Competitive Inhibition: The Root Cause of Unintentional Opioid Misuse
Many medications require the same enzyme to be metabolized. When these medications are taken together, they compete for access to that enzyme. Picture multiple cars vying for the same parking space – they won’t all fit in one space together!
• Many commonly-prescribed medications (including antidepressants and beta-blockers) require the CYP2D6 enzyme metabolic pathway.
• The use of these drugs in combination with opioids metabolized by CYP2D6 can result in two drugs fighting for the same enzyme. (In the parking lot, the bigger, faster car usually wins the space.)
• As opioids usually have less affinity (weaker binding to the enzyme) than other medications seeking CYP2D6, the non-opioid medications will be metabolized first.
• Consequently, the expected pain relief effect does not occur.
• Lack of pain relief results in a prescribing cascade of higher doses and unwanted effects, including drug misuse and abuse.