Drugs Used in Tuberculosis

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Curative Therapy

A significant advancement in the treatment of tuberculosis has taken place in recent years. The development of resistance to drugs is prevented by using two or more drugs. The long duration of treatment (1 to 2 years) has been shortened by the introduction of short course chemotherapy. The problem of poor compliance to drugs is minimised by the introduction of intermittent supervised therapy called DOTS (Directly Observed Treatment Short Course) under revised National Tuberculosis Control Programme. Three types of treatment regimens used are described below:

Conventional Course Chemotherapy: This consists of streptomycin, INH and thiacetazone or ethambutol for 12-18 months. However since failure rates are high, and compliance poor, it is not recommended nowadays.

Short Course Chemotherapy: A 6 to 9 month regimen consisting of isoniazid, rifampicin, ethambutol, and pyrazinamide daily for 2 to 3 months, followed by isoniazid and rifampicin daily for 4-6 months, has been found to be satisfactory, provided that it is fully

supervised. The patient s disease is catagorized depending on the extent of disease. The treatment is carried out in two phases. In the initial phase four drugs are to be taken daily, or thrice weekly, for 2 months. Then sputum examination is done. If it is positive for TB organisms, drugs are continued for another month. In the second phase or the continuation phase, two or three drugs are to be taken for 6 to 8 months.

Drugs

The drugs used in the treatment of tuberculosis can be divided into first and second line drugs. Foods such as meat, milk, cereals, legumes, and yeast are rich in vitamin B6 . A diet containing these may help in preventing peripheral neuritis.

First Line Drugs

Isoniazid (Isonex)

Isoniazid is a first line drug. It is a bactericidal drug and kills both extracellular and intracellular bacteria. It interferes with the cell wall (mycolic acid) synthesis of the bacteria. It is the best drug for treatment of tuberculosis with respect to efficacy, safety, cost, ease of administration, and patient acceptance. It may be administered alone for prophylaxis, or in combination with other drugs for chemotherapy, of disease. It is almost always required for combination treatment in DOTS.

Adverse Effects: It increases excretion of vitamin B6 (pyridoxine) which may result in numbness, pain, tiredness, weakness, pain in the muscles and joints. Patients suffering from diabetes mellitus, malnutrition, or alcoholism should be given 10 mg pyridoxine routinely, If there are pre-existing symptoms of peripheral neuritis, a larger dose of pyridoxine of 50 to 100 mg may be given daily. Other adverse effects are liver damage, mental disturbance and rarely fits. Liver damage is not common in children but may occur in elderly and alcoholics.

Precautions

The doctor should be informed if any symptoms of peripheral neuritis such as a decreased sensation or pain in the muscles occur.

A liver function test (serum transaminase) is advised after a month or two of the treatment. If the serum transaminase exceeds 3 times normal value, the drug should be stopped.

A pyridoxine supplement is necessary in pregnant women, nursing mothers, and infants as this drug is secreted in milk.

The doctor should be consulted if any adverse effects like allergic reactions, arthritis, or difficulty in vision occur.

The drug should be taken regularly as advised by the doctor. Inadequate doses or missing the drug in between may cause a relapse.

If nausea occurs, the drug should be taken with meals, dividing the dose into two halves, that is, half in the morning and half in the evening.