> Western Medicines > Ritonavir


Used for: HIV infection
Chinese name:

What is Ritonavir for?

Ritonavir belongs to a class of medication called HIV protease inhibitors. It decreases the amount of human immunodeficiency virus (HIV) in your body by blocking the action of protease, which is an enzyme that HIV needs to multiply.


It is usually used in combination with Lopinavir to treat HIV infections. HIV is the virus that can cause acquired immunodeficiency syndrome (AIDS).

Ritonavir is not a cure for HIV infection or acquired immunodeficiency syndrome (AIDS), however, it reduces the amount of HIV in your body so that your immune system works better.

How to use it?

Ritonavir is available as a tablet which is taken orally. It may be taken with or without food. Swallow it whole and do not crush, chew, or break the tablet.

Below listed the dosages of Ritonavir. Dosages may vary for different combinations of antiretroviral drugs.


HIV infection (in combination with other antiretroviral drugs)
Initially 300 mg every 12 hours for 3 days. Increase in steps of 100 mg every 12 hours over no longer than 14 days, then increase to 600 mg every 12 hours.

Initially 250 mg per m2 body surface area twice daily. Increase in steps of 250 mg per m2 every 2-3 days, then increase to 350 mg per m2 twice daily. The maximum dosage is 600 mg per dose, used twice daily. Note that this regimen has poor tolerability.


Low-dose booster to increase the effect of other protease inhibitors
100-200 mg once or twice daily.

What are the side effects of Ritonavir?

Common side effects of Ritonavir include diarrhoea, nausea, vomiting, abdominal pain, fatigue, metallic taste, skin rash, difficulty sleeping and muscle/joint pain.

Who should not take Ritonavir?

  • People allergic to Ritonavir or any component of the formulation
  • Patients with acute porphyria
  • Patients who are currently taking medications that treat enlarged prostate, heart disease, stomach problems, gout, headache or migraine, high cholesterol, mental illness, allergies or certain antibiotics

Pharmacist Tips:

  • Continue to take all HIV medications exactly as prescribed by your doctor to limit the risk of transferring HIV to others.
  • Use an effective barrier method, such as condoms or dental dams, during sexual activity to reduce the risk of transmission of HIV.
  • Do not share personal items that may have contacted blood or other body fluids, such as needles/syringes, toothbrushes and razors.
  • Ritonavir may reduce the effectiveness of oral contraceptives. Consider using another form of contraception while taking Ritonavir.

Common dosing schedule:
Ritonavir should be taken every 12 hours. Try to take it at the same time each day.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Ritonavir may interact with:

Ritonavir interacts with many drugs. Do not take Ritonavir if you are taking:

Please notify your doctor or pharmacist if you are taking the above or any other medication, dosage adjustments might be needed.

Where to buy Ritonavir in Hong Kong?

In Hong Kong, Ritonavir is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Ritonavir in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Available dosage
  • 25mg/100mg (Tablets)
  • 100mg (Tablets)
Drug class
Sub class
HIV Protease Inhibitors
Other drugs in same class