Excessive polypharmacy and cumulative prescribing of drugs predisposing to adverse drug events in residents of 147 care-homes: a cross-sectional analysis

Problem

Background

GPs provide the majority of medical care for care-home residents who have complex cognitive and physical needs, are often older and have more long-term conditions than adults not living in care-homes. Reduced renal, cognitive and sensory function, and altered pharmacokinetics and pharmacodynamics put older people at increased risk of adverse drug events (ADEs). Polypharmacy is associated with potentially harmful drug-drug and drug-disease interactions and ADEs are the primary cause of 10% of hospital admissions in older adults. Previous estimates of polypharmacy are based on studies examining a limited number of care-home residents and small numbers of drugs.

Aim

To determine the prevalence of polypharmacy and cumulative prescribing contributing to specific ADEs in a complete geographical population of care-home residents.

Approach

Method

Cross-sectional analysis of prescribing for all residents of 147 care-homes in two health board areas in Scotland. Systemically pharmacologically active drugs prescribed within the 56 days prior to 31st March 2017 were included. Duplicated prescriptions were removed. Polypharmacy was deemed presence of prescriptions for ≥5 distinct drugs within the study period. Cumulative prescribing of medications increasing the risk of eight ADEs (anticholinergic effects, bleeding, constipation, heart failure, hypotension, renal injury, sedation and urinary retention) was identified by counting drugs identified as being associated with each ADE, referring to a Cumulative Toxicity Tool. The number of drugs co-prescribed within each ADE group was counted as measure of potential risk of each ADE.

Counts/percentages of polypharmacy and ADE group co-prescribing, multilevel logistic regression modelling and two-level hierarchical logistic regression (identifying between care-home and associations with resident and care-home characteristics examined by intra-cluster coefficient [ICC]) was performed using R (v3.2.5). Statistical significance was assumed at 5%, ORs were reported with 95% CIs.

Findings

Results

4324 people were included; 71.4% were women and 48.1% were aged ≥85 years. Polypharmacy was seen in 71.5% of women and 68.2% of men. Mean number of drugs prescribed per person was 6.3 (SD 3.3). Adjusted regression models showed smaller care homes and third sector/local authority run care-homes had higher levels of polypharmacy. Two-level hierarchical multi-level modelling - in progress. Co-prescribing of drugs associated with ADEs was common across all ADE groups with highest levels in constipation and sedation, where 39.9% and 34.0% of residents (consecutively) were co-prescribed ≥2 drugs. 20.6% of residents were prescribed an opiate and 18.1% a antipsychotic drug (constipation), and 20.6% of residents were prescribed an opiate and 19.6% an SSRI (sedation).

Consequences

Conclusion

Polypharmacy and co-prescribing of drugs associated with ADEs was widespread in care-home residents, people who are particularly vulnerable to harm. Further research is needed to support bespoke medication reviews that balance the need for symptomatic relief of symptoms and long-term preventative therapies against the potential risks of prescribing specific drugs and polypharmacy.