Incidence of ADRS in the Elderly

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Chapter: Pharmacovigilance: Drugs and the Elderly

Many studies have suggested that ADRs are a common problem in elderly patients and are the cause of 3%–12% of hospital admissions in this age group.


Many studies have suggested that ADRs are a common problem in elderly patients and are the cause of 3%–12% of hospital admissions in this age group (Williamson and Chopin, 1980; Smucker and Kontak, 1990; Lindley et al., 1992; Moore et al., 1998; Mannesse et al., 2000; Onder et al., 2002). Various risk factors have been identified. These include prescription of unnecessary or interacting drugs or drugs with relative or absolute contraindica-tions (Lindley et al., 1992). One of the most impor-tant predictors of ADRs is the total number of drugs given simultaneously (Leach and Roy, 1986; Bax et al., 1987).

Medication selection is known to be an impor-tant factor influencing the likelihood of ADRs, and prescribing practices change as safer, superior alter-natives to existing medications become available. In the 1990s, Beers and colleagues developed explicit criteria for potentially ‘inappropriate medications’ in elderly patients, and more recently, these criteria were updated (Fick et al., 2003). Studies have used these criteria to identify the prevalence of the problem and found approximately one in five elderly patients to be on at least one inappropriately prescribed medica-tion (Sloane et al., 2002; Van der Hooft et al., 2005). It has also been demonstrated that ADRs are partic-ularly likely in patients who have had a fall before admission or in those presenting with gastrointestinal bleeding or haematuria (Mannesse et al., 2000). More recently, Hajjar and colleagues (2003) have attempted to identify possible risk factors for ADRs in older outpatients using a literature search to identify poten-tial factors followed by a two-round survey based on the Delphi consensus method of an expert panel of five physicians and five pharmacists. The panel iden-tified nine patient characteristics including polyphar-macy, multiple chronic medical problems, previous ADRs and dementia. The most prevalent medication-related risk factors were opioid analgesics, warfarin, NSAIDs, anticholinergics and benzodiazepines.

Fewer studies have been done to determine the inci-dence of ADRs during hospital admission, but the incidence is about 5% with a range from 1.5% to over 20% (Seidl et al., 1966; Hurwitz, 1969; Skott and Geise, 1984; Leach and Roy, 1986; Lindley et al., 1992). The incidence is higher in the elderly. For example, in a prospective study of 1160 in-patients who were prescribed medication during admission, 10.2% experienced an ADR, and in patients over 60 years the incidence was higher, at 15.4% (Hurwitz, 1969). Seidl et al. (1966) found that while 13.6% of a resident hospital population in the United States acquired an ADR during hospitalisation, the incidence was as high as 24% in patients in their 80s. In addi-tion, ADRs have been shown to be risk factors for delayed discharge from hospital (Skott and Geise, 1984) as well as early hospital readmission (Chu and Pei, 1999). Finally, in the out-patient population, about 5%–10% of patients have ADRs (Chrischilles, Segar and Wallace, 1992b, Gurwitz et al., 2003).

Some medicines are much more likely than others to cause problems when prescribed to elderly people. Three groups of drugs consistently cause problems in this age group: cardiovascular drugs, non-steroidal anti-inflammatory drugs (NSAADs) and drugs acting on the central nervous system. In one study, for exam-ple, antihypertensives, diuretics and -adrenoceptor blockers accounted for 55% of reported ADRs (Chrischilles et al., 1992a). Regardless of which drug class causes the adverse event, and whether this results in or prolongs hospital admission, ADRs clearly repre-sent a significant cause of morbidity in the elderly.

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