Investigation of the influence of acetylsalicylic acid on the steady state of long-term therapy with theophylline in elderly male patients with normal renal function

Effects of aspirin on arylamine N -acetyltransferase activity and DNA adducts in human bladder tumour cells

Aspirin (acetylsalicylic acid) was used to determine the inhibition of arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in a human bladder tumour cell line (T24). The activity of NAT was measured by high-performance liquid chromatography, assaying for the amounts of N-acetyl-2-aminofluorene and N-acetyl-p-aminobenzoic acid and remaining 2-aminofluorene and p-aminobenzoic acid. Two assay systems were used: one with cytosol and the other with intact cells. High-performance liquid chromatography was also used to analyse for the 2-aminofluorene-DNA adducts. Intact bladder tumour cells were used. The results demonstrated that NAT activity and 2-aminofluorene-DNA adduct formation in human bladder tumour cells were inhibited by acetylsalicylic acid in a dose-dependent manner. The effects of acetylsalicylic acid on the values of the apparent K(m) and V(max) were also determined in both examined systems. The data also indicated that acetylsalicylic acid decreased the apparent values of K(m) and V(max) from human bladder tumour cells in both cytosol and intact cells.

Concurrent administration of donepezil HCl and theophylline: assessment of pharmacokinetic changes following multiple-dose administration in healthy volunteers

AIM

The aim of the study was to evaluate the pharmacokinetics of theophylline administered alone, and in combination with donepezil HCl, following multiple-dose administration of both drugs in healthy volunteers.

METHODS

This was an open-label, randomized, two-period crossover study in healthy male volunteers (n=12). During each treatment period, subjects received either titrated-dose theophylline alone, or in combination with donepezil (5 mg, once daily) for 10 consecutive days. On day 10 of each treatment period, serial blood samples for the determination of theophylline concentrations in plasma were measured up to 24 h. Treatment periods were separated by a 3-week, drug-free washout. Plasma concentrations of theophylline were determined by HPLC with UV detection.

RESULTS

No statistically significant differences in theophylline pharmacokinetics (Cmax, AUC or tmax) were observed between theophylline administered alone and in combination with donepezil. No clinically significant changes in vital signs, ECG parameters or clinical laboratory tests were observed in any subject during any treatment period.

CONCLUSIONS

Concurrent administration of donepezil HCl does not alter the pharmacokinetic profile of theophylline following multiple-dose administration of both drugs in healthy volunteers. These findings suggest that donepezil may be safely co-administered with theophylline without a need for dose modification or additional monitoring procedures.

Effects of aspirin on arylamine N-acetyltransferase activity in Klebsiella pneumoniae

This study was designed to assess the effects of aspirin on arylamine N-acetyltransferase (NAT) activities in the bacterium Klebsiella pneumoniae using high performance liquid chromatography to measure the acetylation of 2-aminofluorene (2-AF) with or without aspirin. Cytosols or suspensions of K. pneumoniae with or without specific concentrations of aspirin co-treatment showed different percentages of 2-AF acetylation. The data indicated that there was decreased NAT activity associated with increased levels of aspirin in K. pneumoniae cytosols and in intact bacteria. For the cytosol examination, the apparent values of Km and Vmax decreased 0.59- and 0.58-fold after co-treated with 40 microM aspirin, respectively, for 2-AF. For the intact bacteria examination, the apparent values of Km and Vmax decreased 0.60- and 0.67-fold after co-treated with 40 microM aspirin, respectively, for 2-AF. This report is the first demonstration to show that aspirin can decrease N-acetyltransferase activity in the bacterium K. pneumoniae.