title: Diltiazem treatment impairs theophylline elimination in patients with bronchospastic airway disease.
abstract: On the basis of reports that diltiazem may bind to the hepatic microsomal enzymes and inhibits the metabolism of some co-administered drugs, and to determine the effects of diltiazem on theophylline pharmacokinetics in patients with bronchospastic airway disease, we have investigated the effect of a 180-mg daily dose of oral diltiazem during 5 days on theophylline clearance in eight patients with that disease. Theophylline half-life increased 24%, from 5.7 +/- 1 to 7.5 +/- 1.8 h (p < 0.05), and total body theophylline clearance showed a decrease of 22%, from 87.3 +/- 20 to 68.3 +/- 18.6 ml/min (p < 0.05) after diltiazem therapy. The apparent volume of distribution was unchanged. This reduction in theophylline clearance is likely produced by inhibition of its metabolism by diltiazem. A clinically important drug interaction may occur with theophylline when diltiazem therapy is given concurrently in patients with bronchospastic airway disease.
authors.affiliation: Clinical Pharmacology Unit, Hospital Santa Cruz, Liencres-Cantabria, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Soto
authors.forename: J A
authors.initials: JA
authors.lastname: Sacristan
authors.forename: M J
authors.initials: MJ
authors.lastname: Alsar
mesh_terms: D000368:Aged; D001986:Bronchial Spasm / Q000188:drug therapy / Q000378:metabolism*; D004110:Diltiazem / Q000009:adverse effects*; D004347:Drug Interactions; D005260:Female; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged; D013806:Theophylline / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D013806:Theophylline; D004110:Diltiazem