it is predicted to affect more than 115 million people globally by 2050.3 it is a progressive , neurodegenerative disorder that is usually diagnosed in people over 65 years of age.4 donepezil is a reversible acetylcholinesterase inhibitor that has been approved for use for ad .
it is believed to inhibit the breakdown of the neurotransmitter acetylcholine and compensate for the deficiency of acetylcholine in brain.5,6 in previous clinical trials , it has been shown to improve cognitive function in patients for a wide range of ad severity , from very mild to moderate - to - severe.711 the most common adverse events ( aes ) with donepezil , as well as with other cholinesterase inhibitors , are nausea , vomiting , diarrhea , and dizziness , all of which are symptoms linked to cholinergic hyperstimulation.12,13 these effects are dose - related and largely depend on the plasma fluctuations.14 when donepezil is orally administered , it is well absorbed and reaches peak plasma concentrations ( cmax ) in 34 hours.15 the plasma concentration of donepezil then decreases until the next dose is administered.16 by reducing cmax and slowing the time that it takes to reach cmax ( tmax ) , the potential for these aes may be attenuated .
the advantages of transdermal drug delivery for ad have already been reported : reduced dosing frequency , improved bioavailability , reduced side effects , and improved patient compliance due to simple application.1719 for this reason , rivastigmine , one of the acetylcholinesterase inhibitors , has already been developed as a transdermal patch.16,20,21 the transdermal donepezil patch was also developed for the advantage of providing smooth and steady delivery of donepezil through the skin ; a transdermal patch would decrease cmax and lengthen tmax while maintaining drug exposure.17 according to in vivo studies , when transdermal donepezil ( 40 mg / kg , 2.14 cm ) was applied to the abdominal skin of male sprague - dawley rats , the cmax at steady state ( 52.2 ng / ml ) was maintained for 48 hours with the donepezil formulation using oleic acid.22 the company icure pharmaceutical lncorporated ( anseong , gyeonggi - do , republic of korea ) , which manufactures the donepezil patch that was used in this study , also conducted in vivo studies to evaluate pharmacokinetics .
when a single dose of 5 mg / kg oral solution was administered to hairless wistar yagi rats , the cmax was 41.4 ng / ml with a tmax of 1 hour .
when 8.75 mg/2.5 cm , 17.5 mg/5 cm , and 35 mg/10 cm donepezil patches were applied to hairless wistar yagi rats , the cmax values were dose - proportional ( 36.5 ng / ml , 64.4 ng / ml , and 129.1 ng / ml , respectively ) with tmax values of 2436 hours.23 the aim of this randomized , single - blind , placebo - controlled , single - dose , dose - escalation study was to investigate the tolerability and the pharmacokinetics of the novel donepezil patch in healthy male subjects .
each healthy male volunteer who was 2045 years of age and had a body mass index ( bmi ) of 2026 kg / m was eligible for this study .
volunteers were considered to be in good health on the basis of these criteria , which were assessed within the 4 weeks prior to the first administration of the study drug : medical history ; physical examinations ; vital sign measurements ( blood pressure , heart rate , and body temperature ) ; 12-lead electrocardiograms ( ecgs ) ; clinical laboratory tests ( hematology , blood chemistry , and urinalysis ) ; serology ( hepatitis b surface antigen , hepatitis c virus antibody , and hiv antigen / antibody ) ; and urine drug screening ( amphetamine , methamphetamine , barbiturate , cocaine , opiate , benzodiazepine , cannabinoid , and methadone ) . each subject with a known allergy or hypersensitivity to donepezil or with a history of drug abuse
the study protocol was approved by the ministry of food and drug safety ( mfds ) and the institutional review board of the asan medical center ( amc ) , seoul , republic of korea .
the study was conducted at the clinical trial center of the amc from may 2013 to september 2013 .
all subjects provided written informed consent before screening tests , and this study was conducted in accordance with the declaration of helsinki and international conference of harmonization ( ich ) guidelines for good clinical practice .
this study was designed as a randomized , single - blind , placebo controlled , dose - escalation study . in this study , a 3.5 mg / cm
donepezil patch was applied as a single dose of 43.75 mg/12.5 cm , 87.5 mg/25 cm , or 175 mg/50 cm .
there were 12 subjects per group , nine of whom were given active patches and three of whom were given placebos .
the subjects were admitted to the hospital on the day before drug administration . on the morning of day 1 , each subject received a single application to the upper back with a patch - on period of 72 hours .
all subjects were discharged on day 5 ( 24 hours after patch removal ) , and they revisited the hospital on days 6 , 7 , 8 , 10 , 12 , and 14 to assess the tolerability and the pharmacokinetics of donepezil .
follow - up visits were performed 1822 days after the patch application . for pharmacokinetic analysis ,
sequential blood samples were collected prior to and at 4 , 8 , 12 , 24 , 48 , 70 , 72 , 74 , 76 , 80 , 96 , 120 , 144 , 168 , 216 , 264 , and 312 hours after patch administration .
all blood samples for the determination of donepezil concentrations were drawn into heparinized tubes and separated by centrifugation at 1,800 g for 8 minutes at 4c and stored at 70c until analysis .
the adhesive properties of each patch were evaluated every 12 hours ( within approximately 30 minutes ) from time 0 ( the time of adhesion ) through 72 hours ( before patch removal ) after the application of donepezil patch .
the adhesiveness of patch was graded according to the criteria in table 1.24 tolerability was assessed throughout the study by using vital sign measurements ; ecgs ; clinical laboratory tests ( hematology , blood chemistry , and urinalysis ) ; physical examinations ; and monitoring of aes .
aes were recorded in terms of symptoms and signs , duration , intensity , relationship to the study drug , action taken , outcome , and seriousness .
assessment of skin irritation was performed immediately after the removal of the patch ( 72 hours ) as well as 1 , 12 , and 24 hours after patch removal ( at 73 , 84 , and 96 hours after patch application , respectively ) by using a skin irritation scoring system ( table 1).24 after the subject was discharged , the skin irritation score was assessed at every outpatient visit until that subject experienced an irritation score of 0 .
plasma concentrations of donepezil were determined by using validated high performance liquid chromatography ( hplc ) coupled with tandem mass spectrometry .
the sample extracts were analyzed by using hplc ( nonospace si-2 3133 ; shiseido , tokyo , japan ) and an unison uk - c18 column ( 3.0 m , 50 mm * 2.0 mm ; imtakt , kyoto , japan ) with a mobile phase consisting of ammonium formate with 0.1% formic acid and acetonitrile with 0.1% formic acid ( 40:60 , v / v ) . the ms system ( api-4000 ; ab sciex , framingham , ma , usa ) was operated in positive ion electrospray mode with multiple reaction monitoring . for donepezil and the internal standard , the precursor - to - production reactions that were monitored were mass - to - charge ratios ( m / z ) , 380.391.1 and 256.2167.1 , respectively .
calibration curves covered the concentration range of 0.180 ng / ml ( r>0.99 ) . by using this assay ,
interday accuracy ranged from 96.27% to 105.98% , and interday precision , expressed as percent coefficient of variation ( % cv ) , ranged from 0.7% to 4.3% .
in addition , intraday accuracy and precision ( % cv ) ranged from 97.23% to 104.92% and from 1.4% to 5.3% , respectively .
 time profiles of donepezil in the subjects were analyzed by using a noncompartmental method and winnonlin 6.1 ( pharsight corporation , princeton , nj , usa ) .
the terminal elimination rate constant ( z ) was estimated by linear regression of the terminal log - linear portion of the plasma concentration  time curves .
concentration curve ( auc ) from time 0 to the last measurable time ( auclast ) was calculated by the trapezoidal rule , and the auc extrapolated to infinity ( aucinf ) was obtained as follows : 
 aucinf = auclast+clast/z(1)for which clast is the last quantifiable concentration .
the t1/2 was calculated for each participant as follows : 
 t1/2=ln(2)/z(2 ) all statistical analyses were performed by using sas 9.3 ( sas korea , seoul , republic of korea ) and phoenix winnonlin 6.1 ( pharsight corporation ) .
each healthy male volunteer who was 2045 years of age and had a body mass index ( bmi ) of 2026 kg / m was eligible for this study .
volunteers were considered to be in good health on the basis of these criteria , which were assessed within the 4 weeks prior to the first administration of the study drug : medical history ; physical examinations ; vital sign measurements ( blood pressure , heart rate , and body temperature ) ; 12-lead electrocardiograms ( ecgs ) ; clinical laboratory tests ( hematology , blood chemistry , and urinalysis ) ; serology ( hepatitis b surface antigen , hepatitis c virus antibody , and hiv antigen / antibody ) ; and urine drug screening ( amphetamine , methamphetamine , barbiturate , cocaine , opiate , benzodiazepine , cannabinoid , and methadone ) . each subject with a known allergy or hypersensitivity to donepezil or with a history of drug abuse
the study protocol was approved by the ministry of food and drug safety ( mfds ) and the institutional review board of the asan medical center ( amc ) , seoul , republic of korea .
the study was conducted at the clinical trial center of the amc from may 2013 to september 2013 .
all subjects provided written informed consent before screening tests , and this study was conducted in accordance with the declaration of helsinki and international conference of harmonization ( ich ) guidelines for good clinical practice .
this study was designed as a randomized , single - blind , placebo controlled , dose - escalation study . in this study ,
a 3.5 mg / cm donepezil patch was applied as a single dose of 43.75 mg/12.5 cm , 87.5 mg/25 cm , or 175 mg/50 cm .
there were 12 subjects per group , nine of whom were given active patches and three of whom were given placebos .
the subjects were admitted to the hospital on the day before drug administration . on the morning of day 1 , each subject received a single application to the upper back with a patch - on period of 72 hours .
all subjects were discharged on day 5 ( 24 hours after patch removal ) , and they revisited the hospital on days 6 , 7 , 8 , 10 , 12 , and 14 to assess the tolerability and the pharmacokinetics of donepezil .
follow - up visits were performed 1822 days after the patch application . for pharmacokinetic analysis ,
sequential blood samples were collected prior to and at 4 , 8 , 12 , 24 , 48 , 70 , 72 , 74 , 76 , 80 , 96 , 120 , 144 , 168 , 216 , 264 , and 312 hours after patch administration .
all blood samples for the determination of donepezil concentrations were drawn into heparinized tubes and separated by centrifugation at 1,800 g for 8 minutes at 4c and stored at 70c until analysis .
the adhesive properties of each patch were evaluated every 12 hours ( within approximately 30 minutes ) from time 0 ( the time of adhesion ) through 72 hours ( before patch removal ) after the application of donepezil patch .
tolerability was assessed throughout the study by using vital sign measurements ; ecgs ; clinical laboratory tests ( hematology , blood chemistry , and urinalysis ) ; physical examinations ; and monitoring of aes .
aes were recorded in terms of symptoms and signs , duration , intensity , relationship to the study drug , action taken , outcome , and seriousness .
assessment of skin irritation was performed immediately after the removal of the patch ( 72 hours ) as well as 1 , 12 , and 24 hours after patch removal ( at 73 , 84 , and 96 hours after patch application , respectively ) by using a skin irritation scoring system ( table 1).24 after the subject was discharged , the skin irritation score was assessed at every outpatient visit until that subject experienced an irritation score of 0 .
plasma concentrations of donepezil were determined by using validated high performance liquid chromatography ( hplc ) coupled with tandem mass spectrometry .
the sample extracts were analyzed by using hplc ( nonospace si-2 3133 ; shiseido , tokyo , japan ) and an unison uk - c18 column ( 3.0 m , 50 mm * 2.0 mm ; imtakt , kyoto , japan ) with a mobile phase consisting of ammonium formate with 0.1% formic acid and acetonitrile with 0.1% formic acid ( 40:60 , v / v ) .
the ms system ( api-4000 ; ab sciex , framingham , ma , usa ) was operated in positive ion electrospray mode with multiple reaction monitoring . for donepezil and the internal standard , the precursor - to - production reactions that were monitored were mass - to - charge ratios ( m / z ) , 380.391.1 and 256.2167.1 , respectively .
calibration curves covered the concentration range of 0.180 ng / ml ( r>0.99 ) . by using this assay ,
interday accuracy ranged from 96.27% to 105.98% , and interday precision , expressed as percent coefficient of variation ( % cv ) , ranged from 0.7% to 4.3% .
in addition , intraday accuracy and precision ( % cv ) ranged from 97.23% to 104.92% and from 1.4% to 5.3% , respectively .
the plasma concentration  time profiles of donepezil in the subjects were analyzed by using a noncompartmental method and winnonlin 6.1 ( pharsight corporation , princeton , nj , usa ) .
the terminal elimination rate constant ( z ) was estimated by linear regression of the terminal log - linear portion of the plasma concentration  time curves .
concentration curve ( auc ) from time 0 to the last measurable time ( auclast ) was calculated by the trapezoidal rule , and the auc extrapolated to infinity ( aucinf ) was obtained as follows : 
 aucinf = auclast+clast/z(1)for which clast is the last quantifiable concentration .
the t1/2 was calculated for each participant as follows : 
 t1/2=ln(2)/z(2 ) all statistical analyses were performed by using sas 9.3 ( sas korea , seoul , republic of korea ) and phoenix winnonlin 6.1 ( pharsight corporation ) .
a total of 36 healthy korean volunteers were enrolled , and 36 subjects were administered the study drugs and completed the study . expressed as mean  standard deviation , the mean characteristics of the study participants were as follows : the mean age was 27.654.54 years ; the mean weight was 67.067.76 kg ; and the mean height was 173.794.87 cm . the mean plasma concentration 
after the application of the donepezil patch , serum donepezil concentration increased slowly and peaked between ~7476 hours ( ~24 hours after patch removal ) and declined with a t1/2 of ~63.7794.07 hours ( table 2 ) . in this study ,
the dose - normalized cmax and aucinf values were not statistically significant ( p=0.5986 and p=0.3392 , respectively ) .
after patch application , the cmax and aucinf increased in a dose - proportional manner ( figure 2 ) .
only one subject reported that the  patch detached  ; this happened more than 61 hours after patch application ( table 3 ) .
the values for average donepezil residue ( residual dose / loading dose * 100 [ % ] ) in the patch 72 hours after application were as follows : 81.1%3.2% for the 43.75 mg/12.5 cm group , 80.4%4.4% for the 87.5 mg/25 cm group , and 78.4%2.5% for the 175 mg/50 cm group .
included in the tolerability analysis were 36 subjects , all of whom applied donepezil patch .
eleven subjects experienced a total of 14 aes , among which ten events in seven subjects were considered  possibly related  to the study drug ( table 4 ) .
all aes were mild except for one case of hypertriglyceridemia in the 43.75 mg/12.5 cm group .
an increase in triglycerides ( 1,318 mg / dl ) without any symptoms was observed at the follow - up visit , and the decreased level was checked on subsequent visit .
two application - site aes included skin discoloration and papules ; both were resolved without sequelae .
likewise , there were no clinically significant abnormalities in vital signs , physical examinations , or electrocardiograms .
the distributions of individual skin irritation scores after patch removal are shown in figure 3 . immediately after patch removal ( 72 hours after application ) ,
most of the subjects experienced irritation scores of 1 ( minimal erythema ) . all subjects experienced irritation scores of 0 ( no evidence of irritation ) by the day 12 outpatient visit ( approximately 264 hours after patch application ) .
irritation scores of 4 , 5 , 6 , or 7 were not observed during the entire study .
a total of 36 healthy korean volunteers were enrolled , and 36 subjects were administered the study drugs and completed the study . expressed as mean  standard deviation , the mean characteristics of the study participants were as follows : the mean age was 27.654.54 years ; the mean weight was 67.067.76 kg ; and the mean height was 173.794.87 cm .
the mean plasma concentration  time profiles of donepezil are shown in figure 1 . after the application of the donepezil patch , serum donepezil concentration increased slowly and peaked between ~7476 hours ( ~24 hours after patch removal ) and declined with a t1/2 of ~63.7794.07 hours ( table 2 ) . in this study ,
the dose - normalized cmax and aucinf values were not statistically significant ( p=0.5986 and p=0.3392 , respectively ) .
after patch application , the cmax and aucinf increased in a dose - proportional manner ( figure 2 ) .
only one subject reported that the  patch detached  ; this happened more than 61 hours after patch application ( table 3 ) .
the values for average donepezil residue ( residual dose / loading dose * 100 [ % ] ) in the patch 72 hours after application were as follows : 81.1%3.2% for the 43.75 mg/12.5 cm group , 80.4%4.4% for the 87.5 mg/25 cm group , and 78.4%2.5% for the 175 mg/50 cm group .
included in the tolerability analysis were 36 subjects , all of whom applied donepezil patch .
eleven subjects experienced a total of 14 aes , among which ten events in seven subjects were considered 
all aes were mild except for one case of hypertriglyceridemia in the 43.75 mg/12.5 cm group .
an increase in triglycerides ( 1,318 mg / dl ) without any symptoms was observed at the follow - up visit , and the decreased level was checked on subsequent visit .
two application - site aes included skin discoloration and papules ; both were resolved without sequelae .
likewise , there were no clinically significant abnormalities in vital signs , physical examinations , or electrocardiograms .
the distributions of individual skin irritation scores after patch removal are shown in figure 3 . immediately after patch removal ( 72 hours after application ) ,
all subjects experienced irritation scores of 0 ( no evidence of irritation ) by the day 12 outpatient visit ( approximately 264 hours after patch application ) .
irritation scores of 4 , 5 , 6 , or 7 were not observed during the entire study .
to our knowledge , this is the first published study to investigate the tolerability and pharmacokinetics of the donepezil patch in healthy subjects . after application ,
the donepezil patch provided a smooth and sustained plasma concentration  time profile over the entire patch - on period of 72 hours . for the highest dose of donepezil ( 175 mg/50 cm ) administered in this study , about 20% of the dose ( approximately 35 mg )
was released from the patch over the 72-hour application . as per the clinical pharmacology and biopharmaceutics review ,
the pharmacokinetic profile of 10 mg single - dose oral donepezil was reported to produce an aucinf of 885.30249.10 ng / ml and a cmax of 20.905.00 ng / ml.25 systemic exposure ( aucinf ) after a 72-hour application of 175 mg/50 cm was about three times higher than after the single dose of a 10 mg oral tablet , while the cmax with the patch was similar to the cmax with a 10 mg dose of oral donepezil .
thus , this transdermal dose ( about 35 mg/72 hours ) is expected to produce exposure ( auc ) similar to 3 days of 10 mg oral donepezil but with a lower cmax . in the 43.75 mg/12.5 cm group ,
the % cv of aucinf was larger than in the other treatment groups ( 58.6% in the 43.75 mg/12.5 cm group , 24.5% in the 87.5 mg/25 cm group , and 32.2% in the 175 mg/50 cm group ) .
of the nine subjects in the group , two showed lower clearances ( 28.1 and 28.7 l / hour ) than average ( 72.3 l / hour ) , so the aucinf of each of these subjects was higher ( 1556.5 ngh / ml and 1526.8 ngh / ml , respectively ) than average aucinf ( 808.5 ngh / ml ) .
although we did not evaluate the different genotypes , the difference between cyp2d6 could have been one of the reasons for the large interindividual variability . in a recent population pharmacokinetic study in which donepezil clearance was evaluated in cyp2d6 genotypes ,
cyp2d6-poor metabolizers demonstrated a 32% lower clearance than did cyp2d6-extensive metabolizers.26 the disadvantages of transdermal delivery include skin irritation and imperfect adhesion to the skin.19 in this study , the results for skin irritation indicate that the skin reactions to the study drug were mild .
the highest score was 3 ( erythema and papules ) ; this was seen in two subjects , and the condition was resolved to 0 ( no evidence of irritation ) within 8 days .
except for one subject , the individual adhesion scores ranged between 0 ( 90% adherence ) and 2 ( adherence of 50% to < 75% ) for 72 hours .
first , these results were obtained from healthy male subjects ; the tolerability and pharmacokinetics of donepezil patch may differ in female or elderly ad patients .
second , donepezil accumulated in plasma by four to seven - fold until the steady state ; further evaluation and comparison of the steady - state pharmacokinetics of the donepezil patch is needed.27 on the basis of the findings of this study , the investigation of multiple doses in healthy volunteers or elderly ad patients may be helpful to evaluate steady - state pharmacokinetics and to prove the optimal way to treat ad with donepezil .
this study represents the first assessment of a single - dose donepezil patch in human subjects .
 backgrounddonepezil is an acetylcholinesterase inhibitor indicated for alzheimer s disease . 
 the aim of this randomized , single - blind , placebo - controlled , single - dose , dose - escalation study was to investigate the safety , tolerability , and pharmacokinetics of the donepezil patch in healthy male subjects.methodseach healthy male subject received a single transdermal donepezil patch ( 72 hours patch - on periods ) of 43.75 mg/12.5 cm2 , 87.5 mg/25 cm2 , or 175 mg/50 cm2 . 
 serial blood samples were collected up to 312 hours after patch application . 
 the plasma concentrations of donepezil were determined by using a validated liquid chromatography  tandem mass spectrometry method . 
 pharmacokinetic parameters were obtained by noncompartmental analysis . 
 tolerability of the patches and performance of the patches ( adhesion , skin irritation , residual donepezil content in the patch ) were assessed throughout the study.resultsthe study was completed by 36 healthy subjects . after patch application , the maximal plasma donepezil concentration ( cmax ) and 
 the area under the curve ( auc ) increased in a dose - proportional manner . 
 median time to cmax was ~7476 hours ( ~24 hours after patch removal ) , and mean t1/2 was ~63.7793.07 hours . 
 the average donepezil residue in the patch after 72 hours was ~73.9%86.7% of the loading dose . 
 there were neither serious adverse events nor adverse events that lead to discontinuation . 
 skin adhesion of the patch was good in 97.2% of the subjects . 
 all skin irritations after patch removal were mild and were resolved during the study period.conclusionthe donepezil patch appeared to be generally well tolerated and adhesive . 
 pharmacokinetic analysis of the donepezil patch demonstrated linear kinetics . 
Introduction
Materials and methods
Subjects
Study design
Tolerability
Determination of donepezil concentrations
Pharmacokinetic assessment and statistical analysis
Results
Study participants
Pharmacokinetic analysis
Tolerability
Discussion
Conclusion