Polypharmacy increases non-adherence and is the biggest risk factor for ADEs €“ it is implicated in up to 17 per cent of hospital admissions. In addition, polypharmacy and multi-morbidity increase drug-drug/disease interactions. Contributing factors include:

• Multiple long-term conditions
• Increasing age
• Therapeutic advancements and increased accessibility to medicines
• Prescribing cascade (where the adverse effect of a drug is mistaken for a new symptom and a second drug is inappropriately prescribed)
• Performance targets driven by clinical guidance
• Multiple prescribers 
• Reluctance to stop medicines and poor evidence for withdrawal
• A €pill for every ill€ and psychosocial issues
• Patient or carer demand
• Poor patient engagement and communication.

Non-adherence to medicines in older people is multifactorial and both intentional and unintentional non-adherence often co-exist in the same individual. For example, an older person may be 100 per cent adherent with their analgesics, unable to manipulate their inhalers, forget to take their antibiotics and be unwilling to take a diuretic for fear of side effects. It is important therefore to identify the reasons behind the non-adherence and to give the appropriate information and support to meet the specific needs identified. 

ADEs are more common in older people and are implicated in 16.6 per cent of hospital admissions. Most are dose-related, predictable and preventable. Polypharmacy also means the risk of a drug error post-discharge is up 70 per cent as a result of poor transfer of information and frequent drug changes. 

Many ADEs in older people remain undiagnosed because they are atypical, vague and non-specific (e.g. confusion, unsteadiness, constipation, falls). Asking open questions during patient consultations is essential when identifying and resolving any ADEs. 

An ADE should be suspected when an older person presents with new symptoms. Common ADEs include gastrointestinal and haematological reactions, falls, delirium and anticholinergic symptoms.

Frail patients living in domiciliary settings may face additional challenges with medicines optimisation compared to robust or fit older people, such as:

• Over-reliance on telephone consultations and third parties to speak on their behalf
• A home environment with inadequate facilities for medicines storage and keeping medicines within easy reach 
• Poor or delayed access to medicines supply leading to stockpiling and wastage
• Considerable involvement of non-clinical staff (e.g. relatives, friends, carers and care workers) with managing complex medicines issues
• Aligning carer visits with administration time for critical and PRN or 'as needed' medicines
• Complex issues with capacity and consent
• Safeguarding and unintentional overdose.