Ethambutol Hydrochloride

Clinical summary

Indications and usage INDICATIONS AND USAGE Ethambutol hydrochloride is indicated for the treatment of pulmonary tuberculosis. It should not be used as the sole antituberculous drug, but should be used in conjunction with at least one other antituberculous drug. Selection of the companion drug should be based on clinical experience, considerations of comparative safety and appropriate in-vitro susceptibility studies. In patients who have not received previous antituberculous therapy, i.e., initial treatment, the most frequently used regimens have been the following: Ethambutol plus isoniazid Ethambutol plus isoniazid plus streptomycin. In patients who have received previous antituberculous therapy, mycobacterial resistance to other drugs used in initial therapy is frequent. Consequently, in such retreatment patients, ethambutol should be combined with at least one of the second line drugs not previously administered to the patient and to which bacterial susceptibility has been indicated by appropriate in-vitro studies. Antituberculous drugs used with ethambutol have included cycloserine, ethionamide, pyrazinamide, viomycin and other drugs. Isoniazid, aminosalicylic acid, and streptomycin have also been used in multiple drug regimens. Alternating drug regimens have also been utilized. Dosage and administration DOSAGE AND ADMINISTRATION Ethambutol hydrochloride should not be used alone, in initial treatment or in retreatment. Ethambutol hydrochloride should be administered on a once every 24-hour basis only. Absorption is not significantly altered by administration with food. Therapy, in general, should be continued until bacteriological conversion has become permanent and maximal clinical improvement has occurred. Ethambutol hydrochloride is not recommended for use in pediatric patients under thirteen years of age since safe conditions for use have not been established. Initial Treatment In patients who have not received previous antituberculous therapy, administer ethambutol hydrochloride 15 mg/ kg (7 mg/lb) of body weight, as a single oral dose once every 24 hours. In the more recent studies, isoniazid has been administered concurrently in a single, daily, oral dose. Retreatment In patients who have received previous antituberculous therapy, administer ethambutol hydrochloride 25 mg/kg (11 mg/lb) of body weight, as a single oral dose once every 24 hours. Concurrently administer at least one other antituberculous drug to which the organisms have been demonstrated to be susceptible by appropriate in-vitro tests. Suitable drugs usually consist of those not previously used in the treatment of the patient. After 60 days of ethambutol hydrochloride administration, decrease the dose to 15 mg/kg (7 mg/lb) of body weight, and administer as a single oral dose once every 24 hours. During the period when a patient is on a daily dose of 25 mg/kg, monthly eye examinations are advised. See Table for easy selection of proper weight-dose tablet(s). Weight-Dose Table 15 mg/kg (7 mg/lb) Schedule Weight Range Daily Dose Pounds Kilograms ----------------- In mg Under 85 lbs. Under 37 kg ----------------- 500 85 – 94.5 37 – 43 ----------------- 600 95 – 109.5 43 – 50 ----------------- 700 110 – 124.5 50 – 57 ----------------- 800 125 – 139.5 57 – 64 ----------------- 900 140 – 154.5 64 – 71 ----------------- 1000 155 – 169.5 71 – 79 ----------------- 1100 170 – 184.5 79 – 84 ----------------- 1200 185 – 199.5 84 – 90 ----------------- 1300 200 – 214.5 90 – 97 ----------------- 1400 215 and Over Over 97 ----------------- 1500 25 mg/kg (11 mg/lb) Schedule Under 85 lbs. Under 38 kg ----------------- 900 85 – 92.5 38 – 42 ----------------- 1000 93 – 101.5 42 – 45.5 ----------------- 1100 102 – 109.5 45.5 – 50 ----------------- 1200 110 – 118.5 50 – 54 ----------------- 1300 119 – 128.5 54 – 58 ----------------- 1400 129 – 136.5 58 – 62 ----------------- 1500 137 – 146.5 62 – 67 ----------------- 1600 147 – 155.5 67 – 71 ----------------- 1700 156 – 164.5 71 – 75 ----------------- 1800 165 – 173.5 75 – 79 ----------------- 1900 174 – 182.5 79 – 83 ----------------- 2000 183 – 191.5 83 – 87 ----------------- 2100 192 – 199.5 87 – 91 ----------------- 2200 200 – 209.5 91 – 95 ----------------- 2300 210 – 218.5 95 – 99 ----------------- 2400 219 and Over Over 99 ----------------- 2500 Warnings and cautions WARNINGS Ethambutol hydrochloride may produce decreases in visual acuity which appear to be due to optic neuritis. This effect may be related to dose and duration of treatment. This effect is generally reversible when administration of the drug is discontinued promptly. However, irreversible blindness has been reported. (See PRECAUTIONS and ADVERSE REACTIONS ). Liver toxicities including fatalities have been reported (see ADVERSE REACTIONS ). Baseline and periodic assessment of hepatic function should be performed. Drug interactions Drug Interactions The results of a study of coadministration of ethambutol hydrochloride (50mg/kg)