A patient receiving a beta-blocker (propranolol) for hypertension is given epinephrine for anaphylaxis. An unexpected dangerous effect in this scenario would be:
- A Severe hypertension due to unopposed alpha-1 vasoconstriction from epinephrine, with reflex bradycardia due to blocked beta-1 receptors ✓
- B Additive beta-2 mediated bronchodilation
- C Tachycardia due to epinephrine overcoming beta-1 blockade
- D Paradoxical hypotension due to combined vasodilation
Explanation
Epinephrine stimulates both alpha and beta receptors. Beta-1 stimulation increases heart rate (normally producing tachycardia), beta-2 causes vasodilation, and alpha-1 causes vasoconstriction. When non-selective beta-blockers like propranolol are present, beta-1 (rate increase) and beta-2 (vasodilation) effects are blocked, leaving unopposed alpha-1 vasoconstriction from epinephrine — causing severe hypertension. Simultaneously, the baroreceptor reflex attempts to counteract hypertension by slowing the heart but beta-1 block prevents compensatory tachycardia, worsening the hypertensive episode and potentially causing severe bradycardia with hypertension — a dangerous combination.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.