Two-phase derivatization of pentazocine with chloroformate esters and determination by gas chromatography

Two-phase derivatization with chloroformate esters of tertiary amines that contain a phenol group has been studied. The derivatives were analysed by gas chromatography with sensitive and selective detectors. The N,O-bis derivative of pentazocine was formed using an aqueous phase at pH 9.8, with tetrabutylammonium ion for extraction of the phenolate ion as an ion-pair. The organic phase comprised methylene chloride with trichloroethyl chloroformate or ethyl chloroformate. At pH 10.7 the derivative was hydrolysed by hydroxide ions extracted into the organic phase. Hydrolysis also occurred when more lipophilic counter-ions such as tetrapentyl-ammonium ions were used. Two-phase derivatization could also be achieved with toluene or ethyl acetate as the organic phase, although the reaction rate was considerably slower. The method was also applied to the assay of pentazocine in plasma. The best results were achieved after selective extraction of pentazocine from plasma, two-phase derivatization with ethyl chloroformate and determination by mass spectrometry or thermionic detection. The minimum detectable concentration of pentazocine was 10 ng/ml in a 1-ml plasma sample.

Steady state pharmacokinetics of trimethoprim 300 mg once daily in healthy volunteers assessed by two independent methods

The steady state pharmacokinetics of trimethoprim was determined after 300 mg orally once daily to 6 healthy volunteers for 9 days. The microbiological assay of plasma level was unreliable at trimethoprim concentrations greater than 4 micrograms/ml, so results from an HPLC-assay are given. Steady state was present after 3 days. The plasma concentration peaked 1 to 4 h (mean 2.0 h) after the dose at a mean of 6.0 micrograms/ml (range 3.1-9.5 micrograms/ml); the minimum value was 1.5 micrograms/ml (range 0.6-2.9 micrograms/ml). The mean AUCss was 77 micrograms/ml X h and the mean plasma clearances was 67 and 74 ml/min on Days 8 and 9. Renal clearance was about 60% of the plasma clearance. The average plasma half life was 10.6 h (range 8.7-15.3 h). Thus, there was considerable interindividual variation in all pharmacokinetic parameters. 72 h after the last dose trimethoprim was detectable in plasma in only 1 of the 6 subjects. The minimum urinary concentration of trimethoprim during treatment was always well above (range 22 to 220 micrograms/ml) the MIC values for most urinary tract pathogens. Therefore, a daily dose of 300 mg trimethoprim results in a therapeutic concentration in urine at steady state that lasts throughout the dosing interval and in most subjects probably lasts also for a further 24 h. Trimethoprim administration raised mean serum creatinine from 67 to 97 mumol/l, probably due to competitive inhibition of the tubular secretion of creatinine.

Clinical pharmacology of pyridostigmine and neostigmine in patients with myasthenia gravis

Determination of plasma concentration of pyridostigmine in 20 myasthenic patients on maintenance therapy revealed rather small intraindividual variations within a dose interval. The predose concentration varied considerably between different patients and up to seven fold in patients on the same daily dose. No pharmacokinetic interaction between pyridostigmine and neostigmine was found in five patients studied. In six patients the decrement in the deltoid muscle was studied in parallel with determination of the plasma concentrations following administration of pyridostigmine or neostigmine. In these patients the existence of a "bell-shaped" dose response curve is suggested with the maximal effect at a concentration of 30-60 ng/ml for pyridostigmine and 5-15 ng/ml for neostigmine.

Coronary heart disease risk factors in bus and truck drivers. A controlled cohort study

Fifty-two bus and truck drivers and a control group of 52 male industrial workers were studied with regard to risk factors for coronary heart disease (CHD) as well as some psycho-social and occupational indicators. The main results were: higher mean values for serum cholesterol, serum triglycerides and blood pressure in the driver group, indicating a markedly higher risk of CHD in the driver group. The two groups were matched for age, socio-economic status, dietary habits, smoking habits and alcohol consumption. In the study the groups were found to be equal as regards CHD-inheritance, physical activity in leisure time, and relative body weight, W/H2. No CO could be traced in the vehicles. The psycho-social and occupational indicators showed considerable differences. The average score for the exposure factor "tempo/time-limit/urgency in job" was 50% higher, and the number of persons with the characteristic "type-A coronary-prone behaviour" was 30% higher in the driver group than in the control group. The difference in blood lipids and blood pressure increased with age. It is suggested that the higher CHD-risk in the driver group is associated with two factors: (1) greater psychic pressure in the working situation; (2) the selection of more type-A persons to driver occupations. A probable, but not commonly accepted theory, is that these psychosocial indicators may influence the traditional risk factors in a harmful way.

Occupational handling of cytostatic drugs

The bacterial fluctuation test and measurement of the frequency of sister chromatid exchanges were used for evaluation of the exposure of different groups of hospital personnel to cytostatic drugs. Increased mutagenic activity in the urine was detected only in personnel working with inadequate safety precautions, e.g., lack of a ventilated safety cabin for preparation of parenteral solutions. Although such a safety cabin was used within the hospital pharmacy, increased mutagenic activity was detected in the urine of prescriptionists preparing parenteral cytostatic drugs. After a change of glove material and improvement of ventilation in the safety cabin, no work-related increase in urinary mutagenic activity was seen. None of the different groups tested, showed any increase in the frequency of sister chromatid exchanges. It is therefore concluded that handling of cytostatic drugs according to the issued safety recommendations including working in a well ventilated safety cabin, will not result in any enhancement of mutagenic activity in the urine related to work.

Simultaneous determination of ketobemidone and its N-demethylated metabolite in patient plasma samples by gas chromatography mass spectrometry with selected ion monitoring

An analytical procedure has been developed for the simultaneous determination of ketobemidone and its N-demethylated metabolite, norketobemidone. After isolation from plasma and re-extraction to acidic aqueous phase, the two aminophenols were extracted as ions pairs with tetrabutylammonium to dichloromethane, where derivatization with ethyl chloroformate took place. Determination was performed by gas chromatography mass spectrometry with selected ion monitoring. Ketobemidone and norketobemidone could be detected in plasma in a concentration of 1 ng ml-1 and 3 ng ml-1, respectively. Determinations were performed down to 5 ng ml-1. The relative standard deviation of the method in the analysis of 10 ng ml-1 of ketobemidone and norketobemidone, respectively, was 8% and 9% (n=10). The absolute recovery of unconjugated ketobemidone and norketobemidone through the method at the 100 ng ml-1 level was 91% and 85%, respectively. The method was applied to the determination of ketobemidone and norketobemidone in plasma from patients given ketobemidone. The concentrations of unconjugated norketobemidone was too small to be detected.

The influence of a hospital drug committee's recommendations on the use of analgesics as evaluated by drug-use data

Drug-use data in a large university hospital have been used as a means for evaluating the influence of the recommendations given by a drug committee on the use of analgesics. The results generally show a reasonable adherence to the recommendations in the hospital. A selected clinic, the Department of Oncology, where special efforts were directed, showed particularly close adherence to the guidelines given.

Single-dose kinetics and bioavailability of ketobemidone

The single-dose kinetics and the oral and rectal bioavailability of ketobemidone have been studied in patients after surgery. Plasma concentrations were determined following intravenous administration of Ketogin 2 ml, containing ketobemidone chloride 10 mg and the spasmolytic substance N, N-dimethyl-3, 3-diphenyl-l-methylallylamine chloride 50 mg and following oral or rectal administration of Ketogin. Ketobemidone was analyzed by gas chromatography-mass spectrometry using a deuterated internal standard. Ketobemidone disappeared rapidly from plasma after i.v. or oral administration, yielding a mean plasma half-life between 2.25 and 2.45 h. After rectal administration the plasma half-life was somewhat prolonged (3.27 h), probably due to late absorption., The bioavailability of oral ketobemidone was 34% +/- 16% s.d. (n = 6), and when given rectally 44% +/- 9% s.d. (n = 5). In contrast to earlier investigations performed without plasma analysis, ketobemidone was found to have a rapid elimination when given intravenously, orally or rectally.

Clinical evaluation of oral methadone in treatment of cancer pain

A dose-adjustment program for oral methadone and the long-term effects of the analgesic therapy have been evaluated in 15 patients with incurable cancer. Rapid and continuous pain relief without serious side-effects was achieved by "ad libitum" dosage in the first 3-5 days. Thereafter, a dosage based on each patients's subjective need was instituted. The mean daily dose was 44 during the first day and it decreased to 22 mg daily at the end of the dose-adjustment week. Three patients did not complete the program because of insufficient effect or severe nausea. Among the 12 patients who chose to continue the methadone treatment after the initial dose-adjustment period, four continued the therapy to their death, three discontinued the therapy due to insufficient effect, and three due to adverse reactions. In one case it was possible to stop the treatment due to decreased pain. The treatment period in these 12 patients varied between 8 and 270 days. Oral methadone offers good pain relief for long periods of time in this group of patients and has obvious advantages as compared to long term parenteral therapy with narcotic analgesics.

Multiple dose kinetics of ketobemidone in surgical patients

Twelve patients scheduled for major abdominal surgery were selected for a study of the kinetics of ketobemidone during the day of surgery and in a follow-up study 3-5 days after surgery. In six patients ketobemidone was administered as ketobemidone plain and in the other six, it was given as Ketogin, a combination formula containing a spasmolytic substance in addition to ketobemidone. Plasma samples were collected for approximately 24 h following induction of anesthesia, during which time multiple doses of ketobemidone were administered. A single-dose study was performed 3-5 days after surgery using the same drug. No significant differences were found between the two formulations of ketobemidone. Plasma clearance did not change significantly between the two periods of study, being 18.0 +/- 4.4 ml . kg-1 . min-1 peroperatively and 21.7 +/- 7.6 ml . kg-1 . min-1 postoperatively. Peroperative Vd area was significantly larger than post-operative Vd area, 5.84 +/- 2.62 l . kg-1 and 3.63 +/- 0.38 l . kg-1, respectively. T1/2 terminal decreased from 3.84 +/- 1.6 h peroperatively to 2.06 +/- 0.44 h postoperatively.

Pharmacokinetics of pethidine during anaesthesia and patient-controlled analgesic therapy

The pharmacokinetics of pethidine has been studied in 12 patients subjected to major intraabdominal surgery. Pethidine and norpethine were analyzed in plasma samples collected during anesthesia and during patient-controlled administration of small intravenous doses of pethidine in the early postoperative period. A second study on the pharmacokinetics of pethidine was performed on the 3-5th postoperative day. The plasma clearance of pethidine was significantly lower in the preoperative study (8.9 +/- 1.8 ml x kg x min-1) compared with the postoperative study (12.0 +/- 3.1 ml x kg x min-1). Volume of distribution (Vd) was not significantly influenced, being 4.25 +/- 1.72 l x kg-1 peroperatively and 3.14 +/- 0.84 l x kg-1 postoperatively. Elimination half-life decreased from 5.91 +/- 3.57 h peroperatively to 3.25 +/- 1.40 h postoperatively. The kinetics of pethidine in the postoperative study agreed with pethidine kinetics reported for healthy volunteers. The fraction of unbound pethidine decreased from 0.26 +/- 0.1 peroperatively to 0.18 +/- 0.1 postoperatively. Norpethidine, a metabolite of pethidine, has been claimed to be responsible for several side effects like respiratory depression and convulsions during pethidine therapy. No side effect attributable to norpethidine was observed in the self-administration period. Norpethidine plasma concentrations did not exceed 500 ng/ml. The altered pethidine pharmacokinetics during anesthesia and the ensuing postoperative hours and the interindividual differences of the disposition of the drug strongly suggest that pethidine should be given by individualized regimens in surgical patients.

Patient-controlled analgesic therapy: clinical experience

Fifty-six surgical patients self-administered i.v. narcotic analgesics to combat postoperative pain. Analgesic demand per h was 2.7 +/- 1.1 mg of morphine, 26 +/- 10 mg of pethidine or 2.3 +/- 0.8 mg of ketobemidone, which reflects the equianalgesic ratios. Acute respiratory depression was seen in two hypovolaemic patients as evidenced by a raised PaCO2 on air breathing. Carbon dioxide retention disappeared upon correction of hypovolaemia. Late respiratory complications of short duration were encountered in 13%. Drowsiness and dry mouth were the most frequent complaints. Self-administered analgesia was considered highly satisfactory by the patients.

Postoperative demand for analgesics in relation to individual levels of endorphins and substance P in cerebrospinal fluid

Fourteen adult patients were allowed to self-administer small intravenous doses of pethidine to relieve postoperative pain. Thirteen of the patients obtained subjectively satisfactory analgesia while establishing steady-state levels of pethidine in plasma. The individual demand for pethidine was related to individual levels of fraction I endorphins and substance P-like immunoreactivity in the cerebrospinal fluid (CSF). There was a significant and inverse relationship between preoperative fraction I concentrations in CSF and the individual mean pethidine concentrations in plasma (P less than 0.05) and CSF (P less than 0.02) during self-administration. In the 24 h period encompassing surgery and postoperative self-administered analgesia, substance P decreased in 7 patients with calculated CSF pethidine great than 200 ng/ml, but remained virtually unchanged in 7 patients with calculated CSF pethidine less than 200 ng/ml. The results suggest a role for endorphins in the modulation of acute pain and are compatible with experimental evidence for an inhibitory effect of opiates on substance P release.

Patient-controlled analgesic therapy, Part III: pharmacokinetics and analgesic plasma concentrations of ketobemidone

The effects of anaesthesia and surgery on the pharmacokinetics of ketobemidone were studied in 12 patients. Plasma ketobemidone concentrations were assayed with a mass-fragmentographic method. The peroperative Vd(area) was 5.9 +/- 2.6L/kg and the terminal half-life was 3.9 +/- 1.7 h. In the postoperative period Vd(area) decreased to 3.7 +/- 0.4L/kg and the terminal half-life to 2.1 +/- 0.4 h. Plasma clearance (Clp) did not change significantly, peroperative Clp being 18 +/- 4.3 ml/min/kg and postoperative Clp being 22 +/- 7.5 ml/min/kg. The pharmacokinetics of ketobemidone were not influenced by the addition of a spasmolytic agent in the commercial combination ketobemidone preparation 'Ketogin'. Postoperative pain was relieved in 15 patients by patient-controlled intravenous administration of ketobemidone by means of a programmable drug injector. The mean ketobemidone consumption was 2.3 +/- 0.8 mg/h, which produced a mean plasma concentration of 28 +/- 11 mg/ml. Pseudosteady-state plasma concentrations of ketobemidone were established with a mean minimum effective concentration (MEC) of 25 +/- 11 ng/ml. Ketobemidone 'plain' and 'Ketogin' did not differ significantly in these respects. Analgesia was considered by all patients to be satisfactory.

Patient-controlled analgesic therapy, Part IV: pharmacokinetics and analgesic plasma concentrations of morphine

The influence of anaesthesia and surgery on the pharmacokinetics of morphine was studied in 10 patients. Plasma concentrations of morphine were assayed by gas chromatography with electron capture detection. All patients were studied on the day of surgery and again 3 to 7 days later. Mean +/- SD for peroperative Vd(area) was 6.3 +/- 3.6 L/kg and for the terminal half-life was 3.8 +/- 2.3 h. In the postoperative period, Vd(area) decreased to 3.7 +/- 1.4L/kg and the terminal half-life to 2.2 +/- 1.1 h. Plasma clearance (Clp) remained constant, peroperative Clp being 20 +/- 7.0 ml/min/kg and postoperative Clp 21 +/- 6.0 ml/min/kg. Postoperative pain was relieved by patient-controlled administration of intravenous doses of morphine by means of a programmable drug injector. The mean morphine consumption was 2.6 +/- 1.2 mg/h, which produced a mean plasma concentration of 21 +/- 12 ng/ml with a calculated mean minimum effective concentration (MEC) of 16 +/- 9 ng/ml. In 1 patient, temporary hypercapnia was seen during a period of hypovolaemia. Analgesia was considered satisfactory by all patients.

Patient-controlled analgesic therapy. Part I: Pharmacokinetics of pethidine in the per- and postoperative periods

The influence of anaesthesia and surgery on the pharmacokinetics of pethidine (meperidine) was studied in 12 patients. Plasma pethidine concentrations in central venous blood collected during anaesthesia and the ensuing postoperative hours were by gas chromatography with electron capture detection. Postoperative analgesia was accomplished by patient-controlled intravenous administration of small doses of pethidine. The NONLIN program was used to calculate pharmacokinetic parameters for each individual. A single dose study of pethidine kinetics was carried out in all patients 3 to 5 days postoperatively. Mean +/- SD for peroperative Vd area was 4.3 +/- 1.7L/kg and for the elimination half-life was 6.1 +/- 3.6h. In the postoperative period Vdarea was 3.2 +/- 0.8L/kg and the elimination half-life was 3.2 +/- 1.4h. Plasma clearance increased from a peroperative value of 8.9 +/- 1.9 ml/min/kg to a postoperative value of 12 +/- 3.0 ml/min/kg. The changes in elimination half-life and plasma clearance are significant. The postoperative pharmacokinetics of pethidine were in accordance with those reported for healthy volunteers. The fraction of unbound pethidine was significantly reduced postoperatively - from 0.26 +/- 0.10 (peroperatively) to 0.18 +/- 0.10 (3 to 5 days later).

Patient-controlled analgesic therapy, Part II: Individual analgesic demand and analgesic plasma concentrations of pethidine in postoperative pain

20 survival patients were allowed to self-administer small intravenous doses of pethidine to relieve pain after major abdominal surgery. Pethidine injections were given by means of a programmable drug injector. Pethidine consumption varied from 12 to 50mg/h with a mean +/- SD of 26 +/- 10mg/h. The mean measured plasma concentration of pethidine during self-administration was 551 +/- 182 ng/ml, with a range of 132 to 896 ng/ml. Minimum effective concentrations averaged 455 +/- 174 ng/ml. Individual pethidine consumption and mean plasma concentrations did not differ between men and women, and were not correlated to variations in age, anthropometric factors, plasma clearance or elimination rate constant for pethidine. Individual consumption of pethidine was consistent, with stable plasma concentrations throughout most of the trial period. Pseudo-steady-state plasma concentrations of pethidine were established and maintained at widely different levels. 19 of the 20 patients obtained subjectively satisfactory analgesia.

Monitoring acetazolamide treatment

Electron capture gas chromatography was used to determine plasma concentrations after various doses of acetazolamide. In 40 patients steady state plasma concentrations were determined for daily doses of 187.5, 375, 750, and 1000 mg. Mean plasma concentrations increased with increasing dosages but there were marked interindividual variations. Part of the interindividual variation was explained by a positive correlation between age and plasma concentration. In 10 patients with previously untreated glaucoma intraocular pressure (IOP) responses and plasma concentrations were determined for increasing doses of acetazolamide. Increasing IOP reductions were obtained up to a dose of 750 mg while a daily dose of 1000 mg acetazolamide had no further effect on IOP. The relationship between IOP reduction and plasma concentration showed great interindividual variations, from a pressure reduction of 11 mmHg at 6 micrograms/ml acetazolamide to a pressure reduction of 0 mmHg at 11 micrograms/ml. As a rule, the maximal effect on IOP was obtained at a plasma concentration between 5 and 10 micrograms/ml. In most patients a daily dose of 1000 mg resulted in plasma concentrations above 10 micrograms/ml.

Extractive alkylation of 6-mercaptopurine and determination in plasma by gas chromatography-mass spectrometry

An analytical procedure was developed for the determination of 6-mercaptopurine in plasma. Owing to the polar character and low plasma concentration of the compound, extraction and derivatization was carried out directly from the plasma sample by extractive alkylation. Determination was made using gas chromatography-mass spectrometry with multiple-ion detection. Conditions with respect to the rate of formation and the stability of the derivative formed in the extractive alkylation step were evaluated. The selectively of the method to azathioprine and to metabolites was thoroughly investigated. No 6-mercaptopurine was formed from azathioprine added to water or plasma and run through the method. The method enables the detection of 2 ng of 6 mercaptopurine in a 1.0-ml plasma sample. Quantitative determinations were done down to 10 ng/ml 6 mercaptopurine in plasma.

Utilization of antiparkinson drugs in Norway, Sweden, Denmark and Finland 1975-1979

Defined daily doses per day and 10(3) inhabitants [Formula: see text] of the different types of antiparkinson agents have been compared in the period 1975-1979 for Norway, Sweden, Denmark and Finland. A marked increase in the utilization of L-DOPA containing drugs has taken place especially in Sweden following the introduction of the "combined drugs" (L-DOPA + decarboxylase inhibitor). Statistically, nearly all patients with parkinsonism in Sweden have since 1977 been treated with L-DOPA, while in the other nordic countries about 10% of the patients are not on this therapy. These data are discussed in relation to the current concept of pharmacotherapy of parkinsonism. Further, many patients treated with neuroleptic drugs do in addition take anticholinergic agents. Drug utilization figures indicate this method of treatment to be most common in Denmark and Sweden.

Quantitative determination of the urinary excretion of ketobemidone and four of its metabolites after intravenous and oral administration in man

The urinary excretion of ketobemidone and its metabolites has been quantified in man after intravenous and oral administration. The metabolism of ketobemidone was found to proceed via 4 metabolic pathways: N-demethylation, ring-hydroxylation, O-methylation, and conjugation. The metabolites were isolated and identified after hydrolysis of the corresponding conjugates. A mean total recovery of about 80% of the dose was found in urine as ketobemidone and metabolites after oral and iv administration, conjugated metabolites amounted to 34-68% of the dose. After iv administration the recovery of unchanged ketobemidone in urine was 13-24%, and after oral administration it was 3-10%. Norketobemidone constituted 10-37% of the dose irrespective of route of administration. 4'-Hydroxyketobemidone amounted to 3-12% of the dose. Neither ketobemidone N-oxide nor metabolites formed after reduction of ketobemidone could be detected in the urine. Less than 2% of the dose was found in feces after iv administration.

Patient-controlled dose regimen of methadone for chronic cancer pain

Fourteen patients with severe cancer pain participated in a trial of methadone given in a fixed dose (10 mg) but at intervals selected by the patients themselves during the loading phase. The aim was to achieve rapid pain relief while avoiding the risk of toxicity from accumulation of methadone. As expected, the dosage intervals increased gradually over the first few days of treatment, the daily dose decreasing from 30-80 mg on the first day to 10-40 mg at the end of the week. Plasma concentrations of methadone varied sevenfold after four to five days (0.24 to 1.75 mumol/1; 7.4 to 54.2 microgram/100 ml). Eleven patients reported complete or almost complete pain relief and elected to continue with methadone after the study. In no case was treatment withdrawn because of intoxication. From these findings a patient-controlled dosage regimen of oral methadone may be an effective and safe alternative to parenteral narcotic medication, adjusting both for individual variation in pain intensity and for pharmacokinetics.

Clinical pharmacokinetics of ketobemidone. Its bioavailability after rectal administration

The pharmacokinetic constants and rectal bioavailability of the narcotic analgesic ketobemidone were determined in six male patients after surgery. Plasma concentrations were measured following intravenous administration of Ketogin 2 ml, containing ketobemidone chloride 10 mg, and a spasmolytic compound N,N-dimethyl-3,3-diphenyl-1-methylallylamine chloride 50 mg, and following rectal administration of one suppository of Ketogin, containing ketobemidone chloride 10 mg and the spasmolytic component 50 mg. Following intravenous administration, the disposition of ketobemidone followed a biexponential pattern with a fast distribution phase and a slower elimination phase: the plasma half-life (t1/2) was 2.42 +/- 0.41 h (m +/- SD). After rectal administration, the disposition of ketobemidone fitted a one-compartment model. The elimination half-life was 3.27 +/- 0.32 h. The mean rectal bioavailability for ketobemidone was 44% +/- 9%. The pharmacokinetic constants of the spasmolytic component, N,N-dimethyl-3,3-diphenyl-1-methylallylamine, were also determined in five of the patients, both after intravenous and after rectal administration. The plasma half-life was 3.07 +/- 0.53 h and 3.79 +/- 1.14 h, respectively. The rectal bioavailability was estimated to be 33% +/- 14%.

Neonatal depression after obstetrical analgesia with pethidine. The role of the injection-delivery time interval and of the plasma concentrations of pethidine and norpethidine

Pethidine (100 mg) was administered i.m. to women in labor at different times before delivery. The interval before respiration in the newborn became sustained was shorter if pethidine was given less than one hour before delivery. The respiratory rate of the newborn increased after naloxone injection in 40 per cent of the cases, mostly when intrauterine exposure to pethidine exceeded one hour. The plasma concentrations of pethidine and norpethidine were measured in mother and newborn. The concentrations in the umbilical vein and artery indicted a continuous net transfer of pethidine from mother to fetus for approximately two hours. This correlated with the clinical finding of maximal neonatal depression 2-3 hours after maternal injection. The concentrations of norpethidine increased with a longer time interval between injection and delivery, but were probably too low to have any effect on the newborn. Neonatal depression seems to be related to the amount of unmetabolized pethidine that has been transferred from mother to fetus but not to norpethidine as had been suspected earlier.

Pharmacokinetics and oral bioavailability of pyridostigmine in man

The pharmacokinetics of pyridostigmine was evaluated after intravenous injection in two healthy male volunteers and after oral administration to five subjects. Plasma concentrations of pyridostigmine were determined after ion pair extraction from plasma and analysis by gas chromatography - mass spectrometry with chemical ionization, using d6-pyridostigmine as internal standard. Degradation of pyridostigmine in vitro was compensated for by use of the deuterated internal standard and by rapid cooling and separation of plasma after blood sampling. After intravenous administration of pyridostigmine 2.5 mg the plasma elimination half-life was 1.52 h, the volume of distribution was 1.43 l/kg and the plasma clearance 0.65 l/kg x h. The pharmacokinetic constants were very similar after oral administration of pyridostigmine 120 mg; the elimination half-life was 1.78 +/- 0.24 h, the volume of distribution 1.64 +/- 0.29 l/kg and the plasma clearance was 0.66 +/- 0.22 l/kg x h. The bioavailability was calculated to be 7.6 +/- 2.4%. When pyridostigmine was taken together with food, the time to reach the peak plasma concentration was prolonged from 1.7 to 3.2 h. Bioavailability, however, was not influenced by concomitant food intake. "Steady-state" plasma concentrations of pyridostigmine were measured in myasthenic patients on their ordinary dose schedule of cholinesterase inhibitor drugs. More than a seven-fold difference in steady-state plasma concentration was found between patients taking approximately the same daily dose of pyridostigmine.

Plasma concentrations after bath treatment and oral administration of trioxsalen

An analytical method comprising homogenous extraction and determination by gas chromatography mass spectrometry has been developed for the quantitation of trioxsalen in plasma. The limit of sensitivity of the method has been 2 ng/ml of trioxsalen. The method was used to monitor concentrations of trioxsalen in plasma after a 40 mg oral dose or after trioxsalen bath treatment. The concentrations in plasma after oral administration did not exceed 3 ng/ml, while in 2 patients after bath treatment trioxsalen could be determined (2-3 ng/ml). The low plasma concentrations found throw light on the poor UV-sensitizing properties found after oral trioxsalen therapy.

Investigation of the Urinary excretion of pethidine and five of its metabolites in man using selected ion monitoring

The urinary excretion in man of pethidine and five of its metabolites (norpethidine, pethidinic acid, norpethidinic acid, p-hydroxypethidine and pethidine N-oxide) after a single intramuscular dose has been investigated using analytical procedures based on selected ion monitoring. New methods for the determination of p-hydroxypethidine and pethidine N-oxide have been developed, and the selectivity and sensitivity of the procedures are discussed. Only some 5% of the administered dose was excreted as unchanged pethidine. The mean urinary excretion of norpethidine was 16.4%. Pethidinic acid and norpethidinic acid constituted the major fraction of the dose excreted in urine. The total excretion of pethidinic acid and norpethidinic acid was 41.7 and 23.2%, respectively. Pethidine N-oxide constituted less than 0.5% of the excreted amount, and p-hydroxypethidine could only be detected in the urine of two of the patients. A mean total recovery of about 90% of the dose was found in urine as pethidine and the five metabolites.

Electron-capture gas chromatography of plasma sulphonylureas after extractive methylation

Conditions for the extractive alkylation of eight sulphonylurea hypoglycemic drugs have been evaluated. Extractive methylation of the compounds was achieved within 90 min using tetrabutylammonium as counter-ion (0.1 M at pH = 6.9) with 5% methyl iodide in dichloro-methane as organic phase. Mass spectral analysis showed derivatives methylated at the sulphonamide nitrogen. A higher pH or use of tetrapentylammonium as counter-ion caused hydrolysis of the sulphonylureas. The derivatives showed a high electron-capture response with minimum concentrations detectable in the range 1-4 x 10(-16) moles sec-1. Therapeutic plasma concentrations of glipzide and tolbutamide were determined by direct extractive methylation of the compounds from the plasma sample. The glipizide derivative was determined by electron-capture gas chromatography down to about 20 ng/ml in a 0.5-ml plasma sample. The relative standard deviation at the 0.2 microgram/ml level of glipizide was 6% (n = 6). The corresponding figure in the determination of tolbutamide at the 10 microgram/ml level was 3% (n = 10).

Clinical pharmacokinetics and oral bioavailability of ketobemidone

The basic pharmacokinetics and oral bioavailability of ketobenmidone have been studied in 6 patients after surgery. Plasma concentrations were first determined following intravenous administration of Ketogin 2 ml, containing ketobemidone chloride 10 mg and the spasmolytic N,N-dimethyl-3,3-diphenyl-1-methylallylamine chloride 50 mg, and then, on the second postoperative day, following oral administration of 2 tablets of Ketogin, each containing ketobemidone chloride 5 mg and the spasmolytic agent 25 mg. The average oral bioavailability of ketobemiodone was 34% +/- 16% (SD, n = 6). The mean plasma half-life of elimination (t1/2 beta) was about the same following oral (2.45 +/- 0.73 h; SD, n = 5) as after intravenous administration (2.25 +/- 0.35 h; SD, n = 6). The low oral bioavailability and rapid elimination of ketobemidone demonstrated in this study suggest that the usual dosage recommendation for oral Ketogin (ketobemidone 5--10 mg every 6--7 h) in patients with severe pain is too low.

Quantitation of CSF concentrations and biological activity of probenecid metabolites

The concentrations of probenecid and four of its metabolites have been examined in plasma and CSF by electron capture gas chromatography after extractive methylation. The plasma concentration of each of the metabolites was in the range 1,5-15 micrograms/ml and constituted less than 10% of the parent compound. The penetration into CSF of the metabolites was lower than that of probenecid. The concentration of each of the metabolites was below 0,2 microgram/ml and the total concentration never exceeded 10% of the probenecid concentration. The inhibitory effect of the metabolites on uptake was tested in rabbit renal cortex using 3H-p-amino-hippuric acid. The inhibitory effect was low. From the low activity and relatively low concentrations of the metabolites do not contribute to the probenecid-induced blocking effect of acid transport from the CSF.

Patient controlled analgesic therapy in the early postoperative period

Fourteen patients with postoperative pain were allowed to self-administer preset doses of pethidine intravenously via a logic-controlled motor syringe. Plasma samples were collected during anaesthesia and the postoperative self-administration period, and the concentrations of pethidine and nor-pethidine were determined. Separate single-dose studies in eight patients yielded pharmacokinetic parameters which made possible computer simulations of continuous plasma concentration curves for the anaesthesia and postoperative self-administration period. The consumption of pethidine showed great interindividual variations with a mean consumption for the entire group of 26 mg per hour. The patients established steady-state plasma concentrations with far less than the maximum amount of pethidine allowed. The mean measured plasma concentration of pethidine which provided adequate analgesia was 738 +/- 149 ng/ml. Simulated and measured plasma concentrations were in close agreement. The individual mean drug consumption per hour during self-administration correlated closely with the individual elimination rate of pethidine. No serious side effects were observed. Thus, patient-controlled analgesic therapy offers an individualized analgesic supply to meet an analgesic demand which is governed by each patient's appreciation of pain.

Analysis of nicotine as a trichloroethyl carbamate by gas chromatography with electron-capture detection

Nicotine was subjected to reaction at 90 degrees with trichloroethyl chloroformate in the presence of pyridine to form a carbamate in which the pyrrolidine ring was opened. Upon heat treatment, this carbamate partially formed the corresponding olefin. About 10 pg could be detected with an electron-capture detector and 60 pg with an alkali flame-ionization detector. The extraction was studied with 14C-labelled nicotine. Methylene chloride was suitable for extraction from diluted plasma, whereas toluene containing 5% of heptafluorobutanol was used in a re-extraction step and also as the chloroformate reaction medium. Due to a nicotine blank the limit for quantitative determinations was 10 ng/ml in plasma (sample volume 1 ml). N-n-Propylnornicotine was used as an internal standard. The precision at the 30 ng/ml level was +/- 8.8% (n = 7).

Extractive alkylation of sulphonamide diuretics and their determination by electron-capture gas chromatography

The extractive alkylation of 11 sulphonamide diuretics has been evaluated using tetrabutylammonium, tetrapentylammonium or tetrahexylammonium as counter ion at different pH values and methyl iodide in methylene chloride as the organic phase. The sulphonamides are methylated within 20 min with tetrahexylammonium as counter ion in 0.2 M sodium hydroxide at 50 degrees. The derivatives have been identified by mass spectral and nuclear magnetic resonance analysis. Relative retentions of the derivatives are given using 1% SE-30 as the stationary phase. A contaminant, dimethylsulphuric acid, occurs in methyl iodide and seriously disturbs the gas chromatographic analysis. The application of the extrative alkylation to biological samples is demonstrated by the direct analysis of acetazolamide in serum. 0.1 M tetrapentylammonium in 0.5 M sodium hydroxide is suitable as the aqueous phase with 1.6 M methyl iodide as alkylating reagent in methylene chloride. The trimethyl derivative of acetazolamide formed has been determined by electron-capture gas chromatography down to 0.5 microgram/ml in a 0.1-ml serum sample. The relative standard deviation at the 10 microgram/ml level is 6.6% (n = 10).

Untreated psychiatric disability. A study of disabled persons with major psychiatric health impairment, having never received psychiatric treatment

The presented investigation, from a county seemingly representative of the average for Norway, showed that at least 15% of male Disability Pensioners with a psychiatric primary diagnosis, become pensioned without having had any psychiatric treatment. The purpose of the investigation was to describe this group of untreated psychiatric disabled, both numerically and regarding social, personal and nosological factors. It was found that the absence of treatment was due to lack of opportunity, but to the pensioner's own attitude, a stubborn resistance to being defind as a psychiatric patient. This is enhanced by a general tendency in our culture to choose, when possible, the role of a somatic patient rather than that of a psychiatric patient. The untreated group of male Disability Pensioners had a normal distribution of social status and stability, and showed a strong preponderance of neurosis-like conditions, combined with pains and other symptoms from the musculo-skeletal system in 51% of the clients. Among War Pensioners there were also found many untreated psychiatric disabled, especially ex-wartime seamen, showing a surprisingly constant syndrome of mixed anxiety and asthenia. The material comprised 150 males, 101 applicants for Disability Pension and 49 for War Pension, all untreated.