pentobarbital will lessen the level or result of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Observe.pentobarbital will lower the level or effect of etravirine by influencing hepatic enzyme CYP2C9/10 metabolism. Use Warning/Keep track of.pentobarbital will lower the level or effect of fosamprenavir by impacti