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Eat, drink . . . and be wary of drugs
Take at least one hour before or one hour after a meal" says the label on the breast-cancer drug lapatinib (which goes by the brand name Tykerb). Sounds simple. But behind that directive lies a complex story. GlaxoSmithKline (GSK), the maker of lapatinib, first noticed the profound effect of food on the drug during preclinical studies in animals, then later in humans before the drug was approved. In a cohort of six patients, for example, they found that taking lapatinib with a low-fat breakfast led to a three-fold increase in total drug exposure compared to fasting. GSK wanted, and needed, to know more about this effect before seeking approval from the Food and Drug Administration. So the company sought out a noted clinical pharmacologist, Dartmouth's Lionel Lewis, M.D.
Surprising: Lewis led a study in which 27 patients were given a 1,500-mg dose of lapatinib three times, one week apart. They took the drug three ways, in random order: after an overnight fast, with a low-fat breakfast, and with a high-fat breakfast. The results were "surprising," says Lewis. The low-fat breakfast produced a 2.67-fold average increase in lapatinib's concentration in the body over time compared to fasting. The difference was even greater-4.25-fold-with a high-fat breakfast. Lewis also found tremendous variability from one patient to another when food was involved. "This caused [GSK] a little bit of concern," says Lewis. Hence the instructions on the drug's label.
The fact that diet can affect a drug's concentration in the body is not a new revelation. Physicians have become increasingly aware of the role diet plays in how drugs work, says Lewis. Red wine and some juices, for example, are known to dramatically alter certain drugs' action. Sometimes the mechanism is easy to tease out. Other times, as with lapatinib, it's "very complicated," adds Lewis. In his study, published in the June issue of the Journal of Clinical Oncology, he was able to rule out several mechanisms but unable to pinpoint the exact mode of action. Nevertheless, as this study shows, it may not be as important for patients to know how food affects a drug's concentration, as it is to know how dramatically it does so.
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