59 - Characteristics of antituberculous drugs

Drug Most Common Side Effects Tests for Side Effects Drug Interactions Isoniazid- Bactericidal to both extracellular and intracellular organisms. Pyridoxine, 10 mg orally daily as prophylaxis for neuritis; 50–100 mg orally daily as treatment. Peripheral neuropathy, hepatitis, rash, mild CNS effects. AST and ALT; neurologic examination. Phenytoin (synergistic); disulfiram. Rifampin- Bactericidal to all populations of organisms. Colors urine and other body secretions orange. Discoloring of contact lenses. Hepatitis, fever, rash, flu-like illness, gastrointestinal upset, bleeding problems, renal failure. CBC, platelets, AST and ALT. Rifampin inhibits the effect of oral contraceptives, quinidine, corticosteroids, warfarin, methadone, digoxin, oral hypoglycemics; aminosalicylic acid may interfere with absorption of rifampin. Significant interactions with protease inhibitors and nonnucleoside reverse transcriptase inhibitors. Pyrazinamide- Bactericidal to intracellular organisms. Hyperuricemia, hepatotoxicity, rash, gastrointestinal upset, joint aches. Uric acid, AST, ALT. Rare. Ethambutol- Bacteriostatic to both intracellular and extracellular organisms. Mainly used to inhibit development of resistant mutants. Use with caution in renal disease or when ophthalmologic testing is not feasible Optic neuritis (reversible with discontinuance of drug; rare at 15 mg/kg); rash. Red-green color discrimination and visual acuity (difficult to test in children under 3 years of age). Rare. Streptomycin- Bactericidal to extracellular organisms. Use with caution in older patients or those with renal disease. Eighth nerve damage, nephrotoxicity. Vestibular function (audiograms); BUN and creatinine. Neuromuscular blocking agents may be potentiated and cause prolonged paralysis.

AST, aspartate aminotransferase; ALT, alanine aminotransferase; CBC, complete blood count; BUN, blood urea nitrogen.

58 - Dexrazoxane

Dexrazoxane hydrochloride (Zinecard [Pfizer for USA & Canada]; Cardioxane [Novartis for EU & ROW]) is a cardioprotective agent.

It is used to protect the heart against the cardiotoxic side effects of anthracyclines, such as doxorubicin.

FDA has also approved a dexrazoxane hydrochloride drug, brand name Totect or Savene (developed by TopoTarget), for use as a treatment of extravasation resulting from IV anthracycline chemotherapy. Extravasation is an adverse event in which chemotherapies containing anthracylines leak out of the blood vessel and necrotize the surrounding tissue.

As a derivative of EDTA, dexrazoxane chelates iron, but the precise mechanism by which it protects the heart is not known.