Participants randomized to the CYP2D6-guided arm will have their CYP2D6 genotyping completed prior to surgery (in the absence of any genotyping error) with results reported in the electronic health record (EHR). Patients will be categorized as CYP2D6 PM, IM, NM, or UM based on CYP2D6 genotype/activity score and FDA guidance on drug interactions. Strong inhibitors (e.g. bupropion, fluoxetine, paroxetine) phenoconvert patients to PMs, with moderate inhibitors (e.g. duloxetine, fluvoxamine) reducing CYP2D6 activity scores by 50%.

Participants randomized to the usual care arm will have their DNA collected at the start of the study and stored at the lab until after they have completed their surgery and the 2-week follow-up, at which time, their sample was genotyped with the results reported in the EHR.

Using a standardized consult note, recommendations were made to avoid tramadol, hydrocodone, codeine, and oxycodone in PMs, IMs, and UMs and to use an alternative opioid (e.g. morphine, hydromorphone) or non-opioid (e.g. NSAID). Consideration of tramadol as the first-line opioid will be recommended for NMs.

The feasibility of clinical implementation was measured by the percentage of approached patients who agreed to be the study. This was measured by the number of patients approached and the number of patients who enrolled in the study.

The feasibility of implementing a genotype-guided opioid prescribing approach for participants undergoing an elective surgical procedure was analyzed by the percentage of participants in the genotype-guided arm and usual care arm with a high-risk CYP2D6 phenotype. CYP2D6 phenotypes were based on CYP2D6 genotype and phenoconversion. High-risk CYP2D6 phenotypes were poor metabolizers (PM), intermediate metabolizers (IM), ultrarapid metabolizers (UM), and ranged phenotypes such as normal to ultrarapid metabolizers and intermediate to ultrarapid metabolizers.

The feasibility of clinical implementation was measured by the percentage of participants in the genotype-guided arm for whom a clinical phenotype-guided recommendation was accepted by the clinician. Study recommendations were considered accepted for participants with a high-risk phenotype if an alternative opioid (e.g., hydromorphone, morphine) was prescribed. For CYP2D6 normal metabolizers (NM), consult recommendations were accepted if tramadol was prescribed. Participants were typically prescribed a tramadol-based regimen where in most cases hydrocodone, or another opioid, was prescribed concomitantly with tramadol as is usual practice at the clinics where participants were enrolled. Participants whose genotype resulted after the preoperative appointment were excluded from the analysis of acceptance of consult recommendations. Data for this outcome were only collected from participants in the genotyped-guided arm with CYP2D6 results returned prior to the preoperative appointment.

Composite pain intensity was compared between the genotype-guided arm and usual care arm 2 weeks after surgery. The first two scales in the PROMIS Pain Intensity item bank assess pain intensity utilizing a 7-day recall period (items include the phrase "the past 7 days") while the third scale asks the patient to rate their pain intensity "right now." Each of the 3 scales (worst pain, average pain, and current pain) used to calculate the composite pain intensity score has a range of 1 to 5, with the following text assigned to the numeric scale, 1 -"had no pain", 2 -"mild", 3 -"moderate", 4 -"severe", and 5 -"very severe." The mean composite pain intensity ranges from 1-5. The higher the composite pain score, the more pain and thus worse outcomes.