ABSTRACT
The relative risks of developing TB must be weighed against the risks of INH ther apy. All patients should be monitored for both compliance with therapy and adverse ef fects. Patients should be informed to notify their health care provider immediately for prompt evaluation if they experience symptoms suggestive of INH toxicity (anorexia, nausea, vomiting, dark urine, icterus, rash, paresthesias, persistent fatigue, weakness, ab dominal tenderness, or fever of greater than 3 days duration). Factors associated with increased risk of INH-induced hepatitis include advancing age, daily alcohol use, chronic liver disease, injection drug use, and concurrent therapy with medications with additional risks of hepatotoxicity. Postpubertal black and Hispanic women may also be at increased risk. In the absence of risk factors for INH toxicity, patients under 35 years of age should be evaluated monthly for signs and symptoms of toxicity. Patients over age 35 and those with other risk factors for INH toxicity should have hepatic enzymes measured prior to starting therapy and then monthly throughout treatment in addition to monthly clinical evaluation. INH should be discontinued if liver enzymes rise above three times normal values. Fatalities associated with INH-induced hepatitis are rare and are usually associated with continued administration of INH after the onset of drug-induced hepatitis. INH ther apy also carries a risk of peripheral neuropathy through interference with pyridoxine me tabolism. Although this is an uncommon side effect, patients with conditions associated with increased risk for neuropathy (diabetes, uremia, alcoholism, and malnutrition) as well as persons with seizure disorders and pregnant women should receive pyridoxine with INH. INH may also interfere with metabolism of certain drugs. Concurrent use with phenytoin leads to elevation of the levels of both INH and phenytoin, necessitating close monitoring of phenytoin levels and dosage adjustment.
