Page 19 of 44

PH8.6 | PH8.6 | Leprosy Pharmacotherapy — SDL Guide — SDL Guide (Part 3)

Clinical Decision-Making in Leprosy Pharmacotherapy

Applying leprosy pharmacotherapy requires several key clinical judgements that go beyond drug choice:

Distinguishing Type 1 from Type 2 reactions: This clinical differentiation directly determines pharmacological management. Key discriminators:
- Type 1: occurs in borderline leprosy; pre-existing patches become red and swollen (upgrading of pre-existing disease); peripheral nerve involvement (acute neuritis); treated with prednisolone.
- Type 2 (ENL): occurs in LL/BL; new erythematous nodules (different from pre-existing patches); systemic features (fever, iritis, orchitis); treated with thalidomide (men/post-menopausal) or clofazimine (fertile women) ± prednisolone for neuritis.
- In both reactions: continue MDT. Never stop MDT for a lepra reaction — it is not a drug adverse effect.

Management in pregnancy: Dapsone and rifampicin are considered safe in pregnancy. Clofazimine — limited human data but used when benefits outweigh risks. Thalidomide is absolutely contraindicated. Type 1 reactions in pregnant women: prednisolone (carefully tapered; usual pregnancy-related concerns apply). ENL in pregnant women: clofazimine preferred.

Managing dapsone hypersensitivity syndrome: Occurs 4–6 weeks into therapy — high fever, morbilliform rash, hepatitis, lymphadenopathy. Resembles infectious mononucleosis. Mechanism: likely T-cell mediated (similar to carbamazepine hypersensitivity). Management: stop dapsone immediately and permanently; treat with prednisolone (40–60mg/day); substitute with clofazimine or ofloxacin in the regimen.

Adherence and stigma: Clofazimine-induced skin pigmentation is a major barrier to treatment adherence, particularly among lighter-skinned patients or those engaged in professions where appearance matters. Anticipate this discussion at treatment initiation — explain the mechanism (drug concentration in melanocytes), the reversibility (6–12 months after stopping), and the clinical importance of completing treatment. Social support from the NLEP's disability prevention programmes and self-help groups improves adherence.

After MDT completion: Skin lesions continue to resolve for 1–2 years after completing MDT — reassure patients that fading is expected. Monitor for late reactions (Type 1 reactions can occur years post-MDT). Monitor for nerve function impairment even after cure. Shoes, protective footwear, and wound care for anaesthetic feet prevent secondary disability.

Self-Assessment: Leprosy Pharmacotherapy

Test your knowledge with these clinical scenarios:

Scenario A: A 40-year-old man is diagnosed with multibacillary leprosy (8 lesions, smear BI 2+). He is started on MB MDT (rifampicin + clofazimine + dapsone). At 2 weeks, his family members are alarmed to see his skin turning brownish-orange and urine becoming darker. He is otherwise well; no fever, no skin lesions changing. He calls to say he wants to stop the medicine. What is happening and how do you counsel him?

Discussion: The orange-brown skin and body-fluid discolouration is a predictable, harmless, and expected effect of clofazimine — a highly lipophilic dye that deposits in skin, fat, and reticuloendothelial tissue. It is NOT drug toxicity, an allergic reaction, or liver disease. The darker urine may reflect clofazimine in urine. Reassure the patient: this is expected, harmless, and reversible (will fade over 6–12 months after completing MDT). Emphasise that stopping MDT would be a serious mistake — clofazimine discolouration is a cosmetic inconvenience, not a medical emergency. Continuing MDT is essential to cure and prevent disability.

Scenario B: A 30-year-old male with lepromatous leprosy develops severe ENL — multiple crops of painful nodules, fever 39°C, bilateral iritis, and no response to 2 weeks of prednisolone 40mg/day. The treating physician considers thalidomide. What is the dose, mechanism, and key monitoring plan?

Discussion: Thalidomide is appropriate in this male patient with severe steroid-refractory ENL. Dose: 100–300mg/day initially, then taper to maintenance 50–100mg/day. Mechanism: inhibits TNF-α (a key mediator of ENL inflammation) and reduces neutrophil chemotaxis. Key monitoring: (a) peripheral neuropathy — thalidomide causes dose-dependent, irreversible sensorimotor neuropathy (unrelated to leprosy neuropathy); do not confuse. Check nerve conduction studies at baseline and 6-monthly; stop if neuropathy worsens. (b) DVT/PE risk — thalidomide is prothrombotic, especially with dexamethasone co-administration. Continue MB MDT throughout ENL management.

Scenario C: A 25-year-old woman on PB MDT (rifampicin + dapsone) reports that her periods were regular until she started MDT 2 months ago — now her last 2 periods have been very light. She is on a combined oral contraceptive pill for family planning. She is worried about whether something is wrong. What is your explanation?

Discussion: Rifampicin is a potent CYP3A4 inducer that accelerates metabolism of ethinylestradiol and progestins in combined oral contraceptive pills, reducing their plasma levels to subtherapeutic concentrations. The lighter periods may reflect reduced endometrial exposure to hormones — and more importantly, contraceptive failure is very likely. Counsel: (1) OCP will not reliably prevent pregnancy during rifampicin treatment; (2) Switch to a non-hormonal contraceptive (copper IUD, condoms) or injectable progesterone (noting progesterone is also induced — reduced efficacy); (3) This is a rifampicin drug interaction, not a leprosy effect; it will resolve after completing MDT. Continue MDT.