Generic Name: cobicistat

Pronunciation: N/A

Abbreviation: N/A

Other Market Name: N/A

Drug Class: Pharmacokinetic Enhancers

Company: Gilead Sciences

Approval Status: Approved

Generic Version Available: No

Experimental Code: GS-9350

Drug Indication

Used as a booster in recommended, alternative and other regimens for treatment-naïve people living with HIV, as indicated by the U.S. Department of Health and Human Services (DHHS) Panel on Antiretroviral Guidelines for Adults and Adolescents. Visit for the full DHHS guidelines.

General Info

Tybost is a pharmacokinetic enhancer, a drug used to boost the blood levels of select HIV medications to make them more effective.

Tybost is available as a single drug or in the fixed-dose combination drugs Evotaz, Prezcobix and Stribild.


Adult Dose: 150 mg once a day in combination with antiretrovirals that require boosting

Pediatric Dose: N/A

Dosing Info: Take with food.

Side Effects

The most common side effects of Tybost, in clinical trials that also included Reyataz,and Truvada, were diarrhea, nausea, jaundice and ocular icterus (yellowing of the skin and eyes), and rash.

 Tybost can cause minor increases in serum creatinine, a potential sign of kidney toxicity. These increases do not appear to affect creatinine clearance (CrCl), an even better indicator of kidney health. However, Tybost should not be used in combination with regimens containing tenofovir disoproxil fumarate (e.g., Viread or Truvada) by people with CrCL below 70 mL/min. CrCl should be tested before and during treatment with regimens containing Tybost and tenofovir disoproxil fumarate.

The risk and severity of other side effects will depend on the HIV medications with which Tybost is combined.

Drug Interactions

The following medications should not be taken while you are being treated with a regimen containing Tybost:
Acid reflux/heartburn medications: Propulsid (cisapride)
Antibiotics: Rifadin (rifampin)
Antimigraine medications: Methergine, Methylergometrine (methylergonovine); Ergostat, Cafergot, Ercaf, Wigraine (ergotamine); Ergotrate, Methergine (ergonovine); or D.H.E. 45, Migranal (dihydroergotamine)
Anti-gout: Colcrys (colchicine)
Chemotherapeutic drugs: Camptosar (irinotecan, if Tybost is being used with Reyataz or as a component of Evotaz)

Cholesterol-lowering drugs (statins): Zocor (simvastatin) and Mevacor (lovastatin)
Heart medications: Ranexa (ranolazine) and Multaq (dronedarone)
HIV medications: Crixivan (indinavir) or VIramune/Viramune XR (nevirapine), if Tybost is being used with Reyataz or as a component of Evotaz.
Antipsychotics: Latuda (lurasidone) and Orap (pimozide)
Sedatives: Versed (midazolam) and Halcion (triazolam)
Enlarged prostate: Uroxatral (alfuzosin)
Pulmonary Hypertension: Revatio (sildenafil)
Herbal products:
St. John’s wort

Do not combine Tybost with other products containing cobicistat or ritonavir, including combination products. Examples include: Evotaz, Genvoya, Prezcobix, Stribild, Norvir, or Kaletra. Tybost is not interchangeable with Norvir and should only be used with Reyataz or once-daily Prezista; it shouldn’t be combined with other protease inhibitors including 600 mg twice-daily Prezista, Lexiva (fosamprenavir), Invirase/Fortovase (saquinavir), or Aptvirus (tipranavir). Tybost should not be used with Viramune/Virmamune XR (nevirapine) or Intelence (etravirine); Sustiva (efavirenz) should also be avoided in all patients using Tybost plus Prezista (or Prezcobix) or when Tybost is combined with Reyataz (or used as Evotaz) in treatment-experienced patients.

Tybost can increase the levels of many other drugs in the body, potentially increasing the risk of serious side effects. Dosage adjustments or substitutions may be necessary if you are prescribed certain medications from any of the following drug classes: antiarrhythmics, antibiotics, cancer chemotherapeutic drugs, anticoagulants, anticonvulsants, antidepressants, antifungals, anti-gout medications, antimalarial drugs, beta-blockers, calcium channel blockers, corticosteroids (oral and inhaled), endothelin receptor antagonists, hepatitis C medications, statins, hormonal contraceptives, immune-suppressants, inhaled beta agonists, narcotic medications (for pain and opioid dependence), neuroleptics/anti-seizure medications, erectile dysfunction drugs, and sedatives/hypnotics. Consult the Tybost package insert for more details:

Other Info

Before taking this medication, tell your doctor if you have kidney disease or liver disease (including hepatitis B). In addition, tell your doctor if you are pregnant or planning to become pregnant, if you are breast feeding, and all your medical conditions.

It is also very important that your health care provider and pharmacist know all prescription and over-the-counter medications and supplements you are taking at all times while using an HIV treatment regimen that contains Tybost.

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Last Reviewed: July 15, 2016