Does phenylephrine increase blood pressure (BP) similarly to pseudoephedrine?

From the Guidelines

Phenylephrine can raise blood pressure, but it is generally less effective at doing so than pseudoephedrine when taken orally. While both medications are decongestants that work by constricting blood vessels, they differ in their mechanisms and effects on blood pressure. Oral phenylephrine has poor bioavailability and minimal systemic effects, resulting in limited blood pressure elevation for most people 1. In contrast, pseudoephedrine is well-absorbed orally and more consistently raises blood pressure by stimulating both alpha and beta adrenergic receptors, causing vasoconstriction and increased heart rate.

Some key points to consider:

• Phenylephrine is extensively metabolized in the gut, which reduces its efficacy as an oral decongestant compared to pseudoephedrine 1.
• The efficacy of phenylephrine as an oral decongestant has not been well established, and it may not be as effective as pseudoephedrine in relieving nasal congestion 1.
• Both phenylephrine and pseudoephedrine can cause side effects such as insomnia, loss of appetite, irritability, and palpitations, and should be used with caution in patients with certain conditions, such as cerebrovascular or cardiovascular disease, hyperthyroidism, closed-angle glaucoma, and bladder neck obstruction 1.
• People with hypertension, heart disease, or those taking certain medications should exercise caution with both medications, but pseudoephedrine generally poses a greater risk for significant blood pressure elevation 1.
• Notably, phenylephrine is much more potent when administered intravenously in medical settings than in its oral form.

It is essential to carefully consider the risks and benefits of using oral decongestants, especially in children below age 6 years, and to monitor patients for changes in blood pressure when using these medications 1. Additionally, screening for substances that may increase blood pressure or interfere with the blood pressure-lowering effect of antihypertensive medications is crucial, and reducing or eliminating these substances should be considered when appropriate 1.

From the FDA Drug Label

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action Phenylephrine hydrochloride is an α-1 adrenergic receptor agonist. 12. 2 Pharmacodynamics Phenylephrine is the active moiety. Metabolites are inactive at both the α-1 and α-2 adrenergic receptors. Following parenteral administration of phenylephrine hydrochloride, increases in systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, and total peripheral vascular resistance are observed The onset of blood pressure increase following an intravenous bolus phenylephrine hydrochloride administration is rapid and the effect may persist for up to 20 minutes.

Yes, phenylephrine can raise blood pressure. The mechanism by which it does this is through its action as an α-1 adrenergic receptor agonist, leading to increased systolic, diastolic, and mean arterial blood pressure, as well as total peripheral vascular resistance 2.

• Key effects of phenylephrine include:
  • Increase in systolic blood pressure
  • Increase in diastolic blood pressure
  • Increase in mean arterial blood pressure
  • Increase in total peripheral vascular resistance
• These effects are rapid in onset and can persist for up to 20 minutes after administration 2.

From the Research

Comparison of Phenylephrine and Pseudoephedrine

• Phenylephrine and pseudoephedrine are both used as decongestants, but their effects on blood pressure (BP) differ 3, 4, 5, 6.
• Studies have shown that pseudoephedrine can increase BP in some individuals, particularly those with hypertension 4, 5.
• In contrast, phenylephrine has been found to have no significant effect on BP in normotensive subjects when used at recommended oral doses as a nasal decongestant 3, 4.
• However, one study found that topical phenylephrine, 10%, can cause a short-lived increase in BP, but this effect is not clinically relevant 7.
• A comparison of the two drugs found that pseudoephedrine was more effective in relieving nasal congestion than phenylephrine, but neither drug had a significant effect on non-nasal symptoms 6.
• The effects of phenylephrine on BP are generally considered to be minimal, and it is often used in nasal and eye drops without significant concerns about its impact on BP 4, 7.

Effects on Blood Pressure

• Pseudoephedrine has been shown to increase BP in some individuals, particularly those with hypertension 4, 5.
• Phenylephrine, on the other hand, has been found to have no significant effect on BP in normotensive subjects when used at recommended oral doses 3, 4.
• Topical phenylephrine, 10%, can cause a short-lived increase in BP, but this effect is not clinically relevant 7.
• The differences in the effects of phenylephrine and pseudoephedrine on BP may be due to their different mechanisms of action and pharmacokinetic properties 3, 4, 5, 6.

Clinical Implications

• The choice between phenylephrine and pseudoephedrine as a decongestant should be based on individual patient needs and medical history 3, 4, 5, 6.
• Patients with hypertension should be cautious when using pseudoephedrine, as it may increase BP 4, 5.
• Phenylephrine may be a safer alternative for patients with hypertension, but its effectiveness as a decongestant may be lower than that of pseudoephedrine 3, 4, 6.