Analysis of Pharmacist Interventions Used to Resolve Safety Target of Polypharmacy (STOP) Drug Interactions
Background: Statin drug interactions commonly increase the risk of muscle-related toxicities. The medical literature supports consultative pharmacist interventions to resolve drug interactions, but studies demonstrating autonomous pharmacist interventions are lacking.
Objective: To evaluate the complementary impact of using pharmacist-led protocols and pharmacists with prescriptive authority to resolve statin drug interactions.
Methods: Pharmacist-led protocols were developed to address gemfibrozil-statin and niacin-statin interactions. Pharmacists discontinued gemfibrozil and niacin by protocol or referred patients to the Patient Aligned Care Team (PACT) Pharmacy Clinic for individualized management. After all drug interactions were addressed, a retrospective quality improvement analysis was conducted. The primary outcome was to evaluate the impact of gemfibrozil and niacin discontinuation by protocol on patients’ triglyceride (TG) laboratory results. The coprimary endpoints were the change in TGs and the percentage of patients with TGs ≥ 500 mg/dL, following pharmacist discontinuation by protocol. Secondary outcomes included the time required to resolve the interactions and a description of the PACT Clinical Pharmacy Specialists' (CPS) pharmacologic interventions.
Results: The gemfibrozil and niacin protocols addressed 397 drug interactions. Seventy-six patients underwent gemfibrozil discontinuation by protocol and had TG laboratory results available. TG levels decreased or increased by < 100 mg/dL for 62 patients (82%), and 1 patient (1.3%) experienced TG elevation above the threshold of 500 mg/dL. Thirty-six patients had niacin discontinued by protocol and available laboratory results. The TG levels decreased or increased by < 100 mg/dL for 33 patients (91.7%), and no patients had TG levels increase above the threshold of 500 mg/dL. The mean time required to resolve both gemfibrozil and niacin drug interactions was 15.5 minutes per patient. A total of 129 patients were referred to the PACT Pharmacy Clinic to manage gemfibrozil and niacin drug interactions. TG laboratory results were available for 80 gemfibrozil patients (74.8%) and 16 niacin patients (72.7%). The PACT CPS made 171 pharmacologic interventions to address drug interactions and the median of 2 encounters per patient.
Conclusions: This single-site quality improvement analysis supports the complementary use of protocols and pharmacists with prescriptive authority to resolve statin drug interactions. These data support expanded roles for pharmacists, across settings, to mitigate select drug interactions.
Limitations
The results of this study are derived from a retrospective chart review at a single VA facility. The autonomous nature of PACT CPS interventions may be difficult to replicate in other settings that do not permit pharmacists the same prescriptive authority. This analysis was designed to demonstrate the impact of the pharmacist in resolving major drug interactions. Patients referred to the PACT Pharmacy Clinic who also had their lipid medications adjusted by a nonpharmacist provider were excluded. However, this may have minimized the impact of the PACT CPS on the patient care provided. As postintervention laboratory results were not available for all patients, some patients’ TG levels could have increased above the 500 mg/dL threshold but were not identified. The time investment was extensive and likely underestimates the true cost of implementing the interventions.
Because notification letters were used to instruct patients to stop gemfibrozil or niacin, several considerations need to be addressed when interpreting the follow-up laboratory results. First, we cannot confirm whether the patients received the letter or the exact date the letter was received. Additionally, we cannot confirm whether the patients followed the instructions to stop the interacting medications or the date the medications were stopped. It is possible some patients were still taking the interacting medication when the first laboratory was drawn. Should a patient have continued the interacting medication, most would have run out and been unable to obtain a refill within 90 days of receiving the letter, as this is the maximum amount dispensed at one time. The mean time to the first laboratory result for both gemfibrozil and niacin was 6.5 and 5.3 months, respectively. Approximately 85% of patients completed the first laboratory test at least 3 months after the letter was mailed.
The protocols were designed to assess whether gemfibrozil or niacin was indicated and did not assess whether the statin was indicated. Therefore, discontinuing the statin also could have resolved the interaction appropriately. However, due to characteristics of the patient population and recommendations in current lipid guidelines, it was more likely the statin would be indicated.22,23 The protocols also assumed that patients eligible for gemfibrozil or niacin discontinuation would not need additional changes to their lipid medications. The medication changes made by the PACT CPS may have gone beyond those minimally necessary to resolve the drug interaction and maintain TG goals. Patients who had gemfibrozil or niacin discontinued by protocol also may have benefited from additional optimization of their lipid medications.
Conclusions
This quality improvement analysis supports further evaluation of the complementary use of protocols and PACT CPS prescriptive authority to resolve statin drug interactions. The gemfibrozil and niacin protocols appropriately identified patients who were less likely to experience an adverse change in TG laboratory results. Patients more likely to require additional medication interventions were appropriately referred to the PACT Pharmacy Clinics for individualized care. These data support expanded roles for pharmacists, across various settings, to mitigate select drug interactions at the Truman VA.
Acknowledgments
This quality improvement project is the result of work supported with resources and use of the Harry S. Truman Memorial Veterans’ Hospital in Columbia, Missouri.
