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Biomedical subjects

D L Azarnoff

Publications and source records attributed to D L Azarnoff.

At least 19 recordsLinked to original sources
PubMed1998

Pharmacokinetics, cortisol release, and hemodynamics after intravenous and subcutaneous injection of human corticotropin-releasing factor in humans.

OBJECTIVE: Two clinical trials investigated the pharmacokinetics of human corticotropin-releasing factor (hCRF), resulting cortisol release, and associated hemodynamic changes. METHODS: In a 3 x 3 Latin square design, subjects were randomized to receive a single dose of 5 microg x kg(-1) hCRF as a 10-minute intravenous infusion, a 180-minute infusion, and a subcutaneous injection in separate study sessions 7 days apart. Twelve additional subjects obtained a subcutaneous dose of either 300, 600, or 1200 microg hCRF on 3 consecutive days. Noncompartmental and compartmental pharmacokinetic analysis was performed. Hemodynamic response was characterized with use of pharmacodynamic models. RESULTS: The volume of distribution at steady state was 9.81 +/- 3.0 and 15.61 +/- 2.9, and the clearance was 256 +/- 40 mL x min(-1) and 345 +/- 90 mL x min(-1) for the 10-minute and 180-minute intravenous infusion, respectively (P < .05). Corresponding elimination half-life was 45 +/- 7 minutes and 37 +/- 10 minutes. Two-compartment and 1-compartment models adequately described the 10-minute and 180-minute infusions, respectively. The bioavailability of hCRF after subcutaneous administration was 67% +/- 17%. Apparent clearance remained unchanged for different subcutaneous doses. Peak plasma cortisol concentrations were similar after subcutaneous and intravenous administration of hCRF. Repetitive administration of hCRF did not result in accumulation but produced a reduced plasma cortisol response. A sigmoidal model related plasma hCRF concentrations to increase in heart rate (maximum, 39 beats x min(-1)). The relationship between the modest decrease in diastolic blood pressure and plasma hCRF concentrations was linear. CONCLUSION: The pharmacokinetics of intravenously administered hCRF were nonlinear, but apparent clearance was constant for various subcutaneous doses. An excellent bioavailability and preserved bioactivity make the subcutaneous route an attractive choice. Repetitive administration of hCRF probably caused tolerance of the cortisol response.

Adult↗
PubMed1993

Computer-controlled infusion of intravenous dexmedetomidine hydrochloride in adult human volunteers.

BACKGROUND: This investigation extended the pharmacokinetic analysis of our previous study, of intravenous dexmedetomidine in 10 healthy male volunteers, and prospectively tested the resulting compartmental pharmacokinetics in an additional six subjects using a computer-controlled infusion pump (CCIP) to target four different plasma concentrations of dexmedetomidine for 30 min at each concentration. METHODS: A three-compartment mamillary pharmacokinetic model best described the intravenous dexmedetomidine concentration versus time profile following the 5 min intravenous infusion of 2 micrograms/kg in our previous study. Nonlinear regression was performed using both two-stage and pooled data techniques to determine the population pharmacokinetics. The pooled technique allowed covariates, such as weight, age, and height of the subjects, to be incorporated into the nonlinear regression to test the hypothesis that these additional covariates would reduce the residual error between the measured concentrations and the predicted values. RESULTS: The addition of age, weight, lean body mass, and body surface area as covariates of the pharmacokinetic parameters did not improve the predictive value of the model. However, the model was improved when subject height was a covariate of the volume in the central compartment. The residual error in the pharmacokinetic model was markedly lower with the pooled versus the two-stage approach. The following pharmacokinetic values were obtained from the pooled analysis of the zero-order dexmedetomidine infusion: V1 = 8.05, V2 = 12.4, V3 = 175 (L), Cl1 = (0.0101*height [cm]) -1.33, Cl2 = 2.05, and Cl3 = 2.0 (L/min). Prospective evaluation of the pooled pharmacokinetic parameters using a computer-controlled infusion in six healthy volunteers showed the precision (average [(absolute error)/measured concentration]) of the CCIP to be 31.5% and the bias (average [error/measured concentration]) to be -22.4%. A pooled regression of the combined CCIP and zero-order data confirmed that the covariate, height (cm), was related in linear fashion to Cl1. A striking nonlinearity of dexmedetomidine pharmacokinetics related to concentration was observed during the CCIP infusion. The final pharmacokinetic values for the entire data set were: V1 = 7.99, V2 = 13.8, V3 = 187 (L), Cl1 = (0.00791*height [cm]) -0.927, Cl2 = 2.26, and Cl3 = 1.99 (L/min). CONCLUSIONS: Pharmacokinetics of dexmedetomidine are best described by a three-compartment model. Addition of age, weight, lean body mass, and body surface area do not improve the predictive value of the model. Additional improvement in CCIP accuracy for dexmedetomidine infusions would require magnification modification of the model based on the targeted concentration.

Adrenergic alpha-Agonists↗
PubMed1990

Pharmacokinetic investigations in elderly patients. Clinical and ethical considerations.

Over the past decade, clinical pharmacokinetic studies in the elderly, both healthy subjects and patients, have burgeoned. This data base has provided a useful first approximation to the understanding of age-related changes in drug disposition. It is now appropriate to reflect on the approach for future studies. The most accessible population, healthy elderly who are otherwise drug-free, may not provide completely relevant data for extrapolation to the very elderly, concurrently medicated patient population. Similarly, the most straightforward study, single dose drug exposure, may provide an incomplete understanding of pharmacokinetics during multiple dose drug administration in the very elderly patient. With careful attention to details of the study and informed consent procedures, it is appropriate to obtain the needed data.

Aged↗
PubMed1984

Peroxisome-associated enzymes and serum lipids in tumour-bearing rats treated with peroxisome-proliferating agents.

Xenobiotic induction of liver peroxisomes is associated with hypolipidemia. To test the involvement of the peroxisome proliferation with the hypolipidemia, male rats were inoculated in the groin with five different tumors: an aflatoxin-induced hepatoma, a lasiocarpine-induced hepatoma, an actinomycin-D-induced mesothelioma, a lasiocarpine-induced squamous cell carcinoma, and a methylnitrosourea-induced fibrosarcoma. After the tumours reached a suitable size, the rats were fed diets containing the peroxisome-proliferating hypolipidemic agents tibric acid (2-chloro-5-[3,5-dimethylpiperidinosulfonyl] benzoic acid) or Wy-14,643 ([4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid) for 2 weeks. Liver and tumor tissues were then assayed for the peroxisome-associated enzymes, catalase and carnitine acetyltransferase, and correlated with serum levels of triglyceride and cholesterol. The presence of the tumors caused a predictable decrease in liver catalase and a slight elevation of liver carnitine acetyltransferase. Serum cholesterol was elevated slightly, while serum triglyceride levels were elevated, unchanged, or decreased in the tumor-bearing rats maintained on control diet. Inclusion of the xenobiotics in the diet caused increases in liver weight, catalase, and carnitine acetyltransferase. Serum triglycerides were decreased in the three groups which were not already decreased, but a decrease in serum cholesterol was only found in one group after only one of the treatments. The latter finding demonstrates that peroxisomal enzyme induction can be dissociated from the decrease in serum cholesterol. The data were further evaluated by testing for correlations between the changes in these components, comparing changes within groups and between groups. These correlations indicate an inverse biological association between liver catalase and serum cholesterol and between liver carnitine acetyltransferase and serum triglyceride. The latter correlation was inverse only for comparisons between groups, suggesting that carnitine acetyltransferase activity is associated with serum triglycerides only during the perturbational state.

Acetyltransferases↗
PubMed1981

Methapyrilene kinetics and dynamics.

A study was undertaken to characterize the H1 receptor blockade, central nervous system depressant properties, and kinetic parameters of methapyrilene in man. Eight healthy subjects received, in random order at weekly intervals, placebo and methapyrilene 20 mg intravenously and 50 mg and 25 mg orally. Methapyrilene exhibited a moderate antihistaminic effect as measured by the reduction of histamine-provoked skin wheals. Sedation and drowsiness were detected only at the first sampling time (0.75 hr) after intravenous doses. The terminal plasma half-life ranged from 1.1 to 2.1 hr, apparent volume of distribution from 2.14 to 6.61 1/kg, and plasma clearance from 0.013 to 0.048 1/min/kg. Systemic bioavailability was low and showed large interindividual differences, ranging from 4% to 46%. Recovery of unchanged drug from the 24-hr urine was under 2% of the doses.

Adult↗
PubMed1980

Pharmacokinetics of hydralazine and its acid-labile hydrazone metabolites in relation to acetylator phenotype.

The pharmacokinetics of hydralazine (H) and its acid-labile hydrazone metabolites were compared in rapid and slow acetylators. Following a 20-mg intravenous infusion, the elimination half-life (t 1/2 beta) and the apparent volume of distribution of H did not differ between the two groups. Plasma clearance estimates approached hepatic blood flow. When a single 100-mg dose of H was given orally, the area under the plasma concentration-time curve (AUC) and a systemic availability (theta) in slow acetylators were, on the average, twice as high as in the rapid acetylators, indicating a difference in the extent of first-pass metabolism of the drug. Furthermore, the observed theta in the slow individuals exceeded theoretical predictions. Hence saturation of first-pass metabolism of H is suggested, and a nonlinear relationship between AUC and oral dose of H was indeed observed in the three subjects studied with two doses. The half-life of decline of the acid-labile metabolites was similar to the t 1/2 beta of H. The AUCs for metabolies were 4--12 times larger than for the parent drug. However, the ratio between the metabolite AUC and drug AUC did not differ irrespective of routes of administration or the acetylator status.

Acetylation↗
PubMed1980

Topical application of lindane cream (Kwell) and antipyrine metabolism.

The transcutaneous absorption of a 1% lindane cream (Kwell) was determined after application according to the official label. By 3 days after application the plasma lindane level increased from nondetectable to 10.3 +/- 2.2 ng/ml. Sufficient lindane was absorbed to increase the plasma clearance of antipyrine from 0.027 +/- 0.009 to 0.037 +/- 0.011 1/kg/hr (p less than 0.05). these findings indicate significant transcutaneous absorption of lindane occurs following a single application and are compatible with the neurological toxicity reported following the topical application of lindane cream.

Administration, Topical↗
PubMed1980

The effect of concurrent oral administration of propranolol and disopyramide on cardiac function in healthy men.

Sixteen healthy men were evaluated for left ventricular performance changes and beta-blockade after therapeutic oral doses of disopyramide and propranolol administered alone and concurrently. The volunteers were randomly assigned to receive one of two drug treatment regimens that differed in the sequence and duration of administration of the drugs. Left ventricular function was assessed by echocardiographically determined ejection fraction (EF) and systolic time intervals. Beta-blockade was assessed by changes in exercise heart rate. Both disopyramide and propranolol exhibited negative inotropic activity, as evidenced by significant, although clinically inconsequential, decreases in EF and increases in the ratio of preejection period to left ventricular ejection time. The negative inotropic effects of a single 200-mg dose of disopyramide and an 80-mg dose of propranolol were comparable, while chronic disopyramide therapy (200 mg every 6 hours for 1 week) had a greater negative inotropic effect than chronic propranolol therapy (80 mg every 8 hours for 1 week). Only propranolol had beta-adrenoceptor blocking activity. When the drugs were administered concurrently, the negative inotropic effects of oral propranolol and disopyramide were neither additive nor synergistic.

Administration, Oral↗
PubMed1979

Metabolic responses to plasma concentrations of theophylline.

We investigated the effect of intravenous infusions of aminophylline on plasma glucose, insulin (IRI), glucagon (IRG), growth hormone (HGH), cortisol, and free fatty acid (FFA) levels in healthy young subjects. Six received an intravenous loading dose of aminophylline (6.0 mg/kg over 20 min) followed by a maintenance dose (0.9 mg/kg/hr) for 100 min. Another 7 subjects initially received smaller loading (3.0 mg/kg) and maintenance (0.45 mg/kg/hr) doses, and after 60 min they received a second loading dose (3.0 mg/kg) followed by a larger maintenance dose (0.9 mg/kg/hr) over 120 min. In these fasting volunteers, infusion of aminophylline, which produced theophylline levels in the usual therapeutic range (10 to 20 microgram/ml) caused small increases in plasma glucose levels without changing IRI, IRG, HGH, or cortisol. There were rapid, pronounced, and prolonged rises in FFA associated with the aminophylline infusion. Increases in FFA paralleled the rise in theophylline levels. It is concluded that routine therapeutic doses of theophylline, i.e., doses that achieve serum levels normally encountered in treatment for bronchial asthma, cause a marked rise in FFA and a slight rise in glucose (8 +/- 3 mg/dl) without changing levels of IRI, IRG, HGH, or cortisol.

Adult↗
PubMed1979

Kinetics of pamatolol, a cardioselective beta adrenoreceptor blocker.

The systemic bioavailability, elimination half-life (t1/2), and plasma concentration--response relationships of pamatolol, a relatively cardioselective beta adrenoceptor blocker, have been measured in healthy subjects. Pamatolol is rapidly and completely absorbed after oral dosing. Elimination t1/2 ranged from 2.9 to 4.6 hr after oral doses and from 2.2 to 5.6 hr after intravenous doses. There was a clear relationship between log plasma pamatolol concentration and sympathetic blockade assessed by reduction of exercise heart rate. Concentration-response curves were essentially identical after oral and intravenous doses. There is no evidence of a first-pass effect, nor is there any evidence of metabolite activity.

Administration, Oral↗
PubMed1979

Tumors in male rats fed ethyl chlorophenoxyisobutyrate, a hypolipidemic drug.

Clofibrate (ethyl chlorophenoxyisobutyrate, Atromid-S), because it contains a chlorinated phenoxy moiety and is the most commonly used hypolipidemic drug in the United States and Europe, was fed at a concentration of 0.5% in the diet of 25 male F344 rats for 72 to 97 weeks, and the animals were inspected for tumors up to a maximum of 129 weeks. Between 72 and 129 weeks, there were 10 rats with a total of 16 tumors. These included 4 hepatocellular carcinomas, an adenocarcinoma of the glandular stomach, papillary carcinoma of the urinary bladder, acinar cell carcinoma of the pancreas, lymphosarcoma involving pancreas, acinar cell adenomas of the pancreas, renal carcinoma, and sarcomas of the lung and parotid gland. Although the number of experimental animals was small, none of these tumors were present in 25 controls, and systematic examination of available literature dealing with spontaneous tumors in several thousand rats indicated that the tumors in clofibrate-fed rats were not spontaneous. A number of the tumors were transplanted through several generations. Clofibrate, like two other hypolipidemic drugs that are carcinogenic, causes peroxisome proliferation. It is speculated that some drugs that cause peroxisome proliferation may represent a new class of chemical carcinogens and that there may be a relationship between peroxisome proliferation and malignant transformation.

Animals↗