Naphazoline

Naphazoline (in the hydrochloride form) is the common name for 2-(1-naphthylmethyl)-2-imidazoline hydrochloride. It is a sympathomimetic agent with marked alpha adrenergic activity. It is a vasoconstrictor with a rapid action in reducing swelling when applied to mucous membrane. It acts on alpha-receptors in the arterioles of the conjunctiva to produce constriction, resulting in decreased congestion. It is an active ingredient in Naphcon-A and Clearine eye drops.

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It has the molecular formula C₁₄H₁₄N₂.HCl and a molecular weight of 246.73 g/mol.

Warnings and contraindications

A few warnings and contraindications that apply to all naphazoline-containing substances intended for medicinal use are:

• Hypersensitivity to naphazoline
• Patients taking MAO inhibitors can experience a severe hypertensive crisis if given a sympathomimetic drug such as naphazoline HCl
• 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 arrythmia and in patients with diabetes, especially those with a tendency toward diabetic ketoacidosis
• 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.