Trecator SC (ethionamide) is a second-line antimycobacterial agent specifically formulated for the treatment of active tuberculosis when primary therapies have failed or are unsuitable due to resistance or intolerance. It is indicated for use as part of a carefully managed combination regimen to combat drug-resistant Mycobacterium tuberculosis. This bacteriostatic agent works by inhibiting the synthesis of mycolic acids, an essential component of the mycobacterial cell wall. Administration requires strict medical supervision due to its side effect profile and potential for significant drug interactions. Its role is critical in multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) tuberculosis treatment protocols, representing a vital tool in global TB control efforts.

Features

• Active Ingredient: Ethionamide 250 mg per scored tablet
• Pharmacologic Class: Second-line antituberculosis agent; thioamide derivative
• Mechanism of Action: Inhibits mycolic acid synthesis, disrupting bacterial cell wall integrity
• Administration: Oral tablet formulation for systemic delivery
• Bioavailability: Nearly complete absorption from gastrointestinal tract
• Metabolism: Hepatic, via extensive sulfoxidation and desulfurization
• Excretion: Primarily renal (as metabolites) with minimal unchanged drug
• Half-life: Approximately 2-3 hours in patients with normal hepatic function
• Special Packaging: Light-resistant containers to maintain stability

Benefits

• Targets Resistant Strains: Effective against tuberculosis bacilli that have developed resistance to first-line agents like isoniazid and rifampin
• Complements Combination Therapy: Works synergistically with other second-line TB drugs to prevent further resistance development
• Oral Administration: Convenient dosing format that supports long-term treatment adherence outside hospital settings
• Penetrates Tissue Barriers: Demonstrates good distribution, including crossing into cerebrospinal fluid for tuberculous meningitis treatment
• Bacteriostatic Action: Effectively suppresses mycobacterial replication while other agents achieve bactericidal effects
• Global Health Impact: Provides critical therapeutic option in regions with high prevalence of drug-resistant tuberculosis

Common use

Trecator SC is specifically indicated for the treatment of active pulmonary and extrapulmonary tuberculosis when first-line treatment has failed or cannot be tolerated. It is never used as monotherapy but always as part of a combination regimen tailored to drug susceptibility testing results. Common clinical applications include multidrug-resistant tuberculosis (MDR-TB), defined as resistance to at least isoniazid and rifampin, and extensively drug-resistant tuberculosis (XDR-TB), which includes additional resistance to fluoroquinolones and injectable second-line agents. It may also be used in cases of documented intolerance to first-line drugs or when laboratory confirmation shows susceptibility to ethionamide despite resistance patterns to primary agents. The medication finds particular utility in treating tuberculous meningitis due to its cerebrospinal fluid penetration capabilities.

Dosage and direction

Dosage must be individualized based on patient weight, hepatic function, and tolerance. The typical adult dosage is 15-20 mg/kg/day, not to exceed 1,000 mg daily, usually administered in divided doses (2-3 times daily) with meals to minimize gastrointestinal upset. Pediatric dosing follows similar weight-based calculations at 15-20 mg/kg/day in divided doses, with maximum daily doses not exceeding 750 mg for children under 50 kg. Treatment initiation typically begins with lower doses (250 mg once daily) with gradual titration over 3-7 days to the full therapeutic dose to improve tolerance. Administration should always occur with food to reduce gastric irritation. The entire daily dose may be given at bedtime for some patients to minimize daytime side effects. Duration of therapy typically extends for 18-24 months in MDR-TB regimens, always in combination with at least three other drugs to which the isolate is susceptible. Regular monitoring of liver function tests is mandatory throughout treatment.

Precautions

Multiple precautions must be observed with Trecator SC therapy. Hepatic function should be assessed before initiation and monitored monthly throughout treatment, as hepatitis may occur in 2-5% of patients. Patients should be educated to report immediately any symptoms of hepatitis (nausea, vomiting, dark urine, jaundice, abdominal pain). Gastrointestinal intolerance is common; taking with meals or dividing doses may mitigate symptoms. Endocrinological monitoring is recommended as ethionamide may cause hypothyroidism, especially in patients with preexisting thyroid disorders; baseline and periodic TSH measurements are advised. Ophthalmological examinations are recommended before and during prolonged therapy due to potential neuroophthalmic effects. Diabetic patients require careful glucose monitoring as ethionamide may interfere with diabetic control. The drug should be used with extreme caution in patients with a history of psychiatric disorders, as neuropsychiatric effects may occur. Alcohol consumption should be avoided due to increased risk of hepatotoxicity.

Contraindications

Trecator SC is contraindicated in patients with known hypersensitivity to ethionamide or any component of the formulation. Severe hepatic impairment or active hepatitis represents an absolute contraindication due to the drug’s hepatotoxic potential. The medication should not be used in patients with severe uncontrolled diabetes mellitus. Concomitant administration with cycloserine is generally contraindicated due to increased risk of central nervous system toxicity. The drug is contraindicated in patients with severe psychiatric disorders that would impair their ability to report adverse effects or adhere to monitoring requirements. Pregnancy represents a relative contraindication; use only if potential benefit justifies potential fetal risk (Category C). Breastfeeding is not recommended during therapy due to excretion in human milk.

Possible side effect

Gastrointestinal disturbances occur most frequently, including nausea (30-50%), vomiting (10-30%), abdominal pain (15-25%), diarrhea (5-15%), metallic taste (20-40%), and excessive salivation (5-20%). Hepatotoxicity may manifest as elevated transaminases (5-10%), clinical hepatitis (2-5%), or rarely jaundice and hepatic failure. Neurological effects include dizziness (10-20%), headache (5-15%), peripheral neuropathy (5-15%), tremors (2-8%), and rarely seizures or psychiatric disturbances (depression, anxiety, psychosis). Endocrinological effects may include hypothyroidism (5-15%), gynecomastia (2-5%), and menstrual irregularities. Dermatological reactions occur in 5-10% of patients, including rash, photosensitivity, and acneiform eruptions. Ophthalmological effects include blurred vision and difficulty with accommodation. Miscellaneous effects may include orthostatic hypotension, arthralgia, and impotence. Most side effects are dose-related and may diminish with continued therapy or dose adjustment.

Drug interaction

Trecator SC demonstrates significant interaction potential. It may potentiate the neurotoxic effects of cycloserine and isoniazid, making concomitant use generally undesirable. Ethionamide may inhibit the metabolism of phenytoin, leading to increased levels and potential toxicity; close monitoring and dose adjustment are necessary. The drug may antagonize the effects of para-aminosalicylic acid (PAS) when administered concurrently. Interactions with antidiabetic agents may occur, potentially necessitating adjustment of hypoglycemic therapy. Ethionamide may enhance the effects of alcohol and other hepatotoxic substances, increasing liver damage risk. Concomitant use with other drugs causing peripheral neuropathy (such as vincristine, cisplatin) may have additive effects. The medication may interfere with thyroid function tests and potentially alter requirements for thyroid replacement therapy. Interactions with CYP450 enzymes, particularly CYP2E1, may affect metabolism of various substrates.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Patients should never double the dose to make up for a missed administration. Consistency in dosing is critical for maintaining therapeutic levels and preventing development of resistance. If multiple doses are missed, patients should contact their healthcare provider immediately for guidance, as interrupted therapy may compromise treatment efficacy and require reassessment of the entire regimen. Documentation of missed doses should be maintained and discussed at regular clinical reviews to identify adherence patterns that might necessitate intervention.

Overdose

Acute overdose may manifest as exaggerated pharmacological effects, particularly severe gastrointestinal distress (nausea, vomiting, abdominal pain), neurological symptoms (dizziness, headache, peripheral neuropathy, possible seizures), and hepatotoxicity. There is no specific antidote for ethionamide overdose. Management consists of immediate gastric lavage if ingestion was recent, followed by activated charcoal administration. Supportive care should include maintenance of hydration and electrolyte balance, antiemetics for persistent vomiting, and monitoring of hepatic and neurological status. Hemodialysis is not likely to be effective due to high protein binding but may be considered in severe cases. Patients should be monitored for at least 24 hours with particular attention to liver function tests. Chronic excessive dosing may lead to cumulative toxicity requiring dose reduction or temporary discontinuation.

Storage

Store at controlled room temperature between 20-25°C (68-77°F), with excursions permitted between 15-30°C (59-86°F). Protect from light and moisture; keep container tightly closed. Do not freeze. Keep out of reach of children and pets. Do not transfer tablets to other containers that are not light-resistant. Discard any medication that shows signs of deterioration (discoloration, unusual odor) or that has expired. Proper disposal should follow local regulations for pharmaceutical waste, typically through take-back programs or mixing with undesirable substance before disposal in household trash. Do not flush medications down the toilet unless specifically instructed to do so.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Trecator SC is a prescription medication that must be used under direct supervision of a physician experienced in the management of tuberculosis, particularly drug-resistant forms. Treatment decisions should be based on individual patient characteristics, drug susceptibility testing, and current treatment guidelines. The prescribing physician should be consulted for complete information regarding indications, contraindications, warnings, precautions, and adverse effects. Patients should not alter their dosage or discontinue therapy without medical consultation. Healthcare professionals should reference the full prescribing information before initiating therapy.

Reviews

Clinical experience with Trecator SC demonstrates its essential role in managing drug-resistant tuberculosis, though with recognition of its challenging side effect profile. Specialists note that while gastrointestinal intolerance is nearly universal initially, it often diminishes with continued therapy and proper dosing strategies. The drug’s effectiveness in combination regimens for MDR-TB is well-established, with culture conversion rates comparable to other second-line agents when used appropriately. Many clinicians emphasize the critical importance of patient education regarding side effect management and the necessity of complete adherence to monitoring protocols. The neuropsychiatric effects are noted as particularly concerning but manageable with dose adjustment in most cases. Overall, despite its toxicity challenges, Trecator SC remains a valuable component of the antituberculosis armamentarium where resistance patterns necessitate its use.