Isoniazid

Type of Medication: Antibiotic

Indications: Treatment (and prophylaxis) of Tuberculosis but always as a combination with other drugs.

Side Effects: Nausea, vomiting, peripheral neuritis with high doses (pyridoxine prophylaxis required), optic neuritis, fits, hypersensitivity reactions including fever, erythema multiforme, purpura.Blood disorders including agranulocytosis, haemolytic anaemia, aplastic anaemis, hepatitis (especially over age of 35:monitor hepatic function), SLE syndrome, pellagra, hyperglycaemia, gynaecomastia

Route of administration: Adult (Oral)

Dose:See BTS guidelines

Administration: Add 10 mg pyridoxine as prophylaxis to peripheral neuropathy see BTS guidelines. Take tablet preferably on an empty stomach, i.e. at least 30 minutes before a meal or 2 hours after a meal

Examples of some Drug Interactions

Interacting drug: Antacids

reduce isoniazid absorption

Interacting drug: Antiepileptics

metabolism of phenytoin and carbamazepine inhibited therefore increased plasma concentrations. Carbamazepine may enhance hepatotoxicity

Interacting drug: Cycloserine

Increased risk of CNS toxicity

Interacting drug: Diazepam

diazepam metabolism inhibited

Interacting drug: General anaesthetics

possible hepatotoxicity

Interacting drug: Ketoconazole

possible reduction of plasma ketaconazole levels.

Interacting drug: Theophyllines

possible increase in theophylline levels