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Unknown General 04f019e4

Which of the following do not increase the action of warfarin?

A
Cimetidine
B
Isoniazid
C
Rifampicin
D
Cotrimoxazole
High-Yield Explanation
Reference: KDT, Essentials of Medical Pharmacology, 7th ed., Pg. 623 and Katzung, Basic & Clinical Pharmacology, 13th ed., Pgs. 876 & 877.   Barbiturates (but not benzodiazepines), carbamazepine, rifampin and griseofulvin induce the metabolism of oral anticoagulants. The dose of anticoagulant determined during therapy with these drugs would be higher: if the same is continued after withdrawing the inducer—marked hypoprothrombinemia can occur—fatal bleeding is on record. Metronidazole, fluconazole, and trimethoprim-sulfamethoxazole also stereoselectively inhibit the metabolic transformation of S-warfarin, whereas amiodarone, disulfiram, and cimetidine inhibit metabolism of both enantiomorphs of warfarin. Barbiturates and rifampin cause a marked decrease of the anticoagulant effect by induction of the hepatic enzymes that transform racemic warfarin.

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