<prompt> A factor that is likely to increase the duration of action of a drug D that is partially metabolized by CYP3A4 in the liver is:Chronic administration of phenobarbital with the drugChronic administration of cimetidine with the drugDisplacement from tissues binding sites by another drugChronic administration of rifampicin  <response>: - Microsomal enzyme inducers- Rifampicin, Phenobarbital- will increase the activity of enzymes, leading to decreased duration of action of a drug.- Microsomal enzyme inhibitor- Cimetidine- will decrease the activity of enzyme resulting in increased duration of action of the drug.- A drug displaced from the binding site gets easily metabolized. 