ethambutol hydrochloride

ethambutol hydrochloride

[eth′əmbyo̅o̅′təl]

a tuberculostatic antibiotic.

indication It is prescribed in the treatment of pulmonary tuberculosis in combination with other drugs.

contraindications Optic neuritis or known hypersensitivity to this drug prohibits its use. It is not recommended for small children.

adverse effects Among the most serious adverse effects are diminished visual acuity and allergic reactions, such as rashes.

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ethambutol hydrochloride

Etibi (CA), Myambutol

Pharmacologic class: Synthetic antitubercular

Therapeutic class: Antitubercular, antileprotic

Pregnancy risk category B

Action

Unknown. Thought to interfere with RNA synthesis of bacterial metabolites, decreasing mycobacterial replication.

Availability

Tablets: 100 mg, 400 mg

⊘Indications and dosages

➣ Adjunct in tuberculosis and atypical mycobacterial infection caused by Mycobacterium tuberculosis

Adults and adolescents: In patients who haven't received previous antitubercular therapy, 15 mg/kg P.O. daily. In patients who have received previous antitubercular therapy, 25 mg/kg P.O. daily, decreased after 60 days to 15 mg/kg daily.

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug

Precautions

Use cautiously in:
• impaired renal or hepatic function, cataracts, optic neuritis, recurrent eye inflammation, diabetic retinopathy, gout
• pregnant patients
• children younger than age 13.

Administration

• Obtain specimens for culture and sensitivity testing, as necessary, before starting therapy and periodically throughout therapy.
• Give with food.

Route	Onset	Peak	Duration
P.O.	Rapid	2-4 hr	24 hr

Adverse reactions

CNS: confusion, disorientation, malaise, dizziness, hallucinations, headache, peripheral neuritis

EENT: optic neuritis, blurred vision, decreased visual acuity, red-green color blindness, eye pain

GI: nausea, vomiting, abdominal pain, GI upset, anorexia

Hematologic: eosinophilia, thrombocytopenia

Hepatic: transient hepatic impairment

Metabolic: hyperuricemia, hypoglycemia

Musculoskeletal: joint pain, gouty arthritis

Respiratory: bloody sputum, pulmonary infiltrates

Skin: rash, pruritus, toxic epidermal necrolysis

Other: fever, anaphylactoid reactions

Interactions

Drug-drug. Aluminum salts: delayed and reduced ethambutol absorption

Other neurotoxic drugs: increased risk of neurotoxicity

Drug-diagnostic tests. Alanine aminotransferase, aspartate aminotransferase, bilirubin, uric acid: increased levels

Glucose: decreased level

Patient monitoring

☞ Watch for serious adverse reactions, such as thrombocytopenia, respiratory problems, and anaphylactoid reactions.
• Monitor liver function tests, CBC, and blood urea nitrogen, creatinine glucose, and serum uric acid levels.
• Give analgesics for drug-induced pain, as prescribed.
• Observe for signs and symptoms of gout.

Patient teaching

• Instruct patient to take with 8 oz of water. If stomach upset occurs, advise him to take with food.
• If patient must take antacids, advise him to take only aluminum-free antacids.
☞ Tell patient to immediately report easy bruising or bleeding, respiratory problems, or signs and symptoms of hypersensitivity reactions.
• Advise patient to report vision changes and to have annual eye exams. Reassure him that visual disturbances will subside within several weeks to months after drug is discontinued.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.