Naphazoline
Naphazoline is a medicine used as a decongestant, and a vasoconstrictor added to eye drops to relieve red eye. It has a rapid action in reducing swelling when applied to mucous membranes. It is a sympathomimetic agent with marked alpha adrenergic activity that acts on alpha-receptors in the arterioles of the conjunctiva to produce constriction, resulting in decreased congestion.
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| Trade names | Clear Eyes, Cleari, Naphcon-A, Rohto | 
| AHFS/Drugs.com | Monograph | 
| Routes of administration  | Ophthalmic drug administration, nasal administration | 
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| ECHA InfoCard | 100.011.492 | 
| Chemical and physical data | |
| Formula | C14H14N2 | 
| Molar mass | 210.274 g·mol−1 | 
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It was patented in 1934 and came into medical use in 1942.[1]
Medical uses
    

Nasal administration
    
Nasal decongestant.[2]
Ophthalmic drug administration
    
Eye drops (brand names Clear Eyes, and Cleari) narrowing swollen blood vessels (ophthalmic arteries, and ophthalmic veins) to relieve red eye.[2]
Temporary red eye can safely be treated when the cause of the redness is established (eg cannabis induces corneal vasodilation[3])[Insufficient Bibliography]. However, continuous use is not recommended without knowing an underlying condition.
Side effects
    
A few warnings and contraindications that apply to all naphazoline-containing substances intended for medicinal use are:
- Hypersensitivity to naphazoline
 - Use in infants and children can result in central nervous system depression, leading to coma and marked reduction in body temperature
 - Should be used with caution in patients with severe cardiovascular disease including cardiac arrhythmia and in patients with diabetes, especially those with a tendency toward diabetic ketoacidosis
 - A possible association with stroke has been suggested.[4]
 
Nasal administration
    
- Extended use may cause rhinitis medicamentosa, a condition of rebound nasal congestion.
 
Ophthalmic drug administration
    
- Stinging
 - Discomfort
 - Irritation
 - Increased red eyes
 - Blurred vision
 - Mydriasis
 - Punctate keratitis
 - Lacrimation (tears)
 - Increased intraocular pressure
 
Contraindications
    
- Patients taking MAO inhibitors can experience a severe hypertensive crisis if given a sympathomimetic drug such as naphazoline HCl
 - Drug interactions can occur with anaesthetics that sensitize the myocardium to sympathomimetics (e.g. cyclopropane or halothane cautiously)
 - Exercise caution when applying prior to use of phenylephrine.
 
Pharmacology
    
Naphazoline is a mixed α1- and α2-adrenergic receptor agonist.[2]
Chemistry
    
The non-hydrochloride form of Naphazoline has the molecular formula C14H14N2 and a molar mass of 210.28 g/mol. The HCl salt form has a molar mass of 246.73 g/mol.
Society and culture
    
It is an active ingredient in several over-the-counter eye drop formulations including Clear Eyes, Rohto, Eucool, and Naphcon-A.[7]
Illicit use
    
The nasal or ophthalmic form of naphazoline has been abused by heroine or cocaine drug addicts.[8][9] It's used as CNS stimulant and vasoconstrictor to enhance primary drug effects.[9]
References
    
- Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 552. ISBN 9783527607495.
 - Hosten LO, Snyder C (2020). "Over-the-Counter Ocular Decongestants in the United States - Mechanisms of Action and Clinical Utility for Management of Ocular Redness". Clinical Optometry. 12: 95–105. doi:10.2147/OPTO.S259398. PMC 7399465. PMID 32801982.
 - Yazulla S (September 2008). "Endocannabinoids in the retina: from marijuana to neuroprotection". Progress in Retinal and Eye Research. 27 (5): 501–526. doi:10.1016/j.preteyeres.2008.07.002. PMC 2584875. PMID 18725316.
 - Zavala JA, Pereira ER, Zétola VH, Teive HA, Nóvak EM, Werneck LC (September 2004). "Hemorrhagic stroke after naphazoline exposition: case report". Arquivos de Neuro-Psiquiatria. 62 (3B): 889–891. doi:10.1590/S0004-282X2004000500030. PMID 15476091.
 - "Naphazoline - FDA prescribing information, side effects and uses". Drugs.com.
 - "naphazoline ophthalmic (eye): Uses, Side Effects, Interactions, Pictures, Warnings & Dosing - WebMD". www.webmd.com.
 - Green SM (2008). "Ophthalmology: Naphazoline". Tarascon Pocket Pharmacopoeia 2009. Jones and Bartlett. ISBN 978-0-7637-6572-9.
 - van Montfrans GA, van Steenwijk RP, Vyth A, Borst C (1981). "Intravenous naphazoline intoxication". Acta Medica Scandinavica. 209 (5): 429–430. doi:10.1111/j.0954-6820.1981.tb11622.x. PMID 7246278.
 - "Naphazoline abuse". Reactions Weekly. 1815 (1): 251. 2020-08-01. doi:10.1007/s40278-020-81577-1. ISSN 1179-2051. S2CID 195174995.
 

