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cobicistat (Tybost)


Generic name: cobicistat

Brand names: Tybost

Class: Booster drugs


Common: Jaundice and rash when used in combination with atazanavir.

Rare: Effects on serum creatinine, loss of virological response due to drug interactions, serious adverse reactions because of drug interactions (see Notes).

When used in conjunction with tenofovir disoproxil fumarate (TDF): renal impairment (including cases of Fanconi syndrome and acute renal failure).

When used in conjunction with atazanavir and Truvada: fatigue, upper abdominal pain, vomiting, depression, insomnia, vivid dreams, musculoskeletal and connective tissue disorders, Fanconi syndrome acquired, nephropathy, nephrolithiasis.


Tablets comprise 150mg cobicistat. Taken in conjunction with atazanavir 300mg OR darunavir 800mg.

Tybost is used to increase the levels of either atazanavir or darunavir (once daily dosing regimen) in the blood. Tybost-boosted atazanavir or darunavir is used in combination with other antiretroivirals.

Tybost must be taken once per day at the same time as either atazanavir or darunavir, with food.


Tybost is taken with food.

Tybost is not interchangeable with the other booster drug, ritonavir (Norvir).

Tybost (in combination with atazanavir and darunavir) may increase the amounts of some medications in the body. Levels of Tybost, atazanavir and darunavir may be altered by some medication. If levels become too high this could lead to serious, life-threatening problems. Decreased levels can lead to Tybost not working and resistance developing.

Please let your doctor know about any other medication (including herbal supplements and over-the-counter medication) you may be taking or planning to take. You should not be taking St John’s Wort (herbal supplement) if you're taking Tybost.

Tybost should not be taken with certain antiretrovirals, your doctor will be able to advise you about this.

Creatinine clearance should be checked before starting Tybost.

Not recommended in combination with tenofovir disoproxil fumarate (TDF) in those who have an estimated creatinine clearance below 70mL/min.

Cobicistat is also used in the combination drugs Stribild (to boost elvitegravir), Rezolsta (to boost darunavir), Genvoya (to boost elvitegravir) and Evotaz (to boost atazanavir).

*Last reviewed on 2/12/2016 Next review: 2/12/2019

Any questions? Email feedback@tht.org.uk Information included on this website was correct at the time of publication.

Data and image supplied by NAM.

Further information on this drug from NAM