Polypharmacy, Dosing Trends, and Drug-Drug Interaction Patterns After High-Level Limb Amputation Surgery

Abstract

The aim of this study was to examine perioperative medication patterns surrounding major amputation surgeries. Design: A retrospective chart review of 216 cases of major amputations (transfemoral, hip disarticulation, hemipelvectomy, forequarter) at an academic hospital was conducted, examining medications, dosing changes, and drug-drug interaction warnings preoperatively and postoperatively.Results: Medications increased in 76.9% (166/216), remained the same in 10.6% (23/216), and decreased in 12.5% (27/216) of cases. Average number of medications was 7 preoperatively and 10 postoperatively. In 189 cases with preoperative medications present, postoperative dosing remained the same for 74.3%, increased for 9.2%, decreased for 7.6%, and was unknown for 8.9% of medications. Increases in each of type C ("monitor therapy"), D ("consider therapy modification), and X ("avoid combination") drug-drug interaction warnings were seen respectively in 59.7%, 62.0%, and 5.1% of cases. Conclusion: Polypharmacy is involved preoperatively and increased postoperatively in most cases of major limb amputation, with agent dosing remaining the same or increased in most cases. Drug-drug interaction warnings also increase. These occur at a time of abrupt changes to the body's size, compartments, and physiologic responses. More research and clinical attention are warranted given anticipated changes in pharmacokinetics and pharmacodynamics.

Estimated glomerular filtration rate based on creatinine, cystatin C, β‐trace protein and β2 microglobulin in patients undergoing nontraumatic lower extremity amputation

“…Patients undergoing nontraumatic lower extremity amputation are characterized by high rates of polypharmacy at baseline 9 and often receive additional medications after amputation that should be dosed according to kidney function 10 . Common postoperative medications include analgesics such as oxycodone and gabapentin, antithrombotics such as enoxaparin and antibiotics such as gentamicin, which all require dose adjustment below certain GFR thresholds.…”

“…Patients undergoing amputation are also more likely to have impaired kidney function at baseline due to comorbidities such as diabetes, hypertension and atherosclerosis 9 . In addition to medications targeting these comorbidities, common postoperative medications include analgesics, antithrombotics and antibiotics that should be dosed according to kidney function 10 . This presents a clinical challenge for appropriate prescribing of renally excreted medications in patients undergoing amputation, particularly when relying on eGFRcre[2009].…”