Cytochrome P450 System
1 page- 1 reference- Respond to discussion board post: CYP 2D6 is an enzyme that is used in metabolizing many drugs on the market today, especially psychotropic drugs (St. Jude, 2021). This enzyme is important because there are people who have are poor metabolizers and people who are fast metabolizers. This means that some people metabolize slower which can reduce the risk of certain cancers, but may also increase the risk for certain illnesses, such as Parkinsons (Moon, 2019). It is important to know this information because metabolizing faster or slower may be manifested as certain side effects or worsening of disease processes and we can see if physically without expensive gene testing.
Certain drugs and medications can inhibit CYP 2D6. These include, CBD oil, Cimetidine, Cocaine, Celcoxib, duloxetine, fluoxetine, paroxetine, and niacin (Moon, 2019). Drugs that are major substrates include, TCAs, codeine, venlafaxine, clozapine, aripiprazole, risperidone, paroxetine (Stahl, 2013). There are many other drugs that can inhibit and induce the enzyme as well. It is important to note if your patient is on a tricyclic antidepressant because alternatives or dose adjustments may be needed. Giving a patient a specific substrate of 2D6 can raise the blood levels of the substrate (Stahl, 2013).
Your patient is currently taking amitriptyline 100 mg daily for depression and insomnia. You notice they have been steadily needing increased doses at each visit. You determine this person is:
Poor metabolizer of CYP 2D6
Fast metabolizer of CYP 2D6
Showing non-compliance of medication regimen.
Fluoxetine and Paroxetine are examples of CYP 2D6 inhibitors: True or False
1 page- 1 reference- Respond to discussion board post: CYP 3A4 is responsible for metabolism of more than 50% of all medications and women have more activity than men (MedSafe, 2014). It is an important enzyme because it is so common and essentially impossible to avoid when prescribing. It is important to take this enzyme into consideration when prescribing because while prescribers can attribute poor patient response for the need to increase or change medications, it is often a result of this enzyme causing reduced plasma concentration of the medication (Horn & Hansten, 2008). Most benzodiazepine class medications are substrates that when combined with an inhibitor can cause excessive CNS depression due to toxicity. Food and herb substances that inhibit CYP 3A4 are Goldenseal, Black pepper, and Grapefruit; while inducing agents include Schisandra and St Johns Wort (MedSafe, 2014). Major psychiatric substrates of this enzyme are Alprazolam, Wellbutrin, Donepezil, Quetiapine, and Ziprasidone (Horn & Hansten, 2008). A major psychiatric inhibitor of this enzyme is Fluoxetine and a major inducers include a number of anti-seizure medications which can greatly reduce the serum concentration of substrates (Horn & Hansten, 2008). Of all the 4 CYP isoforms, 3A4 is the most abundant and has the greatest effect, so is regarded as perhaps the most important of all.
Horn, J. R., & Hansten, P. D. (2008, September 1). Get to know an enzyme: CYP3A4. Pharmacy Times. https://www.pharmacytimes.com/
MedSafe. (2014, March). Drug metabolism – The importance of cytochrome P450 3a4. Medsafe. https://www.medsafe.govt.nz/