Oxymetazoline

Oxymetazoline is a selective α1 adrenergic receptor agonist and α2 adrenergic receptor partial agonist. It is a topical decongestant, used in the form of oxymetazoline hydrochloride. It was developed from xylometazoline at E. Merck Darmstadt by Fruhstorfer in 1961. Oxymetazoline is generally available as a nasal spray. Oxymetazoline is available over-the-counter as a topical decongestant in the form of oxymetazoline hydrochloride in nasal sprays such as Otrivin, Afrin, Operil, Dristan, Dimetapp, Oxyspray, Facimin, Nasivin, Nostrilla, Utabon, Sudafed OM, Vicks Sinex, Zicam, SinuFrin, Drixoraland Mucinex Full Force. In the United States, oxymetazoline 1% cream is approved by the Food and Drug Administration for topical treatment of persistent facial erythema (redness) associated with rosacea in adults. Due to its vasoconstricting properties, oxymetazoline is also used to treat nose bleeds and eye redness due to minor irritation (marketed as Visine L.R. in the form of eye drops). Rebound congestion, or rhinitis medicamentosa, may occur. A 2006 review of the pathology of rhinitis medicamentosa concluded that use of oxymetazoline for more than three days may result in rhinitus medicamentosa and recommended limiting use to three days. In a submission to the Therapeutic Goods Administration, a Novartis representative concluded, 'The justification was not based on evidence.' Citing an existing extensive body of evidence and noting a range of recommended periods from ten to five days, Novartis recommended the established five day period for its use for self-medication without medical consultation as it coincides with the typical duration of the common cold. The Food and Drug Administration places oxymetazoline in category C, indicating risk to the fetus cannot be ruled out. While it has been shown that a single dose does not significantly alter either maternal or fetal circulation, this subject has not been studied extensively enough to draw reliable conclusions. If accidentally ingested, standard methods to remove unabsorbed drugs should be considered. There is no specific antidote for oxymetazoline, although its pharmacological effects may be reversed by α adrenergic antagonists such as phentolamine. In the event of a possibly life-threatening overdose (such as a hypertensive crisis), benzodiazepines should be considered to decrease the likelihood of seizures and convulsions, as well as reduce anxiety and to lower blood pressure. In children, oxymetazoline may produce profound central nervous system depression due to stimulation of central α2 receptors and imidazoline receptors, much like clonidine. Oxymetazoline is a sympathomimetic that selectively agonizes α1 and, partially, α2 adrenergic receptors. Since vascular beds widely express α1 receptors, the action of oxymetazoline results in vasoconstriction. In addition, the local application of the drug also results in vasoconstriction due to its action on endothelial postsynaptic α2 receptors; systemic application of α2 agonists, in contrast, causes vasodilation because of centrally-mediated inhibition of sympathetic tone via presynaptic α2 receptors. Vasoconstriction of vessels results in relief of nasal congestion in two ways: first, it increases the diameter of the airway lumen; second, it reduces fluid exudation from postcapillary venules. It can reduce nasal airway resistance (NAR) up to 35.7% and nasal mucosal blood flow up to 50%.