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What are cyp inducers?

5 Answer(s) Available
Answer # 1 #

CYP enzyme inducers increase the rate of hepatic metabolism, usually through increased transcription of mRNA, and decrease serum concentrations of other drugs metabolized by the same hepatic isoenzyme.

S.Z. FitzSimons
Answer # 2 #

All individuals on drug therapy should receive an evaluation to check for any concurrent medications that may influence the activity of another drug based on their effects on CYP activity. Based on the characteristics of the drug's profile, CYP enzymes can be either induced or inhibited-marking a significant area of concern in patients due to issues with metabolism and clearance. This can cause considerable adverse effects for patients as medications may either accumulate to toxic levels or clear from the system too rapidly, leading to treatment failure. Also, clinicians must be aware of naturally occurring compounds that can alter the actions of CYP enzymes, such as grapefruit juice, nicotine-containing products, and St. John’s Wort, to name a few. Special precautions are necessary for patients who have decreased baseline activity or injury to CYP enzymes.

Additionally, genes play a role in an individual’s natural composition of CYP enzymes and determine their rate of metabolism. Looking into the future of medical advancements regarding pharmacogenomics, genetic polymorphisms of CYP alleles could take precedent in determining the proper therapy and drug dose for individual patients. With this information, we would better be able to predict drug response in patients.

Common cytochrome p450 inducers, inhibitors, and substrates of the primary isozymes mentioned in this article are listed below.






Sidra Nazir
Answer # 3 #

Cytochrome P450 (CYP450) are a group of enzymes encoded by the P450 genes and responsible for the metabolism of most drugs seen in clinical practice.

90% of drugs are metabolised by CYP3A5, CYP3A4, CYP2D6, CYP2C19, CYP2C9 and CYP1A2. CYP3A4 and CYP2D6 are the most significant enzymes.1

Polymorphism is the genetic mutations that give rise to enzymes with different abilities to metabolise drugs. These genetic variabilities are responsible for the inter-individual variability in therapeutic response and toxicity to all major classes of drugs given at the standard dose.

The expression of CYP450 enzymes varies between populations and will greatly influence drug metabolism and response.

For example, CYP2D6 polymorphisms are expressed in four different phenotypes:

Poor metabolisers are characterised by the inability to metabolise drugs via the CYP2D6 metabolic pathway, resulting in an increased risk of adverse effects and toxicity. PM phenotype affects up to 10% of Caucasians and 30% of the Chinese population.2,3

At the other extreme, ultrarapid metabolisers metabolise the drug rapidly, resulting in a lack of therapeutic response in these individuals.

However, the reverse applies to prodrugs (drugs that are converted to their active forms in the body). Poor metabolisers fail to convert the prodrug into its active form leading to a lack of therapeutic response. In contrast, ultrarapid metabolisers rapidly convert the prodrug to its active form, causing potential toxicity.

Ultrarapid metaboliser phenotypes are most prevalent in the North African, Ethiopian and Arab populations, affecting 16% – 28% of the populations. In the rest of the world, the prevalence of ultrarapid metaboliser phenotypes is estimated to be 1% in the Chinese, Japanese and Hispanic populations and 5.5% in Western Europe.3,4

Intermediate metabolisers have a reduced metabolism capacity compared to extensive metabolisers (who are classified as “normal”), therefore are more susceptible to adverse effects.

For example, nortriptyline is a common tricyclic antidepressant and a substrate of CYP2D6. In intermediate metabolisers, the metabolism of nortriptyline is reduced as compared to extensive metabolisers. As a result, the higher plasma concentration of nortriptyline in intermediate metabolisers increases the risk of potential side effects. A dose reduction should be considered in these patients.

Enzyme substrates are drugs or other substances that bind to and are metabolised by the CYP450 enzymes

Examples of CYP450 substrates include:

Inducers increase the expression level of CYP450 enzymes resulting in increased metabolism of drugs and subsequently reducing the therapeutic concentration.

Therefore, potential changes in drug concentration may cause treatment failure. The effects usually develop over several days and may be slow to resolve depending on the half-life of the inducer.

Examples of CYP450 inducers include:

Inhibitors prevent the CYP450 enzymes from working or reduce the rate of an enzyme-catalysed reaction. Consequently, this decreases drug metabolism in the body and increases the potential for toxicity. The effect often occurs quickly and is dose related.

Examples of CYP450 inhibitors include::

Clinical Pharmacist

Bilal Padhi
Answer # 4 #

a Recommend the use of two structurally unrelated CYP3A4/5 substrates to evaluate in vitro CYP3A4/5 inhibition.

Ghita Ahlert
Answer # 5 #
  • Carbemazepines.
  • Rifampicin.
  • Alcohol.
  • Phenytoin.
  • Griseofulvin.
  • Phenobarbitone.
  • Sulphonylureas.
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