Unit 3- Inhibition and Induction of Drug metabolism

CLINICAL PHARMACOKINETICS & PHARMACOTHERAPEUTIC DRUG MONITORING

UNIT-3

Pharmacokinetics of Drug Interaction

Inhibition and Induction of Drug metabolism

 

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Inhibition and Induction of Drug metabolism

Metabolism-based drug-drug and other interactions can have a

significant influence on the use and safety of many drugs.

Induction of drug metabolism can lead to unexpected drops in

drug concentration. The reverse can occur when there is

inhibition of drug metabolism.

The major organ involved in metabolism is the liver and the

major enzyme system involved in drug metabolism is CYP450,

the well-known family of oxidative hemoproteins. The

induction of CYP 450 enzymes in the liver is responsible for the

induction of the metabolism of many drugs.

INDUCTION: The phenomenon of increased drug metabolizing ability of the enzymes by several drugs and chemicals is called enzyme induction.

Several drugs can cause an increase in liver enzyme activity

over time. This in turn can increase the metabolic rate of the

same or other drugs. Phenobarbitone will induce the

metabolism of itself, phenytoin, warfarin, etc.

Carbamazepine is another drug that can induce its metabolism.

Rifampicin has been shown to cause up to twenty times an

increase in midazolam metabolism.

Cigarette smoking can cause increased elimination of

theophylline and other compounds. Dosing rates may need to

be increased to maintain effective plasma concentrations.

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