Enzyme immunoassay of theophylline with the Abbott ABA-100

The effects of cimetidine on theophylline pharmacokinetics at steady state

The effects of cimetidine on the pharmacokinetics of theophylline were studied in seven healthy subjects at steady state after oral dosing. Aminophylline (200 mg) was administered every six hours for three days (A), then aminophylline (200 mg) and cimetidine (300 mg) were administered every six hours for seven days (A-C). Multiple serum theophylline determinations were made after the last dose on each regimen using an enzyme immunoassay. Cimetidine decreased the apparent total body clearance of theophylline an average of 29 percent (range: 18-47 percent) from 39.5 +/- 11.7 to 28.1 +/- 3.4 ml/hr/kg (p less than 0.02). There was no significant change in the volume of distribution; however, the terminal half-life increased from 7.3 +/- 1.5 to 10.1 +/- 2.1 hr (p less than 0.01) during A and A-C, respectively. The increase in the average steady state serum theophylline concentration of 34 percent (range: 23-87 percent) observed in our subjects may have important clinical implications.

Enzyme immunoassay of gentamicin with the Abbott ABA-100 analyzer

The enzyme immunoassay of gentamicin using "EMIT" reagents was adapted to take advantage of the small reagent volume required by the Abbott ABA-100. The method increases fourfold the maximum number of tests per kit. The correlation with the bacterial inhibition method was 98%.

Determination of plasma theophylline by straight-phase high-performance liquid chromatography: elimination of interfering caffeine metabolites

Several authors have recently reported interference in theophylline analysis by paraxanthine (1,7-dimethylxanthine), an important metabolite of caffeine. A method for the determination of theophylline in plasma is described, eliminating caffeine and related compounds by means of straight-phase high-performance liquid chromatography. The resulting procedure is sufficiently rapid, accurate and sensitive to be applied in routine monitoring of therapeutic levels in patients as well as for pharmacokinetic purposes. Although only 0.1 ml of sample is required, concentrations as low as 0.2 mg/l can be measured with acceptable precision. A brief comparative evaluation of this procedure with a radioimmunoassay is made.

Enzyme immunoassay of phenobarbital, phenytoin, primidone, carbamazepine and theophylline with the Abbott VP Bichromatic Analyzer

The enzyme multiplied immunoassay technique (EMIT) for the assay of phenobarbital, phenytoin, primidone, carbamazepine and theophylline was adapted to the Abbott VP Bichromatic Analyzer. Reagent consumption is reduced by the use of a stable working dilution of EMIT reagent B in EMIT buffer. Correlation with the standard EMIT method is excellent. This procedure greatly increases the maximum number of tests per kit. The method is an accurate and economical alternative to the standard EMIT method.