doxazosin and amlodipine

ModerateUsually manageable, but it must be recognised and monitored.

Mechanism

Both drugs cause vasodilation: doxazosin blocks alpha-1 adrenergic receptors, and amlodipine blocks L-type calcium channels. The additive vasodilatory effect on peripheral resistance leads to an exaggerated fall in blood pressure.

What it means clinically

Patients may experience enhanced hypotension, leading to dizziness, lightheadedness, or syncope, especially on standing. The risk is higher in the elderly or volume-depleted patients.

What to do

Monitor blood pressure, heart rate, and symptoms such as dizziness when initiating or increasing the dose of either drug. Advise patients to rise slowly. Consider dose adjustment if hypotension occurs.

Evidence

Well-established pharmacodynamic interaction; clinical observations support additive hypotensive effects.

The two drugs

doxazosinalpha-1 adrenergic blockerRead the monograph amlodipinedihydropyridine calcium channel blockerRead the monograph

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Other interactions involving doxazosin or amlodipine

Educational reference for students and clinicians in training. It does not replace professional judgement, local protocols or current prescribing information.