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A radioenzymatic assay and a "high-performance" liquid chromatographic assay for chloramphenicol were compared by using 52 patient specimens, 24 mock unknowns, and 13 quality control samples. Both methods were found to be rapid, precise, accurate, and sensitive, and either would be suitable for monitoring chloramphenicol concentrations in small volumes of serum. Linear regression analysis of serum chloramphenicol concentrations in patients receiving chloramphenicol succinate yielded a regression equation of Y = 1.04X + 0.274 (X = high-performance liquid chromatographic assay; Y = radioenzymatic assay), with a correlation coefficient of 0.971.

The pharmacokinetics of piperacillin were studied in 15 pediatric patients (age range, 3.3 to 14.3 years). Piperacillin was administered in a dosage of 1.5 +/- 0.4 g/m2 (mean +/- standard deviation) every 4 to 6 h. Peak serum concentrations ranged from 69 to 354 micrograms/ml. The mean elimination half-life was 37.0 +/- 13.3 min, which is shorter than that observed in most adults with normal renal function. The mean elimination half-life in three patients with renal impairment was 60.1 +/- 12.4 min, and the mean ratio of renal clearance to total clearance was 0.57. These results suggest a significant nonrenal elimination of piperacillin. Based on these data, a dosage of 1.5 g/m2 given as a 30-min infusion every 4 h is suggested for children with normal renal function. For patients with renal impairment, the daily dosage could be calculated as follows: corrected dose = normal dose x (0.35 + [0.65 x (ClCr/0.06)]), where ClCr is the creatinine clearance expressed as liters per minute per square meter.

To evaluate the effect of activated charcoal on aminoglycoside pharmacokinetics, six healthy volunteers received tobramycin intravenously with and without multiple oral doses of activated charcoal. Activated charcoal did not have a statistically significant effect on any pharmacokinetic parameter. We conclude that activated charcoal does not enhance tobramycin clearance in subjects with normal renal function when concentrations in serum are within the therapeutic range.

We describe a rapid, precise, and simple procedure for the quantitation of azlocillin in serum and in aqueous solutions by high-pressure, reverse-phase liquid chromatography. This method uses a single precipitation step, detection by dual-wavelength monitoring (220 and 254 nm), and quantitation by comparison with an internal standard. The 10-micron C18 muBondapak column was eluted with 45% (vol/vol) methanol-65% (vol/vol) phosphate buffer. The precision was 4.2 and 5.6% at 50 and 10 micrograms/ml, respectively. The assay was linear up to concentrations of 100 micrograms/ml, with recoveries of 90.4 to 110.5% from serum. The assay was sensitive to 0.4 micrograms of azlocillin per ml. The short turnover time (14 min) and small serum sample size (20 microliters) make the assay ideal for therapeutic drug monitoring and clinical pharmacokinetic studies.

We compared the accuracy, precision, and between-method error of the microbiological assay, the radioenzymatic assay, the homogeneous enzyme immunoassay, and the high-performance liquid chromatographic assay for the quantitation of gentamicin in serum. Precision and accuracy were evaluated by reference samples prepared to contain 0.0 to 32.7 micrograms of gentamicin per ml. Correlations between the methods utilized patient sera with gentamicin concentrations ranging from 0.6 to 13.3 micrograms/ml. All methods were reliable within acceptable limits for routine clinical use; intermethod correlation coefficients exceeded 0.96. Relative to the microbiological assay, the alternative methods offer the advantage of rapid analysis. The elapsed times for acquiring data on a set of 10 specimens under routine operating conditions were 0.5 h by the enzyme immunoassay, 4 h by the radioenzymatic assay, 5 h by the high-performance liquid chromatographic assay, and 10 h by the microbiological assay.

We describe a reverse-phase high-pressure liquid chromatography method for the quantitation of a new quinoline carboxylic acid antimicrobial agent, ciprofloxacin (Bay o 9867). This assay utilizes the intrinsic fluorescence of ciprofloxacin for primary detection but employs UV absorption as a secondary detection system. Mobile phases contained methanol and phosphate buffer and used a common C18 mu Bondapak column. A single precipitation step of a 50-microliter specimen was the only sample preparation necessary. The assay is linear from 2,000 to 10 ng/ml and sensitive to 5 ng/ml. The mean recovery of ciprofloxacin from serum was 105.7%. The coefficient of variation was less than or equal to 3.1% for same-day precision and less than or equal to 6.3% for assay-to-assay precision. Because the assay requires only small specimen volumes and minimal sample preparation and because of its defined characteristics, this assay would be ideal for clinical trials and pharmacokinetics studies of ciprofloxacin.