Saquinavir was the first protease inhibitor to be commonly combined with low-dose ritonavir to boost drug concentrations and simplify dosing. The combination has been used as a salvage strategy since the late 1990s. Several studies have shown that between 40 and 70% of people who have failed another protease inhibitor-based regimen can achieve undetectable viral loads after six months’ treatment with a ritonavir-boosted saquinavir-based regimen, although previous exposure to antiretrovirals and levels of drug resistance, as well as adherence to therapy, play a crucial role in response to treatment.

February 2010 UPDATE

The FDA has notified healthcare professionals and patients that it is reviewing clinical trial data about a potentially serious effect on the heart from the use of Invirase (saquinavir) in combination with Norvir (ritonavir).


Basic info

Generic name saquinavir
Brand name Invirase
Also known as Fortovase
Drug class Protease Inhibitors
Pediatric dosing? Available in doses suitable for children and/or young people.
Availability in Australia Available on the Pharmaceutical Benefits Scheme (PBS) through S100 prescribers since
This drug may be available through clinical trials in Australia.
You may be able to import this drug from overseas for your personal use.
Formulation 200mg hard gel capsules; 500mg tablets

Taking it

Like most anti-HIV drugs, saquinavir must be taken in combination with other drugs to be completely effective. Commonly, saquinavir is combined with one other nucleoside (NRTI) drug and either a protease inhibitor or non-nucleoside, although other combinations are sometimes used. Your doctor will advise you on the right combination of drugs to suit your circumstances.


The normal dose is two 500mg tablets with 100mg ritonavir twice a day

Regardless of what you read on this website or elsewhere, you should always take your medications according to your doctor's instructions. If you're unsure, speak to your doctor or pharmacist.

With or without food

saquinavir should be taken with food

Side effect

All drugs can produce side effects in some people. These may be mild, moderate or severe, so you should be aware of potential side effects before starting any drug, and speak to your doctor if you experience side effects that concern you.

  • Common side effects may include nausea (upset stomach, feeling sick to the stomach), diarrhoea, headache, abdominal discomfort.
  • Less common side effects may include increased levels of blood sugar, increases in cholesterol and triglycerides (blood fats).
  • Rare side effects may include lipodystrophy, diabetes, increased bleeding in haemophiliacs.
  • It's unlikely you will experience all of these side effects, and you may not experience any side effects at all. Before starting any new drug, ask your doctor about side effects you might experience and discuss strategies for dealing with side effects if they do occur. If you experience any significant side effect you should continue taking your medicine and see your doctor as soon as possible.

Interactions with other drugs

Do not combine saquinavir with Tipranavir/ritonavir. These interactions can change the amount of each drug in your bloodstream and cause an under- or overdose. New interactions are being identified all the time. Drugs to watch out for include other ARVs, drugs to treat tuberculosis, for erectile dysfunction (such as Viagra), for heart rhythm (antiarrhythmics), and for migraine headaches. Interactions are also possible with several antihistamines (allergy medications), sedatives, drugs to lower cholesterol, and anti-fungal drugs. Digitalis levels can be dangerously increased by saquinavir. Garlic capsules might lower saquinavir levels. The antacid omeprazole, sold as Prilosec and under other names, can greatly increase saquinavir levels. Saquinavir does not appear to have any significant interaction with methadone, except that saquinavir taken with ritonavir can lower methadone levels. Watch for signs of excessive sedation if you take saquinavir with buprenorphine. Some birth control pills may not work if you are taking saquinavir. Grapefruit juice increases saquinavir levels. Avoid drinking it when taking saquinavir, especially if saquinavir is being boosted with ritonavir. The herb St. John's Wort lowers the blood levels of some protease inhibitors. Do not take it with saquinavir.