Geoff asked
Is there an interaction between Lipitor (Atorvastatin) and grapefruit?
Answer
Grapefruit interacts with many different medications in many different ways. The most notable mechanism is by the inhibition of an enzyme known as CYP3A enzyme. This enzyme is extremely important in the breakdown of many compounds, including drugs like Lipitor and simvastatin. If the enzyme is inhibited, it is no longer working and thus, the compounds do not break down potentially leading to over-exposure of a drug. Consuming both the whole fruit and juice may cause an interaction. One whole grapefruit or 200 mL (about seven ounces) of juice can be enough to cause a clinically important interaction. Most adverse events resulting from grapefruit interactions have been minor. The seriousness of the interaction depends on many factors such as the dose of the drug taken, how much grapefruit was consumed and how potentially toxic the drug is.
In terms of Lipitor, there can be a slight interaction here. The general recommendation is that grapefruit juice should be avoided in patients taking atorvastatin to avoid the potential for drug accumulation and toxicity. This toxicity may manifest itself in the following adverse reactions: muscle pain and weakness, headache and GI complaints. In one study a dose of 240 ml of grapefruit juice along with a single 40 mg dose of atorvastatin resulted in a 37% increase in the concentration of Lipitor.
