RESEARCH ARTICLE

Potentially inappropriate prescribing and drug–drug interactionsamong elderly Chinese nursing home residents in Macao

Cheng Kin Lao • Sao Chan Ho • Ka Kit Chan •

Chon Fai Tou • Henry Hoi Yee Tong •

Alexandre Chan

Received: 15 March 2013 / Accepted: 14 June 2013 / Published online: 28 June 2013

� Springer Science+Business Media Dordrecht 2013

Abstract Background The ageing of the population has

become a concern all over the world, including Macao. In

general, older people are more prone to adverse drug events

which can result from potentially inappropriate medication

(PIM) use and drug–drug interactions (DDIs). Objective

This study was designed to evaluate the prevalence of PIM

use and DDIs among elderly nursing home residents in

Macao, and to find out the factors associated with these

drug-related problems. Setting This study was conducted in

the largest nursing home in Macao, with a bed capacity of

168. Method All data of this cross-sectional study were

collected from medical charts and medication administra-

tion records. PIM use was determined by the screening tool

of older person’s prescription (STOPP) criteria and poten-

tial DDIs were detected using the preset criteria of two

compendia, Drug-Reax and Lexi-Interact. Multivariate

logistic regression analysis was performed to identify the

independent factors associated with each drug-related

problem. Main outcome measures The proportions of

elderly nursing home residents who regularly used PIMs

and who were exposed to DDIs. Results A total of 114

elderly residents were eligible for PIM analysis. They

consumed an average of 6.9 ± 3.1 different medications.

About 46.5 % of them regularly used one or more PIMs.

The prevalence of DDIs was 37.8 % among the 111 elderly

residents who consumed at least two different medications.

An increased number of drugs used was identified as the

independent factor associated with PIM use and DDIs

(p \ 0.05). However, the use of STOPP-related PIMs did

not appear to raise the likelihood of DDIs among the study

population. Conclusion Both PIM use and DDIs are com-

mon among elderly nursing home residents in Macao.

Further studies should be conducted to evaluate the clinical

outcomes of pharmacist-led interventions for elderly resi-

dents in the local nursing home setting.

Keywords Drug interactions � Elderly � Macao � Nursing

home � Potentially inappropriate medication � STOPP

Impacts on practice

• Potentially inappropriate medication use and potential

drug-drug interactions are highly prevalent among

elderly nursing home residents in Macao.

• The number of medications used is found to be

significantly associated with potentially inappropriate

prescribing and drug-drug interactions.

• Elderly nursing home residents with hypertension or a

history of stroke are more likely to experience potential

drug–drug interactions.

• There is room for improvement in detection and

prevention of drugrelated problems among the nursing

home residents in Macao.

Introduction

With its Chinese and Portuguese heritage, Macao is a small

but well-developed gaming city in Southern China. Similar

C. K. Lao (&) � S. C. Ho � K. K. Chan �C. F. Tou � H. H. Y. Tong

School of Health Sciences, Macao Polytechnic Institute, Rua de

Luı́s Gonzaga Gomes, Macao, People’s Republic of China

e-mail: cklao@ipm.edu.mo

A. Chan

Department of Pharmacy, Faculty of Science, National

University of Singapore, Singapore, Singapore

123

Int J Clin Pharm (2013) 35:805–812

DOI 10.1007/s11096-013-9811-y

to other developed regions, Macao faces the problem of

population ageing. The official statistical agency estimates

that the elderly population, defined as 65 years of age or

older, will rise from 7.3 % of total population as in 2011 to

19.2 % by 2036 [1]. Population ageing poses an increasing

burden to health care systems all over the world including

Macao. As the elderly often suffer from multiple chronic

diseases [2], they commonly experience polypharmacy

[3–5]. The complexity of drug regimens, in addition to age-

related physiological changes, renders geriatric patients

vulnerable to drug-related problems including potentially

inappropriate medication (PIM) use and potential drug–

drug interactions (DDIs).

Potentially inappropriate medication use in the elderly is

frequently observed in the nursing home setting. According

to the studies conducted among different countries,

23.7–70 % of elderly nursing home residents were pre-

scribed with at least one PIM [5–8]. Similarly, potential

DDIs are also highly prevalent among the elderly. In Tai-

wan, 25.1 % of nursing home residents experienced DDIs,

among which 72 % were of moderate or major severity [9].

Potential DDIs are among the recognized causes of adverse

drug events. A recent study found that the incidence of

DDI-related adverse drug events was 6 % in elderly out-

patients. About 37 % of the cases led to hospital admission

[10]. Moreover, according to a Finnish nursing home study,

PIMs were consumed by 47.9 % of residents exposed to

DDIs while only 34.2 % of those without DDIs were

identified as PIM users. This significant difference sug-

gested the association between PIM use and potential DDIs

[6].

Over the years, the Macao government has invested

considerable financial resources in health care, with the

elderly as one of the main beneficiary groups. The gov-

ernment-run hospital and outpatient health centers provide

a wide range of free medical services to all elderly per-

manent residents, including prescription medications and

vaccinations [11]. Nonetheless, there is room for

improvement in the long-term care facility sector. Cur-

rently, there are 19 long-term care facilities in Macao, with

only one providing regular medical and nursing care to

residents, while most of the others offer limited to no

nursing care [12]. As health care professionals with

expertise in drug management, pharmacists play a promi-

nent role in optimizing medication use in this setting in

many western countries [13]. On the contrary, pharmacists’

routine involvement in medication reviews for nursing

home residents is lacking in Macao.

Ensuring the appropriateness of prescribing and avoid-

ing DDIs are essential for minimizing the occurrence of

adverse drug events among the elderly. With the rapid

growth of the ageing population, more emphasis should be

placed on the quality and safety of drug use for geriatric

patients. However, there is a lack of published data on

medication usage among the elderly residing in nursing

homes in Macao.

Aim of the study

This study was designed to assess the prevalence of PIM

use and potential DDIs among the elderly residents in a

Macao nursing home, and to identify the factors associated

with each problem. It will serve as the first step for further

investigation on how to enhance pharmacists’ contribution

to preventing drug-related problems in the local long-term

care facilities.

Method

Study design and setting

This was a cross-sectional study conducted in the private,

non-profit Caritas Meng Fai Nursing Home in Macao. The

study protocol was approved by the review committee at

the Macao Polytechnic Institute. All data were de-identified

and a waiver for informed consent was obtained. Caritas

Meng Fai Nursing Home is currently the largest long-term

care facility in Macao, with a bed capacity of 168 [12]. It is

also the only skilled nursing facility with an in-house

medical team consisting of a physician, nurses, a physical

therapist, and an occupational therapist. The medical team

provides around-the-clock care to the residents who are

mostly of poor health or disabled, although the residents

are also managed by other specialized physicians outside of

the nursing home. All medications and supplements are

required to be stored in the in-house pharmacy and dis-

pensed by nurses. Residents are not allowed to keep any

drug or supplement in their own rooms.

Inclusion and exclusion criteria

The study population comprised all residents who were

65 years or older, and consumed at least one scheduled

prescription or over-the-counter medication. All medica-

tions consumed on an as-needed basis, vitamin or mineral

supplements, drugs for topical use, and herbal medicines

were not counted in this study. The residents were excluded

if their medication administration records were unavailable

or incomplete.

Data collection

Eligibility screening and data collection were performed on

a single day (1 August 2011). All data were obtained from

806 Int J Clin Pharm (2013) 35:805–812

123

the eligible subjects’ medical charts. Data collection

parameters included basic demographic information,

diagnoses, certain vital signs and laboratory results such as

serum creatinine, etc. Furthermore, each subject’s medi-

cations (on the day of study) were captured and recorded.

All medications were categorized based on the WHO

anatomical therapeutic chemical (ATC) classification sys-

tem [14]. To ensure the accuracy of data collection, the

data were counterchecked by other investigators in the

research team.

Endpoints

The PIM analysis included all subjects who were eligible

for this study. The screening tool of older person’s pre-

scription (STOPP) was utilized for investigating the prev-

alence of PIM use. STOPP is a relatively new explicit tool

including 65 criteria, which are organized based on phys-

iological systems [15] and display good inter-rater reli-

ability among physicians and pharmacists [16, 17].

The elderly subjects were deemed eligible for the

evaluation of potential DDIs if they regularly used at least

two different medications. The DDI analysis was con-

ducted using two drug compendia: Drug-Reax from Mi-

cromedex 2.0 [18] and Lexi-Interact [19], both of which

are commonly used in clinical settings. However, their

inclusion and severity grading of DDIs are largely incon-

sistent [20]. For the purpose of this study, the potential

DDIs were only included if they were listed in both com-

pendia and considered clinically relevant, defined as

meeting the following two criteria: (1) a severity rating of

contraindicated, major, or moderate and an evidence rating

of excellent, good or fair in Drug-Reax, and (2) a severity

rating of major or moderate and a reliability rating of

excellent, good, or fair in Lexi-Interact. These criteria were

derived and modified based on a previous DDI study that

also utilized two compendia as references [21].

In order to minimize interpretation bias, three raters

were trained to use STOPP and the two DDI compendia.

Each rater evaluated the data set individually and all dis-

agreements were resolved through discussion.

Statistical analysis

Descriptive statistics were utilized to report the prevalence

of PIM use and potential DDIs. Inferential statistics

including Chi Square test and/or Fisher’s Exact test were

used to compare categorical data and all continuous data

were compared using the Student’s t test. In order to

identify the independent factors associated with PIM use

and potential DDIs, multivariate logistic regression analy-

sis was performed on the subject characteristics and/or

comorbidities with p \ 0.05 in the bivariate analysis. The

required sample size was estimated to be at least 108

subjects, based on the prevalence of PIM use and DDIs

from the Finnish nursing home study conducted by Hosia-

Randell et al. [6]. All statistical analyses were performed

by using SPSS for Windows, version 17.0.

Results

Demographics

A total of 156 residents were screened for eligibility.

Following exclusion of the residents who were younger

than 65 years and/or took no medications, 114 (73.1 %)

residents were eligible for the evaluation of PIM use

(Fig. 1). The mean age of eligible subjects was

86.6 ± 8.4 years and two-thirds were females. The sub-

jects consumed an average of 6.9 ± 3.1 different medica-

tions by ATC code, ranging from 1 to 15 (Fig. 2). Among

them, 31 subjects (27.2 %) consumed at least 9 medica-

tions, a cutoff point that has been used to define poly-

pharmacy in previous literature [22].

PIM use

Fifty-three subjects used at least one PIM, accounting for

46.5 % of the study population. Among these subjects, 21

(40 %) consumed two or more PIMs. The most common

PIMs, as determined by STOPP, were duplicate drug

classes, the use of benzodiazepines in patients with a fall

history, and the use of dipyridamole as monotherapy for

cardiovascular secondary prevention (Table 1).

Factors associated with PIM use

Among the subject characteristics, an increased number of

drugs used (p \ 0.001) and the use of psychotropic drugs

(p = 0.025) were significantly associated with the use of

PIMs. No associations were found between PIM use and

age, gender, or certain chronic medical conditions such as

hypertension, diabetes, dementia, Parkinson disease, and

stroke history (all with p [ 0.05). The multivariate logistic

regression analysis demonstrated that the more medications

an elderly subject consumed, the more likely the subject

would use PIMs (OR 1.28, 95 % CI 1.11–1.47) (Table 2).

DDIs

One hundred and eleven elderly subjects were eligible for

the DDI analysis (Fig. 1). Considerable variations were

observed in the results between the two compendia. Based

on the preset criteria of Lexi-Interact, 488 potential DDIs

were recognized. In contrast, 168 potential DDIs were

Int J Clin Pharm (2013) 35:805–812 807

123

detected by using the preset criteria of Drug-Reax. In

overall, 77 potential DDIs were listed in both compendia

and met all the preset criteria. Only 8 of them were listed

as of major severity by both compendia. Of the 111

subjects, 42 (37.8 %) were exposed to one or more

potential DDIs. The number of potential DDIs per subject

ranged from 1 to 7. Seventeen subjects (40.5 %) experi-

enced two or more potential DDIs. The most frequently

encountered DDI was the concomitant use of clopidogrel

and amlodipine (Table 3).

Factors associated with DDIs

Subjects with hypertension (p \ 0.001), diabetes

(p = 0.001), and a history of stroke (p = 0.034) were more

likely to have potential DDIs. The number of drugs used

was also significantly higher among the DDI users

(p \ 0.001). No significant differences between the pres-

ence and absence of DDIs were observed in relation to age,

gender, dementia, Parkinson disease, and the use of psy-

chotropic drugs (all with p [ 0.05). It was also found that

DDI = drug-drug interaction; PIM = potentially inappropriate medication.

Total number of residents

n=156

< 65 years of age

n=38

≥ 65 years of age

n=118

Medication users

n=114

Taking ≥ 1 medication

n=114

With PIM(s)

n=53

Without PIMs

n=61

Taking ≥ 2 medications

n=111

With DDI(s)

n=42

Without DDIs

n=69

Medicationnon-users

n=4

Fig. 1 Flow diagram of the

study population and the

number of residents with or

without PIMs or DDIs. DDI

drug–drug interaction, PIM

potentially inappropriate

medication

2.6% (3)

4.4% (5)4.4% (5)

13.2% (15)

12.3% (14)

11.4% (13)

12.3% (14)

12.3% (14)

7.0% (8)

6.1% (7)

4.4% (5)

6.1% (7)

0.9% (1)

0.9% (1)

1.8% (2)

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Per

cent

age

of s

tudy

pop

ulat

ion

Number of regularly used medications

% of study population(number of residents)

Fig. 2 Distribution of study

subjects by the number of

regularly used medications

(n = 114)

808 Int J Clin Pharm (2013) 35:805–812

123

STOPP-related PIM use did not increase the likelihood of

potential DDIs (p [ 0.05). An increased number of drugs

used (OR 1.53, 95 % CI 1.25–1.86), stroke history (OR

4.26, 95 % CI 1.39–13.05), and hypertension (OR 5.03,

95 % CI 1.12–22.66) were shown to be the independent

factors associated with potential DDIs (Table 4).

Discussion

This is the first study that evaluated the prevalence of drug-

related problems among elderly nursing home residents in

Macao. Our findings suggested that 46.5 % of elderly nurs-

ing home residents used PIMs and 37.8 % were exposed to

potential DDIs. Polypharmacy appeared to be an alarming

issue because 27.2 % of the study population regularly

consumed 9 or more medications. For every one additional

medication prescribed to an elderly resident, the risks for

PIM use and DDIs rose by 27.7 and 52.6 %, respectively.

The high prevalence of PIM use in the Macao nursing

home was consistent with that in the other countries [7, 8].

One of the most commonly encountered PIMs in this study

was benzodiazepine use in patients who were prone to falls.

PIM use involving benzodiazepines was also identified in an

Irish nursing home study [8]. Along with their sedating

effect, long-term use of high doses of benzodiazepines is

associated with an increased fracture risk in the elderly [23].

A recent study has also established a strong relationship

Table 1 Most common PIMs

based on the STOPP criteria

Total PIMs identified = 87

PIM potentially inappropriate

medication

Rank Criterion (concern) Frequency

(% total PIMs)

1st Duplicate drug classes (optimization of monotherapy within a single drug class

should be observed prior to considering a new class of drug)

22 (25.3)

2nd Benzodiazepines in patients who are prone to falls (sedative, may cause reduced

sensorium and impair balance)

11 (12.6)

Dipyridamole as monotherapy for cardiovascular secondary prevention (no

evidence for efficacy)

11 (12.6)

3rd First-generation antihistamines in patients who are prone to falls (sedative and

may impair sensorium)

9 (10.3)

4th Prolonged use ([1 week) of first-generation antihistamines (risk of sedation and

anti-cholinergic side effects)

8 (9.2)

Neuroleptic drugs in patients who are prone to falls (may cause gait dyspraxia

and parkinsonism)

8 (9.2)

5th Proton pump inhibitors for peptic ulcer disease at full therapeutic dosage for

[8 weeks (earlier discontinuation or dose reduction for maintenance/

prophylactic treatment of peptic ulcer disease, esophagitis or gastroesophageal

reflux disease as indicated)

3 (3.4)

NSAID with heart failure (risk of exacerbation of heart failure) 3 (3.4)

Table 2 Bivariate analysis and multivariate logistic regression analysis to identify the independent factors associated with PIM use

Characteristic Bivariate analysis Multivariate analysis

Without PIMs (n = 61) With PIMs (n = 53) p value OR (95 %CI) p value

Age [mean (SD)]a 81.7 (9.4) 81.4 (7.2) 0.887

Gender 0.507

Males [No. (%)] 22 (36.1) 16 (30.2)

Females [No. (%)] 39 (63.9) 37 (69.8)

Stroke history [No. (%)] 38 (62.3) 30 (56.6) 0.537

Hypertension [No. (%)] 41 (67.2) 41 (77.4) 0.229

Diabetes [No. (%)] 17 (27.9) 20 (37.7) 0.262

Dementia [No. (%)] 18 (29.5) 16 (30.2) 0.937

Parkinson disease [No. (%)]b 2 (3.3) 3 (5.7) 0.662

Taking psychotropic drugs [No. (%)] 24 (39.3) 32 (60.4) 0.025c 2.20 (0.99–4.90) 0.052

Number of drugs used [mean (SD)]a 5.9 (3.1) 8.0 (2.8) \0.001c 1.28 (1.11–1.47) 0.001c

CI confidence interval, OR odd ratio, PIM potentially inappropriate medication, SD standard deviationa Student’s t test; b Fisher’s Exact test; c statistically significant; all of the others were done by using Chi Square test

Int J Clin Pharm (2013) 35:805–812 809

123

between fall-induced osteoporotic fractures and PIM-related

hospital admission among frail older people [24]. If a safer

alternative is not available, it is recommended that benzo-

diazepines should be prescribed at the lowest effective dose

for the shortest duration.

In the literature, it is known that discrepancies were

observed among various DDI compendia [20, 25, 26].

Therefore, screening DDIs using more than one reference is

common practice in clinical settings. Drug-Reax and Lexi-

Interact were chosen for the DDI analysis because they are

widely used by healthcare professionals internationally. In

addition, their sensitivity in identifying clinically significant

DDIs is higher when compared with other compendia. Their

major difference is specificity, with Lexi-Interact providing

less specific DDI information [20]. In this study, 488 DDIs

were detected by Lexi-Interact, compared to 168 DDIs by

using Drug-Reax. Among them, merely 100 DDIs were

detected by both compendia. Two potential DDIs classified

as ‘‘contraindicated’’ by Drug-Reax (carbamazepine/nifed-

ipine and phenytoin/nifedipine) were listed as of moderate

severity by Lexi-Interact. This reconfirms the inconsistency

between different DDI compendia, and also rationalizes the

approach to use two compendia as references.

Among the eligible residents, 37.8 % had a total of 77

potential DDIs that met the preset criteria. A Taiwanese

study showed that 25.1 % of nursing home residents had

Table 3 Most common potential DDIs

Rank Potential DDI Drug-Reax Lexi-Interact Frequency

(% total DDIs)Severity Evidence Severity Evidence

1st Clopidogrel Amlodipine Major Excellent Moderate Fair 6 (7.8)

2nd Clopidogrel Nifedipine Major Excellent Moderate Fair 3 (3.9)

Aspirin Enalapril Moderate Excellent Moderate Excellent 3 (3.9)

3rd Clopidogrel Esomeprazole Major Excellent Major Fair 2 (2.6)

Clopidogrel Cilostazol Major Fair Moderate Fair 2 (2.6)

Amlodipine Simvastatin Major Good Major Fair 2 (2.6)

Amlodipine Diltiazem Moderate Good Moderate Good 2 (2.6)

Furosemide Captopril Moderate Good Moderate Good 2 (2.6)

Furosemide Celecoxib Moderate Good Moderate Excellent 2 (2.6)

Furosemide Digoxin Moderate Good Moderate Fair 2 (2.6)

Levodopa Phenytoin Moderate Good Moderate Fair 2 (2.6)

Allopurinol Theophylline Moderate Fair Moderate Good 2 (2.6)

Total potential DDIs that met all preset criteria = 77

DDI drug–drug interaction

Table 4 Bivariate analysis and multivariate logistic regression analysis to identify the independent factors associated with potential DDIs

Characteristic Bivariate analysis Multivariate analysis

Without DDIs (n = 69) With DDIs (n = 42) p value OR (95 %CI) p value

Age [mean (SD)]a 82.1 (8.2) 80.2 (8.7) 0.251

Gender 0.498

Males [No. (%)] 24 (34.8) 12 (28.6)

Females [No. (%)] 45 (65.2) 30 (71.4)

Stroke history [No. (%)] 37 (53.6) 31 (73.8) 0.034c 4.26 (1.39–13.05) 0.011c

Hypertension [No. (%)] 42 (60.9) 39 (92.9) \0.001c 5.03 (1.12–22.66) 0.035c

Diabetes [No. (%)] 15 (21.7) 22 (52.4) 0.001c 2.46 (0.86–7.01) 0.093

Dementia [No. (%)] 19 (27.5) 14 (33.3) 0.517

Parkinson disease [No. (%)]b 2 (2.9) 3 (7.1) 0.365

Taking psychotropic drugs [No. (%)] 39 (56.5) 17 (40.5) 0.101

Number of drugs used [mean (SD)]a 5.9 (2.4) 8.8 (3.0) \0.001c 1.53 (1.25–1.86) \0.001c

PIM use [No. (%)] 32 (46.4) 21 (50.0) 0.711

CI confidence interval, DDI drug–drug interaction, OR odd ratio, PIM potentially inappropriate medication, SD standard deviationa Student’s t test; b Fisher’s Exact test; c statistically significant; all of the others were done by using Chi Square test

810 Int J Clin Pharm (2013) 35:805–812

123

potential DDIs including those of minor severity [9]. The

higher DDI prevalence in this study might result from the

higher average number of medications consumed by the

residents compared with that in the Taiwanese study.

This study has also established that DDIs were signifi-

cantly associated with stroke history and hypertension,

which was consistent with the findings of previous studies

[6, 27]. Hypertension was diagnosed in 92.9 % of the aged

residents with DDIs in this study. The elderly residents

who had a history of hypertension were five times more

likely to experience DDIs. A follow-up evaluation showed

that the hypertensive residents consumed significantly

more medications than their normotensive counterparts,

which might be the explanation of their elevated DDI risk.

The association between antihypertensive drug use and the

occurrence of DDIs was also documented in a previous

study [28]. This reiterates the importance to raise such

awareness among prescribers for older patients, especially

those who have a history of hypertension and/or stroke.

An increased number of drugs used was strongly associ-

ated with both PIM use and potential DDIs among this study

population. Polypharmacy has long been demonstrated to

raise the likelihood of PIM use [5–8, 29, 30] and DDIs [6, 9,

27, 31, 32] among older people. More importantly, poly-

pharmacy is also associated with serious PIM-related

adverse events [33]. Polypharmacy was prevalent in this

study possibly due to the involvement of multiple physicians

in disease management and a lack of pharmacist-led drug

reviews in the local nursing home setting.

Another noteworthy finding was the absence of any asso-

ciation between STOPP-related PIM use and clinically rele-

vant DDIs. Contradictory to such results, a Finnish study

revealed that elderly people managed with the Beers criteria-

related PIMs were more likely to have DDIs, although its DDI

analysis was based on a different compendium [6]. The rela-

tionship between PIM use and DDIs should be further studied.

In the studied nursing home, more than 150 residents are

regularly managed by only one in-house physician. It

provides opportunities for pharmacists to enhance their

clinical role in a city where they are mainly perceived as

sole medication suppliers by the public. As drug experts,

pharmacists can apply their knowledge and collaborate

with physicians to optimize drug therapies for nursing

home residents. Based on the results of a European study,

medication reviews carried out by pharmacists of the

multidisciplinary teams can lead to fewer drugs prescribed

and higher detection and resolution rates of drug-related

problems [34]. Pharmacist-led medication reviews can also

lower the costs of mortality and morbidity associated with

pharmacotherapy [35]. Moreover, pharmacists’ contribu-

tion to patient care is highly appreciated by physicians and

nurses in the long-term care facility setting [34, 36]. Cur-

rently, the data on the other outcomes of pharmacist

services are still questionable in this setting and there is a

need for more studies on this topic [37].

Several limitations can be noted in this study. The rela-

tively small sample size and its single-center nature seem to

adversely influence the generalizability of the results.

However, the studied nursing home is the only one of its kind

in Macao, with a strict policy of drug storage and adminis-

tration that can ensure data accuracy. In addition, certain

laboratory tests such as serum sodium and creatinine levels

are required to assess several criteria of STOPP. Nonethe-

less, some residents did not have these laboratory records

available in their medical charts, which might influence the

PIM analysis. In fact, the prevalence of potential DDIs might

also be subject to underestimation due to the exclusion of

dietary supplements and herbal medicines which are widely

consumed by local people. A lack of evidence-based clinical

information on drug-supplement interactions or drug-herb

interactions makes it impractical to take them into consid-

eration. Furthermore, owing to the regional variation in

medical practice, certain medications such as piracetam and

nicergoline are commonly prescribed by local physicians but

they are not listed in both Drug-Reax and Lexi-Interact.

Lastly, STOPP is an explicit tool which is criterion-based

and takes little or no clinical judgment into account. Even

with such limitation, explicit PIM screening tools are usually

more feasible in practice because the implicit approaches are

more time-consuming and may have low reliability [38].

Conclusion

STOPP-related PIM use and potential DDIs were highly

prevalent among elderly Chinese nursing home residents in

Macao. Polypharmacy was shown to be an issue for the

elderly residents in this setting, which might increase the risk

of drug-related problems. However, the use of PIMs as

determined by STOPP did not increase the likelihood of

potential DDIs. It is imperative to conduct further studies to

assess the clinical outcomes of pharmacist interventions for

the elderly residing in long-term care facilities in Macao.

Acknowledgments The authors gratefully acknowledged the med-

ical and administrative staff of Caritas Meng Fai Nursing Home for

their assistance.

Funding This study was financially supported by the Macao Poly-

technic Institute.

Conflicts of interest No conflicts of interest to declare.

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