Patient and medication factors associated with preventable medication waste and possibilities for redispensing
Patient and medication factors associated with preventable medication waste and possibilities for redispensing
C. L. Bekker 0 1 2 4
B. J. F. van den Bemt 0 1 2 4
A. C. G. Egberts 0 1 2 4
M. L. Bouvy 0 1 2 4
H. Gardarsdottir 0 1 2 4
0 Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Centre , P. Debyelaan 25, 6229 HX Maastricht , The Netherlands
1 Department of Pharmacy, Radboud University Medical Centre , Geert Grooteplein Zuid 10, 6525 GA Nijmegen , The Netherlands
2 Department of Clinical Pharmacy, Division Laboratories and Pharmacy, University Medical Centre Utrecht , Heidelberglaan 100, 3584 CX Utrecht , The Netherlands
3 H. Gardarsdottir
4 Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University , 99, 3584 CG Utrecht , The Netherlands
Background Knowledge on factors related to preventable medication waste and waste-reducing interventions, including redispensing unused medications, is needed to maximise effectiveness. Objective To assess patient and medication factors associated with preventable medication waste and possibilities for redispensing unused medications. Setting Dutch community pharmacies. Methods In this cross-sectional study, pharmacy-staff registered patient and medication characteristics of prescription medications returned to 41 Dutch community pharmacies during 1 week in 2014. Medications were classified as preventable waste if the remaining amount could have been prevented and as theoretically eligible for redispensing if the package was unopened, undamaged and ≥ 6 months until the expiry date. Associations were analysed using multivariate logistic regression. Main outcome measures Proportion of medications classified as preventable waste and as eligible for redispensing, including factors associated with these medications. Results Overall, 279 persons returned 759 (low-cost) medications, and 39.3% was classified as preventable waste. These medications were more frequently used by men than women (OR; 1.7[1.2-2.3]) and by older (> 65 years) than younger patients (OR; 1.4[1.0-2.0]). Medications dispensed for longer periods were more often unnecessary wasted (1-3 months OR; 1.8[1.1-3.0], > 3 months 3.2[1.5-6.9]). Of all returned medications, 19.1% was eligible for redispensing. These medications were more frequently used by men than women (OR; 1.9[1.3-2.9]). Medications chronically used were more frequently eligible for redispensing than acute use (OR; 2.1[1.0-4.3]), and used for longer periods (1-3 months OR; 4.6[2.3-8.9], > 3 months 7.8[3.3-18.5]). Conclusions Over one-third of waste due to medications returned to community pharmacies can be prevented. One-fifth of returned medications can be redispensed, but this seems less interesting from an economic viewpoint.
Community pharmacy; Medication waste; The Netherlands; Pharmacy services; Redispensing; Unused medications
Department of Pharmacy, Sint Maartenskliniek, Hengstdal
3, 6574 NA Nijmegen, The Netherlands
Numerous patients have leftover medication, of which
almost half could have been prevented.
• Pharmacists can help to reduce medication waste by
limiting medication quantities dispensed to patients and
theoretically by redispensing medications that remain
• The majority of medications that are returned to the
pharmacies unused are of low value, making investments
in redispensing unused medications less useful.
Medications account for almost one-fifth of health care
spending in developed countries [
]. However, patients do
not use a substantial proportion of medications dispensed to
], contributing to suboptimal treatment outcomes,
financial waste and harm to the environment.
Various stakeholders in the medication supply chain,
from manufacturer to patient, contribute to medication
waste. Manufacturers may produce unnecessarily large
packages with quantities that exceed the amount required
for treatment. Pharmacists are not always allowed to split
packages into smaller quantities and thus dispense
excessive amounts to the patient. In addition, prescribers may
prescribe medications for a longer period than the patient
actually needs. Even if there is no waste of medication in
the situations above, side effects, unsatisfactory treatment
responses or early discontinuation during medication use
may lead to therapy changes that may result in an excess of
dispensed medication [
]. Patients keep the remaining
amounts for later use, discard them with the household
garbage or return them to pharmacies and waste depots [
Although many studies have described which medications
are returned to pharmacies and for which reasons, knowledge
of the factors relating to medication waste is lacking [
If information were to be available on which medications
are frequently unnecessary wasted, by which patients and in
which situations, then waste-reducing interventions can
specifically target these. Moreover, part of the medication waste
often concerns unopened packages, including medications of
good quality. A possible intervention to decrease the waste
of these good quality medications might be the redispensing
of these medications. In most countries, redispensing unused
medications is not done in clinical practice due to lack of
insight in the quality or legal restraints. However, the debate
about redispensing as waste-reducing intervention is
]. Therefore, more information is needed to assess
which medications that remain unused by the patient could
be eligible for redispensing.
Aim of the study
The aim of this study is to assess which patient-related and
medication-related factors are associated with preventable
medication waste and to explore possibilities for
redispensing unused medications.
The study was approved by the UPPER institutional review
board of the Utrecht University, the Netherlands (UP1408).
This cross-sectional study was conducted in May 2014 in
41 Dutch community pharmacies that are part of the
Utrecht Pharmacy Practice network for Education and Research
(UPPER) of the department of Pharmaceutical Sciences of
the Utrecht University [
]. The pharmacies were located
in both urban and rural areas and covered 2.1% of the total
number of community pharmacies (n = 1981).
Prescription medications that were returned as a routine
practice to the participating community pharmacies
during five consecutive working days in the study period were
included in this study. Medications dispensed outside the
Netherlands, extemporaneously compounded medications
and medical devices such as wound dressings and testing
materials were excluded. Pharmacy students holding a
bachelor’s degree in pharmacy analysed the waste and collected
the data during their final internship prior to receiving their
pharmacy master’s degree. Students received both oral and
written instructions before the start of the study. For each
returned medication, a written record form was completed
with information directly obtained from the person who
returned the medication, after verbal consent and
information derived from the medication label.
• The following patient characteristics were recorded
anonymously: patient’s gender and age, type of prescriber
(general practitioner, medical specialist, dentist or other),
reason for use and reason(s) for returning the medication
(patient deceased, condition resolved, passed expiration
date, no/insufficient effect, treatment changed, adverse
events, inconvenience of use, other [further specified] or
unknown). Furthermore, details about the person who
returned the medication (e.g. user, family, relative, health
professional or other) were also registered.
• The following medication characteristics were recorded:
medication name, strength, returned amount (number of
tablets or capsules, liquids were estimated in milliliter,
dermatologicals were estimated in grams), amount
initially dispensed, prescribed dosage regimen, expiration
date, whether the package was returned unopened (i.e.
unused, yes/no) and whether the package was undamaged
(yes/no). The returned medications were coded according
to the Anatomical Therapeutic Chemical (ATC)
classification system of the WHO [
Data were entered on site into the online survey tool
Lime survey. The first author randomly checked 10% of the
entered patients’ data sheets in terms of data entry and data
validity. Data was considered as precise as less than 1% of all
entered variables were found to be incorrect. Subsequently,
the economic value of each individual returned medication
was calculated by using the Dutch medication prices of May
]. The lowest registered price of each medication
unit was used to determine the minimal economic value of
each returned medication unit. The total economic value was
calculated by multiplying the returned number of units of a
medication (e.g. number of tablets) by the unit price.
Each pharmacy received a unique study code. The
study code list could only be accessed by an independent
researcher who was not a member of the study group.
All returned medications were classified according to
their preventability of medication waste and eligibility for
Firstly, predefined criteria were used to assess the
preventability of the medication waste. This assessment was
done by the pharmacy student who collected the data. This
assessment was based on the patient- and medication
information and subsequently judged on preventability when
one of the following criteria was full filled: (I) when larger
amounts of medication were prescribed than needed for the
expected duration of use, (II) when excessive medication
amounts were prescribed for a terminal patient, (III), when
a pharmacist dispensed more than the prescribed amount,
(IV) in case of a prescription error (e.g. wrong strength
prescribed), (V) when a refill that was no longer needed was
dispensed or (VI) when patients had side effects or
insufficient effect of treatment at the moment of a refill, but still
collected the medication. Medications that could be
classified neither as preventable waste nor as inevitable waste, due
to insufficient data that was not registered, were excluded
from further analysis.
Secondly, the returned medications were classified
theoretically as eligible for redispensing when these met all of
the following criteria: (I) the package was unopened, (II)
the package was undamaged, and (III) there was at least
6 months between the date of returning (end of study date)
and the expiry date.
Regarding proportions, descriptive analyses were made and
expressed as percentages, whereas medians with
interquartile ranges (IQR) were analysed for averages. A univariate
analysis was initially conducted in order to assess potential
associations between explanatory variables and the primary
outcomes waste (yes/no) and eligibility for redispensing
(yes/no). This was followed by a full model multivariate
logistic regression analysis. Explanatory variables included
in both analyses were patient’s gender and age, reason for
returning the medication, duration of use (determined by a
clinical pharmacologist), unit price and amount dispensed
(converted into days by dividing by the daily dose). In
addition, regarding medication waste, the prescriber of the
returned medication was also included but not considered
as a potential association for medications’ eligibility for
The definition of waste could have been biased by the
subjective judgement of the student who collected the
medications at the pharmacy. Therefore, to enhance validity a
sensitivity analysis was conducted to which a returned
medication classified as waste at a certain pharmacy was matched
to a returned medication classified as no waste at the same
pharmacy. Conditional logistic regression, with controlling
for the pharmacy level, was subsequently applied. All
statistical analyses were performed in STATA13.
Characteristics of the returned medications and users
In total, 279 persons returned 759 prescription medications.
Medications were most often returned by the consumer
(59.9%), followed by a family member (31.5%). The returned
medications were most frequently used for gastro-intestinal
disorders (18.5%), nervous system disorders (17.8%) and
cardiovascular disorders (18.1%).
The estimated total economic value of all returned
medications was €7,916 with a median value of €1.75 per
medication (IQR €0.58–6.28). Of the ten most expensive returned
n = 759* (%)
Medication eligible for
redispensing n = 145*
medications, half were considered eligible for redispensing
(Appendix, Table 1).
Medications were returned primarily because ‘patient
was deceased’ (22.4%), ‘condition had resolved’ (19.9%)
and ‘passed expiry date’ (14.6%) Some patients reported
‘other’ reasons such as discontinuation of treatment during
pregnancy, switching to a multi-dose dispensing system or
‘spring-cleaning’ of the house. The main reasons for
returning medications that were eligible for redispensing were
‘patient was deceased’ (30.3%) and ‘treatment changed’
(19.3%) (Table 1).
Factors associated with preventable medication waste
Of the 759 returned medications, 298 medications (39.3%)
were classified as preventable medication waste and 378
medications (49.8%) were classified as inevitable waste.
Due to a lack of information, 83 medications could not be
classified and were therefore excluded from the analysis.
Medications classified as preventable waste were distributed
among all therapeutic classes, and had an average economic
value of €2.36 (IQR €0.72–9.00). Around 80% of the
preventable medication waste was below €15.00. Factors that
were associated with potential preventable medication waste
are presented in Table 2.
Preventable waste was significantly higher among male
patients compared to female patients (OR 1.7 [1.2–2.3]).
Medications used by older patients (> 65 years) were
classified as preventable waste significantly more often than
medications that were originally in use by younger patients
(< 65 years) (OR 1.4 [1.0–2.0]). The type of prescriber, type
of medication use, reason for returning the medication and
the economic value of a medication unit were not
significantly associated with medications defined as preventable
waste. However, a significantly increased risk of preventable
medication waste was found for medications that were
initially dispensed for a longer period (1-3 months OR 1.8
[1.1–3.0] and > 3 months OR 3.2 [1.5–6.9]). Sub analyses
showed that approximately one-third of the medications used
on a chronic basis and two-thirds of the episodic medications
were dispensed for less than 1 month.
The conditional logistic regression showed similar
associations, except for two variables that turned out to be
significant: reason for returning ‘other’ (OR 1.9 [1.1–3.4]) and
medication units valued €1–5 (OR 0.3 [0.1–0.7]) (Appendix,
Factors associated with medications eligible for redispensing
Of all of the returned medications, 145 medications (19.1%)
were classified theoretically as eligible for redispensing,
with a median economic value of €4.60 (IQR €1.45–17.36).
Around 80% of the returned medications were below €25.00.
Factors that were associated with medications potentially
eligible for redispensing are presented in Table 3.
Medications classified as eligible for redispensing were
used by male patients significantly more frequently
compared to female patients (OR 1.9 [1.3–2.9]). Medications
used on a chronic basis were more frequently eligible for
redispensing compared to acute use (OR 2.1 [1.0–4.3]). Of
the returned medications that were initially dispensed for
a longer period, significantly more medications were
eligible for redispensing (1–3 months OR 4.6 [2.3–8.9] and
> 3 months OR 7.8 [3.3–18.5]). The other variables showed
no association with medications eligible for redispensing.
This study showed that of the returned medications, more
than one-third was perceived as preventable waste. This
emphasizes the need to implement waste reducing measures
where possible. Moreover, approximately one-fifth of the
returned medications were potentially eligible for
redispensing. This study also identified several patient- and
medication-related factors that were associated with preventable
waste and possibilities for redispensing.
Male gender was associated with preventable medication
waste. Previous research showed that men more frequently
use medications intended for chronic use (like
cardiovascular diseases), whereas women more often use medications
that are used for acute or episodic treatment (like
antibiotics, painkillers and sleeping pills) [
]. When assessing
the association between the dispensed amount and
preventable waste, medications dispensed for a duration
exceeding one month were associated with preventable waste.
This has also been confirmed by others  and indicates
Preventable n = 298
Inevitable n = 378 (%)
Crude OR (95% CI)
Adjusted OR (95% CI)
Reasons for returning
Patient was deceased
Duration of use
> 3 months
that preventable waste depends strongly on the amount of
medications dispensed. Furthermore, returned medications
classified as waste were more often used by the elderly. An
explanation could be that the elderly often use multiple
medications, which increases the risk of non-adherence,
side-effects and eventually waste [
The proportion of medications that was theoretically
eligible for redispensing is similar to that reported by others
]. One study found that more than 90% of returned
medications were eligible for redispensing, but this study
did not apply the criterion that the original outer package
must be unopened and intact . However, none of those
studies examined determinants of returned medications that
are eligible for redispensing. This study shows that
eligibility of returned medications for redispensing was specifically
associated with male users, chronic therapy duration and
a dispensing period of at least one month. To obtain the
most benefit from redispensing if implemented in clinical
practice, interventions can be specifically designed for
medications that are dispensed to male users, and medications
that are used on a chronic basis or dispensed for at least
one month. Medications dispensed for longer periods more
often consist of multiple packages. Therefore it is more
likely that at least one package is left unopened and thus
eligible for redispensing. This also indicates that interventions
for redispensing unused medications should include patients
to whom multiple packages of a medication are dispensed.
To make redispensing feasible to implement in practice,
multiple stakeholders have reported that patients should be
willing to participate in such a system [
unused medications may succeed if patients are willing to
return all their unused medications to the pharmacy, and
even more important, are willing to use medications that
have been previously dispensed to another patient. In an
internet hotline launched by the Dutch Ministry of Health
where patients and health care professionals were asked to
report on how to combat waste in healthcare, the majority
of suggestions made by patients were to redispense unused
]. Hence, this suggests that patients are
willing to participate in a redispensing system.
Knowing this, waste reducing interventions should
specifically target the amount that is dispensed to patients, such
as dispensing medications for shorter periods, which has
proven to be effective in reducing waste [
implementing this approach for all medications might not
compensate for the reimbursement of additional
dispensing fees by pharmacists. In specific cases of more
expensive medications, it may be cost-effective to shorten the
dispensing period. Our results showed that the most
expensive returned medications consisted of large amounts
(Appendix, Table 1). Similarly, it is questionable if the
redispensing of unused medications is cost saving for all
medications. Nevertheless, there are also benefits to be gained by
reducing environmental harm. Reducing medication waste at
community pharmacies, where the majority of patients use
relatively cheap generic medications, requires a
multifactorial and medication-specific approach [
]. For example,
thoroughly reviewing the medication for older patients, and
discussing which medications are needed, could decrease
the risk of medications being wasted.
To assess the effectiveness of waste-reducing
interventions, studies are needed that assess if changing
dispensing from a 3-month to a 1-month supply reduces waste and
saves costs, taking into account the low costs of the returned
medications. In addition, patients’ views on a supply of
one month should be determined, as this requires more
pharmacy visits and may be a burden to patients. Little research
is conducted on redispensing unused medications. Insight
into the costs of a redispensing system is needed to
determine if implementation is cost-beneficial in the community
and/or outpatient pharmacy. Furthermore, patients’ views on
the redispensing of unused medications should be explored
in terms of their willingness to use medications that have
been dispensed to another patient.
In this study, students subjectively determined if medications
were defined as preventable waste, which may limit validity.
To enhance validity of this data, student received both oral
and written instructions about this classification, with a clear
set of criteria. Regarding all data that the students collected,
and the personal communication that they had with the
persons returning the medications, they were, in our view,
best able to make this judgement. This judgement was not
reviewed by a second person. In our view, a review of the
classifications later on and using the data sheets only would
have been less precise compared to the assessment made on
site. Furthermore, a sensitivity analysis was conducted that
corrected for each pharmacy, i.e. the student that made the
judgement in the pharmacy in the analysis. For instance,
it may have been that a student more frequently classified
returned medications as preventable waste. This analysis
presented similar findings on factors that were associated
with preventable medication waste, indicating that there was
no ‘inter-pharmacy’ variety in classifications.
Three criteria were used to determine if the
medications were potentially eligible for redispensing (package
unopened, intact and at least six months until the expiry
date). However, no information about the home storage
conditions, like temperature exposure, was taken into account.
Literature has shown that patients do not always store their
medications at the recommended temperature [
might affect the quality of medications and thereby patient
safety. Therefore, the proportion of medications that was
considered of good quality and eligible for redispensing
in this study is likely an overestimation. Further, we found
that redispensing unused medications that are returned to
community pharmacies is less feasible when considering
the small proportion deemed eligible and the low costs of
No collection campaign was set up prior to the start of
this study. Knowing that not all patients return their
medications to the pharmacy, but that they also deposit these at
chemical waste depots, keep them in the house or dispose of
them with the garbage, the absolute extent of waste
generated through community pharmacies could not be assessed.
Furthermore, using the lowest medication price unit for
the calculations might have resulted in an underestimation
of the economic value. For many returned medications,
information was lacking on the number of packages that
were returned. Medications classified as eligible for
redispensing could consist of unopened and opened packages,
which might have caused an overestimation of the economic
value of these medications. Finally, in the Netherlands, the
majority of expensive medications, such as most
biologicals, are dispensed by hospital based outpatient pharmacies.
These medications are infrequently returned to community
This study shows that over one-third of the waste due to
medications returned to the community pharmacies can be
prevented. Waste-preventive interventions could specifically
target factors that are associated with preventable
medication waste, such as the dispensing of medications for period
longer than one month. Approximately one-fifth of returned
medications can be redispensed. However, most medications
were of low-cost, which makes redispensing unused
medications in the community pharmacy less interesting from an
economic point of view.
Acknowledgements The authors want to thank all pharmacies that
participated in this study and all students that collected the data. Special
thanks go out to Salma Boudhan and Fatima Elouanajni who facilitated
the coordination and data collection of the study.
Funding This research did not receive any specific grant from funding
agencies in the public, commercial, or not-for-profit sectors.
Conflicts of interest All authors declare they have no conflicts of
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://creativeco
mmons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give appropriate
credit to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
1. OECD Publishing . Health at a Glance 2015 . Paris: OECD indicators; 2015 . p. 220 .
2. Braund R , Yuen YC , Jung J . Identification and quantification of medication returned to Otago pharmacies . NZFP . 2007 ; 34 ( 4 ): 258 - 62 .
3. Braund R , Gn G , Matthews R . Investigating unused medications in New Zealand . Pharm World Sci. 2009 ; 31 ( 6 ): 664 - 9 .
4. Guirguis K. Medications collected for disposal by outreach pharmacists in Australia . Pharm World Sci. 2010 ; 32 ( 1 ): 52 - 8 .
5. Garey KW , Johle ML , Behrman K , Neuhauser MM . Economic consequences of unused medications in Houston, Texas . Ann Pharmacother. 2004 ; 38 ( 7-8 ): 1165 - 8 .
6. Coma A , Modamio P , Lastra CF , Bouvy ML , Mariño EL . Returned medicines in community pharmacies of Barcelona, Spain . Pharm World Sci. 2008 ; 30 ( 3 ): 272 - 7 .
7. Langley C , Marriott J , Mackridge A , Daniszewski R. An analysis of returned medicines in primary care . Pharm World Sci . 2005 ; 27 ( 4 ): 296 - 9 .
8. Law AV , Sakharkar P , Zargarzadeh A , Tai BWB , Hess K , Hata M , et al. Taking stock of medication wastage: unused medications in US households . Res Social Adm Pharm . 2015 ; 11 ( 4 ): 571 - 8 .
9. Mackridge AJ , Marriott JF . Returned medicines: waste or a wasted opportunity? J Public Health . 2007 ; 29 ( 3 ): 258 - 62 .
10. Ekedahl ABE . Reasons why medicines are returned to Swedish pharmacies unused . Pharm World Sci . 2006 ; 28 ( 6 ): 352 - 8 .
11. Wasserfallen J , Bourgeois R , Büla C , Yersin B , Buclin T. Composition and cost of drugs stored at home by elderly patients . Ann Pharmacother . 2003 ; 37 ( 5 ): 731 - 7 .
12. Dias-ferreira C , Valente S , Vaz J . Practices of pharmaceutical waste generation and discarding in households across Portugal . Waste Manag Res . 2016 ; 34 ( 10 ): 1006 - 13 .
13. Persson M , Sabelström E , Gunnarsson B . Handling of unused prescription drugs-knowledge, behaviour and attitude among Swedish people . Environ Int . 2009 ; 35 ( 5 ): 771 - 4 .
14. Vellinga A , Cormican S , Driscoll J , Furey M , Sullivan MO , Cormican M. Public practice regarding disposal of unused medicines in Ireland . Sci Total Environ . 2014 ; 478 : 98 - 102 .
15. Vogler S , Leopold C , Zuidberg C , Habl C. Medicines discarded in household garbage: analysis of a pharmaceutical waste sample in Vienna . J Pharm Policy Pract . 2014 ; 7 ( 1 ): 1 - 8 .
16. West LM , Diack L , Cordina M , Stewart D. A systematic review of the literature on “medication wastage”: an exploration of causative factors and effect of interventions . Int J Clin Pharm . 2014 ; 36 ( 5 ): 873 - 81 .
17. Bekker CL , Gardarsdottir H , Egberts TCG , Bouvy ML , van den Bemt BJF. Redispensing of medicines unused by patients: a qualitative study among stakeholders . Int J Clin Pharm . 2017 ; 39 ( 1 ): 196 - 204 .
18. Lenzer J. US could recycle 10 million unused prescription drugs a year, report says . BMJ . 2014 ; 349 : g7677 .
19. Tchen J , Vaillancourt R , Pouliot A . Wasted medications, wasted resource . Can Pharm J . 2013 ; 146 ( 4 ): 181 - 2 .
20. Pomerantz J . Recycling expensive medication: why not ? MedGenMed . 2004 ; 6 ( 2 ): 4 .
21. Mcrae D , Allman M , James D. The redistribution of medicines: could it become a reality? Int J Pharm Pract . 2016 ; 24 ( 6 ): 411 - 8 .
22. Koster ES , Blom L , Philbert D , Rump W , Bouvy ML . The Utrecht pharmacy practice network for education and research: a network of community and hospital pharmacies in the Netherlands . Int J Clin Pharm . 2014 ; 36 ( 4 ): 669 - 74 .
23. WHO Collaborating Centre for Drug Statistics Methodology. Guidelines for ATC classification and DDD assignment 2013 . Oslo; 2012 .
24. Z-index . Dutch medicine prices [Internet] . 2014 [cited 2017 Aug 23 ]. www.z-index.nl/g-standaard.
25. Loikas D , Wettermark B , Von Euler M , Bergman U , Schenckgustafsson K. Differences in drug utilisation between men and women: a cross-sectional analysis of all dispensed drugs in Sweden . BMJ Open . 2013 ; 3 : e002378 .
26. SFK. Men more expensive , women more [Dutch] [Internet] . 2008 [cited 2017 Aug 23 ]. https://www.sfk.nl/publicaties/ PW/ 2008 /2008- 27 .html.
27. Maeng DD , Ann L , Wright EA . Patient characteristics and healthcare utilization patterns associated with unused medications among medicare patients . Res Soc Adm Pharm . 2017 ; 13 ( 6 ): 1090 - 4 .
28. Hajjar ER , Cafiero AC , Hanlon JT . Polypharmacy in elderly patients . Am J Geriatr Pharmacother . 2007 ; 5 ( 4 ): 345 - 51 .
29. Al-Siyabi K , Al-Riyami K . Value and types of medicines returned by patients to sultan qaboos university hospital pharmacy , Oman. Sultan Qaboos Univ Med J . 2007 ; 7 ( 2 ): 109 - 15 .
30. Toh MR , Chew L . Turning waste medicines to cost savings: a pilot study on the feasibility of medication recycling as a solution to drug wastage . Palliat Med . 2017 ; 31 ( 1 ): 35 - 41 .
31. VWS . Report hotline Wastage in healthcare-I [Dutch] . Ministry of Health, Welfare and Sport; 2013 .
32. Millar J , McNamee P , Heaney D , Selvaraj S , Bond C , Lindsay S , et al. Does a system of instalment dispensing for newly prescribed medicines save NHS costs? Results from a feasibility study . Fam Pract . 2009 ; 26 ( 2 ): 163 - 8 .
33. White KG . UK interventions to control medicines wastage: a critical review . Int J Pharm Pract . 2010 ; 18 ( 3 ): 131 - 40 .
34. Vlieland ND , Gardarsdottir H , Bouvy ML , Egberts TCG , Van Den Bemt BJF. The majority of patients do not store their biologic disease-modifying antirheumatic drugs within the recommended temperature range . Rheumatology . 2016 ; 55 ( 4 ): 704 - 9 .