Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis. This illness primarily targets the lungs but can affect other parts of the body, spreading through the air when an infected person coughs or sneezes. Although TB is a serious condition, it is curable. Its treatment is distinct from common bacterial infections, relying on a prolonged course of specific antibiotics.
The Standard Multi-Drug Treatment Plan
The standard for treating drug-susceptible TB is a multi-drug regimen. Using several antibiotics at once prevents the bacteria from developing resistance to any single medication. The four primary first-line antibiotics are Isoniazid, Rifampin, Pyrazinamide, and Ethambutol.
Treatment is structured into two phases. The first is the intensive phase, which typically lasts for two months and involves taking all four medications daily. This initial stage is designed to rapidly kill the most active bacteria, reducing the patient’s infectiousness and symptoms.
The continuation phase follows, generally involving only Isoniazid and Rifampin. This stage lasts for an additional four to seven months, bringing the total treatment duration to at least six months. The goal of this longer phase is to eliminate any remaining dormant bacteria, which can persist and cause a relapse if not fully eradicated.
Potential Side Effects of Treatment
The powerful antibiotics used to treat tuberculosis can cause a range of side effects. Patients should report any new symptoms to their healthcare provider. Each of the first-line drugs carries its own profile of possible side effects.
- Rifampin is known for causing a harmless but sometimes alarming red-orange discoloration of body fluids like urine and tears.
- Isoniazid can lead to peripheral neuropathy (nerve damage causing tingling in the hands and feet), which is often preventable with a vitamin B6 supplement.
- Pyrazinamide may cause joint pain and can increase uric acid levels, potentially triggering a gout attack.
- Ethambutol is associated with vision problems that can affect color vision and acuity, requiring regular eye exams during treatment.
The combination of drugs can also lead to general side effects like nausea, loss of appetite, and abdominal pain. A more serious concern with Isoniazid, Rifampin, and Pyrazinamide is liver inflammation (hepatitis). Symptoms such as yellowing skin, dark urine, or persistent fatigue require immediate medical attention. Patients must not stop taking their medication unless explicitly told to do so by a doctor.
The Critical Role of Treatment Adherence
Completing the full course of medication as prescribed is necessary to cure the disease. Patients often feel better within a few weeks, but this does not mean the infection is gone. Stopping treatment prematurely can lead to severe consequences.
Incomplete treatment can lead to a relapse, where the patient becomes sick and infectious again. More importantly, non-adherence can lead to the development of drug-resistant bacteria. When treatment is inconsistent, surviving bacteria can mutate, rendering first-line drugs ineffective.
This resistance complicates future treatment. To help patients complete the long regimen, healthcare systems often use Directly Observed Therapy (DOT). In DOT, a healthcare worker observes the patient taking their medication to encourage completion and prevent relapse and drug resistance.
Treating Drug-Resistant Tuberculosis
When tuberculosis bacteria become resistant to first-line antibiotics, the disease is known as drug-resistant TB. The most common type is multidrug-resistant TB (MDR-TB), defined by resistance to at least Isoniazid and Rifampin. An even more severe form, extensively drug-resistant TB (XDR-TB), is resistant to Isoniazid, Rifampin, any fluoroquinolone, and at least one second-line injectable drug.
Treatment for drug-resistant TB involves second-line drugs, which are less potent and have a higher likelihood of causing severe side effects. A regimen for MDR-TB requires at least four effective drugs based on the specific resistant strain. These regimens often include medications from different classes, such as fluoroquinolones, injectable agents like amikacin or kanamycin, and other oral drugs like linezolid or bedaquiline.
The treatment duration for drug-resistant TB is much longer, often lasting 18 to 24 months or more. Success rates for treating MDR-TB are lower than for drug-susceptible TB, with global cure rates around 48%, and even lower for XDR-TB.