Impact of removal and restriction of me-too medicines in a hospital drug formulary on in- and outpatient drug prescriptions: interrupted time series design with comparison group

Abstract

Background The study covered in- and out-of-hospital care in a region in north-western Spain. The intervention evaluated took the form of a change in the hospital drugs formulary. Before the intervention, the formulary contained four of the five low molecular weight heparins (LMWHs) marketed in Spain. The intervention consisted of withdrawing two LMWHs (bemiparin and dalteparin) from the formulary and restricting the use of another (tinzaparin), leaving only enoxaparin as an unrestricted prescription LMWH. Accordingly, the aim of this study was to evaluate the effect on in- and outpatient drug prescriptions of removing and restricting the use of several LMWHs in a hospital drugs formulary. Methods We used a natural, before-after, quasi-experimental design with a control group and monthly data from January 2011 to December 2016. Based on data drawn from official Public Health Service sources, the following dependent variables were extracted: defined daily doses (DDD) per 1000 inhabitants per day (DDD/TID), DDD per 100 stays per day, and expenditure per DDD. Results The two compounds that were removed from the formulary registered an immediate decrease at both an intra- and out-of-hospital level (66.6% and 55.6% for bemiparin and 73.0% and 92.2% for dalteparin, respectively); similarly, the compound that was restricted also registered an immediate decrease (36.1% and 9.0% at the in- and outpatient levels, respectively); in contrast, the remaining LMWH (enoxaparin) registered an immediate, significant increase at both levels (44.9% and 32.6%, respectively). The intervention led to an immediate reduction of 6.8% and a change in trend in out-of-hospital cost/DDD; it also avoided an expenditure of €477,317.1 in the 21 months following the intervention. Conclusions The results indicate that changes made in a hospital drugs formulary towards more efficient medications may lead to better use of pharmacotherapeutic resources in its health catchment area. Electronic supplementary material The online version of this article (10.1186/s13012-019-0924-0) contains supplementary material, which is available to authorized users.

Impact on In‐ and Out‐of‐Hospital Drug Prescriptions of Including a More Expensive Me‐Too Antidepressant in a Hospital Drug Formulary: a Controlled Longitudinal Study

“…The out-of-hospital effects recorded in this new study would not appear to be as strong or as immediate as those observed in other therapeutic groups in the same settings with the same methodology (e.g., the case of low-molecular-weight heparins). 10 This agrees with a study that shows that the intensity of induction depends on the therapeutic drug class. 13 Our results also indicate that the inclusion of a new drug tends to have a more long-term effect, unlike withdrawal from the formulary, which seems to have a more immediate effect.…”

“…Trends in out-of-hospital desvenlafaxine and venlafaxine (defined daily doses per 1000 inhabitants per day [DDD/TID]) impact would be mitigated by large discounts from the pharmaceutical industry), 7,[9][10][11]35 but can also be transmitted to out-of-hospital costs (though in our case, these did not turn out to be statistically significant in the model with control group).…”

“…13 Our results also indicate that the inclusion of a new drug tends to have a more long-term effect, unlike withdrawal from the formulary, which seems to have a more immediate effect. 10 This in turn indicates that the effect depends, not only on the class of drug (e.g., stronger in the case of cardiovascular drugs), 10 but also on the type of change made to the formulary (different according to whether this consists of withdrawal, inclusion, or drug-use restriction).…”

“…17 The induction effect of the hospital formulary toward the ambulatory setting would account for the interest shown by pharmaceutical companies in making the kind of major price discounts at an intrahospital level which have been reported by some studies (and can result in a given medication's cost to the hospital being practically zero). 10,11,13,18,40,44 It would also explain the association observed between the number of requests made by some physicians for new drugs to be added to formularies and their interactions with the pharmaceutical companies marketing such medications. 39 We feel that our outcomes are extremely relevant because they show that the addition of a new medicine to the HDF has a direct effect, not only on in-hospital prescribing, but also on out-of-hospital prescribing.…”

“…To control for the possible autocorrelation of residuals (perturbations), we added autoregressive terms to the model. From the β7 regression coefficient, we estimated the annual, long‐term, post‐intervention percentage changes, taking the value prior to the date of the intervention as reference 9,10,22 …”