Trecator SC (Ethionamide) vs Other TB Drugs: A Practical Comparison

Sep, 25 2025

Trecator SC is a brand‑name formulation of ethionamide, an oral antibiotic used primarily for multidrug‑resistant (MDR) and extensively drug‑resistant (XDR) tuberculosis. It belongs to the thioamide class and works by inhibiting mycolic acid synthesis, a key component of the mycobacterial cell wall. Typical adult dosage ranges from 500mg to 1g daily, divided into two doses, and treatment courses often span 12-24months depending on disease severity.

Why Ethionamide Is Chosen for MDR‑TB

Ethionamide’s strength lies in its activity against MDR‑TB, the form of tuberculosis resistant to at least isoniazid and rifampin. Because it targets a different biosynthetic pathway, it remains effective when first‑line drugs fail. However, the drug’s high incidence of gastrointestinal upset and hepatotoxicity means clinicians must monitor liver enzymes every 2-4weeks.

Key Characteristics of Trecator SC

• Mechanism: Inhibits mycolic acid synthesis (thioamide class).
• Typical dose: 500mg-1g per day, divided BID.
• Half‑life: Approximately 2-3hours; steady‑state reached in 2days.
• Common side‑effects: Nausea, vomiting, anorexia, peripheral neuropathy, hepatotoxicity.
• Cost (US): $150-$250 per month for the 250mg capsules (price varies by pharmacy).

Alternative Anti‑TB Agents to Consider

When deciding whether Trecator SC is the right fit, it helps to line up the most frequently used alternatives. Below are brief snapshots of each.

Isoniazid - a first‑line drug that inhibits mycolic acid synthesis, dosed at 300mg daily, cheap (<$10/month), but prone to hepatotoxicity and resistance in MDR‑TB.

Rifampin - a potent bactericidal agent that blocks RNA polymerase, 600mg daily, inexpensive, but induces hepatic enzymes and can cause orange body fluids.

Fluoroquinolones (e.g., levofloxacin, moxifloxacin) - DNA gyrase inhibitors, 500-750mg daily, moderately priced, risk of tendon rupture and QT prolongation.

Bedaquiline - a diarylquinoline targeting ATP synthase, 400mg loading then 200mg three times weekly, high cost (>$1,000/month), but highly effective for XDR‑TB.

Delamanid - a nitro‑imidazooxazole interfering with mycolic acid synthesis, 100mg twice daily, similar cost to bedaquiline, limited availability outside Europe.

PAS (para‑aminosalicylic acid) - a folate pathway antagonist, 4-8g daily, cheap, notorious for severe GI distress.

Cycloserine - interferes with cell wall peptidoglycan, 250-500mg BID, cheap, neuropsychiatric side‑effects.

Clofazimine - a phenazine dye with bactericidal activity, 100mg daily, low cost, causes skin discoloration.

Linezolid - oxazolidinone that blocks protein synthesis, 600mg daily, expensive (~$500/month), risk of bone‑marrow suppression.

Side‑By‑Side Comparison

Pros and Cons at a Glance

• Trecator SC - Strong activity against resistant strains but needs liver monitoring and can cause severe nausea.
• Isoniazid - Cheap and well‑studied; ineffective when resistance is present.
• Rifampin - Powerful and cheap; limited use in MDR‑TB due to cross‑resistance.
• Fluoroquinolones - Oral, good penetration; risk of tendon injury especially in older adults.
• Bedaquiline - Game‑changer for XDR‑TB; cost and QT monitoring are barriers.

Practical Considerations for Clinicians and Patients

When you sit down with a patient diagnosed with MDR‑TB, ask these three questions:

1. What is the resistance profile from the latest drug‑susceptibility test?
2. Does the patient have baseline liver dysfunction or a history of neuro‑psychiatric illness?
3. Can the health system afford high‑cost agents like bedaquiline or linezolid?

Answering them guides you toward a regimen that balances efficacy, safety, and affordability. For example, a patient with normal liver enzymes but limited budget may receive ethionamide plus a fluoroquinolone and cycloserine, while a patient with cardiac issues would avoid bedaquiline.

Related Concepts and Guidelines

The World Health Organization (WHO) released its 2023 consolidated guidelines on drug‑resistant TB, categorizing drugs into GroupsA,B, andC. Understanding where ethionamide sits (GroupC) helps clinicians prioritize higher‑ranked agents first. Additionally, monitoring for hepatotoxicity is essential for any regimen containing ethionamide, isoniazid, or rifampin. Similarly, drug resistance patterns evolve rapidly; regular sputum cultures and molecular tests keep the regimen up to date.

When to Switch From Trecator SC

If a patient experiences grade3 or higher liver enzyme elevation (ALT/AST >5×ULN) or cannot tolerate the GI side‑effects after two weeks of optimized anti‑emetic therapy, clinicians should consider replacing ethionamide with an alternative from GroupB (e.g., levofloxacin) or, if available, a newer agent like delamanid.

Future Directions

Research is ongoing into shorter, all‑oral regimens that may eventually phase out thioamides. Trials combining bedaquiline, pretomanid, and linezolid show promising cure rates in under six months. Until those regimens become widely accessible, ethionamide remains a useful tool, especially in resource‑limited settings where newer drugs are scarce.