An estimated 70% of all U.S. cancer cases diagnosed in 2030 will be among older adults, and the risk of adverse drug reactions and interactions will undoubtedly rise as more elderly patients are prescribed multiple medications. Clinicians with increased awareness of these potential adverse events can help prevent or manage them, researchers wrote in a Lancet review.

“The people most at risk from polypharmacy are those who see several doctors, have prescriptions dispensed at several pharmacies, have concurrent comorbidities and are elderly,” wrote researchers Judith Lees, B Pharm, of the Royal Adelaide Hospital Center in Australia and Alexandre Chan, Pharm D, of the National Cancer Center in Singapore.

In one study at a U.S. university hospital, nearly all cancer patients (96%) were taking a mean of 5.5 prescription medications in the three days before their next cycle of chemotherapy. In addition, 71% reported using an average 2.2 OTC agents, and 69% were taking an average 1.9 vitamins, herbs or supplements.

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At another Canadian cancer center, 92% of elderly patients were taking one or more drugs at the time of their cancer diagnosis and nearly half of these patients were identified as having moderate to severe potential drug issues.

The authors listed several potentially inappropriate medications for elderly cancer patients that primary-care providers may have a hand in discontinuing. These include tricyclic antidepressants, sedating antihistamines, long-acting benzodiazepines associated with increased sedation, analgesics including tramadol or dextropropoxyphene and some nonsteroidal anti-inflammatory drugs, including indomethacin (Indocid).

Providers should also be alert about the potential for adverse drug reactions with commonly used medications among cancer patients and consider changing or discontinuing those with a high frequency of adverse events, such as anticoagulants (specifically warfarin) and benzodiazepines.

The use of antihypertensives, lipid-lowering agents, antiplatelet drugs and anticoagulants used for primary or secondary prevention also may need to be reconsidered in patients with metastatic cancer.

Lees J, Chan A. Lancet Oncology. 2011; doi:10.1016/S1470-2045(11)70040-7