TB Drug Comparison Tool
This tool compares key attributes of Isoniazid and other anti-TB drugs to help understand their roles in treating tuberculosis.
Class: First-line bactericidal
Dosage: 5 mg/kg daily (max 300 mg)
Uses: Latent TB, part of 4-drug regimen
Side Effects: Hepatotoxicity, peripheral neuropathy
Resistance Risk: Low when used with other first-line drugs
Class: First-line bactericidal
Dosage: 10 mg/kg daily (max 600 mg)
Uses: Active TB, part of 4-drug regimen
Side Effects: Hepatic enzyme rise, orange fluids, interactions
Resistance Risk: Moderate; synergy reduces risk
Class: First-line bacteriostatic
Dosage: 15–25 mg/kg daily
Uses: Active TB, especially high-bacillary load
Side Effects: Optic neuritis, color vision loss
Resistance Risk: Low when combined
Class: First-line bactericidal (acidic pH)
Dosage: 20–25 mg/kg daily (2 months)
Uses: Intensive-phase drug in standard regimen
Side Effects: Hepatotoxicity, hyperuricemia
Resistance Risk: Low with proper combination
Class: Second-line injectable aminoglycoside
Dosage: 15 mg/kg IM daily
Uses: MDR-TB, when oral options limited
Side Effects: Ototoxicity, nephrotoxicity
Resistance Risk: High if used alone
Class: Fluoroquinolone (second-line)
Dosage: 750 mg daily
Uses: MDR-TB, rifampin-intolerant cases
Side Effects: Tendon rupture, QT prolongation
Resistance Risk: Moderate; resistance develops quickly
Class: Diarylquinoline (novel)
Dosage: 400 mg daily 2 wks, then 200 mg TIW
Uses: MDR-TB, part of all-oral regimens
Side Effects: QT prolongation, hepatic effects
Resistance Risk: Low when combined with other new drugs
Quick Decision Guide
- Latent Infection: Isoniazid alone for 6-9 months or 3-month weekly Isoniazid-Rifapentine combo
- Drug-Sensitive Pulmonary TB: Four-drug regimen (INH, RIF, EMB, PZA) for 2 months, followed by INH-RIF for 4 months
- Hepatic Impairment: Reduce or omit INH and PZA; consider RIF, EMB, and fluoroquinolone
- Pregnancy: Safe to use INH and RIF; avoid Streptomycin due to fetal ototoxicity
- MDR-TB: All-oral regimen including Bedaquiline, Levofloxacin, and possibly Linezolid
Key Monitoring Points
- Baseline liver function tests before starting INH, RIF, or PZA
- Visual acuity and color vision testing when EMB is part of regimen
- Serum uric acid levels if PZA is used for more than 6 weeks
- Quarterly ECGs for patients on Bedaquiline or Levofloxacin
- Peripheral neuropathy assessment in patients on INH; give pyridoxine 25 mg daily
Common Pitfalls to Avoid
- Skipping pyridoxine with INH → leads to numbness or tingling
- Not checking drug interactions with RIF → affects contraceptives, antiretrovirals, anticoagulants
- Using Streptomycin without auditory monitoring → early hearing loss can be irreversible
- Stopping therapy early due to mild liver enzyme rise → small increases are common
- Prescribing Bedaquiline without ECG baseline → missed QT prolongation can cause arrhythmia
When a doctor needs to treat tuberculosis, the first drug that often comes to mind is Isoniazid. But the landscape of TB therapy includes several other agents, each with its own strengths and drawbacks. This guide walks you through the most common alternatives, compares their key attributes, and helps you decide which one fits a particular case.
What is Isoniazid?
Isoniazid is a bactericidal antibiotic specifically active against Mycobacterium tuberculosis. It is classified as a first‑line anti‑TB drug and is often used in both active disease and latent infection.
- Typical adult dose: 5mg/kg (max 300mg) daily.
- Key side effects: hepatotoxicity, peripheral neuropathy (preventable with pyridoxine).
- Mechanism: inhibits mycolic acid synthesis, compromising the bacterial cell wall.
How Rifampin
Rifampin is a broad‑spectrum antibiotic that also targets the bacterial RNA polymerase. It is a cornerstone of the standard four‑drug regimen for active TB.
- Typical adult dose: 10mg/kg (max 600mg) daily.
- Key side effects: orange‑red body fluids, liver enzyme elevation, drug‑drug interactions.
- Use: active TB, also effective for latent infection when combined with Isoniazid.
Understanding Ethambutol
Ethambutol interferes with the bacterial cell wall by blocking arabinogalactan synthesis. It is added to prevent resistance when the patient’s bacterial load is high.
- Typical adult dose: 15-25mg/kg daily.
- Key side effects: optic neuritis (vision changes), which are reversible if detected early.
- Role: part of the initial intensive phase in drug‑sensitive TB.
Pyrazinamide
Pyrazinamide works best in acidic environments, such as the intracellular compartments where TB bacteria hide. It shortens the overall treatment duration.
- Typical adult dose: 20-25mg/kg daily for the first two months.
- Key side effects: hyperuricemia, hepatotoxicity.
- Use: intensive‑phase drug in the standard regimen.
When Streptomycin
Streptomycin is an injectable aminoglycoside that disrupts protein synthesis. It is now reserved for multidrug‑resistant (MDR) TB or when oral options are limited.
- Typical adult dose: 15mg/kg intramuscularly daily.
- Key side effects: ototoxicity, nephrotoxicity.
- Current status: not part of first‑line therapy in most countries.
Exploring Levofloxacin
Levofloxacin is a fluoroquinolone with activity against TB strains resistant to first‑line drugs. It is taken orally and penetrates well into lung tissue.
- Typical adult dose: 750mg daily.
- Key side effects: tendon rupture, QT prolongation, gastrointestinal upset.
- Indication: MDR‑TB regimens, alternative when rifampin cannot be used.
The newer Bedaquiline
Bedaquiline targets the ATP synthase of Mycobacterium tuberculosis, a mechanism not shared by older drugs. It has become a vital component of the all‑oral MDR‑TB regimen.
- Typical adult dose: 400mg daily for 2 weeks, then 200mg three times per week.
- Key side effects: QT interval prolongation, hepatic enzyme elevation.
- Regulatory status: approved by WHO for MDR‑TB under careful cardiac monitoring.
The disease context: Tuberculosis
Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, affecting primarily the lungs but capable of spreading to any organ. Treatment success hinges on selecting the right drug combination for the right duration.
Side‑by‑side comparison of the main agents
| Drug | Class | Typical Dose (Adult) | Primary Use | Major Side Effects | Resistance Risk |
|---|---|---|---|---|---|
| Isoniazid | First‑line bactericidal | 5mg/kg daily (max 300mg) | Latent TB, part of 4‑drug regimen | Hepatotoxicity, peripheral neuropathy | Low when used with other first‑line drugs |
| Rifampin | First‑line bactericidal | 10mg/kg daily (max 600mg) | Active TB, part of 4‑drug regimen | Hepatic enzyme rise, orange fluids, interactions | Moderate; synergy reduces risk |
| Ethambutol | First‑line bacteriostatic | 15‑25mg/kg daily | Active TB, especially high‑bacillary load | Optic neuritis, color vision loss | Low when combined |
| Pyrazinamide | First‑line bactericidal (acidic pH) | 20‑25mg/kg daily (2 months) | Intensive phase of active TB | Hepatotoxicity, hyperuricemia | Low with proper combination |
| Streptomycin | Second‑line injectable aminoglycoside | 15mg/kg IM daily | MDR‑TB, when oral options limited | Ototoxicity, nephrotoxicity | High if used alone |
| Levofloxacin | Fluoroquinolone (second‑line) | 750mg daily | MDR‑TB, rifampin‑intolerant cases | Tendon rupture, QT prolongation | Moderate; resistance develops quickly |
| Bedaquiline | Diarylquinoline (novel) | 400mg daily 2wks, then 200mg TIW | MDR‑TB, part of all‑oral regimens | QT prolongation, hepatic effects | Low when combined with other new drugs |
Choosing the right drug: practical decision points
Here are some concrete scenarios and what they imply for drug selection:
- Latent infection in a healthy adult: Isoniazid alone for 6‑9months (or a 3‑month weekly Isoniazid‑rifapentine combo). No need for the other agents.
- Newly diagnosed drug‑sensitive pulmonary TB: The classic four‑drug regimen (Isoniazid, Rifampin, Ethambutol, Pyrazinamide) for two months, followed by Isoniazid‑Rifampin for four months.
- Hepatic impairment: Reduce or omit Isoniazid and Pyrazinamide; consider a regimen based on Rifampin, Ethambutol, and a fluoroquinolone.
- Pregnancy: Isoniazid and Rifampin are generally safe; avoid Streptomycin because of fetal ototoxicity.
- MDR‑TB (resistance to Isoniazid and Rifampin): Build an all‑oral regimen including Bedaquiline, Levofloxacin, and possibly linezolid, guided by susceptibility testing.
Monitoring and managing side effects
Regardless of the chosen drug, regular follow‑up is essential.
- Baseline liver function tests (ALT/AST) before starting Isoniazid, Rifampin, or Pyrazinamide.
- Visual acuity and color vision testing at month 1 and month 2 when Ethambutol is part of the regimen.
- Serum uric acid levels if Pyrazinamide is used for more than six weeks.
- Quarterly ECGs for patients on Bedaquiline or Levofloxacin, especially if they have cardiac risk factors.
- Peripheral neuropathy assessment in patients on Isoniazid; give pyridoxine 25mg daily to prevent nerve damage.
Common pitfalls and how to avoid them
Even seasoned clinicians can trip up. Below are typical mistakes and quick fixes.
- Skipping pyridoxine with Isoniazid: Leads to numbness or tingling. Always prescribe 25mg pyridoxine daily.
- Not checking drug interactions with Rifampin: Rifampin induces many cytochromeP450 enzymes, lowering the levels of contraceptives, antiretrovirals, and some anticoagulants. Review the patient’s medication list thoroughly.
- Using Streptomycin without auditory monitoring: Early hearing loss can be irreversible. Conduct baseline audiometry and repeat after two weeks.
- Stopping therapy early because of mild liver enzyme rise: Small, transient increases are common; continue with close monitoring unless enzymes rise > three times the upper limit.
- Prescribing Bedaquiline without ECG baseline: Missed QT prolongation can precipitate arrhythmia. Get a baseline ECG and repeat monthly.
Frequently Asked Questions
Can I use Isoniazid alone for active TB?
No. For active disease, Isoniazid must be combined with other drugs (Rifampin, Ethambutol, Pyrazinamide) to prevent resistance and ensure cure.
Is Rifampin safe during pregnancy?
Rifampin is generally considered safe in pregnancy and is included in WHO’s recommended regimen for pregnant women with TB.
What is the advantage of Bedaquiline over older drugs?
Bedaquiline targets a novel bacterial enzyme, making it effective against strains that resist Isoniazid and Rifampin. It also allows an all‑oral regimen, avoiding painful injections.
How long should I take Isoniazid for latent TB?
The standard course is 6months, though a 9‑month regimen is used when adherence is a concern. A 3‑month weekly Isoniazid‑rifapentine combo is another evidence‑based option.
Do I need to monitor blood sugar while on Pyrazinamide?
Pyrazinamide can raise uric acid, not blood sugar. Routine glucose checks aren’t required unless the patient has diabetes.
Hey folks, great rundown! I especially love how you highlighted the need for pyridoxine with INH – it saves a lot of nerve pain. Keep it up!
While the table is thorough, it glosses over the pharmacogenomic nuances that dictate isoniazid metabolism. Not everyone metabolizes the drug at the same rate, leading to variable hepatotoxicity profiles. Moreover, the emphasis on Bedaquiline’s novelty ignores its cost barriers in low‑income settings. The recommendation to monitor QT intervals is sound, yet many clinicians lack ECG access. So, the tool, though polished, feels a bit detached from real‑world constraints.
From a clinical pharmacology perspective, the comparative dosages are accurately presented. It is crucial to note that Rifampin’s enzyme induction can diminish concomitant drug levels, a point that clinicians must vigilantly monitor. The inclusion of peripheral neuropathy assessment for INH underscores best practice. Overall, the guide provides a solid foundation for regimen selection.
The melodramatic flair of this comparison tool makes me feel like I'm reading a blockbuster script, complete with heroic drug protagonists and villainous side effects. Isoniazid struts onto the stage as the beloved lead, flashing a badge of low resistance risk, only to be trailed by the ever‑dramatic Bedaquiline with its QT‑prolongation plot twist. Rifampin, the flamboyant side‑kick, turns everything orange and steals the limelight with endless drug‑drug interactions. Ethambutol, the visual artist, paints your optic nerves with a potential palette of color blindness. Pyrazinamide, the acid‑loving rebel, dives into the intracellular battlefield, but leaves a trail of liver enzyme fireworks. Streptomycin, the old‑school mercenary, whispers threats of ototoxicity while demanding daily injections. Levofloxacin swoops in as the smooth‑talking anti‑hero, promising tendon safety yet secretly plotting a QT‑elongation surprise. The guide wisely reminds us to give pyridoxine with INH, lest we surrender to peripheral neuropathy's numb embrace. Monitoring liver function becomes a ritualistic rite of passage for anyone daring to prescribe the first‑line quartet. For pregnant patients, the reassurance that INH and Rifampin are safe feels like a comforting lullaby amid a chorus of caution. When hepatic impairment looms, the suggestion to ditch INH and PZA reads like a strategic retreat in a chess match. MDR‑TB regimens now feature the dazzling Bedaquiline, turning the once‑grim prognosis into a hopeful saga. However, the cost and accessibility of such novel agents remain the shadowy antagonist lurking behind the scenes. Clinicians must juggle ECGs, visual acuity tests, and serum uric acid levels like circus performers on tightropes. In the end, this tool is a cinematic masterpiece of pharmacology, replete with drama, heroes, and plot twists – 🎬💊🔥
Sure, those side‑effects are just part of the fun.
You've got this! Remember, when you start INH, add pyridoxine right away – it's a simple step that prevents a lot of trouble. Keep an eye on liver enzymes weekly for the first month; a mild rise is usually okay. If a patient feels tingling in the feet, that’s a red flag – bump up the B6 dose. Also, educate the patient about orange urine from Rifampin so they aren't scared. Consistent follow‑up will keep the regimen on track.
Look, the table is solid but dont forget that streptomycin needs proper audiometry – otherwise you risk silent hearing loss. Also rifampin can make the hair dye turn orange, which is a funny side effect but can mess with some patients. The cost of bedaquiline is high, so not every clinic can afford it. Finally, always double‑check dosage calculations; a 5mg miscalc can be big.
Hey there, love how the guide blends clinical detail with patient‑friendly tips. I’m curious about the cultural considerations of DOTS programs in different regions – something that could be added. Also, the visual monitoring for ethambutol is crucial, especially in communities with high baseline eye issues. A quick note on diet: pyridoxine absorption can be affected by certain foods. Overall, great job making it accessible.
Oh great, another drug table, just what we needed.
Wow, this comparison really pulls together everything you need to know in one place – kudos to the author. Starting with isoniazid, you get a cheap, effective drug but you have to watch out for liver health, especially in older patients. Rifampin’s enzyme induction is a double‑edged sword: it helps kill the bacilli but can mess up other meds like birth‑control, which many patients forget. Ethambutol’s optic neuritis risk is scary, but regular vision testing catches it early before permanent damage sets in. Pyrazinamide shortens therapy length but brings its own liver concerns and can raise uric acid, so we should monitor gout patients closely. For MDR‑TB, the move to all‑oral regimens with bedaquiline and levofloxacin is a game‑changer, yet the QT monitoring adds a layer of complexity that not every clinic can handle. Bottom line: a solid, comprehensive guide that still leaves room for local adaptation.
Nice summary, but honestly the table could use some color to make the side‑effects pop.
The moral here is clear: don't skip pyridoxine, don't ignore liver tests, and definitely don't forget the eye checks. It's a bit preachy but necessary. Otherwise, well done.
Philosophically speaking, each drug is a piece in the puzzle of eradicating a centuries‑old scourge. The balance between efficacy and toxicity mirrors life's own trade‑offs. Monitoring is not just a protocol; it's a dialogue between patient and physician. When we respect that conversation, outcomes improve.
Sure, just another reason to distrust pharma.
Great tool! 😄 It’ll definitely help a lot of us on the floor.
Interesting take, Chris, but I think the guide actually does a decent job highlighting cost issues. While you mention enzyme induction, many clinics now have decision‑support software that flags interactions. Also, the QT monitoring suggestion is realistic given portable ECG devices are becoming common. So perhaps the tool isn’t as detached as you suggest.