Pharmacology: Mechanism of Action: Oxymetazoline is a direct-acting sympathomimetic agent which has a vasoconstrictor effect on mucosal blood vessels. Sympathomimetic agent mimic the actions produced by stimulation of postganglionic sympathetic or adrenergic nerves, including vasoconstriction of blood vessels supplying skin and mucous membranes. Topical use of Oxymetazoline has the advantage of selective of site of action and more rapid action than do oral agents. It acts within a few minutes and the effects last for up to 12 hours. Nasal congestion is frequently a symptom of conditions such as rhinitis. They act by vasoconstriction and redistributing local blood flow to reduce oedema of the nasal mucosa thus improving ventilation, drainage and nasal stuffiness.
Nasal drops: Sympathomimetic agents are widely employed as nasal decongestants to provide symptomatic relief.
Pharmacokinetics: Most sympathomimetic agents undergo enzymatic degradation in the gut and first-pass metabolism of the liver. They are inactivated by the enzymes catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO). The metabolites are excreted in the urine mainly as their glucuronide and ethereal sulphate conjugates. Oxymetazoline, however, is an imidazoline derivative and is more resistant to the inactivating enzymes of liver and other tissues. It is thus longer action and metabolised at a slower rate than the catecholamines such as ephedrine or phenylephrine. When used in the form of nasal drops or spray it acts with a few minutes and the effects lasts for several hours.