pentobarbital will reduce the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Observe.pentobarbital will decrease the extent or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Observe.pentobarbital will lower the level or influence of lumacaftor/ivacaftor