Effect of ranitidine on the pharmacokinetics of theophylline in patients with obstructive pulmonary disease

: Investigations were performed on 20 patients with mild and moderately severe forms of bronchiale asthma or chronic obstructive bronchitis. Theophylline for oral use (sustained release form) and Ranitidine (second generation H2-blocker) were used in the first group of patients (7 females and 3 males, average age 37.9). Dosage of theophylline from patients sera was monitored at 3, 6 and 12 hours, beginning with the initial morning dose. The second group of patients (9 females and 1 male, average age 46.3) were on Ranitidine therapy, along with 250 mg intravenous theophylline-ethylene-diamine. Fractionated dosage of theophylline was done within 12 hours. Pharmacokinetic parameters were calculated according to the concentration of theophylline in the sera of patients in the second group. Significant differences were not found by statistical analysis (T-test) in the pharmacokinetic parameters of theophylline although significantly higher concentrations of theophylline were found in the sera of patients in the first group. This indicated that there are individual differences on the metabolism of theophylline drugs with concomitant use of Ranitidine.