Adverse Drug Effects: A Nursing Concern

8 Adverse Drug Effects: a nursing concernAdverse drug reactions are defined by the World Health Organisation(1966) as any noxious, unintended and undesired effect of adrug which occurs at doses used in humans for prophylaxis, diagnosisor therapy. A meta-analysis of 39 prospective studies carried outin the United States over a period of 32 years identified the overallincidence of adverse reactions as 6.7% and of fatal adverse reactionsas 0.3% of hospitalized patients (Lazarou et al., 1998). The authorsestimated that in 1994, 2 216 000 hospitalised patients had seriousadverse drug reactions and 106 000 had fatal adverse drug effects,making these reactions between the fourth and fifth leading cause ofdeath. However, a recent study by Jha et al. (1998) suggests that theincidence of adverse drug events may be higher than previouslyreported, and that the method used to collect the data affects thenumber and type of adverse reactions identified.When adverse effects occur Smith (1984) suggests that there ‘iseither something wrong with the drug, something wrong with thepatient or something wrong with the doctor or prescriber. Thus,these three factors should always be analysed when dealing withadverse effects (Table 1.5). The drug classes most frequently implicatedin adverse reactions are shown in Table 1.6. As far as patientvariables are concerned, extremes of age (see Chapter 6), gender,genetic polymorphism (Chapter 2) and race (Chapter 5), and intercurrentdisease (Chapter 2) can all predispose to adverse reactions.As far as gender is concerned in general, women appear to be atgreater risk of adverse drug reactions than men are, and increaseddrug exposure does not account completely for the difference (Leeand Beard, 1997). For example, women are reputed to be moresusceptible to blood dyscrasias, with phenylbutazone and chloramphenicol,to histaminoid reactions to neuromuscular blocking drugs,and to reactions involving the gastrointestinal tract.PharmokineticsPharmokinetics is the study of what the body does to a drug overtime. It explores the processes of absorption, distribution, metabolismand excretion (Table 1.7). Each of these processes will occur at aspecific rate characteristic for that drug, and the overall action of thedrug - be it therapeutic or toxic - will be dependent on theseprocesses. This chapter and the next will examine each of the fourprocesses in turn.