when one does not have baseline: a comparison of different options

Dopamine D(2) receptor occupancy of antipsychotic drugs is calculated relative to the subject's D(2) receptor binding potential (BP) in the drug-free state (baseline BP). Because baseline BP is seldom known in patients with schizophrenia, population means from unrelated control samples are often used to estimate it. However, this is likely to introduce bias and error into the occupancy measure. There is thus a need for a method to reliably estimate baseline BP for patient populations in whom it may be impractical or unethical to get baseline measurements. It has been previously found that the relationship between plasma concentration and dopamine receptor occupancy by antipsychotic drugs follows a sigmoid E(max) model. Based on this, we developed a method for calculating dopamine D(2) receptor occupancy by antipsychotic drugs using an inhibitory E(max) model (I(max) method) that estimates individual baseline BPs. To validate this, we compared the result from the I(max) method with actual occupancy and estimated occupancy calculated from the average baseline BP (substitution method). The data for validation were obtained from two different receptor occupancy studies with the antipsychotic medications YKP1358 and aripiprazole. We estimated the reliability between the true measured occupancy and the predicted occupancy using the intraclass correlation coefficient (ICC), and the variability of occupancy was also compared between the I(max) and substitution methods. In YKP1358 study, all the ICCs of the I(max) method were above 0.8, but those of the substitution method showed values lower than 0.8. In aripiprazole study, the ICCs of the I(max) method were higher than those of the substitution method, but all the ICCs showed higher values than 0.8. The variability of I(max) method was significantly smaller than that of substitution method in both studies. The I(max) method shows better reliability and less variability than the substitution method. The I(max) method can be applied for receptor occupancy study, and bring more reliability and accuracy to the occupancy study in patients with schizophrenia.

In vivo activity of epoxide hydrolase according to sequence variation affects the progression of human IgA nephropathy

Epoxyeicosatrienoic acid (EET) regulates the functional integrity of the endothelium. It is hypothesized that the activity of epoxide hydrolase (EPHX2), which determines EET concentration through hydrolysis, may affect the progression of glomerulonephritis. Here, we evaluated the relationship between genetic variations, the in vivo activity of EPHX2, and progression of IgA nephropathy (IgAN). Three single-nucleotide polymorphisms (SNPs) [rs41507953 (K55R), rs751141 (R287Q), and rs1042032] were traced in 401 IgAN patients and 402 normal healthy controls. The in vivo activity of EPHX2 was assessed by measuring substrates/metabolites of the enzyme. None of the polymorphism frequencies differed significantly between patients and controls. However, patients carrying the variant allele (A) of rs751141 possessed better kidney survival than those with the wild-type allele (G; P < 0.001). This association remained significant after adjustment for several risk factors (hazard ratio 1.83, 95% confidence interval 1.13-2.96, P = 0.014). Vascular damage was more prominent in kidney biopsies from patients carrying the G allele of rs751141. The in vivo activity of EPHX2, assessed by the epoxyoctadecenoic acid/dihydroxyoctadecenoic acid ratio using liquid chromatography/mass spectrometry analysis, was elevated in patients with the G allele. The expression of EPHX2 in the human kidney was independent of the sequence variation of the rs751141 allele. Variant rs41507953 was not present in this cohort, and rs1042032 was not associated with progression. Thus the specific measures which regulate EPHX2 activity should be designed for potential therapeutics.

Effects of pregnane X receptor (NR1I2) and CYP2B6 genetic polymorphisms on the induction of bupropion hydroxylation by rifampin

We investigated genetic polymorphisms in the pregnane X receptor (NR1I2) in Korean individuals (n = 83) and the effects of NR1I2 genotypes on rifampin-mediated induction of bupropion hydroxylation. The pharmacokinetics of bupropion and hydroxybupropion were evaluated after an oral dose of bupropion (150 mg) administered before and after rifampin treatment for 7 days in 35 healthy subjects. The area under the time-concentration curve (AUC) ratio of hydroxybupropion to bupropion in CYP2B6*6 carriers was significantly lower than that in CYP2B6*6 noncarriers in both the basal and rifampin-induced states (p = 0.012). Among the CYP2B6*6 carriers (n = 13), the NR1I2 TGT (-25385T + g.7635G + g.8055T) carriers exhibited a significantly lower AUC ratio, representing the CYP2B6 hydroxylation activity, compared with the TGT noncarriers, in the induced state (11.9 versus 20.3, p = 0.045). The percent difference in the AUC ratio between the basal and induced states was also significantly different (212% versus 58.8%, p = 0.006). However, no significant difference was observed among the NR1I2 TGT genotypes for the CYP2B6*6 noncarriers (n = 22). In conclusion, it is suggested the NR1I2 TGT genotype decreases the bupropion hydroxylation induced by treatment with rifampin, particularly in CYP2B6*6 carriers.

Effect of ketoconazole on the pharmacokinetics of udenafil in healthy Korean subjects

AIMS

Udenafil is a phosphodiesterase 5 inhibitor used for the treatment of erectile dysfunction. It is metabolized to DA-8164, a major metabolite, by CYP3A4. This study was performed to investigate the effect of ketoconazole, a known CYP3A4 inhibitor, on the pharmacokinetics of udenafil.

METHODS

An open-label, two-period, fixed-sequence crossover study was performed in 12 healthy male volunteers. They received a single 100-mg oral dose of udenafil. Following a 5-day interval, 400 mg of ketoconazole was administered once a day for three consecutive days. On day 3 of ketoconazole treatment, a second 100 mg of udenafil was dosed concomitantly. Blood samples were collected at time points up to 48 h without ketoconazole treatment and up to 72 h with ketoconazole co-administration. The plasma concentration of udenafil was determined using liquid chromatography-tandem mass spectrometry.

RESULTS

Following ketoconazole co-administration, the mean C(max) and AUC(last) of udenafil (95% confidence interval) increased 1.9-fold (1.60, 2.27) and 3.2-fold (2.82, 3.63), respectively. The median time to reach the C(max) was delayed in the co-administrated treatment, while the mean terminal elimination half-life (t(1/2)) remained relatively unchanged regardless of ketoconazole co-administration. The metabolic AUC ratio (AUC(last) of DA-8164/AUC(last) of udenafil) was 1.71 when udenafil was administered alone, and the value decreased to 0.19 when udenafil was dosed in the presence of ketoconazole. Regarding safety assessments, no clinically significant difference or serious adverse event was observed.

CONCLUSIONS

The systemic exposure of udenafil increased significantly when it was administered with ketoconazole. Dose adjustment may be required when these drugs are used together.

Pharmacokinetics and pharmacodynamics of LC15-0444, a novel dipeptidyl peptidase IV inhibitor, after multiple dosing in healthy volunteers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* The importance of efficient drug development using biomarkers has been increasingly emphasized, from preclinical studies to clinical trials. * However, as yet few validated or qualified biomarkers are used in early-stage drug development in terms of clinical pharmacology and disease pathophysiology.

WHAT THIS STUDY ADDS

* This first-time-in-human study provides evidence of the pharmacological activity of LC15-0444 in humans, by using dipeptidyl peptidase IV activity and active glucagon-like peptide-1 concentrations. * LC15-0444 possesses pharmacokinetic and pharmacodynamic characteristics that support a once-daily dosing regimen.

AIMS

LC15-0444 is a selective and competitive inhibitor of dipeptidyl peptidase (DPP) IV with potential for the treatment of Type 2 diabetes. The aim was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD) profiles after multiple oral ascending doses of LC15-0444 in healthy male subjects.

METHODS

A dose block-randomized, double-blind, placebo-controlled, parallel group study was performed in three groups with 10 subjects (eight for active drug; two for placebo) per group; each group received 200, 400 or 600 mg of LC15-0444 once daily for 10 days. Blood and urine samples were collected up to 24 h after the first dosing and up to 72 h after the last dosing.

RESULTS

The LC15-0444 concentration-time profiles exhibited characteristics of multicompartment disposition. No dose- or time-dependent change in PK parameters was observed. Mean elimination half-life was in a range 16.6-20.1 h in the dose groups. Mean renal clearance and fraction of unchanged drug excreted in urine was 18.6-21.9 and 0.40-0.48 l h(-1), respectively. In the steady state, mean accumulation ratios by dose groups were between 1.22 and 1.31. More than 80% inhibition of DPP IV activity from baseline was sustained for >24 h in all dose groups.

CONCLUSIONS

This study provides evidence of the pharmacological activity of LC15-0444 in humans. LC15-0444 possesses PK and PD characteristics that support a once-daily dosing regimen.

Influence of Ginkgo biloba extract on the pharmacodynamic effects and pharmacokinetic properties of ticlopidine: an open-label, randomized, two-period, two-treatment, two-sequence, single-dose crossover study in healthy Korean male volunteers

BACKGROUND

Ginkgo biloba extract is an herbal medicine used in the treatment of vascular disorders that may be coadministered with antiplatelet agents such as ticlopidine. Regulatory authorities requested evaluation of the pharmacodynamic and pharmacokinetic interactions between these entities, according to the drug-development guidance for fixed-dose combination formulations in Korea.

OBJECTIVE

This study was performed to evaluate the potential pharmacodynamic and pharmacokinetic interactions between ticlopidine and Ginkgo biloba extract.

METHODS

An open-label, randomized, 2-period, 2-treatment, 2-sequence, single-dose crossover study was conducted in healthy Korean male volunteers. All volunteers were randomly assigned to a sequence group for the 2 treatments, which consisted of ticlopidine 250 mg alone and ticlopidine 250 mg with Ginkgo biloba extract 80 mg, separated by a 1-week washout period between the treatments. Bleeding time was determined just before dosing and at 5, 12, and 48 hours after dosing. Platelet aggregation was evaluated before dosing and at 4, 8, 26, and 48 hours after dosing. Blood samples (8 mL) from each of the volunteers were collected from an indwelling intravenous cannula inserted into a forearm vein before dosing and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, and 48 hours after dosing. Ticlopidine concentrations were determined by a validated method using HPLC and ultraviolet detection. Adverse events were identified using general health-related questions, vital signs, physical examinations, ECGs, and laboratory tests.

RESULTS

A total of 24 healthy men participated in the study (mean [SD] age, 24.1 [4.3] years; weight, 66.6 [7.4] kg; height, 174.7 [5.0] cm). The baseline corrected bleeding times were not significantly different between the ticlopidine-alone and ticlopidine/ Ginkgo biloba groups, and changes in platelet aggregation were not significantly different between the groups. Likewise, the pharmacokinetic parameters of ticlopidine were not significantly different between the groups; the geometric mean ratios of the ticlopidine/ Ginkgo biloba group to the ticlopidine-alone group were 1.03 (90% CI, 0.92-1.16) for C(max), 1.08 (90% CI, 0.98-1.19) for AUC(0-last), and 1.10 (90% CI, 1.00-1.20) for AUC(0-infinity). A total of 28 adverse events were reported: 11 in the ticlopidine-alone group and 17 in the ticlopidine/Ginkgo biloba group. The adverse events judged to be possibly related to ticlopidine in the ticlopidine-alone group were epigastric discomfort (2 cases), diarrhea (1), skin eruption (1), and a feeling of being cold (1) or hot (1). The adverse events judged to be related to ticlopidine or Ginkgo biloba in the ticlopidine/Ginkgo biloba group were epigastric discomfort (2), diarrhea (2), nausea (2), and headache (1).

CONCLUSIONS

In this small group of healthy Korean men, the addition of a single dose of Ginkgo biloba extract did not prolong the bleeding time and was not associated with additional antiplatelet effects compared with the administration of ticlopidine alone. The coadministration of Ginkgo biloba extract with ticlopidine was not associated with any significant changes in the pharmacokinetic profile of ticlopidine compared with ticlopidine administered alone.

Effect of food on the pharmacokinetics of the oral phosphodiesterase 5 inhibitor udenafil for the treatment of erectile dysfunction

AIMS

Udenafil is a cyclic guanosine 3',5'-monophosphate-specific phosphodiesterase type 5 (PDE5) inhibitor developed for the treatment of erectile dysfunction. The aim was to evaluate the effect of food on the pharmacokinetics of udenafil.

METHODS

An open, randomized, three-way crossover study was conducted. Fifteen healthy male volunteers received a single 200-mg oral dose of udenafil while fasting, after a low-fat meal, and after a high-fat meal separated by 7-day washout periods. Serial blood samples were taken up to 48 h after oral administration.

RESULTS

Under fasting conditions, udenafil was rapidly absorbed and t(max) was observed typically 1.5 h after administration. The mean t(max) values after a low-fat meal and a high-fat meal were 2.6 and 2.1 h, respectively. The ratios (90% confidence intervals) of the geometric means compared with the fasting condition for C(max) and AUC(last) were 0.79 (0.70, 0.90) and 0.96 (0.89, 1.03) in the low fat-fed condition, respectively, and 1.01 (0.89, 1.15) and 1.03 (0.96, 1.11), respectively, in the high fat-fed condition.

CONCLUSIONS

The t(max) of udenafil was delayed under the fed conditions. However, although the C(max) was reduced by approximately 21% in the low fat-fed state, overall bioavailability was not affected when taken with food.

Pharmacokinetic comparison of a new glimepiride 1-mg + metformin 500-mg combination tablet formulation and a glimepiride 2-mg + metformin 500-mg combination tablet formulation: a single-dose, randomized, open-label, two-period, two-way crossover study in healthy, fasting Korean male volunteers

BACKGROUND

Coadministration of glimepiride and metformin has been used to achieve glucose control. Because compliance with a multiple medication regimen can be difficult for some patients, combination tablets of glimepiride + metformin might be a suitable alternative for these patients.

OBJECTIVE

This study was conducted to compare the pharmacokinetics of test and reference formulations of glimepiride + metformin fixed-dose combination tablets under fasting conditions to meet the regulatory requirements for marketing approval of a new drug in Korea.

METHODS

This was a single-dose, randomized, open-label, 2-period, 2-way crossover study conducted between March 2007 and May 2007. Healthy fasting Korean men were randomized to 1 of 2 dosing sequences: a single oral administration of a fixed-dose glimepiride 1-mg + metformin 500-mg combination tablet (test) followed by single oral administration of a fixed-dose glimepiride 2 mg + metformin 500 mg combination tablet (reference), separated by a 1-week washout period between doses; or a single oral administration of a fixed-dose glimepiride 2-mg + metformin 500-mg combination tablet followed by single oral administration of a fixed-dose glimepiride 1 mg + metformin 500-mg combination tablet, separated by a 1-week washout period between doses. Serial samples of blood were collected up to 24 hours after oral administration, and drug concentrations in plasma were determined by HPLC-MS/MS. Tolerability was assessed based on adverse events and changes in clinical parameters. Serious adverse events included those that resulted in death, a life-threatening condition, congenital anomaly or birth defect, or required hospitalization or prolongation of existing hospitalization.

RESULTS

A total of 30 healthy male subjects (mean age, 25.6 years [range, 20-36 years]; weight, 69.5 kg [range, 58.2-90.7 kg]) participated in the study. After administration of the test and reference formulations, glimepiride was rapidly absorbed, reaching C(max) with a median T(max) of 1.75 and 2.0 hours, respectively, and then declined exponentially with an average t(1/2) of 8.2 and 8.5 hours. The individual C(max) and AUC(last) of glimepiride were observed to be proportionally increased according to the administered glimepiride dose. The mean (SD) dose-normalized Cmax values of glimepiride 1 and 2 mg were 168.2 (54.9) and 149.9 (47.4) ng/mL/mg, respectively; the mean dose-normalized AUC(last) values of glimepiride 1 and 2 mg were 681.5 (190.3) and 635.8 (194.1) ng x h/mL/mg. Individual plots of dose-normalized C(max) and AUC(last) values identified a similarity between the 2 groups but no significant between-group differences. A total of 25 adverse events (12 after the test dose and 13 after the reference dose) were reported by 13 of the 30 subjects. All adverse events were considered mild. Twenty-one adverse events were considered related to the study drug (8 after the test dose and 13 after the reference dose). Adverse events believed to be related to the test formulation were diarrhea (4 cases), dizziness (1), headache (1), tingling sensation (1), and weakness (1). Adverse events believed to be related to the reference formulation were diarrhea (6 cases), headache (3), cold sweats (1), dyspepsia (1), epigastric discomfort (1), and lethargy (1). There were no clinically significant findings in the laboratory test results or vital sign monitoring during the study. There were no serious adverse events reported.

CONCLUSIONS

The C(max) and AUC(last) of glimepiride increased proportionally according to the administered glimepiride dose in this study of healthy, fasting Korean men. The safety profiles of the 2 combination tablets were comparable.

Population pharmacokinetics of artesunate and dihydroartemisinin following single- and multiple-dosing of oral artesunate in healthy subjects

Background

The population pharmacokinetics of artesunate (AS) and its active metabolite dihydroartemisinin (DHA) were studied in healthy subjects receiving single- or multiple-dosing of AS orally either in combination with pyronaridine (PYR) or as a monotherapy with or without food.

Methods

Data from 118 concentration-time profiles arising from 91 healthy Korean subjects were pooled from four Phase I clinical studies. Subjects received 2-5 mg/kg of single- and multiple-dosing of oral AS either in combination with PYR or as a monotherapy with or without food. Plasma AS and DHA were measured simultaneously using a validated liquid chromatography- mass spectrometric method with a lower limit of quantification of 1 ng/mL for both AS and DHA. Nonlinear mixed-effect modelling was used to obtain the pharmacokinetic and variability (inter-individual and residual variability) parameter estimates.

Results

A novel parent-metabolite pharmacokinetic model consisting of a dosing compartment, a central compartment for AS, a central compartment and a peripheral compartment for DHA was developed. AS and DHA data were modelled simultaneously assuming stoichiometric conversion to DHA. AS was rapidly absorbed with a population estimate of absorption rate constant (Ka) of 3.85 h^-1. The population estimates of apparent clearance (CL/F) and volume of distribution (V2/F) for AS were 1190 L/h with 36.2% inter-individual variability (IIV) and 1210 L with 57.4% IIV, respectively. For DHA, the population estimates of apparent clearance (CLM/F) and central volume of distribution (V3/F) were 93.7 L/h with 28% IIV and 97.1 L with 30% IIV, respectively. The population estimates of apparent inter-compartmental clearance (Q/F) and peripheral volume of distribution (V4/F) for DHA were 5.74 L/h and 18.5 L, respectively. Intake of high-fat and high-caloric meal prior to the drug administration resulted in 84% reduction in Ka. Body weight impacted CLM/F, such that a unit change in weight resulted in 1.9-unit change in CLM/F in the same direction.

Conclusions

A novel simultaneous parent-metabolite pharmacokinetic model with good predictive power was developed to study the population pharmacokinetics of AS and DHA in healthy subjects following single- and multiple-dosing of AS with or without the presence of food. Food intake and weight were significant covariates for Ka and CLM/F, respectively.

Population pharmacokinetic modelling of aripiprazole and its active metabolite, dehydroaripiprazole, in psychiatric patients

AIMS

The aims of this study were to develop a combined population pharmacokinetic model for both aripiprazole and its active metabolite, dehydroaripiprazole, in psychiatric patients and to identify to what extent the genetic polymorphisms of cytochrome P450 (CYP) enzymes contribute to the variability in pharmacokinetics (PK).

METHODS

A population pharmacokinetic analysis was performed using NONMEM software based on 141 plasma concentrations at steady state from 80 patients receiving multiple oral doses of aripiprazole (10-30 mg day(-1)).

RESULTS

A one-compartment model with first-order kinetics for aripiprazole and dehydroaripiprazole each was developed to describe simultaneously the concentration data. The absorption rate constant was fixed to 1.06 h(-1). The typical value of apparent distribution volume of aripiprazole was estimated to be 192 l. Covariate analysis showed that CYP2D6 genetic polymorphisms significantly influenced the apparent clearance of aripiprazole (CL/F), reducing the interindividual variability on CL/F from 37.8% CV (coefficient of variation) to 30.5%. The CL/F in the CYP2D6 IMs was approximately 60% of that in CYP2D6 EMs having two functional alleles. Based on the CYP2D6 genotype, the metabolic ratios were calculated at 0.20-0.34. However, the plasma concentration : dose ratios of dehydroaripiprazole were not different across the CYP2D6 genotype.

CONCLUSIONS

This population pharmacokinetic model provided an adequate fit to the data for both aripiprazole and dehydroaripiprazole in psychiatric patients. The usefulness of CYP genotyping as an aid to select the starting dose should be further investigated.

Lack of association between ABCB1, ABCG2, and ABCC2 genetic polymorphisms and multidrug resistance in partial epilepsy

ATP-binding cassette (ABC) transporters participate in drug disposition and response in various conditions, and many polymorphisms in ABC transporter genes have been recognized in association with altered transporter functions of various drugs. Studies on epilepsy have focused on the C3435T polymorphism of the ABCB1 gene, but other ABC transporters are also thought to be involved in the transport of antiepileptic drugs. We have evaluated the functional polymorphisms of ABCB1, ABCG2, and ABCC2 genes with regard to epilepsy drug response in partial epilepsy, and have investigated the potential of combined effects of polymorphisms in more than one transporter gene. We studied 6 genetic polymorphisms in 3 transporter genes in 193 drug responders and 198 nonresponders. There was no significant difference between the two groups, and we did not observe any combined effects of ABCB1 and ABCG2 genetic polymorphisms. Our study suggests that genetic polymorphisms in ABC transporters may not be significant predictors of drug response in epilepsy patients.

Taq1A polymorphism in the dopamine D2 receptor gene as a predictor of clinical response to aripiprazole

We investigated whether the clinical response to aripiprazole differed according to the Taq1A polymorphism in the dopamine D2 receptor (DRD2) gene. In this 26-week, prospective, open-label, double-blind, parallel-group study, 90 patients with schizophrenia, schizoaffective disorder, or schizophreniform disorder were recruited and divided into two groups according to their DRD2 genotype (A1A1, n=14; A1A2+A2A2, n=76). The efficacy assessment included Positive and Negative Syndrome Scale (PANSS) scores and Clinical Global Impression (CGI) scores. Extrapyramidal symptoms were assessed using the Simpson-Angus Scale (SAS), Abnormal Involuntary Movement Scale (AIMS), and Barnes Akathisia Rating Scale (BAS). Plasma prolactin levels were also measured. Patients with the A1A1 genotype showed a more favorable therapeutic response to aripiprazole when assessed using the PANSS ratio. The changes in the SAS score from baseline to week 4 also differed according to the genotype group. There were no significant differences in the changes in the CGI, AIMS, and BAS scores or plasma prolactin level between the two genotype groups. The results suggest an association between the DRD2 Taq1A polymorphism status and the variation in the clinical response to aripiprazole.

Pharmacokinetic interaction of flecainide and paroxetine in relation to the CYP2D6*10 allele in healthy Korean subjects

AIMS

The objectives were to evaluate the effect of CYP2D6 genetic polymorphism on the pharmacokinetics of flecainide, and also on the extent of drug interaction with paroxetine as a CYP2D6 inhibitor after a single oral administration in healthy subjects.

METHODS

An open-label, two-period, single-sequence, cross-over study was performed in 21 healthy Korean male volunteers (seven for CYP2D6*1/*1 or *1/*2, group 1; seven for CYP2D6*1/*10, group 2; seven for CYP2D6*10/*10 or *10/*36, group 3). Subjects were administered 200 mg of flecainide on day 1. After a 7-day wash-out period, subjects were administered 20 mg of paroxetine from day 8 to 14, and 200 mg of flecainide on day 15. Blood sampling was performed up to 72 h after flecainide administration.

RESULTS

Terminal elimination half-life and mean residence time (MRT) were significantly different among three genotype groups after a single oral administration of flecainide (P = 0.021, 0.011, respectively). Area under the concentration-time curve, terminal elimination half-life and MRT increased significantly after paroxetine co-administration only in groups 1 and 2.

CONCLUSIONS

This study reports that the extent of drug interaction between flecainide and paroxetine is influenced by the CYP2D6*10 allele in healthy subjects, which is frequent in Asians.

Safety, tolerability and pharmacokinetics of udenafil, a novel PDE-5 inhibitor, in healthy young Korean subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The phosphodiesterase (PDE) type 5 inhibitor is a widely used agent that facilitates penile erection. Udenafil is newly developed as a PDE-5 inhibitor.

WHAT THIS STUDY ADDS

This is the first study to determine the safety, tolerability and pharmacokinetics of udenafil in healthy subjects. Udenafil was safe and well tolerated in healthy Korean subjects. The AUC and C(max) of udenafil increased supraproportionally with increasing dose upon single administration, but there was no significant drug accumulation upon multiple administrations.

AIM

To evaluate the safety, tolerability and pharmacokinetics (PK) of udenafil, a novel phosphodiesterase type 5 inhibitor.

METHODS

A double-blind, randomized, placebo-controlled, dose-rising, parallel-group, single- and multiple-dose study was conducted in healthy Korean subjects. The subjects were allocated to single-dose groups of 25, 50, 100, 200 or 300 mg (eight subjects in each dose group, including two placebos), or to multiple-dose groups of 100 or 200 mg (once-daily dosing for 7 days; nine subjects in each dose group, including three placebos). Serial samples of blood and urine were collected after oral administration and the drug concentrations in plasma and urine were determined by high-performance liquid chromatography. Safety and tolerability were evaluated by monitoring clinical laboratory parameters and adverse events.

RESULTS

Udenafil reached peak plasma concentrations at 0.8-1.3 h, and then declined mono-exponentially with a terminal half-life of 7.3-12.1 h in the single-dose study. The area under the time-concentration curves (AUC) and maximum plasma concentrations (C(max)) increased supraproportionally with increasing dose in the single-dose study. During multiple dosing, a steady state was reached at 5 days and little accumulation occurred after repeated dosing for 7 days. Udenafil was generally well tolerated in these healthy subjects, and no serious adverse events occurred.

CONCLUSIONS

Udenafil was safe and well tolerated in healthy volunteers. The AUC and C(max) of udenafil increased supraproportionally with increasing dose upon single administration, but there was no significant drug accumulation upon multiple administrations.

Angiotensin II type 1 receptor 1166A/C polymorphism in association with blood pressure response to exogenous angiotensin II

BACKGROUND

The angiotensin II type 1 receptor (AT1R) 1166A/C polymorphism is reported to be implicated in cardiovascular diseases. The association between the 1166A/C polymorphism and diastolic blood pressure (DBP) changes in response to exogenous angiotensin II and valsartan was evaluated by pharmacokinetic and pharmacodynamic modeling.

METHODS

Thirteen normotensive, healthy adults (six with the 1166A/A polymorphism and seven with 1166A/C) were enrolled in this clinical study. Angiotensin II was infused continuously over a 2-min period at four different rates (from 5 ng/kg/min and increased by 5 ng/kg/min) at 0 (before valsartan dosing), 2, 4, 8, 12, and 24 h after a single oral dose of valsartan (40 mg). BP was measured serially before and at the end of each rate of angiotensin II infusion. Plasma concentration-time profiles of valsartan were established over a 24-h period. We analyzed data using NONMEM and studied the relationship between the AT1R 1166A/C genotypes and BP responses.

RESULTS

Plasma valsartan concentrations and DBP data best fitted into a two-compartment linear model and E(max) model (E(max) with baseline for angiotensin II and inhibitory E(max) for valsartan), respectively. The ED50 for angiotensin II in the subjects with 1166A/C [95% confidence interval (CI): 4.30 approximately 14.02 ng/kg/min] was significantly lower than in those with 1166A/A (95% CI: 14.23 approximately 28.77 ng/kg/min), while the E(max) for angiotensin II and EC50 for valsartan was similar in both genotype groups.

CONCLUSIONS

These results suggest that exogenous human angiotensin II increases the BP more potently in subjects with 1166A/C than in those with 1166A/A.

Effects of DRD2 and CYP2D6 genotypes on delta EEG power response to aripiprazole in healthy male volunteers: a preliminary study

The aim of the present study was to evaluate the effects of polymorphisms in dopamine D2 receptor (DRD2) and cytochrome P450 (CYP) 2D6 genes on delta EEG power response to aripiprazole in healthy male volunteers. Seventeen volunteers were recruited according to the DRD2 Taq1A genotype, and separated into the following groups: homozygous wild-type (A2/A2, n = 7), heterozygous (A2/A1, n = 5) and homozygous variant-type (A1/A1, n = 5) groups. After enrollment in this study, they were genotyped for CYP2D6. The volunteers received single 10 mg oral doses of aripiprazole, in accordance with an open-label parallel group study design. Plasma levels of aripiprazole and its metabolite were determined and EEGs were obtained simultaneously. The pharmacodynamic parameter was absolute delta power in the Cz channel. The changes of delta power were not different according to DRD2 Taq1A genotypes. As to the CYP2D6 allele, the subjects had the following CYP2D6 genotypes: *10/*10 (n = 4), *1/*10 (n = 5), *1/*5 (n = 2), *1/*1 (n = 3), *2/*41 (n = 1), *2/*2 (n = 1), *2N/*10 (n = 1). Subjects exhibiting the *1/*5 and *1/*10 genotypes showed a trend toward high area under the plasma aripiprazole concentration-time curve (AUC), which was linearly related to area under the EEG response-time curve (AUEC). Our results demonstrate a need for further evaluation of the CYP2D6 genotypic effect on the pharmacodynamics of aripiprazole.

Effect of OATP1B1 (SLCO1B1) variant alleles on the pharmacokinetics of pitavastatin in healthy volunteers

BACKGROUND

Pitavastatin is a potent, newly developed 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor for the treatment of hyperlipidemia. We characterized the effects of organic anion transporting polypeptide 1 B 1 (OATP 1 B 1) alleles *1a, *1b, and *15 on the pharmacokinetics of pitavastatin.

METHODS

Twenty-four healthy Korean volunteers who had previously participated in a pharmacokinetic study of pitavastatin (single oral dose, 1--8 mg) were further investigated. Subjects were grouped according to OATP 1 B 1 genotype. Dose-normalized area under the plasma concentration-time curve (AUC) and peak plasma concentration (C(max)) values were analyzed, because different dosages were administered to subjects, whereas the pharmacokinetics showed linear characteristics.

RESULTS

Dose-normalized pitavastatin AUCs for *1b/*1b (group 1), *1a/*1a or *1a/*1b (group 2), and *1a/*15 or *1b/*15 (group 3) were 38.8+/-13.3, 54.4 +/-12.4, and 68.1+/-6.3 ng.h.mL(-1).mg(-1) (mean+/-SD), respectively, with significant differences between all 3 groups (P=.008) and between subjects carrying and those not carrying the *15 allele (P = .004). Dose-normalized pitavastatin C(max) values were 13.2+/- 3.3, 18.2+/-5.7, and 29.4+/- 9.6 ng.mL(-1).mg(-1) in groups 1, 2, and 3, respectively, and also showed significant differences (P=.003) in a manner similar to that shown by AUC. No significant differences were found between the genotype groups in terms of dose-normalized AUC or C(max) values of pitavastatin lactone.

CONCLUSION

OATP 1 B 1 variant haplotypes were found to have a significant effect on the pharmacokinetics of pitavastatin. These results suggest that the *15 allele is associated with decreased pitavastatin uptake from blood into hepatocytes and that OATP 1 B 1 genetic polymorphisms have no effect on the pharmacokinetics of pitavastatin lactone.

Effect of the genotype on the pharmacokinetics, pharmacodynamics, and drug interactions of intravenous lorazepam in healthy volunteers

OBJECTIVE

Our objective was to investigate the effect of the uridine 5'-diphosphate-glucuronosyltransferase (UGT) 2B15 genetic polymorphism on the pharmacokinetics and pharmacodynamics of lorazepam in basal, inhibited, and induced metabolic states in healthy normal volunteers.

METHODS

Twenty-four healthy subjects were enrolled and grouped into UGT2B15*1/*1 or UGT2B15*2/*2 genotype groups. The pharmacokinetic and pharmacodynamic profiles of intravenous lorazepam were characterized before and after inhibition with 600 mg valproate once daily for 4 days and after induction with rifampin (INN, rifampicin) pretreatment (600 mg once daily for 10 days), with a washout period of 10 days between. The plasma concentrations of lorazepam and lorazepam glucuronide were analyzed before and at 0.25, 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, and 48 hours after lorazepam administration by liquid chromatography-tandem mass spectrometry. Visual analog scale assessments and psychomotor coordination tests were administered before and up to 12 hours after drug administration.

RESULTS

The UGT2B15*2/*2 group showed 0.58-fold (95% confidence interval, 0.43-0.72; P < .0001) lower systemic clearance during the basal state and 1.37-fold (95% confidence interval, 1.05-1.88; P = .037) higher area under the visual analog scale-time curve during the induced state compared with the UGT2B15*1/*1 group. The mean systemic clearance of lorazepam decreased by 20% in the inhibited state and increased by 140% in the induced state. During the inhibited or induced state, absolute values of clearance were consistently lower in the *2/*2 group, but the percent changes from baseline did not differ significantly by genotype.

CONCLUSIONS

Our results suggest that the UGT2B15*2 polymorphism is a major determinant of interindividual variability with respect to the pharmacokinetics and pharmacodynamics of lorazepam.

A variant 2677A allele of the gene affects fexofenadine disposition

BACKGROUND AND OBJECTIVES

There have been considerable disagreements regarding the influence of MDR1 (ABCB1) polymorphisms on the disposition of P-glycoprotein (P-gp) substrates. We speculated that the unknown function of the A allele of exon 21 G2677T/A (Ala893Ser/Thr) provides one of the reasons for the contradictory results. This study was performed to clarify the effects of major MDR1 gene polymorphisms, including a variant A allele in exon 21, on fexofenadine pharmacokinetics.

METHODS

We investigated the occurrence of 3 high-frequency single-nucleotide polymorphisms (SNPs) in exons 12 (C1236T), 21 (G2677T/A), and 26 (C3435T) of the MDR1 gene in 232 healthy Koreans, using a polymerase chain reaction-restriction fragment length polymorphism method, and performed haplotype analysis on these 3 SNPs. A single oral dose of 180 mg fexofenadine hydrochloride was administered to 33 healthy Korean male volunteers, who were divided into 6 groups based on the MDR1 genotype for the G2677T/A polymorphism in exon 21 and the C3435T polymorphism in exon 26.

RESULTS

A strong linkage disequilibrium was observed among the 3 SNPs. The frequencies of the 4 major haplotypes, 1236C-2677A-3435C, C-G-C, T-G-C, and T-T-T, were 16.4%, 18.6%, 21.6%, and 32.2%, respectively. Fexofenadine disposition varied considerably among the groups. In the 2677AA/3435CC genotype group (n=3), the values of area under the concentration-time curve from time 0 to 24 hours [AUC(0-24)] were significantly lower (P=.014) than those of the other 5 genotype groups (GG/CC, GT/CT, TT/TT, GA/CC, and TA/CT). As compared with the 2677GG/3435CC subjects, the AUC(0-24) values were 17% lower in the 2677AA/3435CC subjects and 47% higher in the 2677TT/3435TT subjects (GG/CC versus AA/CC versus TT/TT, 4017 +/- 1137 ng . h/mL versus 3315 +/- 958 ng . h/mL versus 5934 +/- 2,064 ng . h/mL; P=.018). By stratification for genotypes at position 3435, homozygous 3435TT subjects were found to have significantly higher AUC(0-24) (P=.024) and maximum plasma concentration (P=.040) values than CC subjects [AUC(0-24), 5934 +/- 2064 ng . h/mL versus 3998 +/- 1241 ng . h/mL; maximum plasma concentration, 958 +/- 408 ng/mL versus 673 +/- 242 ng/mL].

CONCLUSIONS

The plasma concentrations of fexofenadine after a single oral administration were lower in 2677AA/3435CC subjects than in subjects with the other 5 genotype combinations of the SNPs of G2677T/A and C3435T. These findings confirm the importance of analyzing MDR1 haplotypes and provide a plausible explanation for the conflicting results regarding the effect of MDR1 polymorphisms on the disposition of P-gp substrates.

HAPLOTYPE STRUCTURE AND ALLELE FREQUENCIES OF CYP2B6 IN A KOREAN POPULATION

Cytochrome P450 2B6 (CYP2B6) metabolizes a number of therapeutic drugs and its metabolic activity varies markedly in human liver. Although genetic polymorphisms of CYP2B6 have been reported in noncoding and coding regions, little information is available regarding single nucleotide polymorphisms (SNPs) and their haplotypes in noncoding regions in Asians. Fourteen previously reported SNPs were determined by polymerase chain reaction-restriction fragment length polymorphism or SNaPshot analysis in a Korean population and their haplotypes were inferred from genotype data using an expectation-maximization algorithm. The most common haplotypes were haplotype I, the reference sequence (frequency 0.35), haplotype II (0.19), haplotype III (0.19), and haplotype V (0.12), which together accounted for 85% of all haplotypes. The frequency of haplotype III, which contains -2320C, -1778G, -1186G, -750C, and 15582T, was found to be 2.4-fold higher than that of the *1J allele in Caucasians, and the frequency of haplotype V, which contains -8207C, -1456C, -750C, 516T, and 785G, was 55% of that of the *6B allele in Caucasians. Moreover, haplotype V, the *6B allele, appeared to be completely linked to -8207 within a putative nuclear receptor binding motif, suggesting that lower expressions of the *6B allele may be associated with the presence of noncoding SNPs such as -8207G>C linked to nonsynonymous SNPs. In conclusion, we found 11 previously described polymorphisms and identified four major haplotypes of CYP2B6 in Koreans. The frequencies of the *1J or *6B alleles, which may reduce CYP2B6 enzyme expression, were found to be significantly different between Koreans and Caucasians.

Effect of the CYP3A5 genotype on the pharmacokinetics of intravenous midazolam during inhibited and induced metabolic states*1

OBJECTIVE

Our objective was to investigate the effect of the CYP3A5 genotype on the systemic clearance of midazolam in constitutive, inhibited, and induced metabolic conditions.

METHODS

Nineteen healthy volunteers were grouped with regard to the CYP3A5*3 allele, into homozygous wild-type (CYP3A5*1/*1, n = 6), heterozygous (CYP3A5*1/*3, n = 6), and homozygous variant-type (CYP3A5*3/*3, n = 7) subject groups. The pharmacokinetic profile of intravenous midazolam was characterized before and after itraconazole administration (200 mg once daily for 4 days) and also after rifampin (INN, rifampicin) pretreatment (600 mg once daily for 10 days), with a washout period of 2 weeks in between.

RESULTS

The pharmacokinetic profiles of midazolam and of its hydroxy metabolites did not show differences between the genotype groups under basal and induced metabolic conditions. However, during the inhibited metabolic state, the CYP3A5*3/*3 group showed a greater decrease in systemic clearance than was seen in the CYP3A5*1/*1 group (8.5 +/- 3.8 L. h(-1). 70 kg(-1) versus 13.5 +/- 2.7 L. h(-1). 70 kg(-1), P =.027). The 1'-hydroxymidazolam-to-midazolam area under the plasma concentration-time curve ratio was also significantly lower in the CYP3A5*3/*3 group (0.58 +/- 0.35 versus 1.09 +/- 0.37 for the homozygous wild-type group, P =.026).

CONCLUSIONS

The CYP3A5 genotype did not affect the pharmacokinetics of intravenous midazolam in the basal or induced states. However, during cytochrome P450 (CYP) 3A inhibition by itraconazole, individuals carrying the CYP3A5*1 allele were found to be less susceptible to changes in systemic clearance and showed higher 1'-hydroxymidazolam-to-midazolam area under the plasma concentration-time curve ratios, probably resulting from the relatively CYP3A4-specific inhibition caused by itraconazole.

Pharmacokinetic and pharmacodynamic evaluation of a novel proton pump inhibitor, YH1885, in healthy volunteers

To evaluate the pharmacokinetic and pharmacodynamic characteristics of YH1885, a novel proton pump inhibitor, a single-blind, randomized, placebo-controlled, dose-rising, parallel-group study was conducted in 46 healthy volunteers. The volunteers were randomly allocated to single dose groups of 60 mg, 100 mg, 150 mg, 200 mg, and 300 mg (6 subjects per dose, including 2 placebos) or to multiple-dose groups of 150 mg and 300 mg (once-daily dosing for 7 days; 8 subjects per dose, including 2 placebos). The multiple-dose study was conducted separately after the single-dose study. YH1885 was administered orally after overnight fasting. Serial blood samples, urine samples, and pharmacodynamic measurements were taken. Drug concentrations in plasma and urine were determined by liquid chromatography/mass spectrometry (LC/MS). Pharmacodynamic changes were evaluated by ambulatory intragastric pH monitoring and by serial measurements of serum gastrin concentrations. Assessments of safety and tolerability also were made. Plasma concentrations of YH1885 reached peak levels 1.3 to 2.5 hours after single-dose administration and then declined monoexponentially with a terminal half-life (t(1/2)) of 2.2 to 2.4 hours in dosage groups up to 200 mg in the single-dose study. YH1885 showed linear pharmacokinetic characteristics, and little accumulation occurred after multiple administrations. The parent drug was not detected in urine. Dose-related pharmacological effects were obvious for dose groups of 150 mg and higher in the single-dose study. The mean intragastric pH and the percentage of time at pH>4 were significantly increased. The onset of drug effect was rapid, and maximal effects were observed on the first day of administration during multiple dosing. Serum gastrin levels also showed rapid increases during dosing but with a weak dose-effect relationship. Neither serious nor dose-limiting adverse effects were observed. YH1885 was found to be safe and well tolerated and effectively inhibited acid secretion with dose-dependent increases in intragastric pH. The acid-suppressing efficacy of YH1885 needs to be further evaluated in patients with gastric acid-related diseases.

Rice-body formation in atypical mycobacterial tenosynovitis and bursitis: findings on sonography and MR imaging

OBJECTIVE

This article describes rice bodies found in patients with atypical mycobacterial tenosynovitis and bursitis, emphasizing the sonographic and MR imaging appearances of these small bodies.

CONCLUSION

Rice bodies occur in patients with atypical mycobacterial tenosynovitis and bursitis. When small, rice bodies are better visualized on MR imaging than on sonography, allowing the radiologist to consider appropriate diagnoses.

Omeprazole hydroxylation is inhibited by a single dose of moclobemide in homozygotic EM genotype for CYP2C19

AIMS

The pharmacokinetics of omeprazole and its metabolites in healthy subjects were evaluated to determine if a single dose of moclobemide inhibited CYP2C19 activity.

METHODS

Sixteen volunteers, of whom eight were extensive metabolizers (EM) and eight were poor metabolizers for CYP2C19, participated in two studies. Venous blood samples were collected for 24 h after oral ingestion of 40 mg omeprazole with or without 300 mg moclobemide coadministration. The pharmacokinetic change of omeprazole, omeprazole sulphone and 5-hydroxyomeprazole concentrations were assessed to test for an interaction between omeprazole and moclobemide.

RESULTS

The coadministration of moclobemide in EMs approximately doubled the mean AUC (from 1834 to 3760 ng ml(-1) h) and C(max) (from 987 to 1649 ng ml(-1)) of omeprazole, and increased the AUC of omeprazole sulphone without changing AUC ratio of omeprazole to omeprazole sulphone. Moclobemide coadministration more than doubled the AUC ratio of omeprazole to 5-hydroxyomeprazole (from 2.5 to 5.3) in EMs, too. There was a significant decrease in Cmax and AUC of 5-hydroxyomeprazole in PMs but no significant changes were seen in the results for omeprazole and omeprazole sulphone AUCs.

CONCLUSIONS

A single dose of moclobemide resulted in significant suppression of CYP2C19 activity in EMs. We conclude that physicians prescribing moclobemide should pay attention to its pharmacokinetic interactions even on the first day of coadministration with CYP2C19 substrates.

Tarsal tunnel syndrome caused by talocalcaneal coalition

Tarsal tunnel syndrome caused by talocalcaneal coalition is uncommon. We presented the ultrasonography (US) and magnetic resonance imaging findings of this disease. This is, to our knowledge, the first case report describing the US findings in tarsal tunnel syndrome caused by talocalcaneal coalition.

Internal fixation of valgus-impacted humeral head fractures using the screw-wiring technique

Between February 1996 and July 2000 eight patients (ages 35-74 years) with nine severely impacted humeral head fractures were operated on with the aim of preserving the humeral heads. Patients were treated surgically with open reduction, autologous bone grafting, and internal fixation with a screw-wiring technique. There were no complications and all patients were satisfied with the results. After 10-63 months there was no evidence of nonunion, arthritis, avascular necrosis, or loosening of implants. The mean Constant score was 83 (66-97) points. Results of this study support the observation that four-part valgus-impacted humeral head fractures without significant lateral displacement have a low incidence of avascular necrosis.