Priftin is the brand name for rifapentine, a prescription antibiotic used to prevent and treat tuberculosis (TB). Each tablet contains 150 mg of rifapentine, and it belongs to the rifamycin class of antibiotics, the same family as the more widely known drug rifampin. What makes Priftin notable is its long-acting properties, which allow for less frequent dosing compared to older TB medications.
How Priftin Works
Priftin kills the bacteria that cause tuberculosis, Mycobacterium tuberculosis, by blocking an enzyme the bacteria need to copy their genetic instructions. Specifically, it inhibits DNA-dependent RNA polymerase in TB bacteria. This prevents the bacteria from producing the proteins they need to survive and multiply. The drug targets this enzyme only in TB bacteria, not in human cells, which is why it can fight the infection without directly damaging your own tissue.
What Priftin Treats
Priftin is used for two distinct purposes: treating latent TB infection (where the bacteria are present in your body but aren’t causing symptoms or spreading) and treating active pulmonary TB (where the disease has taken hold in the lungs and is causing illness).
For latent TB, Priftin is part of a regimen known as 3HP. You take it once weekly alongside isoniazid for 12 weeks, totaling just 12 doses. This is a significantly shorter commitment than the older standard of taking isoniazid daily for 9 months, which is one reason it has become a preferred option. The 3HP regimen is approved for adults and children aged 2 years and older.
For active pulmonary TB, the CDC recommends a newer 4-month daily regimen that includes Priftin. This regimen is for patients aged 12 and older who weigh at least 40 kg (about 88 pounds) and whose TB is not drug-resistant. It consists of an 8-week intensive phase using four drugs daily, followed by a 9-week continuation phase with three drugs daily, for a total of 119 doses. The full course should be completed within about 5 months. This is notably shorter than older 6-month TB treatment regimens.
Dosing Details
For the once-weekly latent TB regimen, the Priftin dose is weight-based. Adults and children weighing 50 kg or more take the maximum dose of 900 mg (six 150 mg tablets). Lighter individuals take less: 750 mg for those between about 32 and 50 kg, 600 mg for 25 to 32 kg, 450 mg for roughly 14 to 25 kg, and 300 mg for those between 10 and 14 kg. The companion drug isoniazid is dosed at 15 mg/kg for those 12 and older, up to 900 mg.
For the 4-month active TB regimen, the daily Priftin dose is 1,200 mg. This is taken with food every day for the full course of treatment.
Common and Serious Side Effects
The more commonly reported side effects include rash, increased sweating, fever, chills, cough, sore throat, unusual tiredness, and signs of low blood counts like easy bruising or unusual bleeding. Some people experience urinary symptoms such as painful urination or lower back and side pain.
Liver damage is one of the more serious risks. Warning signs include upper stomach pain or tenderness, dark urine, pale stools, loss of appetite, nausea, vomiting, or yellowing of the skin or eyes. These symptoms need prompt medical attention.
Priftin can also trigger a severe allergic reaction called DRESS syndrome (drug reaction with eosinophilia and systemic symptoms), which involves fever, swollen lymph nodes, and organ inflammation. Anaphylaxis and severe skin reactions like Stevens-Johnson syndrome, though rare, are also possible. Signs of a serious allergic reaction include difficulty breathing or swallowing, hives, and swelling of the face, throat, or tongue.
Drug Interactions to Know About
Priftin is a liver enzyme inducer, meaning it speeds up how your body processes certain other medications. This can make those medications less effective, sometimes dangerously so.
The most clinically important interactions involve HIV medications and hormonal contraceptives. Several HIV antiretrovirals, including atazanavir/ritonavir, darunavir/ritonavir, lopinavir/ritonavir, and nevirapine, should not be taken with Priftin because the drug can lower their levels enough to risk HIV treatment failure and resistance. However, some HIV drugs are safe to use alongside it: dolutegravir, raltegravir, and efavirenz can all be coadministered without dose changes, though dolutegravir dosing may need to be increased in certain situations.
Hormonal birth control is the other major concern. Priftin can reduce the effectiveness of virtually all hormonal contraceptive methods, including pills, implants, vaginal rings, and emergency contraception. If you’re using any hormonal method, you’ll need to use barrier contraception (such as condoms) during treatment and for at least two weeks after your last dose, because the drug’s effects on hormone levels persist briefly after you stop taking it.
Pregnancy and Children
Priftin carries significant concerns during pregnancy. Animal studies found it caused birth defects in rats and rabbits at doses near or below equivalent human doses, including cleft palate and organ abnormalities. Pregnant and nursing women were excluded from the major clinical trials. Among women who became pregnant during studies, spontaneous abortion rates were notable: about 16% in the Priftin group and 13% in the comparison group. Among 14 pregnancies reported during rifapentine use, 4 (29%) ended in first-trimester miscarriage. The drug is classified as pregnancy category C, meaning risk cannot be ruled out.
For children, the once-weekly latent TB regimen is approved down to age 2. A waiver was granted for children under 2 because pediatric studies in that age group were not conducted. The 4-month active TB regimen applies only to those 12 and older.