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3HP FAQs for Pharmacists

What is 3HP?

3HP is one of four regimens CDC recommends for treatment of latent tuberculosis infection.  The term 3HP comes from the regimen duration (once weekly doses for three months) and the abbreviations of each of the two drugs, isoniazid (INH) and rifapentine (RPT), in the regimen.  Some people refer to 3HP as the “12-dose regimen.” This regimen has been recommended in the United States for treating latent TB infection since 2011.

Updated recommendations for the use of 3HP appear in an article in the Morbidity and Mortality Weekly Report (MMWR) published June 28, 2018.

Should I fill one prescription for all 12 doses in the 3HP regimen, or fill one month at a time?

Pharmacists should fill prescriptions one month at a time. Providers are encouraged to write the prescription for one month, with monthly refills.  However, providers may use their discretion for individual patients. Pharmacists should contact their state and local TB programs with specific questions.

Pharmacists should make sure that patients prescribed 3HP receive isoniazid and rifapentine.  A similar rifamycin compound, rifampin, is used in a different treatment regimen for latent TB infection.

What are some of the major drug-drug interactions with the 3HP regimen?

Rifapentine is a rifamycin compound; like rifampin, it induces metabolism of many medications. CDC recommends monitoring of patients when 3HP is prescribed with interacting medications (e.g., methadone or warfarin). Women who use hormonal birth control should be advised to add, or switch to, a barrier method. Women who become pregnant during 3HP treatment should consult their provider.

Information about drug-drug interactions between specific anti-mycobacterial agents including rifamycins (rifampin, rifabutin and rifapentine) and antiretroviral agents is available at Department of Health and Human Services, Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents.  These frequently updated guidelines include a section addressing management of latent TB infection (LTBI) in persons co-infected with HIV, and tables with information on drug interactions. Tables 18 and 19a-e provide up-to-date information concerning drug-drug interactions between specific antiretroviral agents and the several rifamycins, including rifapentine.  Use of concomitant LTBI treatment and antiretroviral agents should be guided by clinicians experienced in the management of both conditions.

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