Evaluating possible pharmacokinetic interactions between tobramycin, piperacillin, and a combination of piperacillin and tazobactam in patients with various degrees of renal impairment.

A study was performed to further investigate the apparent instability of tobramycin when coadministered with piperacillin/tazobactam in subjects with renal impairment. Twenty-six otherwise healthy volunteers between 23 and 74 years of age were studied. Eight subjects had moderate renal impairment, 10 had mild renal impairment, and 8 had normal renal function. Each subject received single doses of piperacillin/tazobactam and tobramycin alone as well as combined doses in a randomized, three-way crossover design. The subjects with normal renal function also received combined doses of piperacillin and tobramycin. Considerable care was taken to protect against in vitro inactivation of plasma and urine samples after collection. No systematic changes in pharmacokinetic parameters were observed. It is concluded that piperacillin, either alone or with tazobactam, did not change the pharmacokinetics of tobramycin in subjects with renal impairment. The apparent in vivo inactivation of tobramycin in the presence of piperacillin or piperacillin/tazobactam reported by others may be an artifact of ex vivo inactivation.

Pharmacokinetic evaluation of zeniplatin in humans.

Zeniplatin, a more water-soluble organoplatinum than cisplatin, was evaluated for clinical pharmacology in the context of a phase II trial in previously treated patients with ovarian carcinoma. A total of 12 patients were given zeniplatin at 120 mg/m2 by rapid intravenous infusion over 90 min, with both blood and urine being sampled. All platinum moieties were analyzed in whole blood, plasma, plasma ultrafiltrate, and urine by atomic absorption, and free zeniplatin was analyzed in plasma ultrafiltrate by specific high-performance liquid chromatography (HPLC). In a comparison of the platinum-time concentration curve, AUC (area under the curve) values indicated that approximately 90% of platinum moieties were bound to circulating plasma proteins. There was no evidence of drug accumulation after repetitive dosing. The terminal half-life (t1/2) of this drug in plasma ultrafiltrate (3.7-7.2 h.) as measured by HPLC was slightly longer than that of carboplatin, whereas total platinum moieties in plasma displayed a long t1/2 (124-154 h). Approximately 60% of platinum moieties could be recovered in the urine within 24 h. These findings suggest that zeniplatin has a pharmacokinetic profile similar to that of carboplatin.

Analysis of enloplatin by liquid chromatography and of platinum by atomic absorption spectrometry in various biological fluids.

Analytical methods were developed and validated for the determination of enloplatin (an anticancer agent) in plasma by reversed-phase LC and for platinum (an elemental component of enloplatin) in plasma, plasma ultrafiltrate (PUF) and whole blood by flameless atomic absorption spectrometry (FAAS). The LC procedure involved protein precipitation with dilute perchloric acid. The supernatant was mixed with sodium phosphate buffer and injected into the LC system. A C18 or a cyano column was used, depending on sample matrix, with UV detection at 230 nm. The LC method was linear from 0.50 to 50.0 micrograms ml-1. Inter-day and intra-day precision (RSD%) and accuracy (relative error%) were < +/- 14%. The FAAS procedure utilized a graphite furnace, a hollow cathode platinum (Pt) lamp, and Zeeman background correction. An aliquot of plasma, PUF, or whole blood was mixed with a solution of Triton X-100 and Antifoam-B and injected into the FAAS system. The FAAS method showed goodness of fit from 0.05 to 10.0 micrograms Pt/ml. Inter-day and intra-day precision and accuracy were < +/- 15%. The methods were developed to support pharmacokinetic studies in humans, dogs and rats.

A placebo-controlled evaluation of single, escalating doses of CL 284,846, a non-benzodiazepine hypnotic.

This report describes the first evaluation in humans of CL 284,846, a non-benzodiazepine compound with a preclinical profile indicative of sedative/hypnotic properties. Healthy, normal male volunteers were assigned randomly to receive single oral doses of 1, 5, 15, 30, or 60 mg of CL 284,846 or placebo on a double-blind basis. Observations were made over the subsequent 25 hours to determine the safety, pharmacokinetic profile, and psychometric effects of the test compound. CL 284,846 was well tolerated in the normal volunteers, causing no significant changes in vital signs, EEG, ECG, hematologic, or clinical chemistry laboratory parameters. Although few adverse events were noted at doses less than 60 mg, at the highest dose (60 mg), all volunteers reported transient neurologically related adverse events (e.g., impaired concentration, difficulty focusing, and impaired coordination), reflecting the central nervous system action of the compound. Although determination of hypnotic efficacy was not an objective in this Phase I study, daytime treatment with 60 mg of CL 284,846 was associated with greater reports of drowsiness and impaired performance on psychomotor tests. However, memory, as assessed by a word recall test, was not affected at any dose of the compound. Pharmacokinetic analyses revealed CL 284,846 to be absorbed and eliminated rapidly (Tmax = 0.9-1.5 hr, T 1/2 = 0.9-1.1 hr), with a dose-proportional AUC (area under cure). Plasma levels of CL 284,859, the primary desethylated metabolite of CL 284,846, were much lower in humans than in other species, indicating that the metabolism of CL 284,846 in humans may differ from that of rodents and dogs. Overall, CL 284,846 was well tolerated, and the authors recommend repeating dose safety and pharmacokinetic studies in healthy volunteers.