Impact of prescribed medications on patient safety in older people

Introduction

Appropriate prescribing for the older adult presents multiple challenges. In a primary care population, nearly 35% of 85–89 year olds were taking 10 or more medications [Hippisley-Cox et al. 2007]. Despite this, the elderly remain underrepresented in clinical trials [Beswick et al. 2008]. Findings from studies undertaken in younger patients cannot always be extrapolated to older adults [Fialová and Onder, 2009]. This renders the practice of evidence-based medicine difficult, leading to both underprescribing and overprescribing. Inappropriate prescribing in the elderly is seen throughout the healthcare system and in the transition between care providers [Spinewine, 2008]. Adverse drug events (ADEs), an umbrella term that encompasses adverse drug reactions (ADRs), medication errors, overdoses, dose reductions and cessation of therapy, are common in the elderly. These have financial implications for the entire population and consequences for clinicians, such as stress-related problems and reduction in prescribing confidence [Cresswell et al. 2007].

Clearly, an awareness of safe prescribing in the elderly is more important than ever for all healthcare workers because of the changing demographics of our population. In this review, we recap first the changes in pharmacokinetics and pharmacodynamics that occur in older people. Second, we discuss the scale of the problem of ADEs and the impact of underprescribing and overprescribing on patient safety. Finally, we consider the appropriate use of high-risk medications and review strategies to improve medication safety across transitions in healthcare settings.

Pharmacokinetics and pharmacodynamics in the elderly

The pharmacokinetic changes that occur with ageing can be subdivided into changes in drug absorption, distribution, metabolism and elimination.

Adverse drug events and adverse drug reactions in the elderly

The occurrence of ADEs is common in the elderly as a result of physiological decline, an increased likelihood of drug–disease interactions due to multiple comorbidities, and an increased likelihood of drug–drug interactions because of polypharmacy [Cresswell et al. 2007]. The scale of the problem varies in the literature because of difference in the study design, types of patient studied and whether the primary end-point studied is ADE or ADR. An ADE has been defined as ‘any injury resulting from the use of a drug’, including harm caused by ADRs, medication errors, overdoses, dose reductions and cessation of therapy [Nebeker et al. 2004]. An ADR is ‘a response that is noxious and unintended and occurs at doses normally used in man for the prophylaxis, diagnosis or therapy of disease, or for modification of physical function’ [World Health Organization, 1972]. The occurrence of ADRs is underreported, compounding the problem of their recognition [Lopez-Gonzalez et al. 2009].

The proportion of hospitalizations in patients over the age of 75 years secondary to ADEs was 30.4% in one study [Chan et al. 2001]. A UK study evaluating inpatients over the age of 16 years identified that 6.5% of admissions were related to an ADR and that patients admitted with ADRs were significantly older than those without ADRs [Pirmohamed et al. 2004]. More recently, a German study identified ADRs in 7.6% of admissions, with elderly females being the most susceptible [Hofer-Dueckelmann et al. 2011]. The ADRs in the elderly can be vague and difficult to distinguish from medical diagnoses and, if unrecognized, can result in a ‘prescribing cascade’ where yet more drugs are added to treat the symptoms, in turn increasing drug–drug interactions and the risk of further ADRs [Rochon and Gurwitz, 1997].

The GerontoNet ADR Risk Score has been developed as a simple method to identify elderly hospital inpatients who are at increased risk of an ADR, in the hope of targeting interventions to this group of patients [Onder et al. 2010]. Using six variables (more than four comorbidities, renal failure, heart failure, liver disease, number of drugs, and previous ADR), a risk score is calculated, with a score of greater than 8 indicating high risk [Onder et al. 2010]. It remains to be seen whether this tool reduces the incidence of ADRs. Computerized physician order entry systems have been suggested to be another means of reducing the incidence of ADEs. However, there is great variability among different systems and the evidence is not clear; one study demonstrated detection rates for potentially fatal prescriptions of only 53% [Metzger et al. 2010].

Identification of prescribing omissions

Much of the literature on drug safety in the elderly has focused on the problem of overprescribing and ADEs in elderly people. However, failure to provide appropriate medications to older adults can also increase harm. Using quality indicators of pharmacological care from the ACOVE (Assessing Care of the Vulnerable Elder) project, one American study reported that the prevalence of omissions of appropriate medicines was 50%, whilst the prevalence of administering inappropriate medication was only 3% [Higashi et al. 2004]. The START tool has been developed to help to screen for underprescribing and has good interrater reliability [Barry et al. 2007; Ryan et al. 2009]. Using this tool, prescribing omissions were detected in 57.9% of patients admitted to an Irish teaching hospital [Barry et al. 2007]. The most commonly omitted drugs were statins in atherosclerotic disease, warfarin in chronic atrial fibrillation, antiplatelet therapy in arterial disease, and calcium and vitamin D supplementation in symptomatic osteoporosis [Barry et al. 2007]. Rather counterintuitively, one study suggested that underprescribing was significantly more common in patients taking more than five medications (43%) than in patients taking four medications or fewer (13.5%) [Kuijpers et al. 2007]. However, these findings were not supported by Steinman and colleagues, who found that underuse was common but did not vary with the total number of medications [Steinman et al. 2006].

There may be valid reasons for underprescribing. These include the reluctance of patients to take medication, and situations in which the time needed to derive clinical benefit exceeds life expectancy or if the focus of care has shifted to symptom palliation [Holmes et al. 2006]. Other explanations may include the desire of the clinician to avoid polypharmacy, fear of ADRs, lack of convincing evidence of benefit in the elderly, low levels of therapeutic expectations or, in some cases, ageist attitudes [Barry et al. 2007].

Identifying inappropriately prescribed medications

The Beers criteria outline the most widely cited list of medications to be avoided in the elderly. Initially developed in the USA to provide a list of 30 drugs to be avoided in nursing-home residents, the criteria were later modified in 1997 and 2003 and now apply to community-dwelling elderly people [Fick et al. 2003]. However, the clinical relevance of the Beers criteria has been questioned because the list is not comprehensive, it includes drugs such as diazepam and amitriptyline that are not absolutely contraindicated in the elderly, and it also includes medications that are unavailable or rarely used in Europe [O’Mahony and Gallagher, 2008].

The STOPP (Screening Tool of Older Persons’ potentially inappropriate Prescriptions) has been devised more recently by the group that created the START tool and has good interrater reliability [Gallagher and O’Mahony, 2008; Ryan et al. 2009]. It has been reported recently that the STOPP criteria, unlike the Beers criteria, are significantly associated with avoidable ADEs, suggesting that they are a more clinically relevant tool [Hamilton et al. 2011]. A randomized controlled trial that compared usual pharmaceutical care with screening using STOPP/START criteria suggested that significantly lower rates of unnecessary polypharmacy and potential drug–drug and drug–disease interactions occurred in the intervention group, as well as reductions in underutilization of medications [Gallagher et al. 2011]. New educational interventions aimed at improving prescribing for the elderly incorporate START and STOPP criteria, which will hopefully raise awareness of these tools [George and Jacobs, 2011]. It remains to be seen whether widespread utilization of these tools reduces the incidence of ADEs and the associated morbidity and mortality.

The safer use of high-risk medications

Certain classes of drugs are associated with increased harm in older people but still have a place in chronic disease management. Amongst others, these include antipsychotics, anticoagulants and opioids. Awareness of the specific risks associated with these medications is a step towards reducing harm.

Improving safety in healthcare settings and across transitions

There are several stages involved in medication provision, including prescribing, transmitting, dispensing, administering and monitoring. The National Patient Safety Agency reported that 12–20% of the 900,000 incidents reported in 2005 were related to medicines; medication errors occur most commonly in the areas of prescribing, dispensing and administration [Fertleman et al. 2005]. Illegible handwriting and consequent misinterpreted prescriptions also result in significant errors [Bell et al. 2004]. Errors in prescribing can be heightened by breakdowns in communication when patients move from one setting to another, and the Royal Pharmaceutical Society has recognized that older people are particularly vulnerable to these [Parsons et al. 2011; Royal Pharmaceutical Society, 2011]. The nature of modern healthcare means that elderly patients often move between their homes, multiple wards within a hospital, intermediate care establishments, and nursing and residential care facilities, encountering multiple healthcare professionals, systems and processes on the way.

On admission, challenges in obtaining an accurate account from a patient may be exacerbated by an acute condition, sensory or cognitive impairment, a lack of access to family members or carers, or language barriers. Therefore, in collaboration with the National Patient Safety Agency, NICE has produced guidance recommending that all patients undergo ‘medicines reconciliation’ on admission to hospital [NICE, 2007]. This process ensures that the medicines prescribed on admission correspond to those that the patient was taking before admission. Most hospitals have ward-based pharmacists to facilitate this. The presence of pharmacists on the post-take ward round has been shown to improve the accuracy of drug history documentation, reduce prescribing costs and decrease the potential risk to hospital inpatients [Fertleman et al. 2005]. Medication discrepancies are also recognized to occur at discharge; one study demonstrated that at least one medication discrepancy occurred in 71% of discharges from hospital to skilled nursing care facilities [Tija et al. 2009]. Cardiovascular medications, opiates, neuropsychiatric medications, hypoglycaemics, antibiotics and anticoagulants accounted for over 50% of discrepant medications [Tija et al. 2009]. The involvement of a pharmacist transition coordinator when discharging elderly people from hospital to long-term care facilities was shown to protect against worsening pain and decreased hospital usage, although no significant impact on ADEs, falls, mobility or confusion was demonstrated [Crotty et al. 2004]. Electronic discharge documents are now used more widely to reduce problems associated with illegible handwritten discharge notes. If other sources are unavailable, these can also act as a source of medication history when patients with recent hospital stays are readmitted.

Several American studies have looked at the use of electronic health records to improve communication between healthcare settings. However, their economic value and validity in reducing ADEs has not yet been adequately demonstrated [Boockvar et al. 2010; Monane et al. 1998]. In the UK, the National Programme for Information Technology in England was a controversial initiative of the Department of Health that was intended to move clinicians in England towards shared electronic records. An evaluation of the summary care record, which holds information on medication, allergies and adverse reactions, did not directly demonstrate evidence of improved safety [Greenhalgh et al. 2010]. However, there was some anecdotal evidence of reduced medication errors, and given that the shared care record was infrequently accessed in secondary care settings, the potential benefits of electronic health records may be reaped with increased usage by physicians [Greenhalgh et al. 2010].

Conclusion

Prescribing medications safely for older people is complex, given their changed pharmacokinetics and altered pharmacodynamic responses, the presence of multiple comorbidities, and the high risk of falls and confusion. Consequently, there is a higher incidence of ADEs and inappropriate prescribing in this age group. Box 1 lists some ‘top tips’ to help the nonspecialist when prescribing in this population. Whilst it is not feasible for all older people to have a comprehensive medication review by a geriatrician, tools such as STOPP and START can be used by nonspecialists, although these cannot replace individualized assessment and clinical judgement. Comprehensive geriatric assessments should be targeted at patients identified to be at high risk by general practitioners, community nurses and other health professionals, and can be offered opportunistically in inpatient and outpatient settings. More studies to assess medication effectiveness in the elderly are needed. Healthcare organizations and individual practitioners must continue to seek methods to reduce the incidence of ADEs in the elderly and to improve safety across healthcare transitions. There may be scope in the future for electronic patient records to improve prescribing across healthcare settings but further work in this area is needed.