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Tybost (Oral)

Generic Name: cobicistat (Oral route)


Commonly used brand name(s)

In the U.S.

  • Tybost

Available Dosage Forms:

  • Tablet

Therapeutic Class: Anti-Infective Agent

Uses For Tybost

Cobicistat is used to increase the effects of atazanavir or darunavir for the treatment of human immunodeficiency virus (HIV) infection. HIV is the virus that causes acquired immune deficiency syndrome (AIDS).

This medicine is available only with your doctor's prescription.

Before Using Tybost

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies have not been performed on the relationship of age to the effects of cobicistat in the pediatric population. Safety and efficacy have not been established.


Although appropriate studies on the relationship of age to the effects of cobicistat have not been performed in the geriatric population, no geriatric-specific problems have been documented to date.


Pregnancy Category Explanation
All Trimesters B Animal studies have revealed no evidence of harm to the fetus, however, there are no adequate studies in pregnant women OR animal studies have shown an adverse effect, but adequate studies in pregnant women have failed to demonstrate a risk to the fetus.

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Alfuzosin
  • Cisapride
  • Colchicine
  • Conivaptan
  • Crizotinib
  • Dabrafenib
  • Dihydroergotamine
  • Doxorubicin
  • Doxorubicin Hydrochloride Liposome
  • Dronedarone
  • Eliglustat
  • Eplerenone
  • Ergonovine
  • Ergotamine
  • Eszopiclone
  • Fentanyl
  • Ibrutinib
  • Irinotecan
  • Isavuconazonium Sulfate
  • Ivabradine
  • Lomitapide
  • Lovastatin
  • Lurasidone
  • Maraviroc
  • Methylergonovine
  • Midazolam
  • Naloxegol
  • Pazopanib
  • Pimozide
  • Primidone
  • Quetiapine
  • Ranolazine
  • Rifampin
  • Riociguat
  • Romidepsin
  • Sildenafil
  • Silodosin
  • Simvastatin
  • St John's Wort
  • Suvorexant
  • Tolvaptan
  • Trabectedin
  • Triazolam
  • Vemurafenib
  • Vinflunine
  • Vorapaxar

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Ado-Trastuzumab Emtansine
  • Afatinib
  • Alfentanil
  • Alprazolam
  • Amiodarone
  • Amobarbital
  • Amprenavir
  • Apixaban
  • Aprepitant
  • Aprobarbital
  • Aripiprazole
  • Armodafinil
  • Artemether
  • Astemizole
  • Atorvastatin
  • Avanafil
  • Bedaquiline
  • Boceprevir
  • Bosentan
  • Bosutinib
  • Brentuximab Vedotin
  • Bromocriptine
  • Budesonide
  • Buprenorphine
  • Buspirone
  • Butabarbital
  • Butalbital
  • Cabazitaxel
  • Cabozantinib
  • Carbamazepine
  • Carvedilol
  • Ceritinib
  • Cilostazol
  • Citalopram
  • Cladribine
  • Clarithromycin
  • Clobazam
  • Clofarabine
  • Clonazepam
  • Clozapine
  • Cyclophosphamide
  • Cyclosporine
  • Dabigatran Etexilate
  • Daclatasvir
  • Dactinomycin
  • Dasabuvir
  • Dasatinib
  • Daunorubicin
  • Delamanid
  • Delavirdine
  • Dexamethasone
  • Diazepam
  • Digoxin
  • Disopyramide
  • Docetaxel
  • Domperidone
  • Donepezil
  • Doxepin
  • Dutasteride
  • Efavirenz
  • Eletriptan
  • Enzalutamide
  • Erlotinib
  • Erythromycin
  • Eslicarbazepine Acetate
  • Ethosuximide
  • Etoposide
  • Etravirine
  • Everolimus
  • Felodipine
  • Flecainide
  • Fluoxetine
  • Fluticasone
  • Fosamprenavir
  • Fosaprepitant
  • Fosphenytoin
  • Glyburide
  • Haloperidol
  • Hydrocodone
  • Idelalisib
  • Ifosfamide
  • Iloperidone
  • Imatinib
  • Isradipine
  • Itraconazole
  • Ivacaftor
  • Ketoconazole
  • Lapatinib
  • Letrozole
  • Levomilnacipran
  • Lidocaine
  • Lopinavir
  • Losartan
  • Lumefantrine
  • Macitentan
  • Mefloquine
  • Mephobarbital
  • Methadone
  • Methohexital
  • Methotrexate
  • Mexiletine
  • Mifepristone
  • Mitotane
  • Mitoxantrone
  • Modafinil
  • Montelukast
  • Morphine
  • Morphine Sulfate Liposome
  • Nafcillin
  • Nateglinide
  • Netupitant
  • Nevirapine
  • Nilotinib
  • Nimodipine
  • Nintedanib
  • Nisoldipine
  • Olaparib
  • Ombitasvir
  • Oxaliplatin
  • Oxcarbazepine
  • Oxycodone
  • Paclitaxel
  • Palbociclib
  • Panobinostat
  • Paritaprevir
  • Pentobarbital
  • Perampanel
  • Phenobarbital
  • Phenytoin
  • Pioglitazone
  • Piperaquine
  • Pixantrone
  • Pomalidomide
  • Ponatinib
  • Prazosin
  • Prednisolone
  • Prednisone
  • Propafenone
  • Quinidine
  • Quinine
  • Regorafenib
  • Retapamulin
  • Rifabutin
  • Rifapentine
  • Rilpivirine
  • Ritonavir
  • Rivaroxaban
  • Roflumilast
  • Rosuvastatin
  • Rufinamide
  • Ruxolitinib
  • Salmeterol
  • Saquinavir
  • Saxagliptin
  • Secobarbital
  • Siltuximab
  • Simeprevir
  • Sirolimus
  • Sumatriptan
  • Sunitinib
  • Tadalafil
  • Tamoxifen
  • Tamsulosin
  • Telaprevir
  • Telithromycin
  • Temsirolimus
  • Teniposide
  • Terfenadine
  • Theophylline
  • Thiopental
  • Ticagrelor
  • Tipranavir
  • Topiramate
  • Topotecan
  • Toremifene
  • Tramadol
  • Trazodone
  • Triamcinolone
  • Ulipristal
  • Vandetanib
  • Vardenafil
  • Verapamil
  • Vilanterol
  • Vilazodone
  • Vinblastine
  • Vincristine
  • Vincristine Sulfate Liposome
  • Vinorelbine
  • Voriconazole
  • Vortioxetine
  • Warfarin
  • Zaleplon
  • Zolpidem

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Atazanavir
  • Darunavir
  • Indinavir
  • Nelfinavir

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Kidney disease—Use with caution. May make this condition worse.

Proper Use of Tybost

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.

This medicine comes with a patient information leaflet. Read and follow these instructions carefully. Read it again each time you refill your prescription in case there is new information. You should talk to your doctor if you have any questions.

This medicine should be taken with food.

Do not change the dose or stop using this medicine without checking first with your doctor. When your supply of this medicine is running low, contact your doctor or pharmacist ahead of time. Do not allow yourself to run out of this medicine.

If you are also taking an antacid containing aluminum or magnesium, take it at least 2 hours before or after cobicistat with atazanavir. Ask your doctor or pharmacist before taking any other medications for your stomach or heartburn.


The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For enhancement of atazanavir or darunavir:
      • Adults—150 milligrams (mg) once a day, taken with atazanavir 300 mg once a day or darunavir 800 mg once a day.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

If you miss a dose of cobicistat with atazanavir or darunavir by less than 12 hours, take the missed dose of cobicistat with atazanavir or darunavir right away. However, if you miss a dose of cobicistat with atazanavir or darunavir by more than 12 hours, wait and take the next dose at your usual time. Do not double doses.


Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Do not use this medicine if the seal on the bottle is broken or missing. Keep the bottle tightly closed. Keep the medicine in the original bottle that you were given at the pharmacy.

Precautions While Using Tybost

Your doctor will want to check your progress at regular visits, especially during the first few weeks that you take this medicine. Blood and urine tests may be needed to check for any unwanted effects.

Do not use this medicine together with atazanavir or darunavir if you are also using any of the following: alfuzosin (Uroxatral®), cisapride (Propulsid®), dronedarone (Multaq®), indinavir (Crixivan®), irinotecan (Camptosar®), lovastatin (Altoprev®, Mevacor®), midazolam (Versed®), nevirapine (Viramune®), pimozide (Orap®), rifampin (Rifadin®), sildenafil (Revatio®), simvastatin (Simcor®, Zocor®), St John's wort, triazolam (Halcion®), or ergot medicines (dihydroergotamine, ergotamine, methylergonovine, Cafergot®, Migranal®). Doing so may cause serious unwanted effects.

Using this medicine together with tenofovir may cause kidney problems (including Fanconi syndrome). Tell your doctor right away if you have bloody urine, decreased frequency or amount of urine, increased thirst, loss of appetite, lower back or side pain, nausea, vomiting, swelling of the face, fingers, or lower legs, troubled breathing, unusual tiredness or weakness, or weight gain.

This medicine does not decrease the risk of transmitting the HIV infection to others through sexual contact or by contaminated blood. Make sure you understand and practice safe sex, even if your partner also has HIV. Avoid sharing needles with anyone.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Tybost Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Less common
  • Abdominal or stomach pain
  • bloody urine
  • chills
  • clay-colored stools
  • dark urine
  • decreased frequency or amount of urine
  • dizziness
  • fast heartbeat
  • fever
  • headache
  • hives or welts, itching, or rash
  • hoarseness
  • increased thirst
  • irritation
  • joint pain, stiffness, or swelling
  • loss of appetite
  • lower back or side pain
  • nausea and vomiting
  • pain in the groin or genitals
  • redness of the skin
  • sharp back pain just below the ribs
  • swelling of the eyelids, face, lips, hands, lower legs, or feet
  • tightness in the chest
  • troubled breathing or swallowing
  • unpleasant breath odor
  • unusual tiredness or weakness
  • vomiting of blood
  • weight gain
  • yellow eyes or skin
Less common or rare
  • Dark-colored urine
  • muscle cramps or spasms
  • muscle pain or stiffness

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common or rare
  • Diarrhea
  • discouragement
  • feeling sad or empty
  • irritability
  • loss of interest or pleasure
  • trouble concentrating
  • trouble sleeping
  • upper abdominal or stomach pain

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

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