Treatment of latent TB infection reduces the risk of progression to active tuberculosis disease. A 6-month course of isoniazid is about 70% effective in preventing progression, and a 12-month course is about 90% effective. Further study showed that a 9-month regimen is almost as effective as the 12-month regimen, the basis for the current recommendation of 9-months as the optimal course. (See figure 1 in http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4906a1.htm )
A summary of treatment options is found in the Guidelines for Primary Care Providers (CDC). Isoniazid is used most often because of it is the best studied and does not have as many drug interactions as rifampin. The major adverse reaction is hepatoxicity, whose risk is increased with age and with pregnancy and post-partum period. A 4-month course of rifampin is used in those who do not tolerate isoniazid, or in whom it is contraindicated, and as a relatively liver-sparing alternative. Weekly rifapentine-isoniazid for 12 weeks is the shortest regimen, the most expensive, and requires directly-observed treatment (DOT).
Symptoms and compliance should be monitored during treatment. Whatcom County Health Department TB program refills medication monthly. Clinicians ensure that a symptom review is done before providing additional medication, as well as pill counts that help in evaluating compliance. Patients at high risk of progression to active disease (young children, especially those who are close contacts to active cases, and severely immunosuppressed patients) should have DOT (sometimes referred to as directly-observed preventive treatment (DOPT) to differentiate it from DOT for active TB disease.)
Documentation of diagnosis and treatment are an important part of a patient’s permanent health record, and by ensuring that the patient has a detailed summary, future unnecessary testing and treatment can be avoided. The CDC provides templates for testing and treatment documentation in Appendix E of the Guidelines for Primary Care Providers (PDF).