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Steps to Implementing Pharmacogenomics (PGx) in Your Practice
PGx and Prodrugs
Patient X is a 24 year-old white female who just delivered a baby 3 days ago and is breastfeeding her infant. She was discharged with a Rx for APAP with Codeine 300/30 with instructions to take one or two tablets every 4 to 6 hours as needed for pain.
A few days later she presents the baby experiencing:
- labored breathing and
- minimal bowel movements
Patient X also states that she, herself, tends to be:
- sleeping a lot
- feeling drowsy and itchy
She undergoes genetic testing and is found to be a CYP2D6 Ultrarapid Metabolizer (UM), expressing multiple copies of the *2 allele, resulting in enhanced conversion of codeine, a prodrug, to the active form, morphine.
Patient X rapidly metabolizes the codeine to morphine resulting in higher than normal levels and since morphine is distributed also in the breastmilk, the infant receives it during feeding. Both individuals are essentially being overdosed with morphine.
In this case, there are two reasonable options:
1. Reduce the dose of codeine, or better
2. Use a different analgesic
For more information on codeine and PGx testing, go to:
https://www.pharmgkb.org/guideline/PA166104996
Next week, we will look at the FDA labeling requirements concerning pharmacogenomics.
Loyd V. Allen, Jr., PhD, RPh
Editor-in-Chief
International Journal of Pharmaceutical Compounding
Remington: The Science and Practice of Pharmacy Twenty-second edition
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