Alpha-1 agonist
Alpha-1 adrenergic receptor agonist
- Vasoconstriction → ↑ blood pressure and reflex bradycardia
- “Fight or flight” effects including ↑ BP, CNS arousal, pupillary dilation and ↓ digestive activity
- stimulant-like sympathomimetic effects
- Hypertension, agitation, or seizures with excessive sympathomimetic stimulation
- Nasal/mucosal vasoconstriction → decongestion
- Prolonged nasal use → rebound congestion
- Contracts bladder neck/prostate → urinary retention
- Appetite suppression
- The opposite effect of prazosin
Drugs with this mechanism (13)
- Clonidine — Central alpha-2 agonist for hypertension, ADHD and withdrawal; sedation and rebound.
- Clonidine ER — Extended-release central alpha-2 agonist for ADHD; sedation and rebound hypertension limit it.
- Desglymidodrine — Active midodrine metabolite that stimulates peripheral alpha-1 receptors; raises standing blood pressure but can cause supine hypertension.
- Dihydroergotamine — Injectable or intranasal ergot for refractory migraine; never combine closely with a triptan.
- Dobutamine — Beta-1 inotrope; titratable within minutes.
- Dopamine — Dose-sensitive endogenous catecholamine agonist used IV for selected shock and hypotension.
- Epinephrine — Endogenous catecholamine; the first-line drug for anaphylaxis and arrest.
- Ergotamine — Ergot alkaloid for migraine; vasoconstrictive, largely supplanted by triptans.
- Methylergonovine — Ergot uterotonic for postpartum hemorrhage; contraindicated in hypertension.
- Norepinephrine — Endogenous catecholamine; the first-line vasopressor for shock.
- Clonidine ER suspension — Extended-release clonidine liquid for ADHD; sedation and rebound hypertension shape use.
- Oxymetazoline — Topical alpha agonist decongestant; rebound congestion with overuse.
- Phenylephrine — Alpha-1 agonist vasopressor and topical decongestant; oral congestion products are ineffective.
Self-check
- What reflex heart-rate change can follow alpha-1-mediated BP elevation?
Bradycardia. - What can prolonged nasal alpha-1 agonist use cause?
Rebound congestion.
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