[The effect of ranitidine on theophylline pharmacokinetics in patients with obstructive lung disease]

The study was performed in 20 patients with mild and moderately severe forms of bronchial asthma or chronic obstructive bronchitis. Theophylline for oral use (sustained release form) and ranitidine was used in the first group of patients (7 females and 3 males, mean years of age 37.9). Dosage of theophylline from patients' sera was monitored prior and at 3, 6, and 12 hours beginning with the initial morning dose. The second group of patients (9 females and 1 male, mean age 46.3 years) were on ranitidine therapy along with 250 mg intravenous theophylline-ethylene-diamine. Fractionated dosage of theophylline was made within 12 hours. Pharmacokinetic parameters were calculated according to the concentration of theophylline in the sera of patients in the second group. In the sera of patients in the first group significantly higher concentrations of theophylline were found at 3 and 6 hour of the initial morning dose (p less than 0.05). In the second group a significant difference was not registered for the assessed pharmacokinetic parameters. This investigation indicates that there are individual differences of the metabolism of theophylline drugs with concommitant use of ranitidine.