Medication Formulation Associated With Dosing Error Risk in the Elderly

Norra MacReady

February 10, 2011

February 10, 2011 — In an analysis of medication administered to residents of long-term care facilities around the United Kingdom, the odds of medication errors ranged from about 4 times greater with liquids to more than 33 times greater with inhalers compared with medications administered in pill or capsule form, lead author David Phillip Alldred, MD, from the School of Healthcare, Baines Wing, University of Leeds, United Kingdom, and coauthors report online February 7 and in the March print issue of BMJ Quality & Safety.

When administering tablets or capsules, 86% of long-term care facilities in the United Kingdom use monitored dosage systems (MDS), consisting of trays with compartments for medications to be taken at different times of day. This is thought to reduce the risk for dosing errors, the authors explain. However, many formulations do not lend themselves to MDS, and despite their widespread use, there is little robust evidence to support the idea that MDS really are safer than the original packaging. The objectives of this study were to evaluate the risks of dosing errors associated with different medication formulations, as well as between tablets and capsules dispensed in MDS and those dispensed in the manufacturer's original packaging.

The authors analyzed data from administration error observation forms on 233 residents in 55 long-term care facilities that had been collected for an earlier study. They grouped medication errors into 5 categories according to delivery system and formulation: tablets or capsules in MDS (53% of observed administrations), tablets or capsules not in MDS (29.3%), liquids (11.9%), inhalers (3.8%), and a combined group of topical, transdermal, and injectable formulations (2.1%).

The mean number of errors per resident associated with tablets and capsules in MDS was .17; for tablets and capsules not in MDS, .20; for liquids, .21; for topical, transdermal, and injectable formulations, .55; and for inhalers, 1.13. On analysis adjusted for age and type of care, among other factors, the odds ratio (OR) of errors associated with tablets and capsules not in MDS was 2.14 compared with medication in MDS (95% confidence interval [CI], 1.02 - 4.51; P = .04). Adjusted analyses showed "a fourfold increase in the odds of an error for liquids (OR 4.31; 95% CI 2.02 to 9.21; p=.0002), a 20-fold increase for topicals/transdermals/injections (OR 19.61; 95% CI 6.90 to 55.73; p<.0001); and a 30-fold increase in the odds of an error for inhalers (OR 33.59; 95% CI 12.51 to 90.19; p<.0001)." Indeed, the investigators say, "half of all inhaler administrations were incorrect, and this represents a highly significant loss of potential clinical benefit, which may reduce quality of life owing to untreated respiratory disease (and represent a significant waste of National Health Service money)."

In the United States, nursing homes have consultant pharmacists who review patients' charts once a month, so "some of these errors may get picked up," says Robert Page, PharmD, associate professor of clinical pharmacology and physical medicine at the University of Colorado in Denver.

Still, says Dr. Page, who was not involved in this study, "these findings are not surprising, as these same issues occur in hospitals and health systems in the US. It's been shown that nurses, physicians, and even pharmacists often don't use the appropriate technique with inhalers, and even when patients are taught how to use them properly, 50% eventually return to their old, incorrect technique. And the administration of liquid medications has long been a problem in nursing homes for a long time."

MDS are not necessarily the answer, however, because many drugs interact when taken together, reducing their clinical efficacy, he added.

Among the study limitations was the use of data from a study "not originally designed to assess differences in error rates between formulations and between medicine delivery systems," the authors point out. Second, the proportion of medicines administered in forms other than tablets or capsules was relatively small, and the study was not powered to investigate the odds of an error for topical, transdermal, and injected preparations individually. The wide confidence intervals associated with the data for liquid and inhaled medications also raise questions.

Still, they conclude, "our study identified that medication administration errors occur frequently with medicines that cannot be packaged into MDS, such as liquids and inhalers, and there is a clear need for medication administration training for care home staff to address this."

Dr. Page agrees. "The best way to correct this problem is through direct pharmacological training and intervention with the staff," he told Medscape Medical News. "There should also be more direct contact between pharmacists and patients."

The study was supported by the Patient Safety Research Programme of the UK Department of Health. The authors and Dr. Page have disclosed no relevant financial relationships.

BMJ Qual Saf. Published online February 7, 2011.