Foods: Grapefruit juice Simvastatin

The most serious adverse effect of simvastatin is myopathy, which rarely may progress to rhabdomyolysis. Abnormalities of liver function may also occur. These effects are dose-dependent, and a number of drugs and foods may inhibit the metabolism of simvastatin, thereby increasing its toxicity. Examples of these are grapefruit juice and erythromycin, both of which should be avoided in patients taking simvastatin. 

Especially the inhibition or induction of cytochrome P450 subtype 3A4 (CYP 3A4) is clinically relevant, because a variety of active substances and food substances (e.g. grapefruit juice) are able to affect this enzyme. Substances inhibiting CYP 3A4 include ciclosporin, dihydropyridines, verapamil, midazolam, paclitaxel, simvastatin, lovastatin, atorvastatin, cimetidine, erythromycin, troleandomycin, ketoconazole (and other azoles). Substances inducing CYP 3A4 include steroids, rifampicin, phenobarbital and St John s wort. 

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