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PH8.5 | PH8.5 | Tuberculosis Pharmacotherapy — SDL Guide — SDL Guide (Part 3)

Self-Assessment: TB Pharmacotherapy

Test your understanding with these case-based questions:

Scenario A: A 45-year-old diabetic woman is diagnosed with pulmonary TB and started on HRZE. At 2 months, sputum smear is still positive. DST results show rifampicin-susceptible, INH-resistant TB. What is the significance of this result and how do you modify the regimen?

Discussion: INH resistance (without rifampicin resistance) = mono-resistant TB, not MDR-TB. Standard Category I regimen should be continued (RIF remains active — the backbone of sterilising activity), but INH can be substituted with or the regimen can be extended to 9 months using RZES (rifampicin + PZA + ethambutol + streptomycin) or a fluoroquinolone-based regimen per WHO guidance. DST prevents inadvertently treating INH-resistant TB with a regimen dominated by an ineffective drug. This case underscores why DST at treatment initiation (especially in areas with high INH resistance rates) is recommended.

Scenario B: A 30-year-old man on HRZE week 4 asks: 'My doctor said to take the tablets on an empty stomach, but I feel very nauseous. Can I take them with breakfast?' How do you counsel him? Does food affect any of the drugs?

Discussion: Rifampicin is best absorbed when fasting (food reduces peak levels by 30–50%). However, in practice, the RNTCP recommends administration 1 hour before or 2 hours after meals; if the patient is non-compliant due to nausea, it is clinically preferable to take with a light meal than to miss doses. Nausea is very common early in ATT; it tends to improve over 4–6 weeks. Symptomatic management: small meals, avoid fatty foods, prescribe antiemetics (metoclopramide or domperidone) for the first 2–4 weeks. Emphasise: nausea does not mean liver damage — if nausea is severe with jaundice or dark urine, come back immediately.

Scenario C: A woman on HRZE for TB reports orange-coloured tears that are staining her contact lenses. She is alarmed. She also mentions she is on a combined oral contraceptive pill. What is your counselling?

Discussion: Orange discolouration of tears, urine, sweat, sputum, and saliva is caused by rifampicin and is harmless — warn the patient this is expected and will resolve on treatment completion. Contact lenses should not be worn during rifampicin treatment (permanent orange staining). More importantly: rifampicin is a potent CYP3A4 inducer that renders standard combined oral contraceptive pills ineffective (failure rate approaches that of no contraception). She must switch to a non-hormonal contraceptive method (condoms, copper IUD, injectable progesterone — though progesterone metabolism is also induced) for the duration of treatment and for 4 weeks after rifampicin completion.