Tuberculosis (TB) and leprosy are chronic infectious diseases caused by Mycobacterium tuberculosis and Mycobacterium leprae respectively. These organisms grow slowly and survive inside body cells, making treatment long and multi-drug based. Both diseases require carefully planned drug combinations to prevent resistance and ensure complete cure.
CHEMOTHERAPY OF TUBERCULOSIS
TB treatment uses multiple drugs together to kill bacteria at different stages and prevent drug resistance. Therapy is divided into two phases: intensive phase and continuation phase.
First-Line Anti-TB Drugs (RIPE)
- Rifampicin (R)
- Isoniazid (H)
- Pyrazinamide (Z)
- Ethambutol (E)
Mechanism of Action
- Isoniazid: Inhibits mycolic acid synthesis (cell wall component)
- Rifampicin: Blocks RNA polymerase → stops RNA synthesis
- Pyrazinamide: Active in acidic environments inside macrophages
- Ethambutol: Blocks arabinoglycan synthesis in cell wall
Standard Treatment Regimen
The common short-course regimen is:
- Intensive Phase (2 months): HRZE (daily)
- Continuation Phase (4 months): HR (daily)
Total duration is usually 6 months for drug-sensitive TB.
Side Effects of First-Line Drugs
- Isoniazid: Nerve damage (prevented by pyridoxine), hepatitis
- Rifampicin: Orange-red urine/tears, liver toxicity, drug interactions
- Pyrazinamide: Hyperuricemia, joint pain, hepatotoxicity
- Ethambutol: Optic neuritis → vision problems
Drug-Resistant TB
- MDR-TB: Resistant to isoniazid + rifampicin
- XDR-TB: Resistant to first-line drugs + fluoroquinolones + injectable second-line drugs
Second-Line Drugs for MDR/XDR TB
- Fluoroquinolones (levofloxacin, moxifloxacin)
- Aminoglycosides (amikacin, streptomycin)
- Ethionamide
- Cycloserine
- Bedaquiline
- Clofazimine
CHEMOTHERAPY OF LEPROSY
Leprosy treatment uses a WHO-recommended multi-drug therapy (MDT) to prevent resistance and achieve complete cure. Duration varies depending on the type of leprosy.
Classification of Leprosy
- Paucibacillary (PB): Mild form, fewer lesions
- Multibacillary (MB): Severe form, many lesions
Drugs Used in Leprosy
1. Dapsone
Inhibits folate synthesis in bacteria.
Side effects: anemia, hemolysis (especially in G6PD deficiency), rashes.
2. Rifampicin
Powerful bactericidal drug against M. leprae.
3. Clofazimine
Has anti-leprosy and anti-inflammatory properties.
Side effects: reddish or brown skin discoloration, dryness, GI issues.
WHO Multi-Drug Therapy (MDT)
For Paucibacillary (PB) Leprosy (6 months)
- Rifampicin – once monthly
- Dapsone – daily
For Multibacillary (MB) Leprosy (12 months)
- Rifampicin – once monthly
- Dapsone – daily
- Clofazimine – daily + monthly supervised dose
Leprosy Reactions
Reactions occur during treatment due to immune responses:
Type 1 Reaction (Reversal Reaction)
Inflammation of existing lesions. Treated with steroids.
Type 2 Reaction (Erythema Nodosum Leprosum – ENL)
Painful nodules, fever, nerve damage. Treated with steroids and clofazimine.
Important Notes
- Both TB and leprosy treatment must be strictly adhered to to avoid resistance.
- Directly observed therapy (DOTS) improves treatment success.
- Rifampicin is a key drug in both diseases.
Detailed Notes:
For PDF style full-color notes, open the complete study material below: