No drug interaction studies have been conducted with amlodipine and valsartan tablets and other drugs, although studies have been conducted with the individual amlodipine and valsartan components. Amlodipine: Impact of Other Drugs on Amlodipine: CYP3A Inhibitors: Coadministration with CYP3A inhibitors (moderate and strong) results in increased systemic exposure to amlodipine and may require dose reduction. Monitor for symptoms of hypotension and edema when amlodipine is coadministered with CYP3A inhibitors to determine the need for dose adjustment [see Clinical Pharmacology (12.3) ] .
CYP3A Inducers: No information is available on the quantitative effects of CYP3A inducers on amlodipine. Blood pressure should be closely monitored when amlodipine is coadministered with CYP3A inducers (e.g., rifampicin, St. John’s Wort). Sildenafil: Monitor for hypotension when sildenafil is coadministered with amlodipine [see Clinical Pharmacology (12.2) ] . Impact of Amlodipine on Other Drugs: Simvastatin: Coadministration of simvastatin with amlodipine increases the systemic exposure of simvastatin.
Limit the dose of simvastatin in patients on amlodipine to 20 mg daily [see Clinical Pharmacology (12.3) ] . Immunosuppressants: Amlodipine may increase the systemic exposure of cyclosporine or tacrolimus when coadministered. Frequent monitoring of trough blood levels of cyclosporine and tacrolimus is recommended and adjust the dose when appropriate [see Clinical Pharmacology (12.3) ] . Valsartan: Agents Increasing Serum Potassium: Concomitant use of valsartan with other agents that block the renin-angiotensin system, potassium-sparing diuretics (e.g., spironolactone, triamterene, amiloride), potassium supplements, salt substitutes containing potassium or other drugs that may increase potassium levels (e.g., heparin) may lead to increases in serum potassium and in heart failure patients to increases in serum creatinine.
If co-medication is considered necessary, monitoring of serum potassium is advisable. Non-Steroidal Anti-Inflammatory Agents Including Selective Cyclooxygenase-2 Inhibitors (COX-2 Inhibitors): In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, coadministration of NSAIDs, including selective COX-2 inhibitors, with angiotensin II receptor antagonists, including valsartan, may result in deterioration of renal function, including possible acute renal failure.
These effects are usually reversible. Monitor renal function periodically in patients receiving valsartan and NSAID therapy. The antihypertensive effect of angiotensin II receptor antagonists, including valsartan, may be attenuated by NSAIDs including selective COX-2 inhibitors. Dual Blockade of the Renin-Angiotensin System (RAS): Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy.
Most patients receiving the combination of two RAS inhibitors do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAS inhibitors. Closely monitor blood pressure, renal function and electrolytes in patients on valsartan and other agents that affect the RAS. Do not coadminister aliskiren with amlodipine and valsartan tablets in patients with diabetes. Avoid use of aliskiren with amlodipine and valsartan tablets in patients with renal impairment (GFR < 60 mL/min).
Lithium: Increases in serum lithium concentrations and lithium toxicity have been reported during concomitant administration of lithium with angiotensin II receptor antagonists. Monitor serum lithium levels during concomitant use.
- If simvastatin is coadministered with amlodipine, do not exceed doses greater than 20 mg daily of simvastatin ( 7 )
- Non-Steroidal Anti-Inflammatory Drug (NSAID) use may lead to increased risk of renal impairment and loss of anti-hypertensive effect ( 7 )
- Dual inhibition of the renin-angiotensin system: Increased risk of renal impairment, hypotension, and hyperkalemia ( 7 )
- Lithium: Increases in serum lithium level and lithium toxicity ( 7 ) Drug Interactions Sildenafil When amlodipine and sildenafil were used in combination, each agent independently exerted its own blood pressure lowering effect [see Drug Interactions (7) ] . Drug Interactions Amlodipine In vitro data in human plasma indicate that amlodipine has no effect on the protein binding of digoxin, phenytoin, warfarin and indomethacin. Impact of Other Drugs on Amlodipine Coadministered cimetidine, magnesium- and aluminum hydroxide antacids, sildenafil, and grapefruit juice have no impact on the exposure to amlodipine. CYP3A Inhibitors Coadministration of a 180 mg daily dose of diltiazem with 5 mg amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. Erythromycin coadministration in healthy volunteers did not significantly change amlodipine systemic exposure. However, strong inhibitors of CYP3A (e.g., itraconazole, clarithromycin) may increase the plasma concentrations of amlodipine to a greater extent [see Drug Interactions (7) ] . Impact of Amlodipine on Other Drugs Coadministered amlodipine does not affect the exposure to atorvastatin, digoxin, ethanol and the warfarin prothrombin response time. Simvastatin Coadministration of multiple doses of 10 mg of amlodipine with 80 mg simvastatin resulted in a 77% increase in exposure to simvastatin compared to simvastatin alone [see Drug Interactions (7) ] . Cyclosporine A prospective study in renal transplant patients (N = 11) showed an average of 40% increase in trough cyclosporine levels when concomitantly treated with amlodipine [see Drug Interactions (7) ] . Tacrolimus A prospective study in healthy Chinese volunteers (N = 9) with CYP3A5 expressers showed a 2.5- to 4-fold increase in tacrolimus exposure when concomitantly administered with amlodipine compared to tacrolimus alone. This finding was not observed in CYP3A5 non-expressers (N = 6). However, a 3-fold increase in plasma exposure to tacrolimus in a renal transplant patient (CYP3A5 non-expresser) upon initiation of amlodipine for the treatment of post-transplant hypertension resulting in reduction of tacrolimus dose has been reported. Irrespective of the CYP3A5 genotype status, the possibility of an interaction cannot be excluded with these drugs [see Drug Interactions (7) ] . Valsartan No clinically significant pharmacokinetic interactions were observed when valsartan was coadministered with amlodipine, atenolol, cimetidine, digoxin, furosemide, glyburide, hydrochlorothiazide, or indomethacin. The valsartan-atenolol combination was more antihypertensive than either component, but it did not lower the heart rate more than atenolol alone. Coadministration of valsartan and warfarin did not change the pharmacokinetics of valsartan or the time-course of the anticoagulant properties of warfarin. Transporters The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic uptake transporter OATP1B1 and the hepatic efflux transporter MRP2. Coadministration of inhibitors of the uptake transporter (rifampin, cyclosporine) or efflux transporter (ritonavir) may increase the systemic exposure to valsartan.