Phenylephrine Molecule

A Phenylephrine Molecule is an Alpha-1 Adrenergic Receptor that ...

• Context:
  • It can be ineffective when taken orally.
  • ...
• Counter-Example(s):
  • Diphenhydramine.
• See: Reflex Bradycardia, Liver, Monoamine Oxidase, Hydrochloride, Agonist, Substituted Phenethylamine, Chemical Classification, Decongestant, Mydriasis.

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References

2024

• Perplexity
  • Phenylephrine is a selective α1-adrenergic receptor agonist, but its effects are indirect and mediated by the release of norepinephrine from cytoplasmic stores rather than through direct binding to α1 receptors.[1][2]
  • The key points regarding phenylephrine's mechanism of action are:
    1. It was previously considered a direct-acting α1 adrenergic agonist based on its potency and intrinsic activity on recombinant α1A receptors.[1]
    2. However, recent studies have shown that phenylephrine's effects are indirect and mediated by the release of norepinephrine from cytoplasmic stores, rather than through direct binding to α1 receptors.[1][2]
    3. The released norepinephrine then activates α1 adrenergic receptors, leading to the observed pharmacological effects such as vasoconstriction and increased blood pressure.[1]
    4. This indirect mechanism explains some unexpected effects of phenylephrine observed in preclinical and clinical studies that could not be easily explained by direct actions on α1 receptors.[1]
  • So in summary, while phenylephrine was previously classified as a direct α1 agonist, more recent evidence indicates its effects are actually mediated indirectly through the release of norepinephrine from intracellular stores, rather than by directly binding and activating α1 adrenergic receptors.
  • Citations:

[1] https://link.springer.com/article/10.1007/s11064-022-03681-2
[2] https://pubmed.ncbi.nlm.nih.gov/9454800/
[3] https://www.jbc.org/article/S0021-9258%2818%2990778-7/pdf
[4] https://pubmed.ncbi.nlm.nih.gov/29889817/
[5] https://www.youtube.com/watch?v=cL5KSzAvB64 

2024

• (Wikipedia, 2024) ⇒ https://en.wikipedia.org/wiki/phenylephrine Retrieved:2024-5-22.
  • Phenylephrine is a medication used as a decongestant for uncomplicated nasal congestion, used to dilate the pupil, used to increase blood pressure (given intravenously in cases of low blood pressure), and used to relieve hemorrhoids. It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, or applied to the skin.

    Common side effects when taken by mouth or injected include nausea, vomiting, headache, and anxiety. Use on hemorrhoids is generally well tolerated. Severe side effects may include a slow heart rate, intestinal ischemia, chest pain, kidney failure, and tissue death at the site of injection. It is unclear whether its use during pregnancy and breastfeeding is safe. Phenylephrine is a selective α₁-adrenergic receptor agonist with minimal to no β-adrenergic receptor agonist activity. It causes constriction of both arteries and veins.

    Phenylephrine was patented in 1933 and came into medical use in 1938. It is available as a generic medication. Unlike pseudoephedrine, abuse of phenylephrine is very uncommon. Its effectiveness as a nasal decongestant has been questioned. In 2023, a Food and Drug Administration panel concluded that the drug was ineffective as a nasal decongestant when taken orally.

2017

• (Wikipedia, 2017) ⇒ https://en.wikipedia.org/wiki/Phenylephrine Retrieved:2017-5-15.
  • Phenylephrine is a selective α₁-adrenergic receptor agonist of the phenethylamine class used primarily as a decongestant, as an agent to dilate the pupil, and to increase blood pressure. Phenylephrine is marketed as an alternative for the decongestant pseudoephedrine, although clinical trials show phenylephrine, taken orally at the recommended dose, to be no more effective than placebo for allergy relief. Phenylephrine can also cause a decrease in heart rate through reflex bradycardia.

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