Grapefruit is suggested as a protector against cardiovascular diseases and cancers. However it is also inhibiting enzyme systems:
• the intestinal cytochrome P – 450 3A4 system, which is responsible for the first pass metabolism of many drugs
• the P – glycoprotein pump, which transports many of these cytochrome P – 450 3A4 substrates
By inhibiting these enzyme systems, grapefruit juice alters the movement of drugs within the body of a many medications and in this way elevates their serum concentrations. This is much more true for elderly as they are more prone to grapefruit-drug interactions.
Research shows that consumption of grapefruit may somewhat delay the absorption of levothyroxine. Thought it has just a slight effect on active drug that enters circulation, called bioavailability.
Have you observed any interaction between grapefruit consumption and medication?