Skip to Content


Generic Name: cobicistat (koe BIK i stat)
Brand Names: Tybost

What is Tybost?

Tybost (cobicistat) reduces the action of enzymes in your liver that break down certain antiviral medicines. This allows the antiviral medicines to be used more safely and effectively at lower doses.

Tybost is given together with atazanavir (Reyataz) or darunavir (Prezista) to treat human immunodeficiency virus (HIV) in adults. HIV is the virus that causes acquired immunodeficiency syndrome (AIDS).

Tybost is not an antiviral medicine and will not treat HIV or AIDS. Tybost is given only to help increase your blood levels of atazanavir or darunavir.

Important information

Cobicistat is not a complete treatment and must be used in combination with other antiviral medicines your doctor has prescribed. However, there are certain antiviral medicines that should not be taken in combination with Tybost. Follow your doctor's medication and dosing instructions very carefully.

Tybost is recommended for use only with atazanavir or darunavir. You should not take Tybost with other protease inhibitor HIV medicines, such as fosamprenavir, nelfinavir, saquinavir, or tipranavir.

You should not take Tybost with darunavir if you are taking darunavir twice daily. You should not take Tybost with atazanavir if you also take indinavir, irinotecan, or nevirapine.

Many drugs can interact with cobicistat and some should not be used at the same time, especially: alfuzosin, cisapride, dronedarone, lovastatin, simvastatin, oral midazolam, triazolam, pimozide, rifampin, sildenafil (for treating pulmonary arterial hypertension), St. John's wort, or ergot medicine (dihydroergotamine, ergotamine, ergonovine, methylergonovine). Tell your doctor about all your current medicines and any you start or stop using.

Before taking this medicine

Tybost is not a complete treatment and must be used in combination with other antiviral medicines your doctor has prescribed. However, there are certain antiviral medicines that should not be taken in combination with Tybost. Follow your doctor's medication and dosing instructions very carefully.

You should not take Tybost if you are allergic to cobicistat.

  • You should not take cobicistat with darunavir if you are taking darunavir twice daily.

  • You should not take cobicistat with atazanavir if you also take indinavir, irinotecan, or nevirapine.

Some medicines can interact with cobicistat and should not be used at the same time. Your doctor may need to change your treatment plan if you use any of the following drugs:

  • alfuzosin;

  • cisapride;

  • colchicine;

  • dronedarone;

  • lovastatin, simvastatin;

  • oral midazolam, triazolam;

  • ranolazine;

  • rifampin;

  • sildenafil (Revatio, for treating pulmonary arterial hypertension);

  • St. John's wort;

  • antipsychotic medicine - lurasidone, pimozide;

  • ergot medicine - dihydroergotamine, ergotamine, ergonovine, methylergonovine; or

  • seizure medication - carbamazepine, phenobarbital, phenytoin.

To make sure Tybost is safe for you, tell your doctor if you have:

  • liver disease; or

  • kidney disease.

Tybost is not expected to be harmful to an unborn baby. However, HIV can be passed to your baby if you are not properly treated during pregnancy. Take all of your HIV medicines as directed to control your infection. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Women with HIV or AIDS should not breast feed a baby. Even if your baby is born without HIV, the virus may be passed to the baby in your breast milk.

Tybost is not approved for use by anyone younger than 18 years old.

How should I take Tybost?

Tybost is usually taken once per day with atazanavir or darunavir. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Take your HIV medicines with food at the same time each day to be sure you do not miss a dose.

If you take Tybost with atazanavir, your doctor may also prescribe a medicine to reduce stomach acid. If so, follow these recommendations, unless your doctor tells you otherwise:

  • If you take an antacid: Take the antacid at least 2 hours before or 2 hours after you take Tybost and atazanavir.

  • If you take a medicine such as cimetidine, ranitidine, Tagamet, Axid, Zantac, Pepcid, and others: You may either take the stomach medicine at the same time you take Tybost and atazanavir; or wait at least 10 hours after taking the stomach medicine to take your Tybost and atazanavir doses.

  • If you take a proton pump inhibitor such as omeprazole, esomeprazole, Nexium, Prevacid, Prilosec, Protonix: Wait at least 12 hours after taking the stomach medicine to take your Tybost and atazanavir doses.

While using Tybost, your blood may need to be tested often. Your kidney function may also need to be tested.

HIV/AIDS is usually treated with a combination of drugs. Use all medications as directed by your doctor. Read the medication guide or patient instructions provided with each medication. Do not change your doses or medication schedule without your doctor's advice. Every person with HIV or AIDS should remain under the care of a doctor.

Store in the original container at room temperature, away from moisture and heat. Keep the bottle tightly closed when not in use.

Tybost dosing information

Usual Adult Dose for HIV Infection:

150 mg orally once a day with food

-This drug must be used with atazanavir or darunavir; the manufacturer product information for these agents should be consulted.
-This drug may be used with atazanavir (300 mg orally once a day) in therapy-naive and therapy-experienced patients.
-This drug may be used with darunavir (800 mg orally once a day) in therapy-naive patients and therapy-experienced patients with no darunavir resistance associated substitutions.
-This drug is not interchangeable with ritonavir and should not be used with darunavir 600 mg twice a day, fosamprenavir, saquinavir, or tipranavir.

Use: To increase systemic exposure of atazanavir or darunavir in combination with other antiretrovirals in the treatment of HIV-1 infection

See also: Dosage Information (in more detail)

What happens if I miss a dose?

Take the missed dose as soon as you remember. If you are more than 12 hours late, skip the missed dose. Then take your combination of medicines (Tybost with atazanavir, or Tybost with darunavir) at your next scheduled dose. Do not take extra medicine to make up the missed dose.

To avoid missing a dose, get your prescription refilled before you run out of medicine completely.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Tybost?

Taking this medication will not prevent you from passing HIV to other people. Do not have unprotected sex or share razors or toothbrushes. Talk with your doctor about safe ways to prevent HIV transmission during sex. Sharing drug or medicine needles is never safe, even for a healthy person.

Tybost side effects

Get emergency medical help if you have any signs of an allergic reaction to Tybost: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • signs of a kidney problem - little or no urinating; painful or difficult urination; swelling in your feet or ankles; feeling tired or short of breath; or

  • liver problems - upper stomach pain, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common Tybost side effects may include:

  • nausea; or

  • jaundice.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

What other drugs will affect Tybost?

Tybost can harm your kidneys. This effect is increased when you also use certain other medicines, including: antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).

Many drugs can interact with Tybost. Not all possible interactions are listed in this medication guide. Tell your doctor about all your medications and any you start or stop using during treatment with Tybost, especially:

  • atorvastatin, bosentan, colchicine, rifabutin, rivaroxaban, rosuvastatin, salmeterol, warfarin (Coumadin, Jantoven);

  • cancer medicine; seizure medicine; an immunosuppressant; narcotic pain medicine, or medicines used to treat narcotic addiction;

  • hormonal birth control (pills, skin patches, vaginal rings);

  • sildenafil (Viagra) or other erectile dysfunction medicines;

  • an antibiotic - clarithromycin, erythromycin;

  • antifungal medicine - itraconazole, ketoconazole, voriconazole;

  • heart or blood pressure medicine - amiodarone, digoxin, disopyramide, flecainide, mexiletine, propafenone, quinidine, timolol;

  • hepatitis C medicine - boceprevir, simeprevir, telaprevir;

  • medicine to treat anxiety, depression, or mental illness - buspirone, perphenazine, risperidone, thioridazine, and others;

  • other HIV medicines - efavirenz, elvitegravir, etravirine, lopinavir, maraviroc, ritonavir, tenofovir, and others; or

  • steroid medicine - budesonide, dexamethasone, fluticasone.

This list is not complete and many other drugs can interact with cobicistat. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.

Where can I get more information?

  • Your pharmacist can provide more information about Tybost.
  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Tybost only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2016 Cerner Multum, Inc. Version: 1.03. Revision Date: 2016-07-13, 9:44:57 AM.