Phenylephrine, a selective α1‑adrenergic agonist used in over‑the‑counter decongestants, can raise systemic vascular resistance and blood pressure, posing a risk of worsening hypertension or precipitating hypertensive crises.
Phenylephrine can cause rapid BP spikes; contraindicated in uncontrolled hypertension.
Use the lowest effective dose and limit duration (≤3 days).
Monitor blood pressure before, during, and after use.
Consider alternative decongestants that lack systemic vasoconstrictive effects.
Phenylephrine stimulates α1‑adrenergic receptors on vascular smooth muscle, causing vasoconstriction and an increase in systemic vascular resistance. In patients with pre‑existing hypertension, this additional vasoconstrictive load can exceed the compensatory capacity of antihypertensive therapy, leading to acute elevations in blood pressure.
Potential adverse effects include marked elevation of systolic/diastolic BP, headache, palpitations, chest pain, and in severe cases, hypertensive emergency with end‑organ damage (e.g., stroke, myocardial infarction).
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