Wade J. Adams

Specific and Sensitive High Performance Liquid Chromatographic Determination of Alprazolam or Triazolam

Abstract A specific and highly sensitive liquid chromatographic procedure has been developed for the rapid determination of intact alprazolam or triazolam in dog serum, using these structurally similar triazolobenzodiazepines as mutual internal standards. The procedure consists of (1) extracting one ml of alkali buffered serum with toluene, (2) evaporating an aliquot of the toluene to dryness, and (3) quantitating the redissolved residue by HPLC using ultraviolet detection (221 nm). Samples were chromatographed on a microparticulate reverse phase column using a mobile phase composed of acetonitrile: isopropanol: water (94:5:1) and a flow rate of 0.75 ml/min. Metabolites of alprazolam and triazolam did not interfere in the assay. The lower limit of detection was approximately 1 ng/ml of serum extracted. The utility of the analytical methodology for the determination of alprazolam or triazolam in pharmacokinetic studies in the dog was demonstrated.

High Performance Liquid Chromatographic Determination of Triazolam in Human Serum

Abstract A high performance liquid chromatographic method which utilizes UV-detection has been developed for the sensitive and specific determination of triazolam in human serum. Using 8-chloro-6-phenyl-l-ethoxymethyl-4H-s-triazolo[4, 3-a][1, 4]benzodiazepine as an internal standard, serum samples were buffered with 2 ml of 4M NaOH and extracted twice with 5 ml aliquots of toluene. The combined toluene extracts were evaporated to dryness and the residue dissolved in the chromatographic mobile phase. The samples were chromatography on a microparticulate reverse-phase column using a 0.06M acetic acid:acetonitrile (61:39) mobile phase. Known metabolites of triazolam did not interfere in the analysis. A linear relationship between peak height ratios and concentrations was observed, with the lower limit of detection being approximately 1 ng of triazolam. The utility of the method was demonstrated by administering therapeutic doses of the drug to human volunteers and monitoring serum triazolam concentrations as...

Influence of H2 receptor antagonists on the disposition of flurbiprofen enantiomers

The effect of oral cimetidine or ranitidine on the pharmacokinetics of the R and S enantiomers of the nonsteroidal anti‐inflammatory drug flurbiprofen and its major metabolite, 4′‐hydroxyflurbiprofen, was evaluated. Nine healthy volunteers participated in a randomized crossover design study with the following treatments: (A) flurbiprofen 200 mg; (B) flurbiprofen 200 mg plus ranitidine 150 mg bid for 7 days before and for 2 days after receiving flurbiprofen and (C) flurbiprofen 200 mg plus cimetidine 300 mg qid for 7 days before and for 2 days after receiving flurbiprofen. Blood and urine samples were collected at various intervals during a 48‐hour period. These samples were assayed stereospecifically for flurbiprofen and its metabolite.

A phase I clinical and pharmacokinetic study of the oral and the oral/intravenous administration of menogaril

SummaryThirty-five patients with advanced refractory cancer were enrolled on this phase I study of menogaril administered orally every 4 weeks at dosages ranging from 85 mg/m2 to 625 mg/m2. An additional 12 patients received alternating oral and IV doses of menogaril (250 mg/m2 IV; 250–500 mg/m2 oral) with accompanying blood and urine sampling for pharmacokinetics analysis. Nausea and vomiting were the dose-limiting toxicities at the 625 mg/m2 dosage level; vomiting was inadequately relieved by prophylactic antiemetics at this dosage level. Other toxicities included sporadic leukopenia at all dosage levels; at dosages of 500 mg/m2 and 625 mg/m2, leukopenia < 3000/μl occurred in 7 of 24 patients. Anemia and thrombocytopenia were much less frequent toxicities. Among the patients receiving IV menogaril, peripheral vein phlebitis, leukopenia and anemia were the predominant toxicities. No antitumor responses were observed, yet one patient with nonsmall cell lung cancer experienced a 30% reduction in metastatic tumor nodules.For the patients receiving alternating oral and IV menogaril, comparative pharmacokinetic analyses were performed by HPLC. After oral administration, maximum plasma concentrations were achieved in an average of 6 hours; maximum plasma concentrations were less than one-quarter of those achieved after intravenous administration. The harmonic mean (±SD) terminal disposition half-life after oral dosing was 29.3 ±9.2 hours; mean systemic bioavailability was 33.6±10.5% after oral dosing. Forty-eight hours after an oral dose, mean cumulative urinary excretions of menogaril and the primary metabolite, N-demethylmenogaril, were 4.00±0.96% and 0.44±0.16%, respectively.Because of the poor tolerance of oral menogaril and minimal evidence of biological activity, this schedule of drug administration is not recommended for phase II evaluation. Based on this and other published studies of oral menogaril, frequent chronic low-intermediate dosages of the drug may be given orally with potentially better tolerance and antitumor activity.

Noncompartmental Analysis for a One-Compartment Model with Equal Absorption and Elimination Rate Constants

In this communication, the calculation of noncompartmental pharmacokinetic parameters during multiple dosing is described for a one-compartment model in which the first-order absorption and elimination rate constants are equal

The Metabolic Background

Preclinical drug absorption, distribution, metabolism and excretion studies, collectively referred to as drug disposition studies, are of fundamental importance to the interpretation and rationalisation of animal pharmacology and toxicology data, and the extrapolation of these data to humans. An assessment of the exposure of animals and humans to a drug and its metabolites must be made on a more scientific basis than can be provided by simply comparing dosage levels. Dose alone is not a satisfactory index of exposure, especially when comparing across species, since the same dose may result in very different levels of exposure because of species variations in drug disposition, particularly variations in metabolism. Not only is the disposition of a drug species-dependent, but also a number of physiological, pathological, genetic and environmental factors are now known to influence the disposition of drugs in the same individual or population (Bousquet, 1970; Smith, 1988).