<s>[INST] context: Isoniazid (lsonicotinic acid hydrazide, H): Isoniazid is the antitubercular drug parexcellence, and an essential component of all antitubercular regimens, unless the patient is not able to tolerate it or bacilli are resistant. lt is primarily tuberculocidal. Fast multiplying organisms are rapidly killed, but quiescent ones are only inhibited. It acts on extracellular as well as on intracellular TB (bacilli present within macrophages); is equally active in acidic and alkaline medium. It is one of the cheapest antitubercular drugs. However, most atypical mycobacteria are not inhibited by INH. Pharmacokinetics: INH is completely absorbed orally and penetrates all body tissues, tubercular cavities, placenta and meninges. Adverse effects :INH is well tolerated by most patients. Peripheral neuritis and a variety of neurological manifestations (paresthesias, numbness, mental disturbances, rarely convulsions) are the most impoant dose-dependent toxic effects. These are due to interference with utilization of pyridoxine and its increased excretion in urine ( see Ch. 67). Pyridoxine given prophylactically 1 10 mg I day) prevents the neurotoxicity even with higher doses, but routine use is not mandatory. INH neurotoxicity is treated by pyridoxine lOO mg/day. Hepatitis, a major adverse effect of iNH, is rare in children, but more common in older people and in alcoholics. It is due to dose-related damage to liver cells and is reversible on stopping the drug. Other side effects are rashes, fever, acne and ahralgia. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:740,741 [/INST] question: Which anti-tubercular drug is implicated in the causation of transient memory loss? | options: A: Ethionamide B: Isoniazid C: Ethambutol D: Pyrazinamide | answer: B </s>