Simvastatininteractions

See full prescribing information for details regarding concomitant use of simvastatin with other drugs or grapefruit juice that increase the risk of myopathy and rhabdomyolysis.

Coumarin Anticoagulants: Obtain INR before simvastatin initiation and monitor INR during simvastatin dosage initiation or adjustment.

Digoxin: During simvastatin initiation, monitor digoxin levels.

7.1 Drug Interactions that

Increase the Risk of Myopathy and Rhabdomyolysis with Simvastatin Simvastatin is a substrate of CYP3A4 and of the transport protein OATP1B1. Simvastatin exposure can be significantly increased with concomitant administration of inhibitors of CYP3A4 and OATP1B1. Table 2 includes a list of drugs that increase the risk of myopathy and rhabdomyolysis when used concomitantly with simvastatin and instructions for preventing or managing them.

Table 2: Drug Interactions that Increase the Risk of Myopathy and Rhabdomyolysis with Simvastatin Strong CYP3A4 inhibitors Clinical Impact: Simvastatin is a substrate of CYP3A4. Concomitant use of strong CYP3A4 inhibitors with simvastatin increases simvastatin exposure and increases the risk of myopathy and rhabdomyolysis, particularly with higher simvastatin dosages.

Intervention: Concomitant use of strong CYP3A4 inhibitors with simvastatin is contraindicated. If treatment with a CYP3A4 inhibitor is unavoidable, suspend simvastatin during the course of strong CYP3A4 inhibitor treatment.

Examples: Select azole anti-fungals (e.g., itraconazole, ketoconazole, posaconazole, and voriconazole), select macrolide antibiotics (e.g., erythromycin and clarithromycin), select HIV protease inhibitors (e.g., nelfinavir, ritonavir, and darunavir/ritonavir), select HCV protease inhibitors (e.g., boceprevir and telaprevir), cobicistat-containing products, and nefazodone. Cyclosporine, Danazol, or Gemfibrozil Clinical Impact: The risk of myopathy and rhabdomyolysis is increased with concomitant use of cyclosporine, danazol, or gemfibrozil with simvastatin. Gemfibrozil may cause myopathy when given alone.

Intervention: Concomitant use of cyclosporine, danazol, or gemfibrozil with simvastatin is contraindicated. Amiodarone, Dronedarone, Ranolazine, or Calcium Channel Blockers Clinical Impact: The risk of myopathy and rhabdomyolysis is increased by concomitant use of amiodarone, dronedarone, ranolazine, or calcium channel blockers with simvastatin.

Intervention: For patients taking verapamil, diltiazem, or dronedarone, do not exceed simvastatin 10 mg daily. For patients taking amiodarone, amlodipine, or ranolazine, do not exceed simvastatin 20 mg daily.

Lomitapide Clinical Impact: Simvastatin exposure is approximately doubled with concomitant use of lomitapide and the risk of myopathy and rhabdomyolysis is increased.

Intervention: Reduce the dose of simvastatin by 50% if initiating lomitapide. Do not exceed simvastatin 20 mg daily (or simvastatin 40 mg daily for patients who have previously taken an 80 mg daily dosage of simvastatin chronically) while taking lomitapide.

Daptomycin Clinical Impact: Cases of rhabdomyolysis have been reported with simvastatin administered with daptomycin. Both simvastatin and daptomycin can cause myopathy and rhabdomyolysis when given alone and the risk of myopathy and rhabdomyolysis may be increased by coadministration.

Intervention: If treatment with daptomycin is required, consider temporarily suspending simvastatin during the course of daptomycin treatment.

Niacin Clinical Impact: Cases of myopathy and rhabdomyolysis have been observed with concomitant use of lipid modifying dosages of niacin-containing products (≥1 gram/day niacin) with simvastatin. The risk of myopathy is greater in Chinese patients. In a clinical study (median follow-up 3.9 years) of patients at high risk of CVD and with well-controlled LDL-C levels on simvastatin 40 mg/day with or without ezetimibe 10 mg/day, there was no incremental benefit on cardiovascular outcomes with the addition of lipid-modifying doses of niacin.

Intervention: Concomitant use of simvastatin with lipid-modifying dosages of niacin is not recommended in Chinese patients. For non-Chinese patients, consider if the benefit of using lipid-modifying doses of niacin concomitantly with simvastatin outweighs the increased risk of myopathy and rhabdomyolysis. If concomitant use is decided, monitor patients for signs and symptoms of myopathy, particularly during initiation of therapy and during upward dose titration of either drug. Fibrates (other than Gemfibrozil) Clinical Impact: Fibrates may cause myopathy when given alone. The risk of myopathy and rhabdomyolysis is increased with concomitant use of fibrates with simvastatin.

Intervention: Consider if the benefit of using fibrates concomitantly with simvastatin outweighs the increased risk of myopathy and rhabdomyolysis. If concomitant use is decided, monitor patients for signs and symptoms of myopathy, particularly during initiation of therapy and during upward dose titration of either drug.

Colchicine Clinical Impact: Cases of myopathy and rhabdomyolysis have been reported with concomitant use of colchicine with simvastatin.

Intervention: Consider if the benefit of using colchicine concomitantly with simvastatin outweighs the increased risk of myopathy and rhabdomyolysis. If concomitant use is decided, monitor patients for signs and symptoms of myopathy, particularly during initiation of therapy and during upward dose titration of either drug.

Grapefruit Juice Clinical Impact: Grapefruit juice can raise the plasma levels of simvastatin and may increase the risk of myopathy and rhabdomyolysis.

Intervention: Avoid grapefruit juice when taking simvastatin.

7.2 Simvastatin

Effects on Other Drugs Table 3 presents simvastatin’s effect on other drugs and instructions for preventing or managing them.

Table 3: Simvastatin Effects on Other Drugs Coumarin Anticoagulants Clinical Impact: Simvastatin may potentiate the effect of coumarin anticoagulants and increase the INR. The concomitant use of simvastatin (20 to 40 mg) and coumarin anticoagulants increased the INR from a baseline of 1.7 to 1.8 in healthy subjects and from 2.6 to 3.4 in patients with hyperlipidemia. There are postmarketing reports of clinically evident bleeding and/or increased INR in patients taking concomitant statins and warfarin.

Intervention: In patients taking coumarin anticoagulants, obtain an INR before starting simvastatin and frequently enough after initiation, dose titration, or discontinuation to ensure that no significant alteration in INR occurs. Once the INR is stable, monitor INR at regularly recommended intervals.

Digoxin Clinical Impact: Concomitant use of digoxin with simvastatin may result in elevated plasma digoxin concentrations.

Intervention: Monitor digoxin levels in patients taking digoxin when simvastatin is initiated.