With the propranolol for your arrhythmia, the juice you have to avoid is grapefruit juice, and that's in fairly large quantities, like of more than 30 oz. I've just been put on a sort of ??cousin? drug to propranolol (mine's called propafenone) for my arrhythmia. The juice can increase the bio-availability of both types of drugs, which can increase your risk for side-effects from the medicine. It does that by blocking an enzyme that helps our bodies metabolize, or properly use, these medicines, which means we risk having higher blood levels of the propranolol and thus are at greater risk of side effects.

FBR did the smart thing and asked for the name of the type of anti-cholesterol medicine you??re taking. I always take the less efficient route because I'm trying to learn this stuff myself for medical school this year. If my pharmacology database is correct, atorvastatin/Lipitor, simvastatin/Zocor, and lovastatin/Mevacor are metabolized by that same pathway in the liver that can be interfered with by grapefruit juice (and cause problems with the anti-arrhythmic drugs, too)??that'd be the cytochrome P450 3A4 enzyme. It says that of those three medicines, the atorvastatin/Lipitor is probably the least affected by grapefruit juice. This likely means that rosuvastatin/Crestor, pravastatin/Pravachol, and fluvastatin/Lescol could be good alternatives for folks who want to drink lots of grapefruit juice, but I can't find any place that explains why that is. Do you know, FBR?

The problem with grapefruit juice and statin drugs is similar what happens with the beta-blockers like propranolol: if the grapefruit juice doesn??t let you metabolize the medicine as effectively, you get higher drug levels in your blood and can have nasty side-effects, including potential liver-toxicity with the statin drugs. That's ??bad mojo? according to my husband, who prescribes statins probably more than any other type of medicine.

So the bottom line is this: if you want to be completely safe, stay away from grapefruit juice and drink other juices with the medicines you??re taking. Wouldn??t it have been nice if I'd just said that to begin with and then stopped writing?! Yep, it would. But this has helped me cement in some information I needed to knock into my own head.