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MYAMBUTOL 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).
MYAMBUTOL ethambutol hydrochloride is not recommended for use in pediatric patients under thirteen years of age since safe conditions for use have not been established.
Patients with decreased renal function need the dosage reduced as determined by serum levels of MYAMBUTOL, since the main path of excretion of this drug is by the kidneys.
Because this drug may have adverse effects on vision, physical examination should include ophthalmoscopy, finger perimetry and testing of color discrimination. In patients with visual defects such as cataracts, recurrent inflammatory conditions of the eye, optic neuritis, and diabetic retinopathy, the evaluation of changes in visual acuity is more difficult, and care should be taken to be sure the variations in vision are not due to the underlying disease conditions. In such patients, consideration should be given to relationship between benefits expected and possible visual deterioration since evaluation of visual changes is difficult. (For recommended procedures, see next paragraphs under ADVERSE REACTIONS.)
As with any potent drug, baseline and periodic assessment of organ system functions, including renal, hepatic, and hematopoietic, should be performed.
Teratogenic Effects: Pregnancy Category C.
There are no adequate and well-controlled studies in pregnant women. There are reports of ophthalmic abnormalities occurring in infants born to women on antituberculous therapy that included MYAMBUTOL. MYAMBUTOL should be used during pregnancy only if the benefit justifies the potential risk to the fetus.
MYAMBUTOL has been shown to be teratogenic in pregnant mice and rabbits when given in high doses. When pregnant mice or rabbits were treated with high doses of ethambutol hydrochloride, fetal mortality was slightly but not significantly (P > 0.05) increased. Female rats treated with ethambutol hydrochloride displayed slight but insignificant (P > 0.05) decreases in fertility and litter size. In fetuses born of mice treated with high doses of MYAMBUTOL during pregnancy, a low incidence of cleft palate, exencephaly and abnormality of the vertebral column were observed. Minor abnormalities of the cervical vertebra were seen in the newborn of rats treated with high doses of ethambutol hydrochloride during pregnancy. Rabbits receiving high doses of MYAMBUTOL during pregnancy gave birth to two fetuses with monophthalmia, one with a shortened right forearm accompanied by bilateral wrist-joint contracture and one with hare lip and cleft palate.
MYAMBUTOL is excreted into breast milk. The use of MYAMBUTOL should be considered only if the expected benefit to the mother outweighs the potential risk to the infant.
MYAMBUTOL (ethambutol hydrochloride) is not recommended for use in pediatric patients under thirteen years of age since safe conditions for use have not been established.
There are limited data on the use of MYAMBUTOL in the elderly. One study of 101 patients, 65 years and older, on multiple drug antituberculosis regimens included 94 patients on MYAMBUTOL. No differences in safety or tolerability were observed in these patients compared with that reported in adults in general. Other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 3/8/2013
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