Nov. 27, 2012 -- The number of drugs that can be risky when taken with grapefruit is on the rise, largely due to the influx of new medications and chemical formulations, a new study shows.

As it stands, there are now more than 85 drugs that may interact with grapefruit. The number of drugs that may result in potentially fatal side effects when mixed with grapefruit increased from 17 to 43 during the past four years. This equates to more than six new potentially risky drugs a year.

The list includes some statins that lower cholesterol (such as atorvastatin, lovastatin, and simvastatin), some antibiotics, cancer drugs, and heart drugs. Most at risk are older people who use more prescriptions and buy more grapefruit.

Here’s what happens: Grapefruit contains furanocoumarins, which block an enzyme that normally breaks down certain medications in the body. When it is left unchecked, medication levels can grow toxic in the body.

It’s not just grapefruits, either. Other citrus fruits such as Seville oranges (often used in marmalade), limes, and pomelos also contain the active ingredients (furanocoumarins), but have not been as widely studied.