by virtue of the discoveries that red eye is caused at least in part by the stimulation of the h 2 receptors in the superficial ocular tissue through the presence of histamine , and that the histamine receptors in the superficial ocular tissues are of the h 2 type , a basis has now been provided for a rational treatment of red eye . by administration of antagonists for histamine h 2 receptors , the action of h 2 agonists such as histamine is blocked , and the ocular condition caused by the presence of such agonists is relieved . a preferred h 2 receptor antagonists is cimetidine , i . e ., n - cyano - n &# 39 ;- methyl - n &# 34 ;-[ 2 -[[( 5 - methyl - 1h - imidazol - 4 - yl ) methyl ]- thio ] ethyl ] guanidine . this compound is already approved for use in humans in the treatment of peptic ulcer . hence it is already known as a safe and effective antagonist for h 2 receptors in man . the h 2 receptor antagonists used in practicing the method of treatment in this invention are preferably topically applied to the eye , e . g . by instillation of a solution of the h 2 antagonist in a suitable non - toxic ophthalmic vehicle . aqueous ophthalmic solutions may be formulated , for example , in accord with the procedures set forth in chapter 83 of remington &# 39 ; s pharmaceutical sciences , 14th edition , mack publishing company . as such , they are sterile and may contain bacteriological preservatives to maintain sterility during use . the quaternary ammonium bacteriostats , for example , such as benzalkonium chloride , are suitable for this purpose . ointments may also be employed as vehicles for the h 2 antagonists used in the treatment of this invention . such ointments may be prepared utilizing known pharmaceutical techniques with conventional petrolatum vehicles . while topical administration of the h 2 antagonists to the afflicted tissues of the eye is the preferred method of administration , other routes for delivering the drug , such as oral or parenteral routes , are not excluded . the effective amounts of h 2 antagonists used in accordance with this invention will vary depending on the potency of the selected antagonist . where known h 2 antagonists are utilized , such as the preferred antagonist cimetidine , the effective amount is readily ascertained by one skilled in the art from simple experiments . by way of example , when utilizing cimetidine as the active ingredient the preferred concentration thereof in aqueous solution will be about 1 % to about 2 % by weight . such a solution will be topically administered to humans in a dosage of 1 - 2 drops per eye . having generally described the invention , a more complete understanding can be obtained by reference to the following specific examples . these examples are presented for purposes of illustration only and they are not intended to be limiting unless otherwise specified . ten normal human subjects participated in the following study which demonstrated the presence of h 2 receptors in the ocular surface and showed that an h 2 antagonist , cimetidine , was effective in preventing red eye caused by administration of the h 2 agonist dimaprit . during phase i of the study , the right eye of each of the ten subjects was treated with one drop of the h 2 blocking agent cimetidine . after 3 minutes had elapsed both eyes were treated with one drop of dimaprit , an h 2 agonist . subjects were evaluated using a slit lamp to observe injection and the presence or absence of chemosis . photographs were taken to document the observed effects . phase ii was undertaken a minimum of 48 hours after phase i . during phase ii , the right eye of each of the same ten subjects was treated with one drop of the h 1 antagonist , antazoline . after 3 minutes had elapsed , both eyes were treated with one drop of dimaprit . subjects were again evaluated at the slit lamp for injection and chemosis , and photographs were taken . the photographs were evaluated in a double masked procedure by six judges . injection was evaluated on a scale of 0 to 3 ( 0 = no redness , 1 = slight , 2 = moderate , and 3 = severe redness ), using photographs taken before the treatment as controls . the results of the evaluation for phase i are shown in table 1 , and those for phase ii in table 2 . table 1__________________________________________________________________________ evaluation time of post cimetidine post dimaprit observa - judge no . judge no . tion postsubject 1 2 3 4 5 6 1 2 3 4 5 6 dimaprit__________________________________________________________________________1 od n . d . 0 0 0 0 0 0 10 min . os 2 2 2 1 1 1 10 min . 2 od n . d . 0 0 0 0 0 0 15 min . 0 0 1 1 1 1 30 min . os 2 2 2 1 1 1 15 min . 2 2 2 3 3 3 30 min . 3 od n . d . 0 0 0 0 0 0 18 min . 0 1 1 1 1 1 0 0 0 0 0 0 30 min . os 1 2 2 2 2 2 18 min . 2 2 2 2 2 2 1 1 1 1 1 1 30 min . 4 od n . d . 0 0 0 0 0 0 15 min . 0 0 0 0 0 0 0 0 0 0 0 0 30 min . os 1 1 1 1 1 1 15 min . 2 2 2 2 2 2 2 2 2 2 1 1 30 min . 5 od n . d . 1 1 1 1 1 1 1 1 1 1 1 2 10 min . 2 2 2 2 2 2 2 2 2 2 2 1 30 min . os 3 3 3 3 3 3 2 2 2 2 2 3 10 min . 3 3 3 3 3 3 3 3 3 3 3 3 30 min . 6 od n . d . 2 2 2 2 2 2 1 1 1 1 1 1 10 min . 2 2 2 2 3 3 2 2 2 2 2 2 30 min . os 3 3 3 3 3 3 2 2 2 2 2 2 10 min . 3 3 3 3 3 3 3 3 3 3 3 3 30 min . 7 od n . d . 1 1 1 1 1 1 1 1 1 1 1 1 20 min . os 2 2 2 2 2 2 1 1 1 1 1 1 20 min . 8 od 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0 20 min . os 1 1 1 1 1 1 1 1 1 1 1 1 20 min . 9 od 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 1 15 min . 0 0 0 0 0 0 30 min . os 1 1 1 1 2 2 1 1 1 1 1 1 15 min . 1 1 1 1 1 1 30 min . 10 od 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 1 1 1 10 min . 1 1 1 1 1 1 1 1 1 1 1 1 25 min . os 2 2 2 2 2 2 1 1 1 1 2 2 10 min . 2 2 3 3 3 3 2 2 2 2 2 2 25 min . __________________________________________________________________________ table 2__________________________________________________________________________ evaluation time of post antazoline post dimaprit observa - judge no . judge no . tion postsubject 1 2 3 4 5 6 1 2 3 4 5 6 dimaprit__________________________________________________________________________1 od 0 0 0 0 0 0 2 2 2 . 5 3 3 2 2 2 2 2 1 30 min . os 3 3 3 3 2 . 5 2 2 1 . 5 1 1 1 30 min . 2 od n . d . 1 1 . 5 1 . 5 1 . 5 2 1 1 1 1 1 10 min . os 2 2 2 2 2 2 2 2 2 2 1 . 5 10 min . 3 od 0 0 0 0 0 1 2 2 2 2 2 2 0 1 1 1 1 1 20 min . 1 1 1 1 1 1 25 min . os 2 2 2 2 2 2 1 1 1 1 1 1 20 min . 1 1 1 1 1 1 25 min . 4 od 0 0 0 0 0 0 1 1 1 1 1 1 15 min . os 1 1 1 1 1 1 15 min . 5 od 0 0 0 0 0 1 2 2 2 2 2 2 10 min . 3 3 3 3 3 3 15 min . os 2 2 2 2 2 2 10 min . 2 2 3 3 3 3 15 min . 6 od 0 0 0 0 0 1 3 3 3 3 3 3 2 2 2 2 2 2 10 min . 3 3 3 3 3 3 2 2 3 3 3 3 25 min . os 2 2 2 2 2 2 1 1 1 1 1 2 10 min . 3 3 3 3 3 3 2 2 3 3 3 3 25 min . 7 od 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 10 min . 2 2 2 2 2 2 2 2 2 2 2 2 25 min . os 1 1 1 1 1 1 1 1 1 1 1 1 10 min . 1 1 1 1 1 1 1 1 1 1 1 1 25 min . 8 od 0 0 0 0 0 1 3 3 3 3 3 3 2 2 2 2 2 2 10 min . 2 2 2 2 2 3 1 1 1 1 2 2 25 min . os 2 2 2 2 2 2 1 1 1 1 1 1 10 min . 2 2 2 2 2 2 1 1 1 1 2 2 25 min . 9 od 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 1 1 1 15 min . 2 2 2 2 3 3 1 1 1 1 1 1 30 min . os 1 2 2 2 2 2 1 1 1 1 1 1 15 min . 2 2 2 2 3 3 1 1 1 1 1 1 30 min . 10 od 1 1 1 1 1 1 3 3 3 3 3 3 2 2 2 2 2 2 10 min . 2 3 3 3 3 3 2 2 2 2 2 2 25 min . os 2 2 2 2 2 2 1 1 1 1 1 1 10 min . 2 2 3 3 3 3 1 1 1 2 2 2 25 min . __________________________________________________________________________ the results of the study were evaluated by computing the mean and standard deviation for each subject in each eye and performing a paired t - test to compare the mean values in od and os in phase i and phase ii respectively . the results were as follows : ______________________________________ phase i phase ii______________________________________mean difference 1 . 033 - 0 . 152standard deviation 0 . 072 0 . 071t statistic 14 . 28 2 . 135p - value & lt ;. 001 0 . 02 & lt ; p & lt ; 0 . 05______________________________________ the results are statistically significant in both instances . however , the difference is very small in phase ii . the results demonstrate that h 2 receptors are present in the ocular surface tissues , and that administration of cimetidine is an effective method of preventing red eye produced by agonists for h 2 receptors . this , of course , indicates that cimetidine is an effective agent in the treatment of red eye and the h 2 antagonists would generally be effective in the treatment of red eye . it should be understood that this invention may be embodied in other specific forms without departing from its spirit or essential characteristics . accordingly , the present embodiments are to be considered in all respects as illustrative and not restrictive , the scope of the invention being indicated by the appended claims rather than by the foregoing description , and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein .
a method for treating red eye by administering to the afflicted eye a composition comprising an anti - inflammatory amount of an antagonist for h 2 receptors in the eye , preferably cimetidine , and a non - toxic , pharmaceutically acceptable , ophthalmological carrier .