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Biomedical subjects

H R Ochs

Publications and source records attributed to H R Ochs.

At least 55 records · Page 3Linked to original sources
PubMed1985

Interaction of ibuprofen with the H-2 receptor antagonists ranitidine and cimetidine.

The influences of cimetidine and ranitidine on single-dose ibuprofen kinetics were evaluated. Thirteen healthy subjects took a single, 600 mg oral dose of ibuprofen on three occasions: in the control state without drug coadministration; during concurrent dosing with cimetidine, 1.2 gm/day; and during concurrent dosing with ranitidine, 150 mg twice daily. Compared with the control state, cimetidine increased the peak serum ibuprofen concentration (64 vs. 56 micrograms/ml), but the value during ranitidine dosing (57 micrograms/ml) was indistinguishable from the control value. There were no significant differences between control, cimetidine, and ranitidine conditions in ibuprofen elimination t1/2 (2.1, 2.1, and 2.0 hours, respectively). Overall there was a significant difference among the control, cimetidine, and ranitidine conditions in ibuprofen oral clearance (52.8, 48.3, and 54.1 ml/min, respectively), but individual differences in cimetidine vs. control and between ranitidine vs. control were not statistically significant. The impairment of ibuprofen clearance by cimetidine is small, and ranitidine had no detectable effect on ibuprofen kinetics. These findings should be further validated during chronic dosing with ibuprofen.

Adult↗
PubMed1985

Age, sex, and nitrazepam kinetics: relation to antipyrine disposition.

Forty healthy men and women 19 to 80 years old received a single 10 mg oral dose of the 7-nitro benzodiazepine nitrazepam. Nitrazepam plasma concentrations were measured during the next 72 hours. Among men, the elderly had a larger volume of distribution (Varea) than did younger subjects (1.96 vs. 1.63 L/kg; P less than 0.05); because clearance did not change with age (0.84 vs. 0.95 ml/min/kg), the prolonged t1/2 in elderly men (28 vs. 20 hours; P less than 0.01) was a result of the larger Varea. Elderly and young women did not differ in nitrazepam Varea (2.58 vs. 2.55 L/kg), t1/2 (26 vs. 27 hours), or total clearance (1.19 vs. 1.09 ml/min/kg). The nitrazepam free fraction in plasma (18% to 19% unbound) was not related to age or sex. Among 18 subjects who also received antipyrine, the clearance of nitrazepam and antipyrine were not correlated (r = 0.23). Thus age minimally influences nitrazepam clearance (accomplished mainly by nitroreduction), which in turn is not significantly related to antipyrine oxidizing capacity.

Administration, Oral↗
PubMed1985

Cerebrospinal fluid uptake and peripheral distribution of centrally acting drugs: relation to lipid solubility.

In an anaesthetized dog model, serum kinetics and CSF entry were determined after i.v. administration of the following 8 drugs: salicylic acid (as acetylsalicylic acid), antipyrine, acetaminophen (paracetamol), lidocaine (lignocaine), trimipramine, amitriptyline, haloperidol, and imipramine. Kinetic variables were evaluated in relation to in-vitro lipophilicity, measured by the reverse-phase high-pressure liquid chromatographic (HPLC) retention index. After correction for individual values of serum binding (determined as the CSF: serum ratio at equilibrium), in-vivo volume of distribution was highly correlated with HPLC retention (r = 0.92). Conversely, the time of peak CSF concentration and the CSF entry half-life were negatively correlated with HPLC retention (r = -0.83 and -0.63, respectively). Thus lipophilicity is a physiochemical property which has an influence on the peripheral distribution of drugs as well as their rate of entry into CSF.

Animals↗
PubMed1985

Kinetics of diazepam, midazolam, and lorazepam in cigarette smokers.

Ten otherwise healthy cigarette smokers (mean, 31 cigarettes per day), and ten nonsmoking control volunteers matched for age, weight, and sex received single intravenous doses of diazepam (5 to 10 mg), midazolam (5 mg), and lorazepam (2 mg) on three separate occasions. Kinetics of each benzodiazepine were determined from multiple serum concentrations measured after each dose. In non-smoking vs smoking subjects, there was no significant difference in mean clearance of diazepam (0.44 vs 0.47 ml/min/kg), midazolam (9.6 vs 7.1 ml/min/kg), or lorazepam (0.96 vs 1.08 ml/min/kg). Thus, differences in pharmacokinetics are unlikely to account for altered sensitivity to benzodiazepines that may occur in cigarette smokers.

Adult↗
PubMed1985

Single-dose kinetics of oral propranolol, metoprolol, atenolol, and sotalol: relation to lipophilicity.

Nine healthy volunteers received single oral doses of the following four beta-adrenergic blocking agents: propranolol (160 mg), metoprolol (100 mg), atenolol (200 mg), and sotalol (320 mg). The kinetics of each drug were determined from multiple serum concentrations measured during 24-48 h after each dose, and in vitro lipid solubility determined using the liquid chromatographic (HPLC) retention index. Oral clearance for the four drugs ranged from 40.2 ml/min/kg for propranolol down to 2.1 for sotalol. Oral clearance was highly correlated (r = 0.99) with in vitro lipid solubility, with propranolol being the most lipophilic drug and sotalol the least. Thus lipophilicity is a physicochemical property of beta-adrenergic blockers that appears to influence their intrinsic clearance after oral dosage.

Adrenergic beta-Antagonists↗
PubMed1984

Disposition of oxazepam in patients on maintenance hemodialysis.

The pharmacokinetics of a single 30-mg oral dose of oxazepam was evaluated in seven patients with chronic renal failure on maintenance hemodialysis and in seven healthy controls matched for age and sex. Based on total (free plus bound) serum oxazepam concentrations, elimination half-life was prolonged in renal patients compared to controls (22 vs 8 h, p less than 0.001) and volume of distribution increased (3.0 vs 1.4 1/kg, p less than 0.02). However, total clearance was similar between groups (1.8 vs 1.9 ml/min per kilogram). These findings were confounded by the increased oxazepam free fraction in serum of renal failure patients (10.3%) as compared to healthy controls (4.3%). Correction for differences in binding indicates similar distribution of unbound oxazepam between groups, but reduced clearance of pharmacologically active unbound oxazepam in renal patients (18 vs 45 ml/min per kilogram). Oxazepam dosage, therefore, may require downward adjustment for renal failure patients on hemodialysis.

Administration, Oral↗
PubMed1984

Nifedipine: kinetics and dynamics after single oral doses.

Serum nifedipine concentrations and hemodynamic changes were evaluated in ten healthy volunteers after a single 40-mg oral dose of nifedipine. Peak serum concentrations averaged 45 micrograms/l, attained 2.7 h after dosage. The mean elimination half-life was 5.9 h (range: 3-12 h). Blood pressure, ventricular rate, and echocardiographically-determined rate of circumferential fiber shortening did not differ between placebo and nifedipine trials. Five additional subjects ingested nifedipine once in the control state and on a second occasion with a standard breakfast. Coingestion of food delayed the peak serum nifedipine concentration but did not alter the area under the serum concentration curve. Thus the pharmacokinetic profile of nifedipine indicates that a three- or four-times-daily dose is, in general, appropriate in clinical practice. Completeness of absorption is not altered by coadministration with food. Adverse hemodynamic effects of single oral doses in healthy persons are not evident.

Administration, Oral↗
PubMed1984

Pharmacokinetics and absolute bioavailability of diltiazem in humans.

Six healthy male volunteers received single doses of diltiazem hydrochloride on three occasions separated by at least 10 days. Modes of administration were: 10-minute intravenous infusion of a 20-mg dose; oral administration of 120 mg in solution form; and oral administration of 120 mg as two 60-mg sustained-release tablets. Diltiazem concentrations were measured by electron-capture gas chromatography in multiple plasma samples drawn during the 36 hours after dosage. Following intravenous administration, mean (+/- S.E.) pharmacokinetic variables were: elimination half-life, 11.2 (+/- 2.1) hours; volume of distribution, 11.1 (+/- 3.0) liters/kg; and total clearance, 11.5 (+/- 0.7) ml/min/kg. Oral diltiazem in solution form was rapidly absorbed, with peak plasma levels attained at 38 (+/- 6) minutes after the dose. Absolute systemic availability averaged 44% (+/- 4%). Oral administration of sustained-release tablets yielded, as predicted, slower absorption, with peak plasma concentrations attained at an average of 165 (+/- 22) minutes after dosage. Thus, oral diltiazem is incompletely bioavailable after oral administration, mainly because of first-pass hepatic extraction.

Administration, Oral↗
PubMed1984

Is temazepam an accumulating hypnotic?

Ten healthy volunteers aged 22 to 30 years received a single 20-mg oral dose of temazepam. Serum temazepam concentrations were measured by gas chromatography at multiple times during the next 48 hours. Mean kinetic variables were: volume of distribution, 1.45 liter/kg; elimination half-life, 8.6 hours; total clearance, 2.33 ml/min/kg. The subjects then received 20 mg temazepam once daily for seven consecutive days. Serum concentrations were measured just prior to each dose and at multiple time points after the last dose. Predose serum levels increased during the first three days of dosage, then increased no further. Mean values measured 24 hours after doses 1 through 6, respectively, were 33, 43, 55, 47, 53, and 51 ng/ml. Based on the area under the serum concentration curve after the last dose compared with that after the first dose, the mean accumulation ratio was 1.32, which was significantly greater than unity. The extent of accumulation was consistent with that predicted from the single-dose study. Postdosage washout half-life averaged 10.2 hours. Thus, temazepam has a pharmacokinetic profile of an intermediate half-life benzodiazepine that produces an intermediate degree of accumulation with multiple dosage.

Absorption↗
PubMed1984

Comparative single-dose kinetics of oxazolam, prazepam, and clorazepate: three precursors of desmethyldiazepam.

Twelve healthy volunteers received a single 40-mg oral dose of the benzodiazepine derivative oxazolam, which serves primarily as a precursor of the active substance desmethyldiazepam (DMDZ). Concentrations of DMDZ were measured in multiple serum samples drawn for up to two weeks after the dose. Peak serum DMDZ concentrations averaged 115 ng/ml, measured at 8.6 hours after dosage. Mean DMDZ elimination half-life averaged 61 hours. Three of the subjects also received 40 mg each of prazepam and clorazepate, two other DMDZ precursors, on separate occasions. Although DMDZ elimination half-life was similar, total area under the curve (AUC) for DMDZ was larger for clorazepate, known to be completely transformed into DMDZ, than for oxazolam or prazepam the extent of whose conversion to DMDZ has not been previously established. After correcting for the different molar equivalent of DMDZ available from each preparation, the DMDZ ratio averaged 0.22 for oxazolam vs. clorazepate and 0.51 for prazepam vs. clorazepate. Thus, both oxazolam and prazepam lead to slow appearance of DMDZ in the systemic circulation. Furthermore the extent of DMDZ formation from oxazolam and prazepam is either incomplete or the drugs are incompletely absorbed. Equivalent doses of oxazolam, prazepam, and clorazepate should not be interchanged in clinical practice.

Adult↗
PubMed1984

Single and multiple dose kinetics of clobazam, and clinical effects during multiple dosage.

Sixteen healthy volunteers, aged 19 to 62 years, took a single 20-mg oral dose of clobazam and the serum concentrations of clobazam and desmethylclobazam were measured for the following 7 days. The mean kinetic variables for clobazam were: volume of distribution 1.31/kg, elimination half-life 24h, total clearance 0.47 ml/min/kg. 13 of the volunteers then took clobazam 5 mg twice daily for 22 consecutive days. Serum concentrations were measured during and after this period. Both clobazam and desmethylclobazam showed slow and extensive accumulation, their steady-state kinetics being entirely consistent with those observed after single doses. Elimination of both compounds after termination of treatment was equally slow. Clinical self-rating of morning sedation indicated a significant increase over baseline in subjective perception of sedation during the treatment period, and this effect persisted into the washout period. However, sedation did not increase in parallel with accumulating levels of clobazam and desmethylclobazam, probably due to functional adaptation or tolerance.

Adult↗
PubMed1984

Disposition of clotiazepam: influence of age, sex, oral contraceptives, cimetidine, isoniazid and ethanol.

Factors influencing the disposition of clotiazepam in man were evaluated in a series of pharmacokinetic studies in healthy volunteers given a single 5 mg dose. Old age caused an increased volume of distribution of clotiazepam in women, and its clearance tended to be reduced in elderly men. Use of oral contraceptives, cimetidine, isoniazid or a single dose of ethanol had no significant effect on the kinetics of clotiazepam. Although clotiazepam is biotransformed by microsomal oxidation, its clearance appears to be relatively uninfluenced by factors known to alter the clearance of other oxidized benzodiazepines.

Adult↗
PubMed1984

Propranolol interactions with diazepam, lorazepam, and alprazolam.

Healthy subjects received single doses of diazepam (5 to 10 mg iv), lorazepam (2 mg iv), or alprazolam (1 mg orally) on two occasions, once in the control state and once with propranolol, 80 mg three times a day. Compliance with the propranolol regimen was verified by measurement of serum propranolol levels (overall means: 100 ng/ml) and by reduction in sensitivity to intravenous metaproterenol to one-thirtieth that of the control value. Propranolol prolonged diazepam elimination t1/2 (58 and 49 hr), reduced its clearance (0.20 and 0.24 ml/min/kg), and increased the 168-hr AUC for desmethyldiazepam, the major metabolite of diazepam (5.63 and 4.81 micrograms/ml . hr). Propranolol had no significant effect on lorazepam t1/2 (13.2 and 12.7 hr) or clearance (1.33 and 1.36 ml/min/kg), nor on alprazolam t1/2 (15.9 and 18.5 hr) or clearance (1.1 and 0.8 ml/min/kg). Thus propranolol induces a small but significant reduction in clearance of diazepam, biotransformed mainly by the oxidative reaction of N-demethylation. Propranolol does not impair lorazepam clearance by glucuronide conjugation nor that of alprazolam by aliphatic hydroxylation.

Adolescent↗
PubMed1984

Pharmacokinetic noninteraction of triazolam and ethanol.

Five healthy volunteers received a single 0.5-mg dose of triazolam on two occasions: once with 100 to 200 ml of water, and on a second trial with 60 ml of commercial vodka mixed with 60 ml of water. There were no significant differences between control and ethanol-coadministration trials in peak serum triazolam level (5.4 vs. 5.4 ng/ml), time of peak level (1.5 vs. 1.6 hours), elimination half-life (2.8 vs. 2.6 hours), or apparent oral clearance (6.6 vs. 7.9 ml/min/kg). The potential pharmacodynamic interaction of triazolam and ethanol is more important than the minimal pharmacokinetic interaction.

Adult↗
PubMed1984

Differential effects of isoniazid and oral contraceptive steroids on antipyrine oxidation and acetaminophen conjugation.

Factors influencing hepatic oxidation of antipyrine and conjugation of acetaminophen were evaluated in volunteers who received 1.0 g of antipyrine intravenously and on a different occasion a 650 mg intravenous dose of acetaminophen. In study one, subjects received both drugs in the control state and at another time during coadministration of isoniazid (INH), 180 mg daily. In control versus INH conditions, mean clearance of antipyrine was reduced from 0.67 to 0.60 ml/min/kg as was clearance of acetaminophen from 4.97 to 4.23 ml/min/kg, but these differences were not statistically significant. In study two, females on low-dose estrogen oral contraceptives (OC) and drug-free controls matched for age received both drugs. Compared to controls, OC users had reduced total clearance of antipyrine (0.71 vs. 0.50 ml/min/kg; p less than 0.005) and prolonged antipyrine t1/2 (9.6 vs. 13.3 h; p less than 0.005). For acetaminophen, however, OC users had higher clearance (5.2 vs. 6.1 ml/min/kg) and shorter t1/2 (2.2 vs. 1.9 h) although differences did not attain statistical significance. Clearance of antipyrine and acetaminophen across both studies was not statistically significantly correlated within individuals (r = 0.22). The capacities for drug oxidation and conjugation appear to be controlled by different mechanisms.

Acetaminophen↗