a person with a positive skin test a normal chest x-ray and no symptoms most likely has only a few tb germs in an inactive state and is not contagious. nevertheless treatment with an antibiotic may be recommended for this person to prevent the tb from turning into an active infection. the antibiotic used for this purpose is called isoniazid. if taken for six to 12 months it will prevent the tb from becoming active in the future. in fact if a person with a positive skin test does not take inh there is a 5%-10% lifelong risk that the tb will become active. taking isoniazid can be inadvisable (contraindicated) during pregnancy or for those with alcoholism or liver disease. also isoniazid can have side effects. the side effects occur infrequently but a rash can develop and the patient can feel tired or irritable. liver damage from isoniazid is a rare occurrence and typically reverses once the drug is stopped. very rarely however especially in older people the liver damage (inh hepatitis) can even be fatal. it is important therefore for the doctor to monitor a patient's liver by periodically ordering blood tests called "liver function tests" during the course of inh therapy. another side effect of inh is a decreased sensation in the extremities referred to as a peripheral neuropathy. this can be avoided by taking vitamin b6 (pyridoxine) and this is often prescribed along with inh. a person with a positive skin test along with an abnormal chest x-ray and sputum evidencing tb bacteria has active tb and is contagious. active tb usually is accompanied by symptoms such as a cough fever weight loss and fatigue. active tb is treated with a combination of medications along with isoniazid. rifampin (rifadin) ethambutol (myambutol) and pyrazinamide are the drugs commonly used to treat active tb in conjunction with isoniazid (inh). four drugs are often taken for the first two months of therapy to help kill any potentially resistant strains of bacteria. then the number is usually reduced to two drugs for the remainder of the treatment based on drug sensitivity testing that is usually available by this time in the course. streptomycin a drug that is given by injection may be used as well particularly when the disease is extensive and/or the patients do not take their oral medications reliably (termed "poor compliance"). treatment usually lasts for many months and sometimes for years. successful treatment of tb is dependent largely on the compliance of the patient. indeed the failure of a patient to take the medications is the most important cause of failure to cure the tb infection. in some locations the health department demands direct monitoring of patient compliance with therapy. surgery on the lungs may be indicated to help cure tb when medication has failed but in this day and age surgery for tb is unusual. treatment with appropriate antibiotics will usually cure the tb. without treatment however tuberculosis can be a lethal infection. therefore early diagnosis is important. those individuals who have been exposed to a person with tb or suspect that they have been should be examined by a doctor for signs of tb and screened with a tb skin test.
how is tuberculosis treated?