some prodrug possibilities of ephedrine however ephedrine is not commonly used ophthalmically and is biologically different in activity than phenylephrine with ephedrine being used orally for nacolepsy bronchial asthma and nasal congestion in contrast the oxazolidine derivative of phenylephrine increases the bulk considerably on the amine function the latter of which is responsible for phenylephrine 39 s activity with the addition of oxazolidine to the amine function the prodrug would be expected to be devoid of alphaadrenergic activity a burger 34 medicinal chemistry 3rd ed wiley interscience 1970 p 1248 accordingly there is a continuing and real need for safe and effective prodrugs of phenylephrine which can be safely and effectively delivered to the eye the prodrug of phenylephrine is not stable in aqueous solution thus it is necessary that effective ophthalmic compositions include the prodrug in an oil suspension the composition of the invention is the only manner in which the prodrug can be delivered to the eye in a non irritating non toxic manner without blurring the vision polydimethylsiloxane of a viscosity of 30 70 centistokes may also for example be combined with the mydriatic drug dapiprazole of the formula iii str2 to provide a non irritating non toxic non blurring ophthalmic composition the compounds of formula ii or iii themselves.