This week, the New England Journal of Medicine reports the results of a study carried out by Butnitz et al. of the Centers for Diseases Control and Prevention (CDC, Atlanta) from 2007 through 2009 on the basis of data from 58 US hospitals to assess adverse drug events resulting in the hospitalisation of people over 65. The authors estimated that nearly 100,000 elderly patients were admitted to hospital each year in the United States as a result of adverse drug events. Two thirds of cases were involuntary overdoses. Four medicaments (or medication classes) were implicated alone or in combination in 67% of hospitalisations caused by adverse drug events: warfarin (Coumadin), an oral anti-coagulant, in itself accounted for 33% of emergency admissions among the over 65s, insulin injections accounted for 14% of admissions, antiplatelet agents (aspirin, clopidogrel, etc) for 13% and oral antidiabetic drugs for 11%.
All these medicaments are widely prescribed in the United States but they have a narrow therapeutic margin and are renowned for being particularly difficult to administer in the correct dosage. However, before this study, the degree to which these medicaments were involved in adverse drug events among the elderly was not known. The population in the United States is ageing and 40% of the over 65s take between 5 and 9 medicaments per day. The risks of adverse drug events are thus likely to increase in the future in the absence of a more effective prevention policy.
None of the four medicaments in question are included in the list of medicaments normally classified as being high risk for the elderly (the HEDIS lists tend rather to cover central analgesic drugs, for example) but which were only implicated in 1.2% of hospitalisation for adverse drug events according to the study by Budnitz et al.
These four medicaments or medication classes are by no means palliative. They are prescribed to deal with serious conditions but, as stated above, all share the need to be prescribed with great care: narrow therapeutic margin, need for continuous blood testing for oral anticoagulants, interactions with other medicaments or food, sometimes resulting in greater activity than that expected for the dose and the weight of the elderly. Preventing such problems is all the more difficult. The authors suggest that the prescription of these medicaments should be both well evaluated with regard to the benefits and risks expected for the patient, that the general practitioner should always be informed when a specialist has prescribed these drugs and that the doctor and pharmacist should work together to monitor and adjust the dose delivered depending on the results.
There are fields of research that have yet to be completed: the discovery of new medicaments for diabetes with wider therapeutic margins would be welcomed as it is not known how to reduce glycemia without risk in the same way as it is now known more or less how to reduce hypercholesterolemia without danger. It would be useful to have oral anticoagulants whose activity does not need to be monitored. Giving greater priority to these four major risks might bring greater benefits in terms of public health rather than concentrating on the medicaments usually considered to be a risk for the elderly but which, in this type of epidemiological study, appear low down on the list of main high risk drugs.
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