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NON-CATECHOLAMINES. Selective α 1 agonists: Phenylephrine & methoxamine Powerful direct stimulants of α 1 -receptors v.c . of b.v . PVR. They B.P. with reflex bradycardia (this effect is more prolonged than that of NE). Metabolized by MAO, but not by COMT.
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Selective α1 agonists: • Phenylephrine & methoxamine • Powerful direct stimulants of α1-receptors v.c. of b.v. PVR. • They B.P. with reflex bradycardia (this effect is more prolonged than that of NE). • Metabolized by MAO, but not by COMT. • Methoxamine has a longer duration of action.
Uses: • Locally: nasal and ocular decongestant to treat rhinitis and conjunctivitis. • Maintenance of B.P. during surgery. • Treatment of hypotension caused by excessive doses of vasodilators or drug induced shock.
Midodrine: • A prodrug that is enzymatically hydrolyzed to desglymidodrine (α1 agonist) • Uses: treatment of postural hypotension. • Oxymetazoline (specific α2a agonist) & Xylometazoline: • Uses: topical decongestants because of their ability to promote v.c. of the nasal mucosa.