Cancer Patients at Risk of Drug Interactions: Drugs for Conditions Other Than Cancer Most Often Involved

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Cancer Patients at Risk of Drug Interactions
Drugs for Conditions Other Than Cancer Most Often Involved
June 7, 2007 01:47:12 PM PST

http://health.yahoo.com/news/176625

More than a quarter of cancer patients may be at risk of potentially
serious drug interactions, according to a recent study in the Journal
of the National Cancer Institute. However, chemotherapy agents were
not the primary culprit, the team from Princess Margaret Hospital in
Toronto, Canada, reports.

Rather, medications received for conditions other than cancer or for
the side effects of cancer treatment were more likely to be involved.

"It was non-cancer drugs interacting with each other," explains
researcher Monika K. Krzyzanowska, MD, MPH, assistant professor in the
department of medicine at the University of Toronto and staff
physician in the department of hematology and oncology at Princess
Margaret Hospital. "In cancer, most of the focus has been on
chemotherapy interacting with other agents, and there was some of
that, but the majority was between the other drugs -- what they were
getting for blood pressure or diabetes -- or those medications
interacting with the medications for supportive cancer care, like
steroids."

Krzyzanowska and colleagues studied 405 adult patients treated in the
follow-up medical oncology clinic of the hospital. They asked
participants about the medicines they were taking, and reviewed their
medical charts. They used a software program and pharmacology
textbooks to flag potential drug interactions.

The team found 276 potential drug interactions in 109 patients (27%).
Most of the potential interactions (77%) were of moderate severity,
meaning the problem that could result would require medical treatment.
Nine percent were of major severity, meaning the interaction could
lead to permanent damage or be life-threatening. The research team
notified the participant's doctor of any serious potential
interactions.

Blood Thinners, Blood Pressure Meds Most Commonly Involved
The drugs that were most likely to interact with chemotherapy drugs
included the blood thinner warfarin (Coumadin) and the water pill
hydrochlorothiazide, which is used to reduce fluid retention and treat
high blood pressure.

But greater numbers of potential interactions were seen between
non-cancer medications. The most frequently noted possibility was
between aspirin and ACE inhibitors or beta-blockers, drugs used to
treat high blood pressure and other heart problems. The researchers
also found potential interactions between aspirin and corticosteroids
(often used to treat side effects of chemotherapy) and between
warfarin and corticosteroids. There were also potential interactions
between the anti-nausea drug prochlorperazine (Compazine) and ACE
inhibitors, and between prochlorperazine/ranitidine and the seizure
medication phenytoin (Dilantin).

The decentralized nature of modern health care may be part of the
problem, Krzyzanowska says. Interactions between the different doctors
a patient is seeing is often limited, particularly if they practice in
different hospitals, making it more difficult to keep up with the
various medications the patient may be taking.

"Family doctors or cardiologists are most likely to be prescribing
blood pressure medications, but they are the least likely to be
referring a patient for cancer treatment," she explains.

Electronic medical records can help, but even they may not be
universally accessible.

Know What Medicines You Take
That means patients really need to keep track of all the medicines
they take.

Krzyzanowska suggests keeping an updated list of your medications to
show each doctor. She also recommends sticking to a single pharmacy
for all prescriptions, if possible, since a pharmacist with access to
all prescription information may be able to flag potentially dangerous
combinations.

Of course, doctors need to keep drug interactions in mind, too,
Krzyzanowska says.

"Be aware that this is an issue, so periodically review the
medications with patients, and when you're adding things, think about
what they're already on," she advises.


Citation: "Potential Drug Interactions and Duplicate Prescriptions
Among Cancer Patients" Published in the April 18, 2007, Journal of the
National Cancer Institute (Vol. 99, No. 8: 592-600). First author:
Rachel P. Riechelmann, MD, Princess Margaret Hospital, Toronto.