Beta-2 antagonist
Beta-2 adrenergic receptor antagonist
- Blocks beta-2 bronchodilation → bronchospasm
- contraindicated in severe asthma (and caution in COPD)
- Reduces skeletal-muscle tremor
- reduces physiologic and medication-induced tremor
- Akathisia treatment
- may reduce peripheral adrenergic activation, tremor/restlessness, and somatic anxiety-like drive
- contribution of β1 vs β2 not clearly defined
- Can mask tremor as a warning sign of hypoglycemia
- Loss of β2-mediated vasodilation → unopposed α1 tone
- β-blockade without prior α-blockade may permit unopposed α1-mediated vasoconstriction → ↑ afterload, ↑ BP, coronary vasospasm
- Insulin resistance
- modestly increased risk of new-onset diabetes (stronger signal with nonselective agents)
- ↓ aqueous humor production → glaucoma treatment (β1 also)
- No clinically available selective β2 antagonists
- all available agents also block β1 receptors
Drugs with this mechanism (6)
- Carteolol — Ophthalmic beta blocker with intrinsic sympathomimetic activity; gentler on lipids than timolol.
- Carvedilol — Nonselective beta-blocker with alpha-1 block; a heart-failure standard.
- Labetalol — Combined alpha/beta blocker; a mainstay for hypertension in pregnancy.
- Pindolol — Nonselective beta blocker whose intrinsic sympathomimetic activity preserves resting heart rate; hypertension.
- Propranolol — Non-selective beta-blocker used for performance anxiety, tremor, and migraine.
- Propranolol ER — Extended-release nonselective beta blocker for hypertension, migraine prevention, and tremor.
Self-check
- What respiratory risk follows beta-2 blockade?
Bronchospasm. - Which warning sign of hypoglycemia can beta-2 blockade mask?
Tremor.
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