During the intensive phase, patients are normally administered a combination of four antibacterial medications: isoniazid, rifampicin, pyrazinamide, and ethambutol. These drugs are taken on a daily basis. In South Africa, for example, they cost approximately R64 for a pack of 112 tablets, with the number of tablets taken daily ranging from 2 to 5, depending on the patient’s weight.
The medications work by disrupting the functioning of the bacteria that cause tuberculosis. Isoniazid and ethambutol inhibit the formation of the bacterial cell wall. Pyrazinamide prevents bacterial growth, while rifampicin makes the bacterium unable to produce vital proteins. Rifabutin is another medication that is sometimes used in place of rifampicin during the intensive phase, but rifampicin is more widely used because of its cheaper cost. These medications are used in combination rather than alone in order to prevent the development of resistant strains of bacteria.
Side effects, particularly nausea and abdominal pain, are relatively common during the first few weeks of therapy. Urine and tears can also turn orange, which is harmless but disconcerting if patients are not warned. More severe side effects, such as joint pain, visual impairment, liver damage, and peripheral neuropathy are less common but can be serious when they do occur. Within a few weeks of beginning treatment most patients will start to feel better. During the intensive phase it is normal for the patient to become non-contagious. The patient’s sputum converts from positive to negative, so that TB bacilli can no longer be detected under a microscope.
Once the intensive phase is completed, the “continuous phase” of treatment begins. During this four-month phase, isoniazid and rifampicin are normally taken alone on a daily basis. In South Africa, these drugs cost approximately R22 to R44 (depending on the dosage) for 56 tablets. If the medications are taken regularly and sputum tests remain negative, this six month course of treatment is standard and the patient is considered cured upon completion.
Many people with tuberculosis also test positive for HIV. This is because a weakened immune system enables tuberculosis infection to develop more easily. In addition, TB speeds up the course of an HIV infection. South Africa has one of the highest rates of TB/HIV co-infection, with 73% of those infected with tuberculosis testing positive for HIV.[i] Therefore it is recommended that all patients with TB be given counseling and testing for HIV infection. TB/HIV co-infected patients should receive antiretroviral treatment regardless of their CD4 count. People diagnosed with TB and HIV should start TB treatment and then begin antiretroviral treatment within two to four weeks.
In South Africa, isoniazid can be used to prevent TB. When used as such, treatment with isoniazid is referred to as isoniazid preventative therapy (IPT). In South Africa, IPT is available in public clinics for people living with HIV. IPT reduces a person’s risk of developing active TB. The standard regimen is 300 mg daily of isoniazid for 6-9 months in adults and adolescents and 5 mg/kg for children. The World Health Organisation now recommends an even longer course of 36 months. However, it is important that IPT only be given to patients who are tuberculin skin test-positive. Long-term IPT may actually be harmful when given to people who are tuberculin skin test-negative.
It is imperative for patients undergoing TB treatment to take their medications as prescribed. It may be tempting for a patient to discontinue medications when feeling better during the intensive phase. But it is crucial to complete the full course of therapy, because skipping doses or stopping treatment too soon may result in the growth of bacteria that are resistant to one or more medications. This leads to a TB infection that is more difficult and expensive to treat. It also increases the risk of relapse after treatmet is completed.
Patients who are resistant to both isoniazid and rifampicin, the most powerful first-line drugs, have Multi-Drug Resistant (MDR) TB. It can be cured using medications that are called second-line drugs. These drugs may include fluoroquinolones; streptomycin; cycloserine; and ethionamide. They are more expensive than first-line drugs and often have more adverse side effects. Treatment for MDR TB takes longer; it can last up to two years. In 2010 in South Africa, almost 10,000 cases of DR TB were diagnosed, but only about 5,000 people received treatment.Delaying treatment for MDR TB increases the risk of transmission.
Treatment Action Campaign. Mobilize Against TB. 30 Aug 2011.
Stop TB Partnership. Isonaizid Preventative Therapy (IPT) for People Living with HIV.