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Adverse drug interactions landing elderly in
ERs
Study shows the most common drugs are often implicated
By Susannah Benady
MONTREAL – A study here of randomly selected elderly emergency patients
underscores the importance of checking for adverse drug interactions,
especially in patients on nonsteroidal anti-inflammatories, antibiotics or
anticoagulants.
The study, done at Montreal's Jewish General Hospital and
published in the Annals of Emergency Medicine, showed the more
medications the patient was taking, the more likely it was that an adverse
drug interaction was the cause of the visit.
On further review of patients' drug regimens, it turned out
almost one-third of all the patients were at risk for at least one adverse
drug interaction in the future, even if the complaint that had brought them
to the ER in the first place was not related to medication side-effects.
This figure rose to 50% for those who presented because of
a drug-related adverse event.
"Emergency physicians must be vigilant in monitoring
elderly patients for medication-related problems," said Dr. Corinne
Michèle Hohl of McGill University, a resident at the Jewish General and one
of the study authors.
The findings underline the need for physicians to take a
very careful medication history, added Dr. Hohl in an interview.
"This includes trying to establish what the compliance
is, what over-the-counter medication the patient might also be taking and
what comorbid conditions the patient has, as well as what the presenting
problem is."
The findings showed that overall, drug-related adverse
events were responsible for 10.6% of emergency department visits by the
elderly.
The study was a retrospective analysis led by Dr. Marc
Afilalo, director of the emergency department at the Jewish General and
Dr. Jerrald Dankoff, assistant professor of emergency medicine at McGill.
The team looked at 283 emergency consultations by randomly
selected patients ages 65 to 100 years during a one-year period, from January
to December 1998.
Of the total number of visits reviewed, 257 involved
patients taking one or more over-the-counter or prescribed medications daily.
On average, patients were taking 4.2 drugs, although more than 13% took at
least eight drugs.
In patients taking two to five medications, the proportion
of drug-related adverse events being the cause of an emergency visit was
11.5%.
The corresponding figure for those taking six or more drugs
was 16.9%. No adverse events were seen in patients taking just one
medication.
The most frequently implicated classes of medications were
nonsteroidal anti-inflammatory drugs, antibiotics, anticoagulants, diuretics,
hypoglycemics, calcium-channel blockers and chemotherapeutic agents.
"Drugs that are most commonly prescribed are the ones
most commonly implicated," said Dr. Hohl.
The symptoms patients presented with included duodenal
ulcers (about 10%), allergic reactions to antibiotics, withdrawal reactions
and even renal failure, she said.
"These were cases identified by the attending
physician as being due to an adverse drug interaction.
"In all the events, the treating physician had to
recognize there was a medication implicated and had to withdraw the
medication, and only if the patient got better could we conclude that it was
an (adverse drug interaction)."
However, she stressed it is possible that some of the
emergency visits were due to adverse drug interactions but were not recorded
as such.
"Because it was retrospective, the study could only
consider the cases that the attending physician had identified as an adverse
drug interaction. But drug-related adverse events are not always obvious and
it is possible some were missed."
The authors are now trying to start a prospective study.
Dr. Hohl added that one of the aims would be to design better tools for ER
physicians.
"Treatments for adverse drug interactions include
withdrawing medication and carefully weighing the cost/benefit to the patient
of taking the medication.
"A physician might consider a different class of
medication. And sometimes it is just a matter of balancing the dose.
"But more specific advice on what ER physicians can do
in these cases is one of the goals of the prospective study."
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