Prospective Randomized Study Using Pharmacogenetics to Customize Postoperative Pain Medication Following Hip and Knee Arthroplasty

Background The purpose of this study is to determine whether pharmacogenetic testing could be used to effectively customize postoperative pain medicine following total joint replacement. Methods Buccal swabs were collected preoperatively from 107 patients. Pharmacogenetic testing was performed for genetic variants on a panel of 16 genes, including CYP2D6, CYP2C9, OPRM1, and CYP1A2, which affect the pharmacodynamics and pharmacokinetics of non-steroidal anti-inflammatory drugs and many opioids. Patients were randomized to a control group or custom group and blinded to their group. The control group was prescribed oxycodone, tramadol, and celecoxib for postoperative pain management. If any of those were not normally metabolized, they were not prescribed to the patients in the custom group, who were given an alternative drug (hydromorphone for narcotics, meloxicam for non-steroidal anti-inflammatory drugs). Patients recorded their pain level (0-10 numeric scale) and all medications taken daily for the first 10 days following surgery. Medication was converted to milligram morphine equivalents (MMEs). Results Genetic variations to medications in our standard postoperative pain management protocol occurred in 24 of the 107 patients (22.4%). The 10-day MME consumed by patients in the control group with genetic variants was 162.6 mg. Patients with variants who had custom postoperative medication consumed only 86.7 MME in the same timeframe (P = .126). The control group demonstrated a higher 10-day average pain level of 4.2 vs the custom group pain level of only 3.1 (P < .05). Conclusion With custom postoperative pain prescriptions based on pharmacogenetic testing, patients were able to achieve lower pain levels while reducing the consumption of pain medication.