ETIBI Tablet Ref.[27886] Active ingredients: Ethambutol

Susceptibility / Resistance

Development of Drug Resistant Bacteria

Prescribing ETIBI Tablets in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to the patient and risks the development of drug-resistant bacteria.

Visual testing should be performed prior to initiating ETIBI (ethambutol) therapy and then periodically during therapy with the drug. Testing should be done monthly in patients receiving more than 15 mg/kg daily. Examinations should include ophthalmoscopy, finger perimetry, and testing of color discrimination. Patients developing adverse ocular effects during ETIBI therapy may show subjective visual symptoms either before or simultaneously with decreases in visual acuity. All patients receiving the drug should be questioned periodically about blurred vision and other subjective visual symptoms and should be instructed to report to their physician any such changes as soon as they are noticed. If substantial changes in visual acuity occur, ETIBI should be discontinued immediately.

Renal, hepatic, and hematopoietic tests should be performed periodically during long-term ETIBI therapy. Serum uric acid concentration measurements may be required during treatment since elevated serum uric acid concentrations frequently occur, possibly resulting in precipitation of acute gout.

ETIBI should be used with caution and in reduced dosage in patients with impaired renal function. The drug should also be used with caution in patients with ocular defects (e.g., cataracts, recurrent ocular inflammatory conditions, diabetic retinopathy) that make visual changes difficult to detect or evaluate; consideration should be given to whether the benefits of ETIBI therapy justify the possible ocular effects in these patients.

Pregnancy

It is recommended that pregnant women with tuberculosis be treated for a minimum of 9 months with multi-drug therapy, including ethambutol. Ethambutol crosses the placenta, resulting in fetal plasma concentrations approximately 30% of maternal plasma concentrations. However, problems in humans have not been documented.

Studies in mice given high doses have shown that ethambutol causes a low incidence of cleft palate, exencephaly, and vertebral column abnormalities. In addition, studies in rats given high doses have shown that ethambutol causes minor abnormalities of the cervical vertebrae. Studies in rabbits given high doses have shown that ethambutol may cause monophthalmia, limb reduction defects, hare lip, and cleft palate.

Breast-feeding

Ethambutol is distributed into breast milk in concentrations approximating maternal serum concentrations. However, problems in humans have not been documented.

Pediatrics

Appropriate studies on the relationship of age to the effects of ethambutol have not been performed in children up to 13 years of age. Ethambutol is generally not recommended in children whose visual acuity cannot be monitored (younger than 6 years of age). However, ethambutol should be considered for all children with organisms resistant to other medications, and in whom susceptibility to ethambutol has been documented or is likely.

Geriatrics

No information is available on the relationship of age to the effects of ethambutol in geriatric patients. However, elderly patients are more likely to have an age-related decrease in renal function, which may require an adjustment of dosage in patients receiving ethambutol.

Drug Interactions

Neurotoxic medications-concurrent administration of ethambutol with other neurotoxic medications may increase the potential for neurotoxicity, such as optic and peripheral neuritis.

The most important adverse effect of ethambutol is optic neuritis with decreases in visual acuity, constriction of visual fields, central and peripheral scotomas, and loss of red-green color discrimination. The extent of ocular toxicity appears to be related to dose and duration of ethambutol therapy, occurring most frequently with daily doses of 25 mg per kg of body weight and after two months of therapy; however, optic neuritis has occurred after only a few days of treatment. Most cases are reversible after several weeks or months. Visual changes may be unilateral or bilateral; therefore, each eye must be tested separately and both eyes tested together.

Peripheral neuritis, with numbness and tingling of the extremities, has been reported infrequently. Increased serum uric acid concentrations and precipitation of acute gout have occurred occasionally in patients receiving ethambutol and are probably the result of decreased renal clearance of urate. Transient impairment of liver function, as indicated by abnormal liver function test results, has also occurred.

Other adverse reactions to ethambutol include dermatitis, pruritus, headache, malaise, dizziness, fever, mental confusion, disorientation, possible hallucinations, joint pain, and rarely anaphylactoid reactions. Gastrointestinal upset, abdominal pain, nausea, vomiting, and anorexia have also occurred occasionally with ethambutol.