May enhance the antihypertensive effects of other antihypertensive drugs such as beta blockers although the combination is generally well tolerated. Enhanced antihypertensive effects may also be seen with concomitant use of drugs such as aldesleukin and antipsychotics that cause hypotension. Nifedipine may modify insulin and glucose responses and therefore diabetic patients may need to adjust their antidiabetic treatment when receiving amlodipine. It is extensively metabolized in the liver by the cytochrome P450 enzyme system, and interactions may occur with other drugs such as quinidine sharing the same metabolic pathway, and with enzyme inducers such as carbamazepine, phenytoin, and rifampicin, and enzyme inhibitors, such as cimetidine and erythromycin. The most serious consequence of drug interactions with Atorvastatin and other statins is the development of myopathy and rhabdomyolysis. Drugs that can cause myopathy when given alone increase the risk of myopathy with all statins: these drugs includes fibric acid derivatives (fibrates or gemfibrozil), and nicotinic acid. Atorvastatin is metabolized by Cytochrome P450 isoenzyme CYP3A4, as are simvastatin and lovastatin, and interactions may occur with drugs that inhibit this enzyme, including ciclosporin, itraconazole, ketoconazole, erythromycin, clarithromycin, HIV-protease inhibitors, nefazodone, amiodarone, and verapamil; there may also be similar interaction with grapefruit juice.
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