Food Interactions - Not Always Bad

Robert W. Griffith, MD

When you get your meds from the pharmacy they may carry a label saying "do not eat grapefruit or drink grapefruit juice when taking this medication". This is an example of a warning about a food-drug interaction. Some substance in grapefruit interferes with the breakdown of the medication in the body, so that drug concentrations from a given dose may be much higher if taken along with grapefruit.

Turning this phenomenon to good account, Chicago researchers have suggested a way to save money on an expensive drug prescription. It's reported in the Journal of Clinical Oncology.

Lapatinib (Tykerb®) is a drug used in combination with another anti-cancer drug to treat advanced breast cancer. The product label states: "should be taken at least one hour before, or at least one hour after, food". The reason for this label? This was how the major clinical study was done, before food-interaction data were available. These data show that the bioavailability - the amount of drug taken that reaches the site of action in the body - is greatly increased by food. By taking lapatinib with food, instead of on an empty stomach, one could use 40% less of the drug. At a monthly cost of $2900 this could result in a saving of $1740 a month. And adding a glass of grapefruit juice to the meal could increase the saving to 80%, or $3480 a month (minus the cost of juice, of course).

We shouldn't expect the manufacturers of lapatinib (GlaxoSmithKline) to do a clinical study to prove this hypothesized saving. After all, they want to sell as much drug as possible. But sooner or later such a study will be done, for lapatinib and other drugs which have well marked drug-food interactions. I'm wondering whether Lipitor® is one of them - it does have a "don't take with grapefruit" label, and it's pretty expensive (until the generic comes along, soon, I hope).

Source
HealthandAge Blog

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