Myambutol Side Effects

Generic name: ethambutol

Note: This document contains side effect information about ethambutol. Some of the dosage forms listed on this page may not apply to the brand name Myambutol.

Some side effects of Myambutol may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to ethambutol: oral tablet

If you experience any of the following serious side effects, stop taking ethambutol (the active ingredient contained in Myambutol) and seek emergency medical attention or contact your doctor immediately:

• an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);

• vision changes (e.g., blurring, red-green color blindness);

• a rash;

• numbness or tingling in your fingers, toes, hands, or feet;

• confusion, disorientation, or hallucinations; or

• fever.

Other, less serious side effects may be more likely to occur. Continue to take ethambutol and talk to your doctor if you experience

• stomach upset, nausea, vomiting, abdominal pain, or decreased appetite;

• headache;

• mild dizziness;

• worsening gout; or

• joint pain.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to ethambutol: oral tablet

Ocular

Ocular side effects have included decreased visual acuity (including irreversible blindness), thought to be caused by optic neuritis. Optic neuropathy (including optic neuritis or retrobulbar neuritis), scotoma, color blindness, and visual defect have been reported.

Retrobulbar neuritis resulting in blurred vision and loss of red-green vision occurs commonly with ethambutol therapy and requires careful monitoring of visual acuity and color discrimination. Optic neuritis occurs more frequently at dosages greater than 15 mg/kg/day. Drug therapy should be discontinued at the first sign of vision defects. Damage may include central or peripheral fibers of the optic nerve. Scotomas are a common occurrence. Damage generally occurs after 2 months of therapy but may occur more rapidly. Predisposing factors may include decreased renal function, diabetes, and preexisting optic neuritis due to alcohol or tobacco consumption. Although vision defects are generally reversible over several months after discontinuation of ethambutol, cases of irreversible blindness and other ocular damage have been reported.

Ocular toxicity may be more severe in patients with renal impairment, possibly due to drug accumulation.

Metabolic

Metabolic side effects have included hyperuricemia and precipitation of acute gout.

Hyperuricemia has been reported in up to 66% of patients receiving ethambutol and is not dependent on the dose. Occasionally, it has led to joint arthralgias and gouty arthritis after 1 to 2 months of therapy. Symptoms generally resolved within 15 days of discontinuing the drug.

Hepatic

Hepatic side effects have included liver toxicities (including fatalities). Transient and asymptomatic elevations in liver function tests have occurred in 10% of patients. Jaundice has been reported rarely.

Elevations in liver function tests, usually without changes in serum bilirubin, have occurred in up to 10% of patients treated with ethambutol. These changes resolved spontaneously despite continuation of drug therapy. Asymptomatic jaundice has also occurred rarely with ethambutol therapy.

Hypersensitivity

Hypersensitivity side effects have included hypersensitivity syndrome and anaphylactic/anaphylactoid reaction. Hypersensitivity reactions have included fever, cutaneous reactions (such as rash or exfoliative dermatitis), eosinophilia with or without drug-induced pulmonary infiltrates, hepatitis, pneumonitis, nephritis, pericarditis, lymphadenopathy, anaphylaxis, lichen-planus reactions, and toxic epidermal necrolysis.

Hypersensitivity reactions have presented as spiking fever, rash, nausea, hypotension, and eosinophilia. Lichen-planus-like reactions including hyperpigmentation and desquamation have occurred rarely, as well as toxic epidermal necrolysis.

Hematologic

Hematologic side effects have included thrombocytopenia, leukopenia, and neutropenia.

Respiratory

Respiratory side effects have included pulmonary infiltrates with or without eosinophilia.

Gastrointestinal

Gastrointestinal complaints are infrequent with ethambutol (the active ingredient contained in Myambutol) therapy and may be associated with a hypersensitivity reaction. Pseudomembranous colitis has been reported when ethambutol was given with rifampin and isoniazid.

Gastrointestinal side effects have included nausea, vomiting, abdominal pain, anorexia, and gastrointestinal upset. Pseudomembranous colitis has been reported.

Nervous system

Nervous system side effects have included headache, dizziness, and numbness and tingling of the extremities due to peripheral neuritis.

Psychiatric

Psychiatric side effects have included mental confusion, disorientation, and possible hallucinations.

Dermatologic

Dermatologic side effects have included dermatitis, erythema multiforme, and pruritus.

Other

Other side effects have included fever and malaise.

Musculoskeletal

Musculoskeletal side effects have included joint pain.

Renal

Renal side effects have rarely included reversible renal insufficiency.

Renal abnormalities include increases in serum creatinine and idiosyncratic interstitial nephritis.

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