Pharmacists identified a considerable number of DRPs, suggesting that medication reviews in community pharmacies can promote medication safety. Older patients frequently used PIMs, which indicated a higher DRP risk. However, only knowledge gaps, more drugs and a patient age between 70 and 84 years were independently associated with an increased DRP risk.
Patient characteristics
With a mean age of 72 years, balanced sex ratio and frequent polypharmacy, our patient sample was comparable to other pharmacy-based studies [22, 28]. Notably, medication plans were common, although not mandatory before 2016. They did, however, not prevent knowledge gaps. While we did not assess completeness of medication plans, other authors found discrepancies in 93% [28]. Knowledge gaps were more common among men and older patients, confirming earlier research [29]. They were less frequent for OTC medications, presumably because these are commonly bought by the patients themselves, with advice from pharmacists.
Potentially inappropriate medication in older patients
The 24% PIM prevalence we determined resembles results from ambulatory care settings (17–25%) [30, 31], emergency wards (17–36%) [8, 32] and health insurances (19–25%) [33,34,35,36], despite methodological differences, such as the absence of daily doses, OTC medications and private prescriptions in insurance data. However, a fourth of the PIMs in our study are OTC medications or commonly prescribed privately, i.e. sedative drugs [37], emphasizing these drugs’ importance for medication safety.
Expectedly, patients with more drugs also used more PIMs. Among women, PIM use was higher as well, caused by more frequent use of psychotropic drugs [38], including common PIMs amitriptyline, diazepam and dimenhydrinate. Both findings confirm results by others [34], who in addition reported a correlation between PIM use and patient age that we cannot confirm. However, their study relied on data from 2007, before the PRISCUS list was published, and awareness about PIM in older patients might have increased since.
Our findings indicate a substantial risk for adverse events, e.g. falls, in older patients. Considering main indications of PIMs, medication safety could benefit particularly from healthcare professionals’ focused attention to drugs for the nervous, musculoskeletal, cardiovascular and genitourinary system.
Prevalence of drug-related problems
The high number (mean: 3.5, median 2) and prevalence (84%) of DRPs likely results from selective inclusion of high-risk patients by pharmacists. Recruiting similarly, others [22] found an even higher number (5.8) and prevalence (95%) of DRPs and information needs. Conversely, DRPs were found in only 18–21% of consecutively included patients [16, 17]. These differences indicate that pharmacists selected predominantly high-risk patients, where possible. In routine-care-settings, comparable DRP numbers have been found: Dutch community pharmacists identified 3.0 DRPs (median: 2) [39] and Australian pharmacists identified 4.9 DRPs per patient [40], however, those medication reviews incorporated clinical data. Altogether, despite methodological differences, the results endorse pharmacists’ ability to successfully identify problems within their patient’s medication. We consider a focus on patients with maximum intervention benefit essential for the efficient conduction of medication reviews on a larger scale.
As in previous studies [18, 22], drug–drug-interactions were the most frequent DRPs, to which several factors may contribute: First, patients used a high number of drugs, which increases the possibility of drug–drug-interactions exponentially [41]. Second, pharmacy software facilitates the identification of drug–drug-interactions with varying clinical relevance. Finally, DRPs were documented for each drug involved in a drug–drug-interaction. Second-most common were drug use and adherence problems, which were frequently resolved without physicians, emphasizing the proficiency of pharmacists in this area of care. Adverse drug reactions, which were prevalent in one-fifth of patients and involve manifest harmful effects, were resolved in nearly 90% of cases.
According to their documentation, pharmacists resolved most DRPs (72.2%) directly with patients. They contacted physicians in 12.7% of cases, a low proportion compared to previous research [22]. Occasionally, pharmacists might have sent patients to see their physicians about DRPs, which is viable for minor problems and inevitable if patients object to direct contact between healthcare professionals. Thus, some DRPs might have required contact between patient and physician subsequently. Regrettably, follow-up-data was not available. To conclude, although pharmacists identified a considerable proportion of DRPs, physicians’ cooperation is essential to resolve DRPs completely, particularly in the 80% Rx drugs in our sample. On the other hand, 20% of all medications were available over-the-counter. Others [42] found that patients had 2.8 more drugs at home than their physicians’ documentation suggested. Since physicians are frequently unaware of their patients’ OTC drugs, pharmacists are well-positioned for medication reviews incorporating both Rx and OTC medications.
Review duration varied considerably, partly resulting from varying numbers of drugs and DRPs. The remainder might be attributable to differences in pharmacists’ experience, communication, research and documentation. The mean duration of 67 min (median: 60) fits in with other studies (35–90 min) [22, 43]. Variation between studies might reflect differences in review procedure and documentation.
Risk factors for drug-related problems
The single most important risk factor for DRPs was the number of drugs. It also increased the number of DRPs, while their proportion remained stable, confirming earlier research [22, 44, 45]. Thus, reducing the number of drugs lowers DRP risk as well as PIM exposure. However, deprescribing is challenging and polypharmacy often results from guideline adherence in multimorbid patients [46]. Deprescribing therefore benefits from interdisciplinary collaboration facilitated by systematic medication reviews [47].
Knowledge gaps, which had already been linked to adherence issues by previous research [29], were another risk factor. Surprisingly, medication plans did not affect DRP risk, possibly because they did not prevent knowledge gaps. Consequently, consolidation of patients’ knowledge on drug indications should be considered an integral part of medication reviews.
Among older patients, the risk for DRPs increased with age, likely attributable to multimorbidity and polypharmacy. Notably, it was lower in very old patients, possibly because of elevated awareness of DRPs in frail patients. Interestingly, patients younger than 65 years were at high risk for DRPs. Pharmacists may have included young patients due to their above-average morbidity. Some authors [45] determined a higher DRP risk for patients over 60 years, whereas others [44] found no influence of age. Sex was neither a risk factor in those studies nor in our own research. Older patients with PIMs were more likely to have DRPs as well. However, this association did not persist in adjusted analysis, suggesting confounding variables such as the number of drugs, which was associated with both PIM and DRP prevalence. Although PIMs did not independently increase DRP risk, they indicated potential to optimize medication safety.
Limitations
Our study had several limitations. First, all data were pharmacist-reported. Varying numbers of DRPs might be partly caused by limited inter-rater-reliability. However, some variation is inevitable in a multi-centered, real-life approach involving hundreds of pharmacists.
Second, this study only included patients who appeared personally and participated in medication anamnesis and discussion. Hence, it excluded other patient groups (e.g. nursing home residents, patients with dementia and immobile patients), for whom transferability of our results might be low. Additionally, patient selection by pharmacists facilitated efficient identification and solution of problems, but limits the generalization of findings.
Third, patients declared that 90% of their drugs were “presently used”. Since this term might be subject to interpretation, particularly for as needed drugs, we included all drugs into analysis. Thus, the numbers of drugs, PIMs and DRPs in use might be up to 10% lower than reported here.