Drug extrapyramidal side effects. CYP2D6 genotypes and phenotypes.

Area of Science:

• Pharmacogenomics
• Neuropharmacology
• Drug Metabolism

Background:

• Cytochrome P450 enzyme CYP2D6 deficiency (poor metabolizers, PMs) affects 5-10% of Caucasians, potentially impairing psychotropic drug metabolism and increasing side effect risk.
• CYP2D6 metabolizes neurotransmitters, influencing extrapyramidal side effect mechanisms.
• This study explores the link between CYP2D6 genetic/phenotypic variations and the occurrence of extrapyramidal drug side effects.

Purpose of the Study:

• To investigate differences in CYP2D6 genotypes and phenotypes between patients who developed extrapyramidal drug side effects and those who did not.
• To determine if CYP2D6 metabolic capacity is associated with the risk of extrapyramidal drug side effects.

Main Methods:

• Genotyping for CYP2D6 using restriction fragment length polymorphism and PCR-SSCP in 65 patients.
• Phenotyping CYP2D6 activity using dextromethorphan in 62 patients.
• Comparing CYP2D6 profiles in a group of 22 patients with extrapyramidal side effects versus 43 patients without.

Main Results:

• A significant over-representation of poor CYP2D6 metabolizer phenotypes was observed in patients with extrapyramidal side effects (45%) compared to those without (14%).
• Patients experiencing side effects had a higher frequency of nonfunctional CYP2D6 alleles and a lower percentage of functional alleles.
• A significantly higher proportion of genotypes with no functional CYP2D6 alleles was found in the group with extrapyramidal side effects (P < 0.00001).

Conclusions:

• Impaired CYP2D6 metabolic capacity is a potential contributing factor to the development of extrapyramidal drug side effects.
• CYP2D6 genotype and phenotype analysis may aid in predicting and preventing adverse drug reactions.