Saquinavir mesylate is a different formulation, designed to be combined with another protease inhibitor that increases the bioavailability of the saquinavir.

History

Saquinavir was the first protease inhibitor (and sixth antiretroviral) approved by the Food and Drug Administration (FDA). It was approved on December 6, 1995, as Invirase®, a poorly-absorbed hard gel capsule which quickly led to viral resistance in many of the pioneer patients.

It was approved again on Nov 7, 1997 as Fortovase®, a soft gel capsule reformulated for improved bioavailability. The manufacturer, Roche, is alleged to have rushed Invirase® to market, but the conditions that prevailed at the time were very bad and there was a lot of pressure to produce products quickly.

Method of activity

When given alone, the HIV Protease Inhibitor (HPI) saquinavir has a very low oral bioavailability. In the clinic, it was found that the oral bioavailability of saquinavir significantly increases when patients also receive the HPI ritonavir. For patients, this has the major benefit that they can take less saquinavir, while maintaining sufficient saquinavir blood plasma levels to efficiently suppress the replication of HIV.

The mechanism behind this welcome observation was not directly known, but later it was determined that ritonavir inhibits the enzyme Cytochrome P450 3A4. Normally, this enzyme metabolizes saquinavir to an inactive form, but with the ritonavir inhibiting this enzyme, the saquinavir blood plasma levels increased considerably. Additionally, ritonavir also inhibits multidrug transporters, although to a much lower extent.

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Other FDA advisories
From American Family Physician, 6/1/05

Other FDA Advisories:

Recall of urine processing kit. The U.S. Food and Drug Administration (FDA) has issued a Class I recall of the ProbeTec ET Urine Processing Kit, which screens for Chlamydia and gonorrhea. Because the kit may cause false-negative results, the FDA is concerned that some patients might not receive treatment. If left untreated, these infections can worsen or cause further disease transmission and complications in pregnant patients.

Combination therapy may cause hepatitis. Studies have found that healthy volunteers could contract drug-induced hepatitis with marked transaminase elevations after taking simultaneous regimens of rifampin (Rifadin) and ritonavir (Norvir)-boosted saquinavir (Fortovase). The drug's manufacturer recommends that physicians not prescribe rifampin for patients taking ritonavir-boosted saquinavir. The combination regimen is used as an antiretroviral therapy for human immunodeficiency virus infection.

Warning labels ordered for two eczema medications. The FDA has announced that it will require warning labels for pimecrolimus (Elidel) and tacrolimus (Protopic), topical creams used to manage eczema. Recent studies on animals and limited case studies on humans have found an increased cancer risk associated with the two medications. Although more studies are needed, the FDA recommends that physicians prescribe these medications only as a second-line, short-term therapy for patients unresponsive to other treatments. The FDA also advises physicians to avoid prescribing them to children younger than two years and to persons with weakened immune systems.

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