Over 47% of Americans use prescription medication and over 20% use 3 or more medications.¹ This extensive prescription drug usage has an annual price tag of over $234 billion.¹ However, the efficacy of a patient’s drug regimen depends on the patient properly adhering to his or her medication. Failure to properly follow medication prescribing instructions could lead to deleterious consequences for the patient, such as increased hospitalizations and even mortality.^2-4 Even though inadequate adherence can be detrimental to a patient’s health, it is estimated that roughly 50% of patients do not take their medication as directed.⁵


Given the issues surrounding medication nonadherence, payers have moved toward promoting the dispensing of larger quantities of medication, as there is some evidence that suggests filling maintenance prescriptions for larger days supply of medication (ie, 60 or 90) can help patients achieve more optimal adherence.^6,7 Traditionally, mail order pharmacies have been one way for patients to obtain such larger prescription sizes for their maintenance medications.⁸ More recently, retail pharmacies began offering fulfillment of 90-day prescriptions in an effort to compete with mail order pharmacies, as well as to give patients another option for filling larger quantities of maintenance medications.⁹


Although obtaining a 90-day supply of medication at retail pharmacies and through mail order pharmacies may beneficially impact medication adherence, there has been limited evidence that suggests this larger prescription size may lead to greater wastage of medication in at least 1 therapeutic class.¹⁰ In the event a patient needs to switch to a different dosage or different drug, they may be left with unused medication from their previous fills. Morgan estimated the cost of this type of medication wastage to be over $1 billion annually just among patients 65 years and older.¹¹


With this in mind, we sought to examine medication wastage for patients filling 90-day supplies of medication compared with those filling 30-day prescriptions. We also conducted a sub-analysis comparing 90-day prescriptions filled at a retail pharmacy with those filled by mail order. We hypothesize that medication wastage will vary by therapeutic class. Furthermore, for 90-day prescriptions, we believe that retail pharmacies will have lower wastage than mail order.


Methods

Patient Population

This was a retrospective analysis that utilized de-identified pharmacy claims and eligibility data from the pharmacy benefit manager, Walgreens Health Initiatives (WHI), covering the period of July 01, 2009, through September 30, 2010. At the time of the study WHI managed clients across the country and in all regions. Patients represented commercial (non-Medicare/Medicaid) members of various client types. A total of 173 clients were included in the study. The study was limited to the following therapeutic classes, identified using the first 4 digits of the generic product identifier (GPI): insulins (GPI 2710), biguanides (GPI 2725), thyroid hormones (GPI 2810), cardioselective beta-blockers (GPI 3320), alpha-beta blockers (GPI 3330), calcium channel blockers (GPI 3400), angiotensinconverting enzyme (ACE) inhibitors (GPI 3610), angiotensin II receptor antagonists (GPI 3615), loop diuretics (GPI 3720), thiazides (GPI 3760), fibric acid derivatives (GPI 3920), HMG CoA reductase inhibitors (“statins” [GPI 3940]), selective serotonin reuptake inhibitors (SSRIs [GPI 5816]), and tricyclics (GPI 5820).


Patients were included in the study if they had a prescription fill for any of the therapeutic classes defined above during a 3-month identification period (July 1, 2009-September 30, 2009) and if they had a prescription fill for the same therapeutic class between January 1, 2009, and June 30, 2009, in order to exclude patients who were new to therapy.


This analysis was further limited to patients who were continuously eligible during the study period and who were 18 years or older at the start of the study. Patients were then followed for 12 months from the date of their initial (index) prescription. We included only patients with >2 prescription fills for a given therapeutic class. In the event a patient filled a prescription for more than 1 therapeutic class during the identification period, the patient was included in each therapeutic class.


Patients were then assigned to their respective groups based on the manner in which their prescriptions were filled. If a patient exclusively filled prescriptions for 30-day supplies they were placed into the “Retail-30” group. If a patient exclusively filled prescriptions for 90-day supplies (regardless of fulfillment channel) they were placed into the “90-Day” group. Patients filling prescriptions for both 30- and 90-day supplies were excluded from the analysis. The 90-Day group was then further divided into those patients who exclusively filled their 90-day prescriptions at a retail pharmacy, “Retail-90,” and those who exclusively filled their 90-day prescriptions through mail order, “Mail.” The Figure details the patient selection.


Outcome Measures

Medication wastage was defined as an excess days supply of medication resulting from a switch in medication within the same therapeutic class or to the same medication but different strength occurring before the expected refill date. Prescriptions meeting this definition, but filled on the same day, were not counted as a switch but rather an augmentation to therapy. Since some treatment regimens with excessive “switching” could appear as wastage, an additional filter was applied to mitigate potential bias or overestimation of wastage: if the difference between the number of drug changes and number of unique drugs was >2 for 30-day prescriptions and >1 for 90-day prescriptions, then the change in drugs/doses was considered concomitant and hence not a switch. For example, a patient in the 30-day group has the following fill pattern: Synthroid 125 mcg filled on August 12, Cytomel 5 mcg filled on August 23, Cytomel 5 mcg filled on September 17, Synthroid 125 mcg filled on September 20, Cytomel 5 mcg filled on October 16, and Synthroid 125 mcg filled on November 15. Since the difference between this patient’s drug changes/switches (4) and unique drugs (2) = 2, this is considered concomitant therapy and not classified as wastage.


Medication wastage was calculated as the sum of the excess days supply divided by the total number of fills which were converted to 30-day equivalents, where excess days supply is the difference between the expected fill date and the actual prescription fill date when a switch occurred. For example, a subset of a patient’s fills shows a 30-day prescription for levothyroxine 100 mcg was filled on April 4, then a 30-day prescription for levothyroxine 88 mcg was filled on April 11. Since the expected fill date is May 4, the excess days supply would equal 23. This patient had 5 fills, so his or her wastage is calculated as 23/5 = 4.6.


Statistical Analyses

A linear regression model was used to adjust for age, gender, and number of therapeutic classes filled in the previous 6 months. A P value of <.05 was considered statistically significant. All statistical analyses were performed using SAS statistical software, version 9.1.3 (SAS Institute Inc, Cary, North Carolina). Results are presented as least square mean values.


RESULTS

The Retail-30 group consisted of 35,418 patients and the 90-Day group (patients using retail, mail, or both) consisted of 24,940 patients. After stratifying 90-Day patients by exclusive fulfillment channel, the Retail-90 group had 17,897 patients and the Mail group had 6033 patients. There were 1010 patients who were excluded from these subgroups because they used both mail and retail. Patient demographics for each group can be seen in Table 1.


As shown in Table 2, days supply wasted per 30 days was significantly lower for the Retail-30 group in 8 out of the 14 therapeutic classes examined; insulins (0.281 vs 0.512, P <.001), biguanides (0.082 vs 0.131, P = .004), thyroid hormones (0.252 vs 0.383, P <.001), cardioselective beta-blockers (0.087 vs 0.144, P <.001), ACE inhibitors (0.102 vs 0.134, P = .015), angiotensin II receptor antagonists (0.117 vs 0.247, P <.001), thiazides (0.024 vs 0.062, P = .004), and HMG CoA reductase inhibitors (0.086 vs 0.118, P <.001). The Retail-30 group also had lower wastage for alpha-beta blockers, calcium channel blockers, and tricyclics, but results were not significant. 90-day patients had less medication wastage for loop diuretics, fibric acid derivatives, and SSRIs, but the differences were not significant.


Table 3 shows wastage results for 90-day prescriptions stratified by fulfillment channel. For the majority (11 out of 14) of therapeutic classes, we found Retail-90 to have lower wastage compared with Mail. However, none of the differences were statistically significant.


DISCUSSION

Side effects and dosing titration are 2 common reasons for medication wastage. For example, of the 14 therapeutic classes included in this study, statin therapy often requires dosing titration to achieve clinical goals and metformin (a biguanide) can cause diarrhea and upset stomach, causing patients to change therapy. Furthermore, for SSRIs, it is common for patients to change therapy because of perceived lack of efficacy; it may take a few months to see effects, but patients do not give them enough time to work.


While our results favor 30-day for 8 out of the 14 therapeutic classes examined, no significant differences were observed in the other 6 therapeutic classes. This finding is important because patients filling prescriptions for a 90-day supply may be able to achieve better adherence to their medication^6,7 without increasing medication wastage for these therapeutic classes, as may be expected with a larger days supply.


Filling larger-quantity prescriptions could also benefit patients and payers through cost savings. Walton et al¹⁰ created a model that predicted that a single 90-day prescription cost $2.45 less than prescriptions for 30-day supplies when considering medication wastage and drug and dispensing costs. Parikh et al¹² performed a similar analysis and found a savings of $6.17 per 90-day prescription filled compared with three 30-day prescriptions.


Focusing only on 90-day prescriptions, while our results did not show a significant difference between Retail-90 and Mail, patients obtaining their prescriptions through mail order may have greater wastage because of automatic dispensing of refills. Mail order pharmacies typically utilize auto-refills to ensure that patients have an adequate supply of medication on hand at all times. However, in the event a patient switches to a different drug or dose, this “automatic” feature may lead to greater wastage, since prescriptions may be sent out prior to the patient notifying the mail order pharmacy of their new prescription. Retail pharmacies have also implemented automatic refills; however, a patient only picks up the medication if needed. If the medication is not picked up, the retail pharmacy would reverse the claim and restock the medication, avoiding any potential for medication wastage.


Additionally, if a patient fills his or her 90-day prescription at a retail pharmacy, they may have the opportunity for face-to-face consultation with a pharmacist. Pharmacist involvement in patient care has been linked to improved health outcomes for patients with chronic conditions.^13-15


To our knowledge, no other studies have examined medication wastage across fulfillment channels for therapeutic classes other than statins. Our medication wastage results for statins are similar to those observed by Walton et al.¹⁰ The authors found the average days supply wasted was higher for Veterans Administration patients filling prescriptions for a 90-day supply of 2 particular statins. We also show wastage to be higher in the 90-Day group for our commercial population.


There are several limitations to our study. It could be possible for a patient to be placed on a supplemental/ secondary drug that is within the same therapeutic class. Our analysis would have misclassified this as wastage. It is also possible for a patient to switch to a medication that is within a different therapeutic class. We did not consider this type of switching in our analysis. Finally, there is significant potential for population bias. If physicians have patients who require dosing titrations, etc, they would probably be more likely to prescribe smaller quantities of medication.


CONCLUSIONS

One drawback for payers implementing a strategy to increase 90-day prescription fulfillment is the potential for increased wastage, which results from discontinuation or switching of therapy while the patient has unfinished supplies. However, for this study, nearly half of the therapeutic classes examined did not have significantly greater medication wastage for 90-day fills. Payers should consider promoting fulfillment of larger-quantity prescriptions for some therapeutic classes as part of a comprehensive benefit plan.
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