Every now and then, I get a chance to leave the confines of the pharmacy and take a closer look at the vast array of offerings in the rest of the market. One of my favorite things to do is to have a student or two join me as we see items that directly or indirectly affect the drug therapies that we dispense, and talk about their real world significance.
Without a doubt the most common interaction that a supermarket pharmacist ever advises patients on are the many interactions with alcohol. We sell alcohol in prodigious quantities. The effects can include increased sedation, internal bleeding, bizarre behavior (even more than the drug or alcohol alone),increased likelihood of puking and lots more. Considering that somewhere around 50% of my patients drink regularly (according to CDC statistics), these interactions need to be addressed when clinically significant.
Food and drug interactions (FDI) may involve a variety of mechanisms to change blood levels and/or effect by altering absorption, protein binding, receptor competition, metabolism, or excretion.
Patients on warfarin (Coumadin) are counseled not to make any sudden changes in their dietary intake of certain green leafy vegetables such as broccoli, brussel sprouts and spinach. These plants are rich in vitamin K which could interfere with the anti-clotting effect of warfarin. Looking around the market, I found several other foods that have reported interactions with warfarin, such as meats, onions and even cranberry juice. High protein may lead to higher levels of circulating proteins to bind the warfarin lessening its effect, cooked onions seem to increase the effect of warfarin, while cranberry juice partially blocks warfarin metabolism. Patients on warfarin need careful monitoring and counseling. It is usually a sudden change in eating habits that results in problems.
Licorice extract, found in most black licorice candies, has a component that increases your cortisol level causing sodium retention and potassium depletion, raising blood pressure thereby countering the effect of many medications used to treat high blood pressure. You have to be a pretty steady licorice eater (about one ounce of candy per day), however, to have any worrisome effect.
Casein and calcium in dairy products can block the absorption of Cipro and some tetracyclines.
Here’s a memory from my youth! If you carefully cut the butter maiden’s knees to the same size of the box of butter she is holding and place the knee cut out over the box of butter, it looks like she is offering her breasts to you! Juvenile, huh? Do men ever grow up?
Disclaimer: These are only a small fraction of the food-drug interactions known. Always ask your pharmacist!