Clinical Application of Pharmacokinetics in Psychiatry

Clinical Application of Pharmacokinetics in Psychiatry

1 Page- 1 Reference- Discussion board reply to: Drug-drug interactions can happen at all levels. When certain medications are absorbed at the same time, they can alter the action of the other and have either an additive or greater effect or have a decreased or antagonistic effect (Drugs.com, 2021). One example of how medications can be altered during absorption is when various meds are given that change the pH or motility of the intestines.

One example of a drug-drug interaction at absorption is Reglan (metoclopramide) and clozapine. The combination of medications can increase CNS depression, seizures, and psychomotor impairment by additive effects (Drugwatch, 2021). Reglan is used to help with gastroparesis. Because it alters GI motility, the clozapine is absorbed more in the system leading to additive effects.

Reference

Drugs.com (2021). How do drug interactions occur Retrieved from https://www.drugs.com/drug_interactions.html#:~:text=A%20pharmacokinetic%20interaction%20may%20occur%20if%20one%20drug,can%20bind%20with%20some%20medications%20and%20block%20absorption (Links to an external site.).

Drugwatch (2021). Reglan & Tardive Dyskinesia. Retrieved from https://www.drugwatch.com/reglan/#:~:text=Reglan%20%26%20Tardive%20Dyskinesia.%20Reglan%20%28metoclopramide%29%20is%20a,nausea%2C%20conditions%20that%20can%20cause%20vomiting%20and%20nausea%2C

1 Page- 1 Reference- Discussion board reply to: Typically, distribution interactions are psychiatric medications only occur when two or more highly protein bound drugs are completing for a small number of binding sites on the plasma proteins.(Stahl, 2020) The risk for protein binding or distribution interactions occurs when the unbound free fraction of the competing drug increases and becomes available to be metabolized. Most of the psychiatric medications that are involved in distribution interactions are mood stabilizers. Medications such as clozapine, risperidone, olanzapine and ziprasidone are usually protein bound (de Leon & Spina, 2018). Typically, these medications are present in the blood in such a little amount that they do not cause significant altered therapeutic actions. In young and healthy patients there is a compensatory drug clearance that allows a larger unbound protein fraction to be available for metabolism. The theorized risk of plasma protein displacement or distribution interactions can cause unnecessary worry for the practitioner who may not be fully aware of the clinical impact on their patient (Demler, 2012).

de Leon, J., & Spina, E. (2018). Possible pharmacodynamic and pharmacokinetic drug-drug interactions that are likely to be clinically relevant and/or frequent in bipolar disorder. Current psychiatry reports, 20(3), 1-24.

Demler, T. (2012). Psychiatric drug-drug interactions: A refresher. US Pharmacist, 37(11), 16-19.

Stahl, S. M. (2020). Prescriber\’s guide: Stahl\’s essential psychopharmacology. Cambridge University Press

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