Effects of hydroxypropyl methylcellulose and polyvinyl alcohol on intraocular penetration of topical fluorescein m man

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1 Effects f hydrxyprpyl methylcellulse and plyvinyl alchl n intracular penetratin f tpical flurescein m man Stephen R. Waltman and Tully C. Patrwicz A slit lamp flurphtmeter was used t measure penetratin f tpical per cent flurescein, in varius vehicles, int human eyes. The technique prvides a sensitive methd fr measuring attained flurescein cncentratins in the anterir segment f the eye. ne-half per cent hydrxyprpyl methylcellulse significantly increased the penetratin f the drug as cmpared t penetratin with 1.4 per cent plyvinyl alchl r aqueus slutins. Dubling the cncentratin f flurescein in the vehicles dubled the attained intracular cncentratins. Very little f the applied drug penetrated int the anterir segment. Key wrds: flurescein, phthalmic vehicles, plyvinyl alchl, methylcellulse, flurphtmeter, drug penetratin, hydrxyprpyl methylcellulse. 0,ne purpse f the vehicles in which tpical eye medicatins are incrprated is t increase intracular penetratin f the drugs disslved in them., plyvinyl alchl, and methylcellulse slutins are the mst cmmnly used phthalmic vehicles. Previus studies have shwn that methylcellulse is eliminated less rapidly thrugh the lacrimal passages than aqueus r plyvinyl alchl slutins. 1 Methyl- cellulse increases the cular penetratin f radiactive dexamethasne in the rabbit and augments the cular hyptensive and mittic effects f pilcarpine in man, cmpared t aqueus slutins. Using a new mdel we have studied the effects f phthalmic vehicles n the intracular penetratin f tpical flurescein in man. Quantitative data n cular penetratin f this drug, in man, in viv, are presented. Frm the Department f phthalmlgy, University f Flrida, Gainesville, Fla. Supprted in part by grants N. EY000 and EY00446 and special fellwship F11 NB VSN frm the Natinal Institutes f Health. Manuscript submitted ct. 8, 1970; revised manuscript accepted Nv., Reprint requests: Dr. T. Patrwicz, Department f phthalmlgy, University f Flrida, Cllege f Medicine, Gainesville, Fla Methds Ten vlunteers, ages 1 t 4, with nrmal cular examinatins were used in the initial phase f the study. Crneal and aqueus humr backgrund flurescence were measured with a slit lamp flurphtmeter. 4 The vehicle under study, cntaining per cent flurescein, was then applied. ne drp was instilled in each lwer culde-sac every 5 minutes fr a ttal f 4 drps in 15 minutes. The drps were administered by ne persn thrughut the study. Usually, five subjects gt ne vehicle and five, anther. Measurements f crneal and aqueus humr flurescein cncen-

2 Vlume 9 Number 1 Intracular penetratin f tpical flurescein in man 967 tratins were made ne, tw, and three hurs after the last drp was administered by an bserver wh was unaware f which vehicles had been applied. Subjects with crneal abrasins n slit lamp examinatin were eliminated. Three t seven days later per cent flurescein, in the same r a different vehicle was applied t the same subjects; the penetratin measurements were repeated. Each subject served as his wn cntrl and had three applicatins f each vehicle in randm rder. Sterile aqueus per cent flurescein slutin (Alcn) with phenylmercuric nitrate 1:5,000 as a preservative was used. Disdium flurescein pwder was added t cmmercially available 1.4 per cent plyvinyl alchl with 0.5 per cent chlrbutanl (Liquifilm Tears-Allergan) r 0.5 per cent hydrxyprpyl methylcellulse with benzalknium chlride 1:10,000 (Ispt Tears-Alcn) t a final cncentratin f per cent. Additin f flurescein pwder t the aqueus per cent slutin gave a 4 per cent flurescein slutin. Drps were dispensed frm their riginal cntainers. T ascertain if applicatin f multiple drps in rapid successin r drp size influenced cular penetratin, fur drps f per cent aqueus flurescein were applied every five minutes fr fur applicatins. In all cases, the cul-de-sac was "flded" and flurescein slutin spilled ver the lwer lid. This was repeated three times and cmpared with applicatin f single drps. In the secnd phase f the study, per cent flurescein in pure slutins f 1.4 per cent plyvinyl alchl r 0.5 per cent hydrxyprpyl methylcellulse were used. There were n preservatives in the slutins. Ten additinal vlunteers were used and the attained intracular cncentratins f flurescein with plyvinyl alchl r hydrxyprpyl methylcellulse were cmpared. Partitin cefficients fr the vehicles were determined by dialyzing.5 ml. f the vehicle against 00 ml. f 0.1M phsphate buffered saline (ph, 7.4) fr 4 hurs withut stirring, and measuring the flurescein cncentratin inside and utside the dialysis tubing. This served as an additinal cntrl fr selective binding t the vehicle r interactin with the preservatives. Results The respnse f the flurphtmeter was linear and reprducible ver the range f flurescein cncentratins studied. The results f all readings frm bth eyes f all subjects were pled fr each vehicle. Prir analysis revealed n difference between the right and left eyes. Fllwing applicatin f any vehicle, peak crneal flurescein cncentratins were at ne hur, fllwed by a slw, steady fall. Methylcellulse gave cnsistently higher crneal flurescein cncentratins than aqueus r plyvinyl alchl slutins. This is shwn in Fig. 1. < e 4H E - Methylcellulse UJ - Plyvinyl Alchl 0- TIME (HURS) Fig. 1. Crneal flurescein cncentiatin after tpical per cent flurescein in varius vehicles.

3 968 Waltman and Patrwicz Investigative phthalmlgy December 1970 LU E cn \ E URh tier I (/) (xl cr H- 9 < I-I Methylcellulse Plyvinyl Achl TIME (HURS) Fig.. humr flurescein cncentratin after tpical per cent flurescein in varius vehicles. Table I. Crneal flurescein cncentratins after tpical applicatin f per cent flurescein in different vehicles (xl~ 4 mg. per milliliter) Vehicle 1.18 ± 0.41 Plyvinyl alchl.60 ± 0.4 Hydrxyprpyl methylcellulse 4.59 ± 0.47 "Each value is the mean and standard errr fr bth eyes f all ten subjects..88 ±.16 ± 4.0 ± ± 0.9 ± 0.1 ± 0.4 Table II. humr flurescein cncentratins after tpical applicatin f per cent flurescein in different vehicles (xl~ 5 mg. per milliliter) Vehicle Plyvinyl alchl Hydrxyprpyl methylcellulse 1.18 ± 0.5*.54 ± ± 0.54 *Each value is the mean and standard errr fr bth eyes f all ten subjects ± 4.64 ± 8.96 ± ± ± ± 0.8 humr flurescein cncentratin rse steadily ver the three hurs. Methylcellulse prduced cnsistently higher flurescein cncentratins than the ther vehicles. This is shwn in Fig.. The crneal and aqueus humr flurescein cncentratins at ne, tw, and three hurs, with the use f the different vehicles are shwn in Tables I and II. Each value is the average f a ttal f 60 measurements frm bth eyes f all subjects. Results were analyzed at the University f Flrida Cmputing Center using prgram BMD08V fr "Analysis f Variance." It was shwn that crneal readings decreased linearly with time at apprximately the same rate fr each vehicle. Methylcellulse prduced significantly higher flurescein cncentratins than aqueus r plyvinyl alchl frm ne thrugh three hurs (p < 0.05 fr aqueus, p < 0.01 fr plyvinyl alchl). The differences be-

4 Vlume 9 Number 1 Intracular penetratin f tpical flurescein in man 969 tween aqueus and plyvinyl alchl were nt significant. humr cncentratins rse frm ne t three hurs, the greatest change ccurring between ne and tw hurs. Tw-hur readings were significantly higher than ne-hur reading (p < 0.01), but the results at three hurs were nt significantly different frm thse at tw hurs. Thrughut the study, methylcellulse resulted in higher aqueus humr flurescein cncentratins than aqueus r plyvinyl alchl (p < 0.01 fr either cmparisn). The differences between aqueus and plyvinyl alchl were nt significant. The findings in individual subjects were in agreement with the aggregate reprted abve. Methylcellulse slutin yielded the highest cular penetratin in eight f the ten subjects, and flurescein penetratin equal t aqueus in anther. In ne subject the penetratin f flurescein was less with methylcellulse than with the aqueus vehicle. Results cmparing pure slutins f flurescein in plyvinyl alchl r methylcellulse were similar t the abve results. Methylcellulse gave cnsistently higher crneal and aqueus humr readings and the time curse f the intracular penetratin was identical t Figs. 1 and. Initial experiments with the use f tw drps fifteen minutes apart gave cular cncentratins apprximately ne half f thse reprted abve. Fur per cent aqueus flurescein slutins resulted in crneal and aqueus cncentratins 78 t 1 per cent higher than the per cent slutin. Results frm the "flding" experiment are shwn in Tables III and IV. They cmpare crneal and aqueus humr cncentratins f flurescein when either ne r fur drps f per cent aqueus flurescein was applied every five minutes fr fur applicatins; there was n difference with either methd. There was cnsiderable inter- and intraindividual variatin in the cular penetratin f tpical flurescein with all vehicles. Individual variatins n repeated tests shwed a tw- t threefld range. There Table III. Crneal flurescein cncentratins after single r multiple drps f tpical per cent aqueus flurescein every five minutes fr fur applicatins (xl~ 4 mg. per milliliter) Drps 1 Single.18" Multiple.0" Average f 60 measurements Table IV. humr flurescein cncentratins after single r multiple drps f tpical per cent aqueus flurescein every five minutes fr fur applicatins (xl" 5 mg. per milliliter) Drps Single Multiple.18".86" "Average f 60 measurements was a tw- t fivefld variatin between the means fr all subjects. Cmparisn f the high and lw readings fr all subjects revealed a five- t eighteenfld variatin. Partitin cefficients were 0.95 fr the aqueus slutin and 0.85 fr the ther tw slutins. There is n significant binding f flurescein by either vehicle. Methylcellulse and plyvinyl alchl added t aqueus flurescein slutins did nt alter the measured flurescein cncentratins. The phs f the methylcellulse and plyvinyl alchl slutins were 7.8 and 7.9, respectively, after additin f the disdium flurescein pwder. Discussin The experiments described abve shw that cmmercially available 0.5 per cent methylcellulse increases the intracular penetratin f tpical flurescein as cmpared t intracular penetratin with 1.4 per cent plyvinyl alchl r aqueus slutins. Methylcellulse prduced crneal and aqueus humr flurescein cncentra-

970 Waltman and Patriici Investigative phthalmlgy December 1970 tins that were 4 per cent higher than with aqueus slutins and 89 per cent higher than with plyvinyl alchl.

5 970 Waltman and Patriici Investigative phthalmlgy December 1970 tins that were 4 per cent higher than with aqueus slutins and 89 per cent higher than with plyvinyl alchl. The differences were cnsistent and reprducible. Results with the use f pure slutins f plyvinyl alchl and methylcellulse gave cmparable results in that cular flurescein cncentratins were 50 per cent higher with methylcellulse. Because different subjects were used fr this part f the study, it was nt pssible t determine the effects f the preservatives by cmparing mean cncentratins with and withut them. The exact mechanism fr this is nt clear. Methylcellulse may prlng the cntact between crnea and drug r may result in a higher initial drug cncentratin in cntact with the crnea. It may reduce the resistance f the epithelial cell layer by alteratin f the tear film surface tensin r by ther means. Drp size appears t be an unimprtant variable in this study. Flding the cul-desac with fur drps f an aqueus slutin prduced results that were identical t single-drp applicatins. This supprts the lder cncept that a single drp f medicatin may be as efficacius as multiple drps given in rapid successin. Analysis f the data reveals that peak crneal and aqueus humr cncentratins f flurescein are reduced by factrs f 1.5 x 10" 5 and.5 x 10~ G, respectively, cmpared t the cncentratin f the applied medicatin. Dubling the cncentratin f the applied drug dubles the peak intracular cncentratin. The results reprted abve apply t flurescein and may r may nt be valid fr drugs f different mlecular weights, sizes, r cnfiguratins. Flurescein is nt used therapeutically and therefre, we are cautius in drawing cnclusins abut the relevance f ur study t clinical situatins. Hwever, we have shwn fr the first time the effects f different vehicles n the penetratin f a drug int the human eye. This was dne by measuring attained intracular drug cncentratins, a methd which is superir t merely measuring the effects f that drug n ther parameters such as pupil size. We are grateful t Jhn Thrnby, Ph.D., f the Bistatistics Unit fr help with the statistical evaluatins. Withut the cntinued interest and endurance f the vlunteers' this study wuld nt have been pssible. REFERENCES 1. Linn, M. T., and Jnes, L. T.: Rate f lacrimal excretin f phthalmic vehicles, Amer. J. phthal. 65: 76, Rsenblum, C, Dengler, R. E., and GeiFry, R. F.: cular absrptin f desamethasne phsphate disdium by the rabbit, Arch. phthal. 77: 4, Hass, J. S., and Merrill, D. L.: The effect f methylcellulse n respnses t slutins f pilcarpine, Amer. J. phthal. 54: 1, Waltman, S. R., and Kaufman, H. E.: A new bjective slit lamp flurphtmeter, INVEST. PHTHAL. 9: 47, 1970.

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