Fosamprenavir; Saquinavir/Efavirenz Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Efavirenz may speed up how quickly your body processes some protease inhibitors. Some protease inhibitors may slow down how quickly your body processes efavirenz.

What might happen:

The amount of protease inhibitor in your blood may decrease and it may not work as well against your HIV infection. The amount of efavirenz in your blood may increase and cause more side effects than normal.

What you should do about this interaction:

To prevent this interaction from occurring with fosamprenavir, your doctor may change the amount of ritonavir you take if you only take fosamprenavir once daily. If you have any concerns, discuss them with your healthcare professional.To prevent this interaction from occurring with saquinavir, your doctor may have you take another protease inhibitor with your saquinavir. If you have any concerns, discuss them with your healthcare professional.If you have any side effects from your medicine, let your healthcare professional know.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Sustiva (efavirenz) US prescribing information. Bristol-Myers Squibb Company October, 2017.
  • 2.Atripla (efavirenz/emtricitabine/tenofovir disoproxil fumarate) US prescribing information. Gilead Sciences, Inc. April, 2017.
  • 3.Lexiva (fosamprenavir calcium) US prescribing information. GlaxoSmithKline September, 2016.
  • 4.Invirase (saquinavir mesylate) US prescribing information. Roche Laboratories, Inc. September, 2016.