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KMID : 0383819900370010052
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Tuberculosis and Respiratory Diseases
1990 Volume.37 No. 1 p.52 ~ p.58
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Drug Interactions between Theophylline and H2-antagonists; Ranitidine, Famotidine
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Cho Sang-Heon
Cho Young-Joo
Kim Mi-Kyung
Kwon Oh-Jung
Lee Chun-Taek
Lee Sang-Do
Min Kyung-Up
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Abstract
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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 ranitidine withdrawal. To investigate drug interactions between ranitidine, famotidine and theophylline, six healthy adults were given a 6 ㎎/㎏ aminophylline intravenously on three occasions; without H2-antagonists, with ranitidine 300 ㎎/day, with famotidine 40㎎/day for 4 days, and strum 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 crossovered. 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 ranitidine 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.
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