Tuberculosis (TB) is an infectious bacterial disease caused primarily by Mycobacterium tuberculosis. Mycobacterium avium complex (MAC) infections are significant in immunocompromised patients, especially those with HIV.
Risk Factors for TB
- Alcoholism and drug misuse
- Immunocompromised states (e.g., HIV/AIDS)
- Overcrowded living conditions
- Chronic debilitating diseases such as diabetes
Common Symptoms of TB
- Persistent swollen lymph nodes
- Weight loss and loss of appetite
- Chronic non-productive cough
- Hemoptysis (coughing blood)
- Night sweats
Classification of Anti-Tuberculosis Drugs
1. First-Line Drugs (Primary treatment)
- Isoniazid (H)
- Rifampicin (R)
- Ethambutol (E)
- Pyrazinamide (Z)
- Streptomycin (S)
2. Second-Line Drugs (Used when resistance or intolerance occurs)
- Ethionamide (ETM)
- Para-aminosalicylic acid (PAS)
- Kanamycin (Kmc)
- Amikacin
- Capreomycin (Cpr)
- Ofloxacin
- Protionamide
First-Line Anti-TB Drugs Details
Isoniazid (H)
- Bactericidal against fast-growing and bacteriostatic against slow-growing M. tuberculosis.
- Well absorbed orally, crosses blood-brain barrier.
- Metabolized in liver; fast and slow acetylators exist.
- Adverse effects: Peripheral neuropathy (prevent with pyridoxine), hepatotoxicity.
- Drug interactions: Inhibits metabolism of phenytoin, carbamazepine, diazepam, warfarin (risk of toxicity).
Rifampicin (R)
- Effective against slow/intermittently dividing organisms.
- Oral absorption, excreted in bile.
- Adverse effects: Hepatotoxicity, orange-red discoloration of urine/sputum.
- Drug interactions: Induces metabolism of many drugs, reducing their efficacy (e.g., nevirapine, oral contraceptives).
Ethambutol (E)
- Good patient tolerance.
- Adverse effects: Optic neuritis causing decreased visual acuity and color blindness (monitor vision regularly).
- Use cautiously in renal impairment.
Pyrazinamide (Z)
- Active especially in acidic environments within tuberculous lesions.
- Oral absorption, hepatic metabolism.
- Adverse effects: Dose-related hepatotoxicity, hyperuricemia (can cause gout), photosensitivity.
Streptomycin (S)
- Given by injection; resistance develops rapidly if used alone.
- Adverse effects: Ototoxicity (tinnitus, vertigo), nephrotoxicity, sensitization.
Second-Line Anti-TB Drugs
- Aminoglycosides (Kanamycin, Amikacin, Capreomycin) used mainly in drug-resistant TB; toxic (ototoxicity, nephrotoxicity), given by injection, poor CSF penetration.
- Para-aminosalicylic acid (PAS): Tuberculostatic, delays resistance but less effective; interferes with rifampicin absorption.
- Ethionamide: Tuberculostatic, active against extra- and intracellular bacteria; side effects include anorexia, rash.
- Cycloserine: CNS toxicity common (psychosis, headache, tremor).
Treatment Principles and Regimens
- At least two drugs are combined to prevent resistance.
- Duration and drug choice depend on sensitivity of M. tuberculosis, lesion site, and severity.
- Treatment often prolonged (6 months or more) to ensure eradication.
- Multidrug-resistant TB (MDR-TB): Resistant to at least isoniazid and rifampicin; requires prolonged second-line therapy (12–24 months).
- Extensively drug-resistant TB (XDR-TB): Resistant to multiple key drugs, very difficult to treat.
