For example, double-strength grapefruit juice administered 3 times daily will increase the concentrations of some statins more than 10-fold, whereas single-strength grapefruit juice taken once daily results in a 2-fold increase. Many studies investigating grapefruit interactions used double-strength grapefruit juice administered multiple times daily. How much grapefruit interacts with simvastatin? Inhibition of CYP3A4 with grapefruit may last for up to 24 hours after a single dose and up to 72 hours after multiple daily dosing. One whole fruit or 200 milliliters of grapefruit juice (a bit less than one cup) can block the CYP3A4 enzymes and lead to toxic blood levels of the drug. Increasing a drug's bioavailability from 5% to 10% will double its concentration in the body, making it more powerful than it's meant to be, resulting in a risk for new or worsened side effects. If CYP3A4 is blocked by an inhibitor such as grapefruit juice, then a much larger amount of simvastatin reaches the blood. The bioavailability of simvastatin is about 5%, which means that only 5% of a dose of simvastatin reaches the blood – the rest is metabolized before it gets there. Grapefruit contains compounds called furanocoumarins that block the effects of CYP3A4 – an enzyme in the wall of your small intestine that breaks down certain substances, including simvastatin. Grapefruit or grapefruit juice can alter enzymes in the body and affect how drugs are changed in the body before they are eliminated. Why does grapefruit interact with simvastatin?ĭrugs or toxins are usually broken down (metabolized) so that they can be eliminated from the body. Occasionally, rhabdomyolysis can cause kidney damage and death. You should not drink grapefruit juice with simvastatin because it can significantly increase blood levels of simvastatin and increase the risk of side effects such as liver damage and a condition called rhabdomyolysis, which is the excessive breakdown of muscle tissue.

Statins and grapefruit interactions