If a side effect is intolerable and the clinician cannot be contacted, the patient should stop all drugs at once. The following discussion of PI-associated side effects focuses on each agent individually. In several studies, nausea, vomiting, abdominal pain, diarrhea, increased hepatic transaminases, and headache occurred most commonly. Diarrhea and nausea were most common. Ritonavir PI safety and tolerability issues arise most prominently with ritonavir.
Some patients experience abdominal pain during the first month of ritonavir therapy.
Other potential side effects include hypertriglyceridemia, elevated liver function tests, circumoral paresthesia, and taste perversion. The severity of ritonavir side effects appears to occur in direct relation to the plasma concentration of the drug. Ritonavir plasma concentrations peak during the first several days of administration, subsequently declining as the drug induces its own metabolism. 3 Table 2 shows the results of two trials assessing the side-effect profile of ritonavir monotherapy. Increases in triglyceride and cholesterol levels were also greater than with the other PIs.