Myambutol Side Effects

Generic Name: ethambutol

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

Not all side effects for Myambutol may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to ethambutol: oral tablet

In addition to its needed effects, some unwanted effects may be caused by ethambutol (the active ingredient contained in Myambutol). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking ethambutol:

Less common
  • Chills
  • pain and swelling of joints, especially big toe, ankle, or knee
  • tense, hot skin over affected joints
  • Blurred vision, eye pain, red-green color blindness, or any loss of vision (more common with high doses)
  • fever
  • joint pain
  • numbness, tingling, burning pain, or weakness in hands or feet
  • skin rash

Some of the side effects that can occur with ethambutol may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common
  • Abdominal pain
  • confusion
  • headache
  • loss of appetite
  • nausea and vomiting

For Healthcare Professionals

Applies to ethambutol: oral tablet


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.


Hyperuricemia has been reported in up to 66% of patients receiving ethambutol (the active ingredient contained in Myambutol) 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.

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


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 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 side effects have included thrombocytopenia, leukopenia, and neutropenia.


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


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


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


Other side effects have included fever and malaise.


Musculoskeletal side effects have included joint pain.


Renal side effects have rarely included reversible renal insufficiency.

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

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