Table 2.

Genes involved with pain and tissue healing

Gene	System measured	Medical necessity	Comments
P450	Drug Metabolism	Pharmacogenomic response tied to narcotic drugs	There are 10 studies relating polymorphisms of this gene and opiate response
Mu receptor	Opioid response including endorphins	Pain sensitivity and intolerance as well as pharmacogenomic response to opiates	There are 10 studies relating polymorphisms of this gene and opiate response
PENK	Precursor to Enkephalins	Pain sensitivity and intolerance	There are 83 studies relating polymorphisms of this gene and enkephalins and opiate response
TNF-α	Inflammation	High risk for development of inflammatory secondary messengers. Required increase in NSAID dosage.	There are 2700 studies relating polymorphisms of this gene and the inflammatory response 3 studies specific to opiate response
DRD2	Dopamine receptors	Dopamine is required for proper pain sensitivity and tolerance. Most opiates work via dopamine to reduce pain. DA is also the anti-stress molecule.	There are 11 studies involving the dopamine d2 receptor and pain mechanisms and 5 studies involving the drd2 gene polymorphisms and pain
eNOS	Oxidative stress	Nitric Oxide deficiency leads to oxidative stress	There are 75 studies relating polymorphisms of this gene and oxidative stress
VEGF	Angiogenesis Factor-required for proper tissue healing	Slow healing process	There are 3423 studies relating polymorphisms of this gene and angiogenesis