What are the potential interactions with Amlodipine (calcium channel blocker)?

From the Guidelines

Amlodipine can interact with several medications, and careful monitoring is required to avoid potentially harmful interactions. When taking amlodipine, it is essential to be aware of the potential interactions with other medications and substances.

• CYP3A4 inhibitors like ketoconazole, itraconazole, ritonavir, and clarithromycin can increase amlodipine levels, while CYP3A4 inducers such as rifampin, phenytoin, and carbamazepine may decrease its effectiveness 1.
• Amlodipine is a substrate of CYP3A4, and its plasma concentrations may be affected by inhibitors or inducers of this enzyme 1.
• Coadministration of multiple doses of amlodipine with atorvastatin, pitavastatin, rosuvastatin, fluvastatin, and pravastatin may be considered 1.
• Other blood pressure medications such as beta-blockers (metoprolol, atenolol) or ACE inhibitors (lisinopril, enalapril) may cause additive blood pressure reduction when combined with amlodipine.
• NSAIDs like ibuprofen and naproxen might reduce amlodipine's blood pressure-lowering effects.
• Simvastatin doses above 20mg daily may need adjustment when taken with amlodipine due to increased risk of muscle pain. These interactions occur because amlodipine is metabolized by liver enzymes that can be affected by other medications, and its blood pressure-lowering mechanism can be enhanced or diminished by drugs affecting similar pathways. Always inform your healthcare provider about all medications you're taking to avoid potentially harmful interactions.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Amlodipine Interactions

• Amlodipine is a dihydropyridine calcium antagonist that can interact with other substances, affecting its efficacy or toxicity 2
• The drug is metabolized by cytochrome P450 3A4 (CYP3A4), and its interaction with CYP3A4 inhibitors can lead to symptomatic hypotension 2
• CYP3A4 inhibitors, such as itraconazole, ketoconazole, clarithromycin, erythromycin, nefazodone, ritonavir, and grapefruit juice, can increase the plasma levels of amlodipine, potentially leading to adverse effects 2, 3
• Amlodipine can also interact with other cardiovascular active substances, such as vasodilators, and caution should be exercised when coadministering these drugs 3
• The interaction between amlodipine and risperidone, an antipsychotic drug, has been studied, and the results suggest a potential pharmacokinetic interaction via CYP3A4, leading to changes in concentration-to-dose ratios 4
• A fixed-dose combination of amlodipine, losartan, and chlorthalidone has been shown to have equivalent pharmacokinetic characteristics and tolerability profiles compared to individual tablets in a loose combination 5
• CYP3A4/5 has been identified as the primary enzyme responsible for the metabolism of amlodipine, with CYP3A4 playing a key role in its metabolic clearance 6

Mechanisms of Interaction

• Amlodipine is primarily metabolized by CYP3A4, and inhibition of this enzyme can lead to increased plasma levels of the drug 2, 6
• The interaction between amlodipine and CYP3A4 inhibitors can lead to symptomatic hypotension, and caution should be exercised when coadministering these drugs 2
• The pharmacokinetic interaction between amlodipine and risperidone is thought to occur via CYP3A4, leading to changes in concentration-to-dose ratios 4

Clinical Implications

• Clinicians should be aware of the potential interactions between amlodipine and other substances, particularly CYP3A4 inhibitors, and monitor patients for adverse effects 2, 3
• The use of amlodipine in combination with other cardiovascular active substances should be approached with caution, and patients should be monitored for potential interactions 3
• The pharmacokinetic interaction between amlodipine and risperidone should be considered when coadministering these drugs, and patients should be monitored for changes in concentration-to-dose ratios 4