Myambutol 400 mg Tablets

Brand name

The drug is known under the trade name Myambutol. This name is registered in pharmaceutical registries and is used to identify the drug in pharmacies, medical institutions and among health care professionals. Myambutol is recognized for its effectiveness in the therapy of certain infectious diseases requiring specific antibacterial action. The name was chosen by the manufacturers to indicate its belonging to the group of antitubercular agents, emphasizing its important role in the complex treatment of such conditions.

International Nonproprietary Name (INN)

The international nonproprietary name of this medicine is ethambutol. This term is adopted by the international community to designate the active substance that provides therapeutic action. Ethambutol belongs to the class of antituberculosis drugs characterized by the ability to inhibit the growth of mycobacteria. The name is standardized by the World Health Organization, which allows unifying the prescription and production of this drug in different countries, regardless of brands.

Form of release

The drug is available in several forms, which provides convenience of use depending on the age of the patient and the specifics of treatment. The main options include:

• Coated tablets with dosages of 100 mg, 200 mg, 400 mg and 800 mg of the active substance, intended for oral administration.
• Capsules with a dosage of 400 mg, used as an alternative to tablets for adults and older children.

Each form is designed for precise dosing and ease of use in the long courses of treatment typical of TB therapy. The choice of form is determined by the physician based on the patient's body weight and stage of disease.

Composition

The main active substance is ethambutol, an antibacterial agent with antituberculosis activity. Auxiliary components depend on the form of release. In tablets, the following are used:

• Microcrystalline cellulose - filler for uniform distribution of the active substance.
• Pregelatinized starch - a binder for the formation of the mass.
• Magnesium stearate - lubricating agent to facilitate the manufacturing process.
• Povidone - solvent to improve the structure.
• Hypromellose and titanium dioxide film coating - for protection and ease of swallowing.

Lactose monohydrate is added to the capsules as a filler and gelatin for the shell. The composition is balanced to ensure stability and bioavailability of the active substance during long-term storage and use.

Pharmacologic Properties

Pharmacodynamics

Myambutol has a bacteriostatic action aimed at inhibiting the growth of mycobacteria, including Mycobacterium tuberculosis. It inhibits the enzyme arabinosyltransferase involved in the synthesis of arabinogalactan, a key component of the cell wall of mycobacteria. This disrupts the formation of the protective structure, slowing the reproduction of pathogens. The drug is particularly effective against actively dividing mycobacteria, which makes it an important element of combination therapy of tuberculosis.

The mechanism of action allows the drug to prevent the development of resistance of mycobacteria to other anti-TB drugs, such as isoniazid and rifampicin, when used together. The effect is manifested within a few days after the start of treatment, providing a gradual reduction in bacterial load.

Pharmacokinetics

Absorption

After oral administration, the active substance is absorbed in the gastrointestinal tract, mainly in the small intestine, reaching maximum plasma concentration in 2-4 hours. Bioavailability is about 75-80%, which ensures sufficient intake of the substance into the systemic bloodstream. Food intake slightly slows down absorption, but does not affect the total absorption, which allows taking the drug independently of meals.

Distribution

The component is well distributed in the body, penetrating into the lungs, kidneys, liver and tissues affected by mycobacteria. Binding to plasma proteins is minimal - about 20-30%, which contributes to the free distribution of the substance. Concentrations in lung tissue and lymph nodes often exceed plasma concentrations, which enhances efficacy in tuberculosis.

Metabolism

Metabolism occurs in the liver with the formation of inactive metabolites such as ethambutol aldehyde and dicarboxylic acid. About 50% of the dose taken undergoes metabolic transformation, while the remainder remains unchanged.

Excretion

Extracted mainly through the kidneys (50-70% unchanged) by tubular filtration and tubule secretion, as well as with bile and feces (20-30%). The elimination half-life is 3-4 hours in patients with normal renal function, but increases in patients with renal failure.

Indications for Use

Myambutol is indicated for the treatment of infections caused by sensitive strains of mycobacteria:

• Lung tuberculosis (all forms, including active and chronic), as part of combination therapy.
• Vnepulmonary tuberculosis: lesions of lymph nodes, bones, kidneys.
• Infections caused by atypical mycobacteria (Mycobacterium avium complex), with confirmed sensitivity.

The drug is used only in combination with other antituberculosis agents to prevent resistance. Administration requires bacteriologic confirmation of the diagnosis.

Contraindications

The use of Myambutol is prohibited in:

• Hypersensitivity to ethambutol or components of the composition.
• Diseases of the optic nerve (optic neuritis, retinopathy).
• Severe renal insufficiency without dose adjustment.
• Children under 2 years of age due to the risk of side effects on vision.

Cautious prescribing in gout, diabetic retinopathy and cataract.

Method of Administration and Dosage

How to take

Tablets and capsules are taken orally, drinking water (150-200 ml), preferably on an empty stomach 1 hour before a meal or 2 hours after for optimal absorption. Patients are advised to avoid concomitant administration with antacids containing aluminum so as not to reduce absorption.

Dosages for adults and children

Dosage depends on body weight and treatment regimen:

• Adults: 15-25 mg/kg body weight once daily (maximum 2.5 g/day), course 6-12 months in combination with other agents.
• Children over 2 years of age: 15-20 mg/kg/day (maximum 1 g/day), duration is determined by a physician.

Dose adjustment for certain conditions

In renal failure:

• Clearance 30-50 mL/min: 15 mg/kg every 24-36 hours.
• Clearance 10-30 mL/min: 15 mg/kg every 48 hours.
• Clearance less than 10 mL/min: 15 mg/kg every 72 hours.

Hepatic insufficiency does not require correction but requires monitoring.

Side Effects

Unwanted reactions include:

• Visual: decreased visual acuity, narrowing of visual fields, color disturbances.
• Gastrointestinal: nausea, vomiting, abdominal pain.
• Nervous: dizziness, peripheral neuropathy.
• Metabolic: hyperuricemia, gout.
• Allergic: rash, itching.

Discontinue if symptoms are severe, especially visual symptoms.

Overdose

Symptoms of overdose

Exceeding the dose is manifested by nausea, vomiting, confusion, visual disturbances, seizures.

First aid measures

In overdose:

• Stop taking.
• Rinse the stomach (within 1-2 hours).
• Provide symptomatic therapy.
• Seek medical attention.

Drug Interactions

Influence on the effects of other drugs

The medication affects:

• Antacids with aluminum: decreased absorption of ethambutol.
• Isoniazid: increased toxicity on vision when taken together.

Compatibility with alcohol and food

Alcohol increases the risk of side effects and is avoided. Food does not affect absorption.

Special Precautions

Use in pregnancy and breastfeeding

Myambutol is acceptable in pregnancy for strict indications (category C). Penetrates into milk, lactation is suspended.

Effects on driving and mechanisms

Visual disturbances may make driving difficult.

Particulars of use in the elderly and children

The elderly require monitoring of vision and renal function. In children under 2 years of age do not use due to the risk of visual impairment.