AUC: ↑ 21% (↑ 10 to ↑ 34) Cmax: ↑ 14% (↑ 4 to ↑ 26) Cmin: ↑ 25% (↑ 7 to ↑ 46) b (inhibition of CYP-mediated oxidative metabolism) When efavirenz was given with ritonavir 500 mg or 600 mg twice daily, the combination was not well tolerated (for example, dizziness, nausea, paraesthesia and elevated liver enzymes occurred).