Why you cannot mix grapefruit and simvastatin?

Answer 1

why can't you drink grapefruit with zocor or simvastatin:

The risk of myopathy and rhabdomyolysis is increased by high levels of statin activity in plasma. Simvastatin is metabolized by the cytochrome P450 isoform 3A4. Certain drugs which inhibit this metabolic pathway can raise the plasma levels of simvastatin and may increase the risk of myopathy. These include itraconazole, ketoconazole, and other antifungal azoles, the macrolide antibiotics erythromycin and clarithromycin, and the ketolide antibiotic telithromycin, HIV protease inhibitors, the antidepressant nefazodone, or large quantities of grapefruit juice ( > 1 quart daily).

Answer 2

Amitryptiline isn't the only medication where you should avoid grapefruits and grapefruit juice while taking them. Anyone using any anti-depressant should be especially careful.

A lot of drugs use the natural enzyme systems in your body to make them accessible to your system and carry them where they need to be so they can be effective. Grapefruit has two enzymes that interfere with these natural enzyme systems in your body; in everyday circumstances it's not dangerous. But when you're on certain types of medication it can alter how your body accesses the drug in the medication and processes it. Depending on the specific medication, you can either end up with too much active in your system at any one time, producing unpredictable or even dangerous results, or too little, so the drugs aren't doing the job they were designed to do. And it can result in hypotension, which means dangerously low blood pressure, dizziness, and blacking out.

It's not just a matter of not using grapefruit juice to swallow the medication when you take it, but having grapefruit at other times. The effect grapefruit has on your enzyme systems has been shown to last in the body for at least 24 hours, and sometimes up to 48, so you need to avoid grapefruit completely.