Oxymetazoline agonist

Kenakin, T. P. (1984). The relative contribution of affinity and efficacy to agonist activity Organ selectivity of noradrenaline and oxymetazoline. Br. J. Pharmacol. 81 131—141. 

Xylometazoline and oxymetazoline are direct-acting agonists. These drugs have been used as topical decongestants because of their ability to promote constriction of the nasal mucosa. When taken in large doses, oxymetazoline may cause hypotension, presumably because of a central clonidine-like effect (see Chapter 11). Oxymetazoline has significant affinity fortx receptors. 

Oxymetazoline (Afrin, Visine, many others). This drug is used in nose drops and nasal sprays to decrease nasal congestion through alpha- 1-mediated vasoconstriction. Higher or systemic doses may also cause hypotension, presumably because central nervous system (CNS) alpha-2 receptors are stimulated in a manner similar to clonidine (see Alpha-2-Selective Agonists ). Oxymetazoline can also be administered as eye drops to decrease redness and minor eye irritation. 

Schoeffier P, Hoyer D. Interaction of the alpha-adrenoceptor agonist oxymetazoline with serotonin 5-HT1A, 5-HT1B, 5-HTlc and 5-HT1D receptors. Eur J Pharmacol 1991 196 213-216. 

The synthetic adrenergic agonists—phenylephrine, naphazoline, oxymetazoline, and tetrahydrozoline—are available as ocular decongestants (Table 13-2). After topical application to the eye, constriction of conjimcti-val blood vessels occurs at drug concentration levels that generally do not cause pupillary dilation. These agents provide only palliative therapy, because they have no effect on the conjimctival response to antigen. 

Oxymetazoline and xylometazoline are alpha-adrenoceptor agonists, which seem to be better tolerated than other topically used drugs of this sort. 

Horie K, Obika K, Foglar R, Tsujimoto G. Selectivity of the imidazoline a-adrenoceptor agonists (oxymetazoline and cirazoline) for human cloned a,-adrenoceptor subtypes. Br J Pharmacol 1995 116 1611-1618. 

Rhinitis a-agonists Acutely reduce secretion Oxymetazoline, Xylometazoline... 

Fitting the data directly to either Equation 5.14 or Equation 5.15 eliminates bias in the data imposed by reciprocal linear curve fitting. Figure 5.21 shows the use of nonlinear curve fitting to measure the affinity of the a-adrenoceptor agonist oxymetazoline in rat anococcygeus muscle after alkylation of a portion of the receptors with phenoxybenzamine. This data shows how all three curves can be used for a better estimate of the affinity with nonlinear curve fitting, a technique not possible with the double reciprocal plot approach where only two dose-response curves can be used. The use of three curves increases the power of the analysis... 

No. Xylometazoline does not have the a, agonist effect of oxymetazoline, even though both are similar drugs. 

Simple 2-benzylimidazoIines (30-33) were prepared by condensation of the appropriate phenylacetonitrile (29) with ethylenediamine either at elevated temperatures or in the presence of catalytic amounts of carbon disulphide Scheme 5.9.). Tolazoline was also prepared in high yield by Neefs method [24]. Tolazoline (30) [25, 26] is a vasodilator but, domazoline (31) [27], xylometazoline (32) [28] and oxymetazoline (33) [29] are all vasoconstrictors. Oxymetazoline was shown to be an agonist for both pre- and post-synaptic a2-adrenergic receptors [30], Tolazoline can be used in animals to give rapid arousal from anaesthesia, for example it is reported to reverse the effect of xylazine with ketamide in wolves [31], white tailed deer [32] and elephants [33], in each case it was fully effective and caused no distress to the animals. It is useful in neonates such as lambs and calves to treat persistent foetal circulation syndrome (persistant pulmonary hypertension) [34] and is recommended for the same condition in human newborns [35, 36]. Oxymetazoline found use in dentistry as a gingival retraction agent [38]. 

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