Famotidine and theophylline pharmacokinetics. An unexpected cimetidine-like interaction in patients with chronic obstructive pulmonary disease.

The results of research studies conducted to date in vitro and in healthy volunteers are practically all concordant in demonstrating the lack of any kind of interference between famotidine and microsomal oxidative metabolism. The pharmacokinetics (elimination half-life, area under the plasma concentration-time curve, clearance and volume of distribution) of theophylline 3.4 mg/kg as an intravenous infusion over 5 min (a dosage previously used to test drug interactions with cimetidine and ranitidine) were evaluated in 7 patients with chronic obstructive pulmonary disease (COPD) and peptic ulcer disease before and after 8 days' treatment with famotidine 40mg at night. The results indicate that famotidine can induce substantial and statistically significant slowing of theophylline elimination with a cimetidine-like interaction profile.