OPRM1

Mu 1 Opioid Receptor Genotyping (OPRM1)

Test Code
OPRM1

CPT Code
81479

Specimen
Whole blood or buccal swabs

Volume
5 mL of whole blood or four buccal swabs

Minimum Volume
3 mL of whole blood or four buccal swabs

Container
Lavender-stopper (EDTA) tube or paper envelope for dried buccal swabs

Storage Instructions
Maintain at room temperature or refrigerate

Cause for Rejection
Hemolyzed specimen; quantity not sufficient

General Purpose and Use
Opioid agonists, such as morphine, hydromorphone, and oxymorphone, exert their analgesic properties via stimulation of the mu-1 opioid receptor. Analgesic efficacy of mu-acting drugs has been linked to the 118A>G single nucleotide polymorphism (SNP) of OPRM1, the gene encoding the mu-1 receptor. The frequency of the variant G allele varies from 10% to 48% depending on the population studied. Studies show that patients carrying the GG (homozygous variant) genotype require much higher opioid doses to achieve pain relief.  Additionally, patients with the AA genotype display higher relapse rates with respect to naltrexone treatment for alcohol dependence.

Alleles detected
118A>G

Limitations
Other variants of the OPRM1 gene that are not detected in this assay may influence drug response. All factors should be considered as part of the overall patient management strategy.

Methodology
Real-time polymerase chain reaction with fluorescence detection.

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