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:
- 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.
Chronic administration of phenobarbital with the drug
Chronic administration of cimetidine with the drug
Displacement from tissues binding sites by another drug
Chronic administration of rifampicin