Roche has updated their US package insert for saquinavir (Invirase) to include the following drug interaction information and include new warnings regarding coadministration of Invirase/ritonavir and digoxin (used in the treatment of various cardiac conditions).

Updated drug interaction information has been added on five products in the product package insert revision:

1. Digoxin. A new warning has been added. Caution should be exercised when saquinavir and digoxin are coadministered. Coadministration results in a significant increase in serum concentration of digoxin; therefore, the serum concentration of digoxin should be monitored and the dose of digoxin may need to be reduced.
2. Garlic capsules. No data are available for the coadministration of saquinavir/ritonavir with garlic capsules. A warning has been added that the coadministration of garlic capsules and saquinavir is not recommended due to the potential for garlic capsules to induce the metabolism of saquinavir, which may result in subtherapeutic saquinavir concentrations.
3. Methadone. Methadone levels are decreased and the dosage of methadone may need to be increased when coadministered with saquinavir/ritonavir.
4. Tipranavir/ritonavir. Combining saquinavir with tipranavir/ritonavir is not recommended due to a decrease in saquinavir levels with coadministration.
5. Omeprazole. When saquinavir/ritonavir is coadministered
   with omeprazole, saquinavir concentrations are increased significantly. If omeprazole or another proton pump inhibitor is taken concomitantly with saquinavir/ritonavir, caution is advised and monitoring for potential saquinavir toxicities is recommended, particularly gastrointestinal symptoms, increased triglycerides, and deep vein thrombosis.

Source: FDA list serve (11 June 2008).
http://www.fda.gov/oashi/aids/listserve/listserve2008.html#61108