Tuberculosis (TB) is a chronic infectious disease caused by bacilli of the Mycobacterium tuberculosis complex , primarily Mycobacterium tuberculosis . Other causative agents include Mycobacterium bovis and Mycobacterium africanum .
Mode of Transmission:
TB is spread via airborne droplet nuclei expelled during coughing, sneezing, speaking, or laughing by individuals with active pulmonary TB.
Clinical Forms of Tuberculosis
- Pulmonary Tuberculosis (PTB): Affects the lungs; most common and infectious form.
- Extrapulmonary Tuberculosis (EPTB): Involves organs outside the lungs such as:
- Lymph nodes
- Spine and bones
- Kidneys, bladder
- Liver
- Gastrointestinal tract
- Skin
- Eyes
Signs and Symptoms
TB should be suspected in patients with a persistent cough >2 weeks , especially if accompanied by:
- Hemoptysis (blood-streaked sputum)
- Fever
- Night sweats
- Unexplained weight loss
- Chest pain
- Shortness of breath
Physical Examination Findings:
- Bronchial breath sounds
- Tachypnea
- Rales (crackles)
- Signs of consolidation
Basic Principles of TB Treatment
- Never use monotherapy (single drug): Prevents resistance.
- Use combination therapy with fixed-dose combinations (FDCs).
- Dosage is weight-based .
- Adherence is critical: Directly Observed Treatment Short-course (DOTS) is recommended.
- Pyridoxine (Vitamin B6) supplementation (25 mg/day) is necessary with isoniazid to prevent peripheral neuropathy .
First-Line Anti-TB Drugs
| Drug | Abbreviation | Mechanism of Action |
|---|---|---|
| Isoniazid | H | Inhibits mycolic acid synthesis |
| Rifampicin | R | Inhibits RNA polymerase |
| Pyrazinamide | Z | Disrupts membrane metabolism |
| Ethambutol | E | Inhibits arabinosyl transferase |
| Streptomycin | S | Inhibits protein synthesis |
Standard Adult TB Treatment Regimen
1. Intensive Phase (2 months):
- Drugs: Rifampicin (R), Isoniazid (H), Pyrazinamide (Z), Ethambutol (E)
- Administered daily under supervision.
2. Continuation Phase:
- Duration: 4–6 months
- Options:
- RH (Rifampicin + Isoniazid) – for 4 months
- RE (Rifampicin + Ethambutol) – for 6 months
Summary:
2RHZE/4RH or 2RHZE/6RE
Treatment of Retreatment Cases
Patients with relapse, treatment failure, or who return after default with smear-positive TB require an extended regimen:
- 2 months: Streptomycin + RHZE (2SRHZE)
- 1 month: RHZE
- 5 months: RHE
Summary:
2SRHZE/1RHZE/5RHE
Weight-Based Dosing Guidelines (Adults)
| Weight (kg) | IM Streptomycin | RHZE (FDC) | RHZ (FDC) | RH (FDC) | RHE | HE |
|---|---|---|---|---|---|---|
| >55 kg | 1 g | 4 tablets | 4 tablets | 4 tablets | 4 | 2 |
| 40–55 kg | 0.75 g | 3 tablets | 3 tablets | 3 tablets | 3 | 2 |
| 30–39 kg | 0.50 g | 2 tablets | 2 tablets | 2 tablets | 2 | 2 |
Note : Patients under 64 years should not receive more than 0.75 g of streptomycin daily.
Pyridoxine (Vitamin B6) Supplementation
- Adults: 25 mg daily when on isoniazid to prevent peripheral neuropathy.
- Children: Not routinely required, unless:
- Serum levels are low
- Receiving high-dose INH (>10 mg/kg)
