Resting Anal Pressure

Topical L-Arginine Gel Lowers Resting Anal PressurePossible Treatment for Anal FissureN.Griffin,M.R.C.S.,*D.D.E.Zimmerman,M.D.,†J.W.Briel,Ph.D.,†H.-J.Gruss,M.D.,‡M.Jonas,F.R.C.S.,*A.G.Acheson,F.R.C.S.,*K.Neal,*J.H.Scholefield,Ch.M.,*W.R.Schouten,Ph.D.†From the*Departments of Surgery and Epidemiology,Queen’s Medical Centre,Nottingham,United Kingdom, the†Department of Surgery,University Hospital Dijkzigt,Rotterdam,the Netherlands,and‡Norgine GmbH, Marburg,Germany.PURPOSE:Exogenous nitric oxide donors,such as glyceryltrinitrate,have been used as treatment for anal fissures;however,headaches develop in60percent of patients.Nitric oxide produced from the cellular metabolism of L-arginine mediates relaxation of the internal anal sphincter.This study investigated whether topical L-arginine gel re-duces maximum anal resting pressure in volunteers.METH-OD:In a two-center study,volunteers received a singletopical dose of L-arginine or placebo(Aquagel TM).Analmanometry was performed for two hours after applicationof400mg of L-arginine gel or placebo gel to the anal vergein25volunteers.Side effects were recorded after singleapplication and also after repeated dosing for three days.RESULTS:L-Arginine reduced maximum anal resting pres-sure by46percent from a median of65cm of water to aminimal value of35cm of water(PϽ0.001,Wilcoxon’ssigned-rank test).The difference between L-arginine andplacebo using repeated-measures testing was significant at P Ͻ0.005.No side effects occurred with either gel;in par-ticular,no episodes of headache were recorded.CONCLU-SION:Topical L-arginine gel significantly lowers maximumanal resting pressure;its onset of action is rapid,and dura-tion is at least two hours(PϽ0.01).L-arginine may havetherapeutic potential,but further evaluation is needed be-fore it can be used as a possible alternative treatment forchronic anal fissure.[Key words:L-arginine;Anal fissures;Resting anal pressures]Griffin N,Zimmerman DDE,Briel JW,Gruss H-J,Jonas M,Acheson AG,Neal KR,Scholefield JH,Schouten WR.TopicalL-arginine gel lowers anal resting pressure:possible treatmentfor anal fissure.Dis Colon Rectum2002;45:1332–1336. C hronic anal fissure is characterized by a linearulcer usually in the posterior midline,often as-sociated with hypertonia of the internal anal sphincter muscle.1–4The cause of anal fissure is uncertain,but it is most likely ischemic in nature with anodermal blood flow being lower in these patients.5The stan-dard in the treatment of this condition is lateral sphincterotomy;however,the risk of incontinence (from5to30percent6)has led to the development of nonsurgical therapies.Topical0.2percent glyceryl trinitrate(GTN)acts as a nitric oxide donor and has been shown to reduce anal resting pressure(ARP), with a corresponding improvement in anodermal blood flow and healing of the fissure in up to70 percent of cases.7,8The incidence of headaches oc-curs in up to60percent of patients7on GTN therapy for fissures;this causes noncompliance and conse-quent treatment failure in up to30percent of patients. L-arginine acts as a substrate for nitric oxide syn-thase in the production of nitric oxide,and previous in vivo work in rats has shown it to be effective in relaxation of the internal anal sphincter.9The present study evaluates the effect of a single dose of topical L-arginine(the substrate for nitric oxide synthase)on maximum anal resting pressure(MARP)in volunteers and the incidence of side effects after repeated dosing to assess whether it may have potential as a new treatment for anal fissure.SUBJECTS AND METHODSThis study took place simultaneously in parallel in two centers(Rotterdam,the Netherlands,and Not-tingham,United Kingdom)as a proof-of-concept study.Local ethical committee approval was obtained by each center.Twenty-five volunteers(14female), median age of26(range,20–51)years,with no prior history of anorectal disease,and who were not using any topical or systemic nitric oxide donor therapy, were recruited into the study after giving informed consent.The study was nonrandomized and was unblinded to the observer.However,the patient was blinded toPresented in part at the meeting of The American Society of Colonand Rectal Surgeons,Boston,Massachusetts,June24to29,2000. Address reprint requests to Miss Griffin:Section of Surgery,E floor, West Block,University Hospital,Queen’s Medical Centre,Notting-ham NG72UH,United Kingdom.1332activity or otherwise of the medication.Manometry was performed with the subject lying in the left lateral position.A five-channel,solid-state catheter(Gael-tec TM,Isle of Skye,United Kingdom)was used with an external diameter of5mm,including4anal pres-sure transducers arranged radially and one rectal transducer.The maximum anal resting pressure was established using a station pull-through technique and a baseline reading recorded for ten minutes.Four hundred milligrams of L-arginine gel(400mg/ml (supplied by Norgine Research Ltd,Northwood, United Kingdom))was then applied topically to the anal verge with the probe in situ,and manometry continued for a further two hours.Any side effects during the study period were noted.In one center, topical L-arginine was then self-administered to the anal verge five times daily for a further three days to evaluate side effects with repeated dosing.Volunteers were instructed to contact the investigator in the event of an adverse reaction to the drug.After a washout period of a minimum of two weeks,volunteers in one center were invited back to repeat the study using a placebo(Aquagel TM,Adams Healthcare,Leeds,United Kingdom).Eleven volun-teers returned and anorectal manometry was per-formed for one hour in the same manner described above.Analysis of manometric recordings was performed using a personal computer.The mean MARP was calculated at0,5,10,15,30,60and120minutes after application of medication or placebo.The Wilcoxon’s signed-rank test and Mann-Whitney U test using the SPSS®for Windows®(SPSS Inc.,Chicago,IL,and Microsoft Corp.,Redmond,WA)program were cho-sen for statistical analysis of each drug.The General Linear Model for repeated measures was used to com-pare the effect of L-arginine and placebo.P values of less than0.05were considered to be statistically sig-nificant.RESULTSThe fall in MARPs after topical application of L-arginine and placebo(expressed as the mean and median values)are shown in Table1for times0,15, 30,45,60,and120minutes.Figure1shows the actual mean MARP with time after application of active or placebo gel.Results After Topical Applicationof L-ArginineAfter administration of topical L-arginine,a statisti-cally significant fall in pressure was achieved within5 minutes and maintained through to120minutes(PϽ0.001at5minutes).There was no further significant fall in pressure after the first five minutes.The median MARP before application of the drug was in the nor-mal range,being65(range,31–107)cm H2O.Topical L-Arginine caused a significant fall in MARP from a median of65cm H2O before application of the drug to a lowest median recorded value of35(range,7–65) cm H2O(PϽ0.001).This represented a fall of46 percent of the maximal value.Pressures remained significantly reduced at the end of the two-hour ob-servation period(PϽ0.01)compared with restingTable1.Fall in Resting Anal Pressures With L-Arginine and Placebo GelTime (min)Fall in Resting Anal Pressures(cm H2O)Arginine PlaceboMean PressureDropMedian PressureDrop*P ValueMean PressureDropMedian PressureDrop*P Value1518.1Ϯ3.216(7–27.5)0.001 4.2Ϯ3.210(Ϫ5–11)0.3 3019.4Ϯ3.720(10–27)0.001 1.4Ϯ4.15(Ϫ16–10)0.7 4516.1Ϯ4.319(7–25)0.006 3.3Ϯ5.8 3.5(Ϫ16–18)0.7 6016.1Ϯ4.320(8–26)0.001Ϫ3.3Ϯ5.5Ϫ1(Ϫ17–17)0.6 12021Ϯ6.513(6–37)0.007Maximaldrop32.9Ϯ3.332(20–45)0.00011.4Ϯ4.211(7–20)0.05Results are expressed as mean(Ϯstandard error of the mean)and median(interquartile range)fall in maximum anal resting pressure.Negative values indicate a rise instead of a fall in the resting anal pressure.*The statistical significance of the fall in maximum anal resting pressure at each time point compared to the maximum anal resting pressure at tϭ0was calculated using Wilcoxon’s signed-rank test.Vol.45,No.10L-ARGININE REDUCES RESTING ANAL PRESSURE1333pressures recorded before topical application of the drug.There were no side effects during the extended study period;in particular,none of the volunteers experienced any headaches.Results After Topical Application ofPlacebo (Aquagel TM )Topical Aquagel caused a fall in MARP from a median of 53(range,29–84cm)H 2O before applica-tion of the drug to a minimal value of 41(range,29–67)cm H 2O.This represented a fall from the maximal value of 23percent.The P value at 60min-utes was not significant (0.6).There were no side effects in any of the volunteers.The difference in the fall in MARPs between L-arginine and placebo using repeated-measures testing was significant at P Ͻparison of maximal fall in MARP in the 11volunteers receiving both L-arginine and placebo by Wilcoxon ’s signed-rank test was highly significant (z ϭϪ2.599;P ϭ0.009).DISCUSSIONThis study had two important findings.First,topical application of a single dose of L-arginine (400mg/ml)to the anal verge causes a significant fall in the MARP.The results on the subset of volunteers involved at one center (Rotterdam,the Netherlands)have been previously reported by the authors.10The fall in MARP was of rapid onset (within 5minutes)and sustained for longer than two hours.The nature of the pressure drop for arginine is thought to be mediatedthrough the action of nitric oxide synthase.The pla-cebo gel caused a smaller,transient,and nonsignifi-cant reduction in MARP which may be related to either the temperature or pH of the gel.This study showed that after single and repeated dosing with topical L-arginine,no side effects were demonstrated in volunteers.Since the effects of L-arginine on sphincter tone is believed to be through the L-arginine –NO pathway,headaches might be ex-pected,as is the case for topical GTN therapy.It is interesting to note that in studies where oral arginine has been given to volunteers and patients in the evaluation of esophageal and gallbladder physiology and interstitial cystitis 11,12(in doses ranging from 1.5g to 30g daily),no headaches were reported.Another explanation may be that L-arginine is working through a different mechanism altogether.If L-arginine can be shown to be free from side effects,especially headaches,this could have impor-tant implications as a potential alternative treatment for anal fissure.It has been suggested that compliance can be an issue in patients prescribed topical GTN;one study showed a compliance rate of only 67per-cent,with the side effect of headaches being a major contributing factor to noncompliance.13The cure rate based on intention to treat may therefore be lower than expected because of patients not adhering to the treatment regime as prescribed;thus,arginine might provide better compliance than GTN.L-arginine serves as the substrate for the enzyme NO synthase (a heme-containing enzyme)to produce citrulline and nitric oxide.In-vitro studies have shown that nitric oxide is the principle inhibitoryneurotrans-Figure 1.Change in mean maximum anal resting pressure after topical L-arginine and placebo gel.P Ͻ0.005on comparison of L-arginine and placebo (repeated-measures testing with General Linear Model).1334GRIFFIN ET AL Dis Colon Rectum,October 2002mitter in nonadrenergic,noncholinergic(NANC)me-diated relaxation of gastrointestinal smooth mus-cle.14–22Using immunocytochemistry,NO synthase has been found in a subpopulation of neurons in the rectal myenteric ganglia in a variety of animal and human tissue.23–25In-vivo studies26,27using low-com-pliance,continuously perfused catheters to measure resting anal pressures in opossums have demon-strated that nitric oxide synthase inhibitor reverses the decrease in baseline pressure in response to either rectal distention or sacral nerve stimulation.The only in-vivo study9investigating the effect of exogenous L-arginine on the internal anal sphincter showed that L-arginine(in concentrations ranging from0.01mg to 10mg),when introduced into the rectum of gently restrained unanesthetized rats,caused a significant reduction in sphincter pressures(PϽ0.05),with higher concentrations of arginine causing a more rapid fall in ARP and the maximal effect being reached at30minutes.CONCLUSIONSThe present study has shown that topical L-arginine has a significant effect on MARP and could have therapeutic potential as a new treatment for anal fis-sures.Its duration of action seems to be similar to topical GTN,but importantly,arginine seems free from side effects.This is an advantage over GTN, where headaches reduce patient compliance.Further pharmacodynamic studies are required to ascertain the duration and mechanism of action of L-arginine on the internal anal sphincter.ACKNOWLEDGMENTThe authors thank Norgine Research Ltd,North-wood,United Kingdom,for providing the L-arginine gel for this study.REFERENCES1.Farouk R,Duthie GS,MacGregor AB,Bartolo DC.Sus-tained internal sphincter hypertonia in patients with chronic anal fissure.Dis Colon Rectum1994;37:424–9.2.Gibbons CP,Read NW.Anal 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MEETINGofThe American Society of Colonand Rectal SurgeonsNew Orleans Hilton RiversideNew Orleans,LouisianaJune21–26,2003Access ASCRS website at 1336GRIFFIN ET AL Dis Colon Rectum,October2002。