Rifampicin and isoniazid are active bactericidal anti-TB drugs which are particularly active against the rapidly growing extracellular organisms and also have bactericidal activity intracellularly. Rifampicin inhibits DNA-dependent RNA polymerase activity in susceptible cells. Specifically, it interacts with bacterial RNA polymerase but does not inhibit the mammalian enzyme. Cross-resistance to rifampicin has only been shown with other rifamycins. It has activity against slow-and intermittently-growing M. tuberculosis. Isoniazid acts against actively growing tubercle bacilli.
Oral Tuberculosis Adult: Each tab contains rifampicin and isoniazid (mg): <50 kg: 3 tab of 150/100 once daily; -50 kg once daily: 2 tab of 300/150 once daily. Should be taken on an empty stomach. Take at least - hr before or 2 hr after meals.
May reduce effectivity of hormonal contraceptives. Reduced absorption with antacids. May decrease plasma concentrations of antivirals (e.g. atazanavir, darunavir, fosamprenavir), atovaquone with rifampicin. Rifampicin may reduce serum levels of anticonvulsants (e.g. phenytoin), antiarrhythmics (e.g. disopyramide), oral anticoagulants, antifungals (e.g. ketoconazole), barbiturates, ?-blockers, Ca channel blockers (e.g. diltiazem), chloramphenicol, clarithromycin, corticosteroids, ciclosporin, cardiac glycosides, clofibrate, dapsone, diazepam, doxycycline, fluoroquinolones (e.g. ciprofloxacin), haloperidol, oral hypoglycemic agents (sulfonylureas), levothyroxine, methadone, narcotic analgesics, progestins, quinine, tacrolimus, theophylline, TCAs (e.g. amitriptyline, nortriptyline) and zidovudine. Increased risk of hepatotoxicity with halothane.
Isoniazid may inhibit the metabolism of anticonvulsants (e.g. carbamazepine, phenytoin), benzodiazepines (e.g. diazepam), haloperidol, ketoconazole, theophylline, and warfarin. May enhance the CNS effects of meperidine, cycloserine, and disulfiram with isoniazid. Loss of glucose control in patients on oral hypoglycaemics with isoniazid.
Hypersensitivity. Patient w/ jaundice. Concomitant use w/ saquinavir/ritonavir combination. History of DM, psychosis, peripheral neuropathy. Patient w/ HIV infection, porphyria, malnutrition, slow acetylator status, epilepsy and alcohol dependence. Hepatic and severe renal impairment. Elderly. Pregnancy and lactation.
GI symptoms (e.g. anorexia, nausea, vomiting, constipation, diarrhoea), alterations in liver function, peripheral neuritis, optic neuritis, headache, drowsiness, convulsions, vertigo, blood disorders (e.g. leucopenia, haemolytic anaemia, aplastic anaemia, eosinophilia), dry mouth, itching w/ or w/o rash, flushing, urticaria, rash, purpura, pancreatitis, oedema, interstitial pneumonitis, hyperreflexia, hyperglycaemia, adrenal insufficiency, gynaecomastia, menstrual disturbances, difficulty in micturition, muscular weakness, myopathy, SLE-like syndrome, pellagra, exfoliative dermatitis, pemphigus, toxic epidermal necrolysis, pemphigoid reactions, orange-red discolouration of urine, saliva and other body secretions; hearing loss and tinnitus, influenza-like symptoms, resp symptoms, collapse and shock, thrombocytopenic purpura, disseminated intravascular coagulation, acute renal failure. Rarely, psychoses, pemphigoid reaction, erythema multiforme, Lyells syndrome and vasculitis.
Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.
Keep below 30°C temperature, away from light & moisture. Keep out of the reach of children.
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