Outpatient Pharmacy Prescriptions During the First Year Following Serious Combat Injury: A Retrospective Analysis

Limited research has analyzed the full range of outpatient medication prescription activity following serious combat injury. The objectives of this study were to describe (1) outpatient medication prescriptions and refills during the first 12 months after serious combat injury, (2) longitudinal changes in medication prescriptions during the first-year postinjury, and (3) patient characteristics associated with outpatient prescriptions.

This was a retrospective analysis of existing health and pharmacy data for a random sample of U.S. service members who sustained serious combat injuries in the Iraq and Afghanistan conflicts, 2010-2013 (n = 381). Serious injury was defined by an Injury Severity Score (ISS) of 9 or greater. These patients typically participate in military rehabilitation programs (eg, amputation care) where prescription medications are essential. Data sources were the Expeditionary Medical Encounter Database for injury-specific data, the Pharmacy Data Transaction Service for outpatient medication prescriptions and refills, and the Military Health System Data Repository for diagnostic codes of pain and psychological disorders. Military trauma nurses reviewed casualty records to identify types of injuries. Using the American Hospital Formulary Service Pharmacologic-Therapeutic Classification system, clinicians identified 13 categories of prescription medications (eg, opioid, psychotherapeutic, immunologic) for analysis. Multivariable negative binomial and logistic regression analyses evaluated significant associations between independent variables (eg, blast injury, traumatic brain injury [TBI], ISS, limb amputation, diagnoses of chronic pain, or psychological disorders) and prescription measures (ie, number or category of medication prescriptions). We also describe longitudinal changes in prescription activity postinjury across consecutive quarterly intervals (91 days) during the first-year postinjury.

During the first-year postinjury, patients averaged 61 outpatient prescriptions, including all initial prescriptions and refills. They averaged eight different categories of medications, primarily opioid, immunologic, gastrointestinal/genitourinary, central nervous system (CNS), nonopioid analgesic, and psychotherapeutic medications (representing 82% of prescriptions) during the first year. Prescription activity generally declined across quarters. There was still substantial prescription activity during the fourth quarter, as 79% of patients had at least one prescription. From 39 to 49% of patients had fourth-quarter prescriptions for opioid, CNS, or psychotherapeutic medications. Longitudinally, we found that 24-34% of patients had an opioid, CNS, or psychotherapeutic prescription during each of the final three quarters. In multivariable analysis, ISS, limb amputation (particularly bilateral amputation), and diagnoses of chronic pain and post-traumatic stress disorder (PTSD) were associated with significantly higher counts of individual and multiple medication prescriptions. TBI was associated with significantly lower numbers of prescriptions for certain medications.

This is one of the first studies to provide a systematic analysis of outpatient medication prescriptions following serious combat injury. The results indicate substantial prescription activity from multiple medication categories throughout the first-year postinjury. Diagnoses of chronic pain, PTSD, and limb amputation and ISS were associated with significantly higher counts of prescriptions overall and more prescription medication categories. This study provides initial evidence to better understand medication prescription activity following serious combat injury. The results inform future research on medication prescription practices and planning for rehabilitation.