Perfarmance of propranolol hydrochloride in certain ophthalmic formulations

Ophthalmic medications are sterile,. isotonic preparations, usually’ introduced into the eye by placing them in contact with conjunctiva and cornea. This is usually accomplished by introducing the vehicle into the upper or lower cul-de-sac or directly onto the surface of the cornea .The use of eye DROPs remains the major method of adminstration for the topical ocular route, the main disadvantage of ophthalmic preparations is the loss of the drug from the eye cavity Many factors contribute to the loss of the drug reservoir from the cul-de-sac. The first factor is the physiological turnover of lacrimal fluid (16% min – 1 in man ) The second factor is the very low holding capacity of the eye towards fluids, amounting in humans which 30ul under static conditions i.e without blinking.The third factor is Physiology of blinking (4 times /hr. in rabbit and 600- 1200 times / hr. in human ).The fourth factor is the Physiology of reflex tearing in response to mechanical, chemical or physiochemical ( pH and osmotic effect), irritation, sometimes induced by the ophthalmic preparation it self.