Anesthetics, hydrocarbon inhalation: Concurrent use with amlodipine may produce additive hypotension; although calcium channel blocking agents may be useful to prevent supraventricular tachycardias, hypertension, or coronary spasm during surgery, caution is recommended during use.
Anti-inflammatory drugs; nonsteroidal (NSAIDs), especially indomethacin: NSAIDs may reduce the antihypertensive effects of amlodipine by inhibiting renal prostaglandin synthesis and/or causing sodium and fluid retention.
Beta-adrenergic blocking agents: Although reports of adverse effects resulting from concurrent use of amlodipine with the beta-adrenergic blocking agents are lacking, caution is recommended given the similarity of amlodipine to nifedipine; concurrent use of nifedipine with the beta-adrenergic blocking agents may produce excessive hypotension and, in rare cases, may increase the possibility of congestive heart failure.
Estrogens: Estrogen-induced fluid retention may tend to increase blood pressure; the patient should be carefully monitored to confirm that the desired effect is being obtained.
Hypotension-producing medications: Antihypertensive effects may be potentiated when amlodipine is used concurrently with hypotension-producing medications; although some antihypertensive and/or diuretic combinations are frequently used for therapeutic advantage, when any of these medications are used concurrently, dosage adjustments may be necessary.
Lithium: Concurrent use with amlodipine may potentially result in neurotoxicity in the form of nausea, vomiting, diarrhea, ataxia, tremors, and/or tinnitus, caution is recommended.
Sympathomimetics: Concurrent use may reduce antihypertensive effects of amlodipine; the patient should be carefully monitored to confirm that the desired effect is being obtained.
Highly protein bound drugs: Caution is advised when using concurrently with amlodipine, changes of the unbound serum concentration of those drugs may occur.