Comprehensive Guide to Ethambutol Hydrochloride: Usage, Dosage, and Side Effects

Summary

Ethambutol hydrochloride is primarily utilized as an adjunctive therapy in the treatment of pulmonary tuberculosis. It is known for its ability to interfere with the synthesis of metabolites in susceptible bacteria, which is crucial in halting the spread of the infection. This article delves into the specifics of ethambutol’s application, including dosage recommendations, potential adverse reactions, and essential considerations for its use.

Dosage and Administration

Initial Treatment

For adults and children over the age of 13 who have not previously received antitubercular therapy, the recommended dosage of ethambutol hydrochloride is 15 mg/kg taken orally as a single daily dose. It is crucial that this medication is administered in conjunction with at least one other antitubercular drug to prevent the development of drug-resistant bacteria.

Retreatment

In cases where retreatment is necessary, the dosage is increased to 25 mg/kg orally daily, administered as a single dose for 60 days or until bacteriological smears and cultures return negative results. After this intensive phase, the dosage should be reduced to 15 mg/kg/day.

Special Considerations

For patients with impaired renal function, a dosage adjustment is necessary to prevent accumulation of the drug, which could lead to increased toxicity. Regular monitoring of renal function is recommended, and dosage should be adjusted based on creatinine clearance rates.

How Supplied

Ethambutol hydrochloride is available in tablet form in two strengths:

• 100 mg
• 400 mg

Mechanism of Action

The exact mechanism by which ethambutol works is not fully understood, but it appears to disrupt the synthesis of key metabolites within the bacterial cell, which inhibits cell division and results in a bacteriostatic effect against Mycobacterium tuberculosis.

Potential Adverse Reactions

Patients taking ethambutol hydrochloride may experience a range of side effects, which include:

• Central Nervous System: Headaches, dizziness, confusion, and in rare cases, hallucinations.
• Cardiovascular: Thrombocytopenia.
• Eyes, Ears, Nose, and Throat: Optic neuritis, which can lead to vision changes.
• Gastrointestinal: Loss of appetite, nausea, vomiting, and abdominal pain.
• Hepatic: Abnormal liver function tests.
• Musculoskeletal: Joint pain.
• Dermatological: Skin reactions such as dermatitis and pruritus, and in severe cases, toxic epidermal necrolysis.
• Other: Anaphylactoid reactions, fever, and elevated uric acid levels, which can precipitate gout attacks.

Drug Interactions

Ethambutol should be used cautiously with aluminum-containing antacids, as these can reduce the absorption of ethambutol. It is recommended to separate the administration of these drugs by several hours to avoid interactions.

Contraindications

Ethambutol is contraindicated in patients with known hypersensitivity to the drug, existing optic neuritis, and in children under the age of 13.

Monitoring and Special Precautions

Before starting treatment with ethambutol, patients should undergo thorough eye examinations including visual acuity and color discrimination tests. These tests should be repeated regularly during treatment. Additionally, liver function tests (AST and ALT) should be performed prior to therapy and monitored periodically.

Patients should be educated on the importance of completing the full course of therapy and reporting any visual disturbances, as these can be indicative of developing optic neuritis, a potentially reversible but serious side effect.

For more detailed information on tuberculosis and its treatment options, visit the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO).

This comprehensive overview of ethambutol hydrochloride underscores its importance in the fight against tuberculosis, while also highlighting the need for careful administration and monitoring to mitigate potential side effects.