Drug interactions put cancer patients at risk

An increasing number of cancer patients are using complementary and alternative medicine (CAM) without their physicians’ knowledge, putting them at risk of adverse interactions with conventional medicine.

Professor Stephen Clarke, from the Faculty of Medicine at the University of Sydney, claimed there had been a significant increase in CAM use in the last 15 years, with studies indicating use in cancer patients now exceeded 80 per cent, of whom more than half (57 per cent) failed to tell their physicians.

“Not surprisingly CAM is big business,” said Professor Clarke. “In the US alone, it has been estimated that cancer patients spend over US$30 billion in out-of-pocket expenses on CAM.”

Professor Clarke said while use of CAM with conventional medicine often had no or minimal effects, in systemically administered herbal medicine and conventional treatments, there were “significant risks of adverse drug interactions” which could result in either “increased drug toxicity or therapeutic failure”.

St John’s wort, for example, had been shown when co-administered with anti-cancer drug imatinib (Glivec), caused the drug to be cleared from the body 43 per cent faster, which could produce reduced efficacy. Other herbs were likely to delay the clearance of other cancers drugs, resulting in more side-effects. “However, in many cases we just don’t know if there is an interaction.”

Professor Clarke urged physicians to be more proactive in obtaining complete medication histories, including herbal use, in all patients receiving cancer chemotherapy.

(Source: Cancer Council Australia: Cancer Forum)

More information

For more information about drugs, including an introduction to pharmacology, generic versus branded drugs, and the meaning of drug schedules and pregnancy categories, see Drugs.