Tuberculosis Treatment and Monitoring
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Direct answer
Daily isoniazid, rifampicin, pyrazinamide and ethambutol for two months, then isoniazid, rifampicin and ethambutol for four — 2HRZE/4HRE as a fixed-dose combination — is the regimen for drug-susceptible tuberculosis under India's National Tuberculosis Elimination Programme, with ethambutol carried into the continuation phase to guard against isoniazid resistance. Pyridoxine 10 to 25 mg daily accompanies isoniazid to prevent peripheral neuropathy. Monitoring rests on monthly sputum examination, weight and adherence checks, with alertness to drug-induced liver injury, the commonest reason for interrupting therapy.
What you must remember
- Intensive phase 2HRZE kills rapidly multiplying bacilli and renders the patient non-infectious within weeks; continuation phase 4HRE (ethambutol retained throughout in India's daily regimen to guard against isoniazid resistance) sterilises residual persisters.
- Give pyridoxine 10 to 25 mg daily to all patients on isoniazid, especially pregnant women, alcohol users, diabetics, malnourished and HIV-positive patients.
- Drug-induced liver injury: check liver function at baseline in risk groups. Withhold antitubercular drugs if transaminases exceed three times the upper limit with symptoms (nausea, vomiting, jaundice), or five times the upper limit without symptoms; pyrazinamide is the usual offender, followed by isoniazid and rifampicin.
- Rechallenge after recovery: reintroduce drugs one at a time, starting with rifampicin, then isoniazid; pyrazinamide is usually omitted permanently if it caused jaundice.
- Sputum follow-up: at the end of the intensive phase and monthly thereafter in smear-positive patients. A persistently positive smear at the end of the intensive phase may extend it by one month; a positive smear later suggests treatment failure and demands drug-susceptibility testing.
- Adverse effects worth marks: rifampicin discolours urine orange and reduces oral contraceptive efficacy; ethambutol causes dose-related optic neuritis (red-green colour blindness) — ask about vision monthly; streptomycin is ototoxic and contraindicated in pregnancy.
- Corticosteroids are adjuncts in tuberculous meningitis and pericardial tuberculosis; treatment is extended to 9 to 12 months in bone, joint, meningeal and disseminated disease.
Six months of a patient, watched
A 35-year-old, 48 kilograms, smear-positive, starts 2HRZE daily by weight band, with pyridoxine because she is pregnant — the groups that most need it are pregnancy, alcohol use, diabetes, malnutrition and HIV. Warned that rifampicin will turn her urine orange and that her oral contraceptive will fail on it, she takes the intensive phase that kills rapidly multiplying bacilli and renders her non-infectious within weeks. Week five brings nausea and scleral icterus, transaminases four times the upper limit: the graded rule applies — withhold antitubercular drugs above three times with symptoms, or five times without — and pyrazinamide, the usual offender, becomes the prime suspect. After liver values recover, rechallenge one drug at a time, rifampicin first, then isoniazid, with pyrazinamide usually omitted permanently if it caused jaundice; if the disease is extensive, fluoroquinolone-based bridging belongs to specialist guidance. Back on full treatment, sputum is checked at the end of the intensive phase and monthly thereafter: Ask about vision monthly — ethambutol's dose-related retrobulbar optic neuritis begins with red-green colour loss — and remember that her meningeal, bone, joint or disseminated counterparts are treated for 9 to 12 months, with corticosteroids adjunctive in tuberculous meningitis and pericardial disease.
Where students slip
The regimen code is where India and the textbook diverge: WHO shorthand writes the continuation phase as HR, but the Indian programme continues ethambutol, so 2HRZE/4HRE is the safe Indian answer. Jaundice management is the second guaranteed stem — the numbers (three times with symptoms, five times without) and the rechallenge order (rifampicin, then isoniazid, pyrazinamide usually gone). The remaining single-liners recycle reliably: orange urine and enzyme induction from rifampicin, colour blindness from ethambutol, ototoxicity and pregnancy contraindication for streptomycin, pyridoxine for the neuropathy of isoniazid, and the five-month definition of failure.
Frequently asked questions
What is the standard regimen for new drug-susceptible TB in India?
Daily 2HRZE/4HRE — two months of isoniazid, rifampicin, pyrazinamide and ethambutol, then four months of isoniazid, rifampicin and ethambutol.
When should antitubercular drugs be withheld for liver injury?
When transaminases cross three times the upper limit with symptoms, or five times the upper limit without symptoms, or if bilirubin rises with clinical jaundice.
Why is pyridoxine given with isoniazid?
Isoniazid causes pyridoxine deficiency and peripheral neuropathy; supplementation prevents it and is mandatory in pregnancy, alcoholism, diabetes and malnutrition.
Which first-line drug causes visual toxicity?
Ethambutol — dose-dependent retrobulbar optic neuritis presenting with red-green colour discrimination loss and reduced acuity.
What defines treatment failure?
A persistently positive sputum smear at five months or later despite regular therapy, prompting drug-susceptibility testing and regime change.
Can a patient on rifampicin use oral contraceptives?
Not reliably — rifampicin induces hepatic enzymes and lowers contraceptive steroid levels, so barrier contraception is advised.