Saquinavir interacts with many drugs. Some of the important interactions are mentioned below. Viewers should consult their health care provider before combining any drugs with saquinavir. Saquinavir should not be used together with triazolam (Halcion), midazolam (Versed), sildenafil (Viagra) and ergotamine derivatives (for example, Ergostat) because saquinavir increases the concentration of these drugs in the body and this could cause serious side effects. Saquinavir also may inhibit the break-down of the cholesterol-lowering drugs lovastatin (Mevacor), simvastatin (Zocor), atorvastatin (Lipitor) and cerivastatin (Baycol). Combining saquinavir with these drugs may increase the occurrence of muscle breakdown (rhabdomyolysis) which is seen when these drugs accumulate in the body.
Clarithromycin (Biaxin) and ketoconazole (Nizoral) may increase blood concentrations of saquinavir and cause increased severity or frequency of side effects from saquinavir. Saquinavir also increases the concentration of clarithromycin. Rifampin (Rifadin) and rifabutin (Mycobutin) decrease blood concentrations of saquinavir and therefore could decrease the effectiveness of saquinavir. The combination of saquinavir and ritonavir should not be combined with rifampin due to the risk of severe liver damage. When digoxin is taken by patients receiving saquinavir (Invirase) with ritonavir (Norvir), the amount of digoxin (Lanoxin) in the body can increase by 50%, possibly leading to side effects such as potentially fatal rhythm disturbances, nausea, vomiting, and diarrhea, blurred or yellow vision; headache; weakness; dizziness; apathy; confusion; and mental disturbances such as anxiety, depression, delirium, and hallucinations.