Cobicistat tablets for HIV (Tybost)

2145 Users are discussing this topic

Cobicistat is one of a number of medicines that you will need to take regularly for HIV.

Take one tablet each day.

Swallow the tablet with a drink of water after a meal.
Type of medicineA pharmacokinetic enhancer
Used forIncreasing the effect of atazanavir or darunavir, which are medicines used for HIV infection in adults
Also calledTybost® 
There are also combination tablets which contain cobicistat: Evotaz® (cobicistat with atazanavir); Genvoya® (cobicistat with emtricitabine and tenofovir alafenamide and elvitegravir); Rezolsta® (cobicistat with darunavir); Stribild® (cobicistat with emtricitabine and tenofovir disoproxil and elvitegravir)
Available asTablets

Cobicistat is prescribed for human immunodeficiency virus (HIV) infection. HIV destroys cells in the body, called CD4 T cells. These cells are a type of white blood cell and are important because they are involved in protecting your body from infection. If left untreated, the HIV infection weakens your immune system so that your body cannot defend itself against bacteria, viruses and other germs. You will be prescribed three or more antiretroviral medicines at the same time, as taking a combination of different medicines is more effective than taking one alone, and also it reduces the risk that the HIV virus will become resistant to any individual medicine. Antiretroviral medicines slow the progress of HIV infection, but do not cure it.

Cobicistat will be prescribed for you by a doctor who is a specialist. You will also have been prescribed either atazanavir or darunavir for the HIV infection. Cobicistat is given to boost the effect of these medicines. Atazanavir and darunavir are both protease inhibitor antiretroviral medicines. Cobicistat helps to improve the effectiveness of these medicines by slowing down their breakdown in the body. This increases the amount of time atazanavir or darunavir is present in your body.

Some brands of cobicistat contain other antiretroviral medicines also (see the list in the table above). Taking one of these brands helps to reduce the number of tablets you need to take each day. Not all of the information in this leaflet applies to the combination brands - please refer to the manufacturer's printed information leaflet from inside the pack for full details about these brands. You will also find more information about each of the individual medicines on our website (see atazanavir, darunavir, emtricitabine, tenofovir, and elvitegravir).

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking cobicistat it is important that your doctor knows:

  • If you are pregnant, trying for a baby, or breast-feeding.
  • If you have any problems with the way your liver works, or if you have problems with the way your kidneys work.
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines which are available to buy without a prescription, as well as herbal and complementary medicines.
  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about cobicistat, and it will also provide you with a full list of the side-effects which you could experience from taking it.
  • Take cobicistat exactly as your doctor tells you to. Take one tablet a day, at the same time as either atazanavir or darunavir.
  • Swallow the tablet whole with a drink of water. Take the tablet after a meal or a snack.
  • If you forget to take a dose, take it as soon as you remember, providing it is within 12 hours of the time you should have taken it. Remember to take the tablet with something to eat. However, if when you remember, it is more than 12 hours late, do not take the dose you missed but instead take your next dose when it is due. Do not take two doses together to make up for the forgotten dose.
  • Keep your regular appointments with your doctor so that your progress can be monitored. You are likely to need regular blood tests to check how well your medicines are working.
  • It is important that you continue to take your antiretroviral treatment regularly. This will help to prevent the HIV from becoming resistant to the medicines you are taking. Even if you miss only a small number of doses, the virus can become resistant to treatment.
  • If you develop an infection soon after you start the treatment, let your doctor know. As a result of taking antiretroviral medicines, your immune system may start fighting an infection which was present before you started the treatment, but which you may not have been aware of.
  • Although treatment with antiretroviral medicines may reduce the risk of you passing HIV to others through sexual contact, it does not stop it. It is important that you use condoms.
  • It is not uncommon for people with HIV to feel low or even depressed, especially soon after the diagnosis has been made and treatment has been started. If you have any feelings of depression, or any distressing thoughts about harming yourself then you should speak with your doctor straightaway.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking cobicistat and antiretroviral medicines.
  • If you buy any medicines, supplements or herbal remedies 'over the counter', check with a pharmacist that they are suitable to take with cobicistat and your other medicines. This is because cobicistat can interfere with some medicines and stop them from working properly.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with cobicistat. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common cobicistat side-effects (these affect more than 1 in 10 people)
What can I do if I experience this?
Feeling sickStick to simple meals - avoid fatty or spicy food
Yellowing of the skin or the whites of the eyes (jaundice)Speak with your doctor as soon as possible
Common cobicistat side-effects (these affect less than 1 in 10 people)What can I do if I experience this?
HeadacheAsk your doctor to recommend a suitable painkiller
Feeling dizzy, tired or sleepyDo not drive and do not use tools or machines while affected
Being sick, diarrhoea, stomach pain, indigestion, windStick to simple meals - avoid fatty or spicy food
Increased appetite, changes in the way things taste, dry mouth, rash, difficulty sleeping, abnormal dreamsIf any of these become troublesome, speak with your doctor
Changes to some blood testsYour doctor will check for these

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • Store the tablets in the original container in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

  • Manufacturer's PIL, Tybost® 150 mg film-coated tablets; Gilead Sciences Ltd, The electronic Medicines Compendium. Dated April 2016.
  • British National Formulary; 71st Edition (March-September 2016) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
29291 (v1)
Last Checked:
Next Review:
The Information Standard - certified member

Did you find this health information useful?

Yes No

Thank you for your feedback!

Subcribe to the Patient newsletter for healthcare and news updates.

We would love to hear your feedback!

Patient Access app - find out more Patient facebook page - Like our page