Antazoline phosphate, 2-[(Nbenzylanilino)methyl]-2-imidazoline dihydrogen phosphate,is a bitter, white to off-white crystalline powder thatis soluble in water. It has a pKa of 10.0, and a 2% solutionhas a pH of about 4.5. Antazoline, like the ethylenediamines,contains an N-benzylanilino group linked to a basicnitrogen through a two-carbon chain.
Antazoline is less active than most of the other antihistaminicdrugs, but it is characterized by the lack of local irritation.The more soluble phosphate salt is applied topicallyto the eye in a 0.5% solution. The less soluble hydrochlorideis given orally. In addition to its use as an antihistamine, antazolinehas more than twice the local anesthetic potency ofprocaine and also exhibits anticholinergic actions.
