Avoid concomitant use w/ skin medications that alter skin barrier or function (eg, Na lauryl sulphate, benzalkonium or benzethonium Cl, astringents, sunscreens, salicylic acid, lactic acid). Increased metabolism w/ substances known to induce drug-metabolising enzymes, specifically cytochrome P450 enzymes eg, anticonvulsants (eg, phenobarb, phenytoin, carbamazepine) & anti-infectives (eg, rifampicin, rifabutin, nevirapine, efavirenz). Concomitant use w/ ritonavir, nelfinavir. Induced metabolism w/ herbal medicine prep containing St. John's wort (
Hypericum perforatum).