Isoniazid skin tests

Tuberculosis Persons with positive tuberculin skin tests and one or more of the following (a) HIV infection, (b) close contacts with newly diagnosed disease, (c) recent skin test conversion, (d) medical conditions that increase the risk of developing tuberculosis, (e) age < 35 Isoniazid, rifampin, or pyrazinamide Excellent... 

Aside from consideration of drug toxicity, some antimicrobial use requires more in tensive risk-benefit analysis. An example of this is the decision to use isoniazid prophylactically to prevent tuberculosis. Because the hepatotoxicity of isoniazid increases in frequency with age, older persons (>45 years) who are candidates for isoniazid prophylaxis (positive skin test) must have additional risk factors for tuberculosis to balance the potential toxic effects. These include evidence of recent skin-test conversion, immunosuppression, or previous gastrectomy. Older patients without additional risk factors are more likely to suffer toxicity from isoniazid than derive benefit from its use. ... 

For recent skin-test converters of all ages, the risk of active TB outweighs the risk for drug toxicity.Pregnant women, alcoholics, and patients with poor diets who are treated with isoniazid should receive pyridoxine (vitamin Bg) 10-50 mg daily to reduce the incidence of central nervous system (CNS) effects or peripheral neuropathies. All patients who receive treatment of LTBl should be monitored monthly for adverse drug reactions and for possible progression to active TB. 

The use of prophylactic isoniazid therapy for transplant patients with evidence of exposure to M. tuberculosis (those with a positive purified protein derivative skin test) remains controversial. Risk of reactivation and development of clinical tuberculosis is enhanced with posttransplant immunosuppression. Some clinicians believe, however, that the risk of isoniazid-induced hepatotoxicity, especially in liver transplant recipients, in whom the rate of hepatotoxicity has been reported as high as 40%, outweighs the benefits of treatment. High-risk patients who may be considered for isoniazid prophylaxis include those with a positive skin test, those with previously diagnosed tuberculosis who may not have been treated adequately, patients in close contact with individuals with active pulmonary disease, and patients with abnormal chest radiographs consistent with old tuberculosis who have not received prior prophylaxis. " ... 

Infliximab therapy is associated with increased incidence of respiratory infections of particular concern is potential reactivation of tuberculosis or other granulomatous infections with subsequent dissemination. The FDA recommends that candidates for infliximab therapy should be tested for latent tuberculosis with purified protein derivative, and patients who test positive should be treated prophylactically with isoniazid. However, anergy with a false-negative skin test has been noted in some patients with Crohn s disease, and some experts routinely perform chest radiographs to look for active or latent pulmonary disease. Infliximab also is contraindicated in patients with severe congestive heart failure. The significant cost of infliximab is an important consideration in some patients. 

The patient s gastrointestinal symptoms diminished, but several months later the patient complained of feeling weak and presented with symptoms of thrush. At this time his CD4 count was 300/pL, viral load was 11,000 copies/rnL, and a tuberculin skin test iim positive. The attending physician prescribed clotrimazole troches, isoniazid plus pyridoxine, and indinavir to supplement the combination of zidovudine and lamivudine. 

Tuberculosis chemoprophylaxis has been retrospectively evaluated in 63 Spanish patients with latent tuberculosis out of 497 with inflammatory bowel disease who were candidates for anti-TNFa therapy [31 ]. Skin tests for tuberculosis were positive in 86% after a single exposure, but 14% needed a booster. There were no susceptibility factors for hepatotoxicity. All but one was treated with isoniazid alone for 6 or 9 months, and only one required chemoprophylaxis withdrawal because of hepatotoxicity. There were no cases of active tuberculosis in the patients who were treated with anti-TNFa therapy. The authors concluded that chemoprophylaxis is safe in patients with inflammatory bowel disease, even in those taking concomitant, potentially hepatotoxic drugs. 

Bomb et al. (1976) report a case of Stevens-Johnson syndrome caused by isoniazid which deared up completely after discontinuation of the drug and corticosteroid therapy. There was recurrence of the skin rash after a test dose of isoniazid, proving that this medicament was the offending agent. 

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