Introduction: Polypharmacy, the use of multiple medications by one individual, is increasingly common among older adults. Caring for the growing number of older people with complex drug regimens and multimorbidity presents an important challenge in the coming years. Areas covered: This article reviews the international trends in the prevalence of polypharmacy, summarizes the results from previous reviews on polypharmacy and negative health outcomes, and updates a previous review on the clinical consequences of polypharmacy by focusing on studies published after 2013. This narrative review, which is based on a literature search in MEDLINE and EMBASE from January 1990 to June 2018, was undertaken to identify relevant articles. Search terms included variations of polypharmacy and multiple medications. Expert opinion: The prevalence of polypharmacy is increasing worldwide. More than half of the older population is exposed to polypharmacy in some settings. Polypharmacy is associated with a broad range of clinical consequences. However, methods to assess the dangers of polypharmacy should be refined. In our opinion, the issue of ‘confounding by multimorbidity’ has been underestimated and should be better accounted for in future studies. Moreover, researchers should develop more clinically relevant definitions of polypharmacy, including measures of inappropriate or problematic polypharmacy.

Objectives: To assess and quantify the risk of drug‐induced dry mouth as a side effect in older people. Design: Systematic review and metaanalysis. Setting: A search of the literature was undertaken using Medline, Embase, Cochrane, Web of Science, and PubMed from 1990 to 2016. Participants: Older people (aged ≥60) who participated in intervention or observational studies investigating drug use as an exposure and xerostomia or salivary gland hypofunction as adverse drug outcomes. Measurements: Two pairs of authors screened titles and abstracts of studies for relevance. Two authors independently extracted data, including study characteristics, definitions of exposure and outcome, and methodological quality. For the metaanalyses, random‐effects models were used for pooling the data and I ² statistics for exploring heterogeneity. Results: Of 1,544 potentially relevant studies, 52 were deemed eligible for inclusion in the final review and 26 in metaanalyses. The majority of studies were of moderate methodological quality. In the intervention studies, urological medications (odds ratio ( OR ) = 5.91, 95% confidence interval ( CI ) = 4.04–8.63; I ² = 62%), antidepressants ( OR = 4.74, 95% CI = 2.69–8.32, I ² = 21%), and psycholeptics ( OR = 2.59, 95% CI = 1.79–3.95, I ² = 0%) were significantly associated with dry mouth. In the observational studies, numbers of medications and several medication classes were significantly associated with xerostomia and salivary gland hypofunction. Conclusion: Medication use was significantly associated with xerostomia and salivary gland hypofunction in older adults. The risk of dry mouth was greatest for drugs used for urinary incontinence. Future research should develop a risk score for medication‐induced dry mouth to assist with prescribing and medication management.