Antileprosy Drugs
On this page
Direct answer
Six months of multidrug therapy for paucibacillary leprosy and twelve months for multibacillary disease — that duration pair is the spine of the National Leprosy Eradication Programme and the most quoted fact in this chapter. Paucibacillary disease (one to five lesions, slit-skin smear negative) receives supervised monthly rifampicin 600 mg plus daily self-administered dapsone 100 mg; multibacillary disease adds clofazimine — 300 mg supervised monthly with 50 mg daily — alongside the other two, all supplied free in blister packs. The toxicities are equally examinable: dapsone causes haemolysis and methaemoglobinaemia with the sulphone syndrome as its hypersensitivity catastrophe, while clofazimine paints the skin red-black and dries it into ichthyosis. Lepra reactions are treated without stopping multidrug therapy: type 1 (reversal) reactions get corticosteroids, type 2 (erythema nodosum leprosum) gets thalidomide, clofazimine and steroids.
What you must remember
- Regimens by classification: paucibacillary — rifampicin 600 mg once monthly (supervised) + dapsone 100 mg daily for 6 months; multibacillary — rifampicin 600 mg monthly + clofazimine 300 mg monthly + clofazimine 50 mg daily + dapsone 100 mg daily for 12 months.
- More than five skin lesions, any positive slit-skin smear, or nerve trunk involvement classifies disease as multibacillary — when in doubt, treat as multibacillary.
- Rifampicin is the most bactericidal antileprosy drug — a single 600 mg dose kills over 99 per cent of viable bacilli — which is why monotherapy must never occur and resistance emerges fast without partners.
- Dapsone: haemolysis (screen G6PD), methaemoglobinaemia with chocolate-brown blood, and the sulphone syndrome — fever, rash progressing to exfoliative dermatitis, lymphadenopathy and hepatitis within the first two months, treated by stopping the drug and giving corticosteroids.
- Clofazimine: reversible dose-related red-black skin and conjunctival pigmentation, ichthyosis and dryness, and abdominal pain from crystal deposition in intestinal macrophages — counsel the pigmentation before the first dose.
- Type 1 (reversal) reaction: upgraded cell-mediated immunity — oedema of existing lesions, tender nerves, new sensory or motor loss; treat with prednisolone 40–60 mg tapering; nerves are the emergency.
- Type 2 reaction (erythema nodosum leprosum): immune-complex crops of tender nodules with fever, iritis, dactylitis; thalidomide 100–300 mg is the most effective agent (strict contraception — the drug of the limb-defect tragedy), with clofazimine and corticosteroids as allies.
- Single-lesion paucibacillary leprosy may take single-dose ROM — rifampicin 600 mg, ofloxacin 400 mg, minocycline 100 mg once.
- Minocycline, ofloxacin and clarithromycin are alternatives in dapsone hypersensitivity; multidrug therapy continues through both types of lepra reaction.
A worked clinical pathway
A 32-year-old presents with a hypopigmented, hypoanaesthetic patch on the thigh and a thickened lateral popliteal nerve. Step one confirms the pathway: slit-skin smear from the lesion sites and ear lobes, sensory testing, and a voluntary muscle and nerve examination — the smear and lesion count decide paucibacillary versus multibacillary, and the classification decides the blister pack. Because a thickened nerve trunk alone up-grades him to multibacillary, he starts the twelve-month course, with counselling about pigmentation over months, monthly supervised dosing, and the paradox to warn about: reactions often first appear after treatment begins.
Three months later he returns with a hot, swollen patch and a suddenly painful, weak foot — a type 1 reaction with threatened nerve function. The programme response runs in order: start prednisolone 40–60 mg daily in a tapering course over weeks, continue the multidrug therapy uninterrupted, splint and rest the affected limb, and record the motor loss date. If instead he had arrived with crops of tender red nodules and fever — erythema nodosum leprosum — thalidomide (with documented contraception in a woman) or clofazimine dose escalation would lead, and iritis would be sought. The unifying rule for the exam: reaction treatment is added, never substituted, and steroids do not replace antibiotics.
Where students slip
The two reaction types are transposed under time pressure — type 1 is the nerve-damaging, delayed-hypersensitivity reaction needing steroids, while type 2 is the immune-complex nodular reaction answering to thalidomide. The second slip is stopping multidrug therapy when a reaction erupts; the correct move is to continue chemotherapy and treat the reaction, because the bacilli are still being cleared. Third, thalidomide prescribed to a woman of childbearing age without contraception counselling repeats history's most famous teratogenic disaster — FMGE asks exactly this. Fourth, the durations are swapped: six months for paucibacillary, twelve for multibacillary, with a single-dose ROM option only for the solitary lesion. Finally, G6PD screening before dapsone and the warning about dark urine and breathlessness (methaemoglobinaemia) mark the safe prescriber.
Frequently asked questions
What is the multidrug therapy regimen for multibacillary leprosy?
Rifampicin 600 mg and clofazimine 300 mg once monthly supervised, with daily self-administered dapsone 100 mg and clofazimine 50 mg, for 12 months — free under the National Leprosy Eradication Programme.
Which drug colours the skin in leprosy treatment?
Clofazimine, causing reversible red-black pigmentation of skin, conjunctiva and body fluids, along with ichthyosis — patients must be warned before starting.
How do type 1 and type 2 lepra reactions differ in treatment?
Type 1 (reversal, nerve tenderness and function loss) is treated with corticosteroids; type 2 (erythema nodosum leprosum) with thalidomide, clofazimine and steroids — multidrug therapy continues in both.
What is the sulphone syndrome?
A dapsone hypersensitivity cluster of fever, rash progressing to exfoliation, lymphadenopathy and hepatitis in the first weeks of therapy; dapsone stops and corticosteroids are given.
When is single-dose ROM used?
For single-lesion paucibacillary leprosy — rifampicin 600 mg, ofloxacin 400 mg and minocycline 100 mg as one supervised dose.
Why can dapsone cause haemolysis?
It is an oxidant stress to erythrocytes, worst in G6PD deficiency, and also causes methaemoglobinaemia — hence G6PD screening and haemoglobin monitoring.