Tuberc Respir Dis.  1990 Mar;37(1):52-58. 10.4046/trd.1990.37.1.52.

Drug Interactions between Theophylline and H2-antagonists; Ranitidine, Famotidine

• KMID: 2528511
• DOI: http://doi.org/10.4046/trd.1990.37.1.52

Abstract

Among the H2 antagonists, cimetidine is known to impair theophylline metabolism. But there are some controversies about the effects of ranitidine and famotidine on theophylline pharmacokinetics We experienced a 53-year-old male patient who showed significant decrease of theophylline clearance with ranitidine and recovery after raniticline withdrawal. To investigate drug interactions between ranticline, famotidine and theophylline, six healthy adults were given a 6 mg/ kg aminophylline intravenously on three occasions, without H2-antagonists, with ranitidine 300 mg/ clay, with famotidine 40 mg/ clay for 4 clays. and serum theophylline levels were measured at 0, 1/ 4, 1/ 2, 1, 2, 4, 8, and 24 hour after aminophylline infusion. Ranitidine and famotidine administrations were cross-overed. Ranitidine decreased theophylline clearance by 14% (range 1% to 22%) and increased elimination half-life by 36% (range 20%to 50%). Our data suggest that clinically significant inhibition of theophylline metabolism by raniticline is largely dependent on pretreatment theophylline clearance Famotidine did not significantly alter theophylline pharmacokinetics, but there was great individual variability. We suggest that regular estimations of serum theophylline level is necessary to avoid theophylline toxicity with H2-antagonists; ranitidine and famotidine.