WHAT IS COBICISTAT?
Cobicistat is a drug used as part of antiretroviral therapy (ART). It is also called Tybost. It is manufactured by Gilead Sciences. Cobicistat is a pharmacologic enhancer. These drugs work by slowing down the liver metabolism of other drugs. Cobicistat itself does not inhibit HIV.
While antiretroviral therapy (ART) is recommended for all people living with HIV, there are no absolute rules about when to start ART. You and your health care provider should consider your CD4 cell count, your viral load, any symptoms you are having, and your attitude about taking ART. Fact Sheet 404 has more information about guidelines for the use of ART.
If you take cobicistat with ARVs, you can reduce your viral load to extremely low levels, and increase your CD4 cell counts. This should mean staying healthier longer.
Cobicistat makes the liver work more slowly. This can increase the blood levels of some drugs, including the integrase inhibitor elvitegravir and protease inhibitors. This can cause some dangerous interactions with other drugs.
HOW IS IT TAKEN?
Cobicistat (Tybost) is taken by mouth as a 150 mg tablet, once-daily.
Cobicistat is used to increase the blood levels of other HIV medications, including the integrase inhibitor elvitegravir and certain protease inhibitors.
Tybost should not be used to replace Norvir when used with darunavir twice daily or the other protease inhibitors, fosamprenavir, saquinavir or tipranavir.
A small amount of cobicistat is included in tablets of Stribild and Genvoya as a booster. Stribild and Genvoya are also manufactured by Gilead Sciences.
WHAT ARE THE SIDE EFFECTS?
The most common side effects of cobicistat when taken with atzanavir are jaundice and icterus (yellowing of the skin and eyes), and nausea. Tell your health care provider if you have any problems while taking cobicistat.
HOW DOES IT REACT WITH OTHER DRUGS?
Cobicistat can interact with other drugs or supplements that you are taking. These interactions can change the amount of each drug in your bloodstream and cause an under- or overdose. New interactions are being identified all the time.
Cobicistat can change the blood levels of oral birth control medications. Alternative methods of birth control are recommended.
There can be dangerous interactions with drugs for pulmonary arterial hypertension or erectile dysfunction such as sildenafil (Viagra) or other drugs with names ending in “-afil”, drugs to treat asthma, and for heart rhythm (antiarrhythmics.)
The herb St. John's Wort (See Fact Sheet 729) lowers the blood levels of some ARVs. Do not take it with cobicistat.
Other drugs to watch out for include other ARVs, drugs to treat tuberculosis (see fact sheet 518), and for migraine headaches. Interactions are also possible with several antihistamines (allergy medications), sedatives, drugs to lower cholesterol and anti-fungal drugs. Make sure that your health care provider knows about ALL drugs and supplements you are taking.