Potential Cytochrome P450 Drug-Drug Interactions among Pediatric Patients Undergoing Tonsillectomy

Objective To evaluate the frequency of potential cytochrome P450 (CYP) drug-drug interactions affecting opioid metabolism among children undergoing adenotonsillectomy. Study Design Case series with chart review. Setting Tertiary care children's hospital. Subjects and Methods A retrospective review was conducted of 1000 patients undergoing adenotonsillectomy at Children's Hospital of Wisconsin. The discharge medication reconciliation form was reviewed. Each patient's list of medications was compared with various published sources to determine whether medications causing CYP inhibition or induction were present. Results There were 157 unique medications with systemic absorption given postoperatively to this patient cohort. Eight percent of patients were on at least 5 medications after surgery other than their posttonsillectomy medication. The 5 most commonly prescribed medications were albuterol, cetirizine, fluticasone nasal spray, montelukast, and polyethylene glycol. Per a list of known CYP inducers and inhibitors published by the US Food and Drug Administration, 30 (3%) patients were on a medication that inhibited CYP3A4; 1 patient was on a CYP3A4 inducer, prednisone; and 46 (5%) patients were on a medication that inhibited CYP2D6. Conclusions A small fraction of patients undergoing adenotonsillectomy are on medications that potentially alter the metabolism of opioid pain medications. Given the narrow therapeutic index of opioids and increased sensitivity to opioids among patients with obstructive sleep apnea, drug-drug interactions need to be considered as they relate to whether an opioid is appropriate and at what dose.