Publications

PURPOSE: Results of a study to estimate the prevalence of look-alike/sound-alike (LASA) medication errors through analysis of Veterans Affairs (VA) administrative data are reported.

METHODS: Veterans with at least 2 filled prescriptions for 1 medication in 20 LASA drug pairs during the period April 2014-March 2015 and no history of use of both medications in the preceding 6 months were identified. First occurrences of potential LASA errors were identified by analyzing dispensing patterns and documented diagnoses. For 7 LASA drug pairs, potential errors were evaluated via chart review to determine if an actual error occurred.

RESULTS: Among LASA drug pairs with overlapping indications, the pairs associated with the highest potential-error rates, by percentage of treated patients, were tamsulosin and terazosin (3.05%), glipizide and glyburide (2.91%), extended- and sustained-release formulations of bupropion (1.53%), and metoprolol tartrate and metoprolol succinate (1.48%). Among pairs with distinct indications, the pairs associated with the highest potential-error rates were tramadol and trazodone (2.20%) and bupropion and buspirone (1.31%). For LASA drug pairs found to be associated with actual errors, the estimated error rates were as follows: lamivudine and lamotrigine, 0.003% (95% confidence interval [CI], 0-0.01%); carbamazepine and oxcarbazepine, 0.03% (95% CI, 0-0.09%); and morphine and hydromorphone, 0.02% (95% CI, 0-0.05%).

CONCLUSION: Through the use of administrative databases, potential LASA errors that could be reviewed for an actual error via chart review were identified. While a high rate of potential LASA errors was detected, the number of actual errors identified was low.

OBJECTIVE: We sought to estimate size and sources of differences in per capita expenditures on primary care medications in the US versus ten comparable countries combined: Australia, Canada, France, Germany, the Netherlands, New Zealand, Norway, Sweden, Switzerland, and the United Kingdom.

METHODS: Using market research data on year 2015 volumes and sales of medicines, we measure total per capita expenditures on six categories of primary care prescription drugs: hypertension treatments, pain medications, lipid lowing medicines, non-insulin diabetes treatments, gastrointestinal preparations, and antidepressants. We quantified the contributions of five drivers of the observed differences in per capita expenditures.

RESULTS: We estimated that the US spent 203% more per capita on primary care pharmaceuticals than did the ten comparable countries. Despite the difference in spending levels, on average, Americans actually purchased 12% fewer days of related therapies than residents of the comparator countries. Most of the observed difference in expenditures was due to higher transaction prices of medicines and the use of a more expensive mix of medicines in the US.

CONCLUSIONS: If utilization patterns and pharmaceutical prices in the US were similar to those in the 10 comparator countries combined, total spending on primary care pharmaceuticals would fall by 30% or more. Such evidence on the level and drivers of US pharmaceutical expenditures should inform policies in this sector.

BACKGROUND: Overlapping use of opioids and benzodiazepines is associated with increased risk for overdose. Veterans receiving medications concurrently from the U.S. Department of Veterans Affairs (VA) and Medicare may be at higher risk for such overlap.

OBJECTIVE: To assess the association between dual use of VA and Medicare drug benefits and receipt of overlapping opioid and benzodiazepine prescriptions.

DESIGN: Cross-sectional.

SETTING: VA and Medicare.

PARTICIPANTS: All veterans enrolled in VA and Medicare Part D who filled at least 2 opioid prescriptions in 2013 (n = 368 891).

MEASUREMENTS: Outcomes were the proportion of patients with a Pharmacy Quality Alliance (PQA) measure of opioid-benzodiazepine overlap (≥2 filled prescriptions for benzodiazepines with ≥30 days of overlap with opioids) and the proportion of patients with high-dose opioid-benzodiazepine overlap (≥30 days of overlap with a daily opioid dose >120 morphine milligram equivalents). Augmented inverse probability weighting regression was used to compare these measures by prescription drug source: VA only, Medicare only, or VA and Medicare (dual use).

RESULTS: Of 368 891 eligible veterans, 18.3% received prescriptions from the VA only, 30.3% from Medicare only, and 51.4% from both VA and Medicare. The proportion with PQA opioid-benzodiazepine overlap was larger for the dual-use group than the VA-only group (23.1% vs. 17.3%; adjusted risk ratio [aRR], 1.27 [95% CI, 1.24 to 1.30]) and Medicare-only group (23.1% vs. 16.5%; aRR, 1.12 [CI, 1.10 to 1.14]). The proportion with high-dose overlap was also larger for the dual-use group than the VA-only group (4.7% vs. 2.3%; aRR, 2.23 [CI, 2.10 to 2.36]) and Medicare-only group (4.7% vs. 2.9%; aRR, 1.06 [CI, 1.02 to 1.11]).

LIMITATION: Data are from 2013 and cannot capture medications purchased without insurance; unmeasured confounding may remain in this cross-sectional study.

CONCLUSION: Among a national cohort of veterans dually enrolled in VA and Medicare, receiving prescriptions from both sources was associated with greater risk for receiving potentially unsafe overlapping prescriptions for opioids and benzodiazepines.

PRIMARY FUNDING SOURCE: U.S. Department of Veterans Affairs.

de Boer and colleagues present a cost-effectiveness analysis based in the Netherlands of two vaccines available for the prevention of herpes zoster. Zostavax® was the first vaccine available for the prevention of herpes zoster in older adults. A live-attenuated vaccine, Zostavax is not free of limitations, which include a relatively low efficacy that wanes over time and its contraindication among immunocompromised individuals. The recently available adjuvanted herpes zoster subunit vaccine Shingrix® overcomes some of these limitations. The herpes zoster subunit vaccine is more efficacious than Zostavax, and it can be administered to immunosuppressed individuals. However, the herpes zoster subunit vaccine is considerably costlier and requires a booster injection. In order to clarify the value of each vaccine, de Boer and colleagues compare the cost-effectiveness of no vaccination, and of vaccination with Zostavax or the herpes zoster subunit vaccine in four cohorts of older adults from the perspective of the Netherlands. Whereas neither vaccine was cost-effective under the willingness-to-pay threshold of €20,000 per quality-adjusted life year, the authors find the herpes zoster subunit vaccine to be cost-effective in some scenarios under a €50,000 per quality-adjusted life year threshold.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-018-1213-5.

OBJECTIVE: To evaluate the effect of dual use of VA/Medicare Part D drug benefits on antihypertensive medication supply in older Veterans with dementia.

DATA SOURCES/STUDY SETTING: National, linked 2007-2010 Veterans Affairs (VA) and Medicare utilization and prescription records for 50,763 dementia patients with hypertension.

STUDY DESIGN: We used inverse probability of treatment (IPT)-weighted multinomial logistic regression to examine the association of dual prescription use with undersupply and oversupply of antihypertensives.

DATA COLLECTION/EXTRACTION METHODS: Veterans Affairs and Part D prescription records were used to classify patients as VA-only, Part D-only, or dual VA/Part D users of antihypertensives and summarize their antihypertensive medication supply in 2010: (1) appropriate supply of all prescribed antihypertensive classes, (2) undersupply of ≥1 class with no oversupply of another class, (3) oversupply of ≥1 class with no undersupply, or (4) both undersupply and oversupply.

PRINCIPAL FINDINGS: Dual prescription users were more likely than VA-only users to have undersupply only (aOR = 1.28; 95 percent CI = 1.18-1.39), oversupply only (aOR = 2.38; 95 percent CI = 2.15-2.64), and concurrent under- and oversupply (aOR = 2.89; 95 percent CI = 2.53-3.29), versus appropriate supply of all classes.

CONCLUSIONS: Obtaining antihypertensives through both VA and Part D was associated with increased antihypertensive under- and oversupply. Efforts to understand how best to coordinate dual-system prescription use are critically needed.

[This corrects the article DOI: 10.1371/journal.pone.0158017.].