From the Guidelines
Phenylephrine, also known as phyneleln, is a decongestant medication that is less efficacious compared to pseudoephedrine due to extensive metabolism in the gut 1.
Key Points
- Phenylephrine is a key ingredient in many over-the-counter cold and allergy products, including nasal sprays and oral medications.
- The medication works by stimulating alpha-1 adrenergic receptors, causing vasoconstriction in the nasal mucosa, which helps to reduce swelling and congestion in the nasal passages.
- However, its effectiveness when taken orally has been questioned due to extensive metabolism in the gut, as noted in a study published in the Journal of Allergy and Clinical Immunology 1.
- Side effects of phenylephrine can include increased blood pressure, headache, dizziness, and nervousness, and it should be used with caution in patients with certain conditions, such as arrhythmias, angina pectoris, coronary artery disease, cerebrovascular disease, and hyperthyroidism 1.
Usage and Precautions
- Phenylephrine is generally well tolerated by most patients with hypertension, but hypertensive patients should be monitored due to interindividual variation in response 1.
- Topical decongestants, including phenylephrine, can be considered for short-term and possibly for intermittent or episodic therapy of nasal congestion, but are inappropriate for regular daily use because of the risk for the development of rhinitis medicamentosa 1.
- Caution is recommended when using decongestants during the first trimester of pregnancy, and topical vasoconstrictors should be used with care in children under the age of 1 year due to the narrow margin between the therapeutic and toxic dose 1.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Definition and Uses of Phenylephrine
- Phenylephrine is a decongestant used to relieve nasal congestion [ 2 ]
- It is also used as a nasal decongestant for over 50 years [ 3 ]
Pharmacokinetics and Safety
- Phenylephrine is rapidly absorbed with median times to maximum plasma concentrations (t max) from 0.33 to 0.5 h [ 3 ]
- The maximum concentration (C max) and total systemic exposure [area under the plasma concentration-time curve from time zero to infinity (AUC∞)] increase disproportionally with increasing dose [ 3 ]
- Phenylephrine shows no consistent effect on heart rate or blood pressure for doses of 25 mg or less [ 2 ]
Effects on the Body
- Phenylephrine may impair host defence mechanisms to infection [ 4 ]
- It promotes bacterial outgrowth after surgical peritonitis [ 4 ]
- Phenylephrine alters phase synchronization between cerebral blood velocity and blood pressure in ME/CFS with orthostatic intolerance [ 5 ]