6 Oct 2025
- 11 Comments
TB Drug Comparison Tool
Trecator SC (Ethionamide)
Inhibits InhA enzyme; blocks mycolic acid synthesis
Dosage: 15–20 mg/kg daily
Side Effects: GI upset, neuropathy, hepatotoxicity, visual changes
Resistance: Effective when Isoniazid- and Rifampin-resistant
Isoniazid
Inhibits KatG enzyme; targets mycolic acid synthesis
Dosage: 5 mg/kg daily
Side Effects: Hepatotoxicity, peripheral neuropathy
Resistance: Common resistance in MDR-TB
Rifampin
Blocks RNA polymerase
Dosage: 10 mg/kg daily
Side Effects: Hepatotoxicity, orange body fluids, drug interactions
Resistance: Resistance seen in MDR-TB
Levofloxacin
Inhibits DNA gyrase
Dosage: 500–750 mg daily
Side Effects: Tendonitis, QT prolongation, GI upset
Resistance: Active against many fluoro-resistant strains
Moxifloxacin
Inhibits DNA gyrase
Dosage: 400 mg daily
Side Effects: QT prolongation, hepatic effects, GI upset
Resistance: Good for XDR-TB when fluoro-resistance is low
Cycloserine
Inhibits alanyl-tRNA synthetase
Dosage: 10–15 mg/kg daily (divided)
Side Effects: Psychiatric symptoms, seizures, GI upset
Resistance: Often used when other options fail
PAS (Para-aminosalicylic acid)
Antagonizes folate pathway
Dosage: 8–12 g daily (split)
Side Effects: Pancreatitis, GI upset, hyperuricemia
Resistance: Reserved for highly resistant cases
Decision Factors
- Resistance Pattern
- Side Effect Tolerance
- Drug Interactions
- Convenience & Pill Burden
- Cost & Availability
How to Use This Tool
This interactive guide compares Trecator SC (Ethionamide) with other TB medications based on mechanism of action, dosage, side effects, and resistance profiles. Use this tool to evaluate which drug might work best for your situation, keeping in mind that decisions should always be made with your healthcare provider.
Tip: When selecting a regimen, consider combining drugs with different mechanisms to maximize effectiveness and reduce resistance risk.
Quick Takeaways
- Trecator SC (Ethionamide) is a second‑line drug for multi‑drug‑resistant TB.
- It works by blocking the synthesis of mycobacterial cell wall fatty acids.
- Common alternatives include Isoniazid, Rifampin, Levofloxacin, and Cycloserine.
- Choosing the right drug depends on resistance patterns, side‑effect tolerance, and drug‑interaction risk.
- Always coordinate with a TB specialist to tailor therapy to your specific case.
What Is Trecator SC (Ethionamide)?
Trecator SC is a brand‑name formulation of Ethionamide, an oral antibacterial used primarily for multidrug‑resistant (MDR) and extensively drug‑resistant (XDR) tuberculosis. First approved in the 1950s, Ethionamide belongs to the thioamide class and is considered a second‑line agent because it is reserved when first‑line drugs fail or the Mycobacterium tuberculosis strain is resistant.
How Ethionamide Works
Ethionamide inhibits the enzyme InhA, which is crucial for the synthesis of mycolic acids-the fatty acids that give TB bacteria their waxy, protective cell wall. Without a sturdy wall, the bacteria can’t survive, making Ethionamide bacteriostatic (it stops growth) rather than outright bactericidal.
Key Benefits of Trecator SC
- Effective against strains resistant to first‑line drugs like Isoniazid and Rifampin.
- Oral administration-no injections needed.
- Can be combined with a variety of other TB medicines to form a potent regimen.
Common Side Effects
Like most second‑line TB drugs, Ethionamide has a notable side‑effect profile. Patients often report:
- Gastrointestinal upset (nausea, vomiting, abdominal pain)
- Peripheral neuropathy-tingling or numbness in hands and feet
- Hepatotoxicity-elevated liver enzymes, sometimes jaundice
- Visual disturbances, especially color‑vision changes
Regular monitoring of liver function and nerve health is essential during treatment.
When Doctors Choose Ethionamide
Ethionamide is typically prescribed when:
- The TB strain is confirmed resistant to Isoniazid and Rifampin.
- Patients cannot tolerate other second‑line drugs due to severe side effects.
- A treatment‑shortening regimen is not feasible, and a longer, robust regimen is required.
Alternative TB Medications
If you’re wondering whether a different drug might be a better fit, here are the most common alternatives that physicians consider alongside Ethionamide.
- Isoniazid - a first‑line bactericidal drug targeting mycolic acid synthesis.
- Rifampin - another first‑line agent that inhibits bacterial RNA polymerase.
- Levofloxacin - a fluoroquinolone with strong activity against resistant TB.
- Moxifloxacin - similar to Levofloxacin but with better penetration into lung tissue.
- Cycloserine - a bacteriostatic agent that interferes with cell wall peptidoglycan synthesis.
- Para‑aminosalicylic acid (PAS) - an older drug that disrupts folate metabolism.
Comparison Table
| Drug | Line (First/Second) | Mechanism | Typical Dose | Major Side Effects | Resistance Profile |
|---|---|---|---|---|---|
| Ethionamide | Second | InhA inhibition (mycolic acid synthesis) | 15‑20mg/kg daily | GI upset, neuropathy, hepatotoxicity, visual changes | Effective when Isoniazid‑ and Rifampin‑resistant |
| Isoniazid | First | KatG catalase‑peroxidase inhibition | 5mg/kg daily | Hepatotoxicity, peripheral neuropathy (B6 deficiency) | Resistance common in MDR‑TB |
| Rifampin | First | RNA polymerase blockade | 10mg/kg daily | Hepatotoxicity, orange body fluids, drug interactions | Resistance seen in MDR‑TB |
| Levofloxacin | Second | DNA gyrase inhibition | 500‑750mg daily | Tendonitis, QT prolongation, GI upset | Active against many fluoro‑resistant strains |
| Moxifloxacin | Second | DNA gyrase inhibition | 400mg daily | QT prolongation, hepatic effects, GI upset | Good for XDR‑TB when fluoro‑resistance is low |
| Cycloserine | Second | Alanyl‑tRNA synthetase inhibition | 10‑15mg/kg daily (divided) | Psychiatric symptoms, seizures, GI upset | Often used when other options fail |
| PAS | Second | Folate pathway antagonism | 8‑12g daily (split) | Pancreatitis, GI upset, hyperuricemia | Reserved for highly resistant cases |
Pros & Cons of Each Alternative
Below is a quick rundown of what makes each drug shine-or fall short-when you compare them to Ethionamide.
- Isoniazid:
- Pros: Fast‑acting, inexpensive, high cure rates in drug‑susceptible TB.
- Cons: Not useful when resistance is present; hepatotoxicity risk rises with age.
- Rifampin:
- Pros: Powerful sterilizing effect; shortens therapy when used with Isoniazid.
- Cons: Major drug‑interaction culprit (inducer of CYP enzymes); resistance limits use.
- Levofloxacin:
- Pros: Strong activity against many MDR strains; oral dosing.
- Cons: Tendon rupture risk in older adults; QT monitoring required.
- Moxifloxacin:
- Pros: Better lung penetration than Levofloxacin; useful in XDR‑TB.
- Cons: More pronounced QT prolongation; expensive in some markets.
- Cycloserine:
- Pros: Works synergistically with many other TB drugs.
- Cons: Neuropsychiatric side effects can be severe; requires close monitoring.
- PAS:
- Pros: Historically proven; can be added when other options are exhausted.
- Cons: High pill burden; GI irritation common.
Choosing the Right Drug: A Decision Guide
When you sit down with your TB specialist, they’ll weigh several factors. Use this checklist to see where each drug lands.
- Resistance pattern: Does the strain resist Isoniazid or Rifampin? If yes, second‑line drugs like Ethionamide, Levofloxacin, or Cycloserine become candidates.
- Side‑effect tolerance: History of liver disease? Avoid drugs with high hepatotoxicity (Ethionamide, Rifampin). Prior psychiatric issues? Be cautious with Cycloserine.
- Drug interactions: Are you on antiretrovirals, anticoagulants, or hormonal contraceptives? Rifampin’s enzyme‑inducing effect may lower their levels.
- Convenience: Pill burden matters. PAS requires several grams per day, which many patients find hard to swallow.
- Cost & availability: In some regions, Levofloxacin may be cheaper than Ethionamide, affecting adherence.
Match your personal health profile against this matrix. Often a regimen combines two or three drugs to cover different mechanisms while balancing toxicity.
Frequently Asked Questions
Can I switch from Ethionamide to another drug if I experience side effects?
Yes. Most clinicians will replace Ethionamide with another second‑line agent, such as Levofloxacin or Cycloserine, after confirming susceptibility and ensuring the new drug covers the same bacterial targets. The switch usually involves a short overlap period to maintain therapeutic levels.
Is Ethionamide safe to use during pregnancy?
Safety data are limited. Animal studies suggest potential teratogenic effects, so most guidelines advise avoiding Ethionamide in the first trimester unless the benefits outweigh the risks. Alternate regimens with safer drugs are preferred for pregnant patients.
How long does a typical Ethionamide‑based regimen last?
For MDR‑TB, treatment usually spans 18‑24 months, with Ethionamide used for at least the intensive phase (6‑9 months). Duration may extend if sputum conversion is slow.
Do I need regular blood tests while on Ethionamide?
Absolutely. Baseline liver function tests (ALT, AST, bilirubin) are drawn before starting therapy, then every 2‑4 weeks for the first three months, and monthly thereafter. Neurological exams are also scheduled to catch early signs of peripheral neuropathy.
What makes Levofloxacin a good alternative to Ethionamide?
Levofloxacin targets DNA gyrase, a completely different bacterial process, so cross‑resistance is rare. It also has a more favorable gastrointestinal profile and doesn’t cause visual disturbances, making it easier for many patients to tolerate.
Next Steps
If you’ve identified potential drawbacks with your current Ethionamide regimen, schedule a follow‑up with your TB care team. Bring this guide, ask for a susceptibility report, and discuss whether a switch to Levofloxacin, Moxifloxacin, or a combination including Cycloserine fits your lifestyle and medical history.
Remember, TB treatment is a marathon, not a sprint. Staying informed about each medication’s strengths and limits helps you stay on track toward a cure.
William Dizon
October 6, 2025Great summary! If you’re just getting started, keep an eye on liver function tests when you’re on Ethionamide, and don’t forget to supplement with vitamin B6 to help with neuropathy.
Jenae Bauer
October 7, 2025Interesting how the guide lays everything out, yet it never mentions the hidden agendas of pharma giants pulling strings behind the scenes. Some say the data on side‑effects is conveniently downplayed, especially when big‑budget trials are involved. I wonder if the “quick takeaways” are just a PR spin. Anyway, stay skeptical, friends.
vijay sainath
October 9, 2025Dude, this whole thing feels like a textbook you’d read in a dusty library. Ethionamide? Yeah, it works, but the GI havoc and visual glitches make me wonder why anyone would willingly swallow it. Plus, the resistance charts read like a horror story for any microbiologist. TL;DR: it’s a necessary evil, not a miracle.
Daisy canales
October 10, 2025Oh wow, another sob story about side effects, how original.
keyul prajapati
October 11, 2025When evaluating Ethionamide alongside the broader TB drug arsenal, it helps to start by acknowledging the clinical context in which each agent is deployed. First‑line drugs such as Isoniazid and Rifampin dominate treatment of drug‑susceptible TB because of their rapid bactericidal activity and relatively favorable safety profile. However, once resistance to these agents emerges, the therapeutic landscape shifts dramatically toward second‑line options, each with unique mechanisms of action. Ethionamide functions by inhibiting the InhA enzyme, thereby blocking mycolic acid synthesis, a pathway distinct from the katG‑mediated inhibition provided by Isoniazid. This distinction grants Ethionamide efficacy against strains that have acquired katG mutations, a common resistance pattern in MDR‑TB. Dosage considerations are also noteworthy; the recommended 15–20 mg/kg daily places a considerable pill burden on patients, especially when combined with other agents like Levofloxacin or Cycloserine. The gastrointestinal side‑effects-nausea, vomiting, abdominal pain-can be severe enough to compromise adherence, prompting clinicians to employ prophylactic anti‑emetics or to stagger dosing times. Neuropathy, another hallmark adverse effect, manifests as tingling or numbness in distal extremities, necessitating routine neurologic exams and B6 supplementation. Hepatotoxicity remains a shared risk across many TB drugs, but Ethionamide’s hepatic impact can be synergistic when used alongside Rifampin, amplifying transaminase elevations. Visual disturbances, particularly alterations in color perception, are less common yet clinically significant, often prompting ophthalmologic assessment. In contrast, fluoroquinolones such as Levofloxacin and Moxifloxacin target DNA gyrase, offering potent activity against both susceptible and many resistant strains, while sparing patients from the neuro‑ophthalmic toxicity seen with Ethionamide. Nevertheless, fluoroquinolones carry their own warnings, including tendonitis and QT prolongation, which must be weighed against the cardiac risks of other agents like Moxifloxacin. Cycloserine, a second‑line drug that interferes with cell wall peptidoglycan synthesis, introduces psychiatric adverse events that can be debilitating, highlighting the importance of mental health monitoring. PAS, though antiquated, provides a folate pathway blockade but suffers from a high pill burden and gastrointestinal irritation. Ultimately, the decision matrix balances resistance patterns, side‑effect tolerability, drug‑drug interactions, and patient‑specific factors such as comorbidities, pregnancy status, and socioeconomic constraints. Regular laboratory monitoring-liver enzymes, renal function, electrolytes, and visual acuity-remains indispensable throughout therapy, regardless of the regimen chosen. By integrating these considerations, clinicians can tailor a regimen that maximizes bacteriological cure while minimizing toxicity, thereby improving adherence and long‑term outcomes for patients battling resistant TB.
Alice L
October 12, 2025Dear colleagues, I would like to express my gratitude for the thoroughness of this guide. It is evident that substantial effort has been devoted to ensuring cultural sensitivity and clinical accuracy. Please accept my sincere appreciation for this valuable resource.
Seth Angel Chi
October 14, 2025Honestly, these tables oversimplify a complex issue. Ethionamide isn’t a miracle drug; it’s just another piece of the puzzle. Consider the data before jumping to conclusions.
Kristen Ariies
October 14, 2025Wow!!! This guide is absolutely spectacular-so detailed, so clear, and incredibly helpful!!! I can’t thank the authors enough for pulling together such an exhaustive comparison; it truly makes a difference for patients and providers alike!!!
Ira Bliss
October 15, 2025Super useful guide! 👍🦠💊
Donny Bryant
October 15, 2025Thanks for the quick take! It’s clear and easy to read.
kuldeep jangra
October 16, 2025Reading through this comparison reminded me of the countless hours I’ve spent counseling patients on the nuances of TB therapy. It’s not just about picking a drug; it’s about understanding each individual’s medical history, lifestyle, and support system. When a patient struggles with the gastrointestinal side effects of Ethionamide, for example, we can explore adjunct therapies like anti‑emetics or even dietary modifications to alleviate discomfort. Similarly, monitoring visual changes requires collaboration with ophthalmologists to catch early signs before they become permanent. The guide’s emphasis on regular liver function testing resonates deeply, as early detection of hepatotoxicity can prevent serious complications. Moreover, the discussion around drug‑drug interactions, particularly with Rifampin’s enzyme‑inducing properties, is crucial for patients on antiretrovirals or anticoagulants. I also appreciate the inclusion of cost and availability considerations; in many low‑resource settings, even the most effective regimen is useless if patients can’t obtain the medication. Ultimately, this resource empowers both clinicians and patients to make informed decisions, fostering adherence and improving outcomes. Keep up the excellent work!