Sign Out
Since the chemotherapy of tuberculosis involves the use of at least 2 drugs, the possible adverse reactions of each drug should be borne in mind as well as a possible interaction when used concomitantly.
Anticonvulsants: Isoniazid inhibits hepatic metabolism of carbamazepine and phenytoin, resulting in increased anticonvulsant concentrations and toxicity in some patients. If isoniazid and carbamazepine or phenytoin are administered concurrently, serum concentrations of the anticonvulsant should be monitored, the patient observed for evidence of toxicity and the dosage of the anticonvulsant should be reduced accordingly.
Aluminum Hydroxide Gel: Decreases gastrointestinal absorption of isoniazid; isoniazid should be administered at least 1 hour before the antacid.
Cycloserine: In combination with isoniazid may result in increased cycloserine CNS side effects such as dizziness or drowsiness.
Disulfiram: Coordination difficulties and psychotic episodes have occurred in patients receiving isoniazid and disulfiram; concurrent administration of the drugs should be avoided.
Rifampin: Hepatotoxicity has been reported to occur more frequently when rifampin and isoniazid are given concurrently. The incidence may be higher in slow isoniazid acetylators, those receiving high doses of isoniazid or those with pre-existing liver disease.
Ketoconazole: Concentrations may be decreased by isoniazid, possibly decreasing the antifungal effect.
Other Drugs: In addition, isoniazid may cause inhibition of metabolism of the following: acetaminophen, corticosteroids, diazepam, oral anticoagulants, primidone and theophylline. The patient should be observed for increased effect or toxicity of these agents.
