Phenylephrine is an amine, an organic derivative of ammonia, belonging to the phenylethanamine class, a selective alpha-1 adrenoreceptor agonist with strong vasoconstrictive properties. 

What it is used for and where

Medical

Phenylephrine is used as an infusion to increase systemic blood pressure (1), as a nasal decongestant and, in combination with other drugs, to treat colds and flu in over-the-counter products.

Safety

Paracetamol-phenylephrine combination oral therapy can potentially increase blood pressure more than phenylephrine alone in subjects with cardiovascular impairment (2).

This study monitored the plasma levels of patients undergoing vitreoretinal surgery to compare the systemic absorption and cardiovascular effects of 2.5 per cent aqueous and 10 per cent viscous ophthalmic solutions of phenylephrine hydrochloride and concluded that phenylephrine eye drops should be administered under close observation so that if an adverse reaction occurs it can be promptly treated (3).

Other undesirable effects have been observed in patients with heart disease (4)

The most relevant studies on this chemical compound have been selected with a summary of their contents:

Phenylephrine studies

• Molecular Formula     C₉H₁₃NO₂
• Molecular Weight   167.20
• CAS  59-42-7 
• UNII    1WS297W6MV
• EC Number   200-424-8 

References_____________________________________________________________________

(1) Pearl RG. Phenylephrine and inhaled nitric oxide in adult respiratory distress syndrome. When are two better than one? Anesthesiology. 1997 Jul;87(1):1-3. doi: 10.1097/00000542-199707000-00001. 

(2) Atkinson HC, Potts AL, Anderson BJ. Potential cardiovascular adverse events when phenylephrine is combined with paracetamol: simulation and narrative review. Eur J Clin Pharmacol. 2015 Aug;71(8):931-8. doi: 10.1007/s00228-015-1876-1. 

(3) Kumar V, Schoenwald RD, Chien DS, Packer AJ, Choi WW. Systemic absorption and cardiovascular effects of phenylephrine eyedrops. Am J Ophthalmol. 1985 Feb 15;99(2):180-4. doi: 10.1016/0002-9394(85)90229-6. 

(4) Antonopoulos A, Nikolopoulos D, Georgiou EK, Kyriakidis M, Proukakis C. Blood pressure elevation after phenylephrine infusion may adversely affect myocardial perfusion in patients with coronary artery disease. Int J Cardiol. 2002 Aug;84(2-3):201-9. doi: 10.1016/s0167-5273(02)00146-8.