药物由骨架型透皮给药装置中扩散-溶出控释的简单表达式郑俊民,杨丽,何友清沈阳药科大学药剂 教研室沈阳110015摘要Chandrasekran-paul(1982)对药物由骨架 系统中的释放,提出下列表达式:本文在常见的实验时间及适当的K值范围内对上式作了简化,药 物释放的累积量与时间的平方根直接成比例,但方程中带有一截距项,即,硝苯地平贴剂及普萘洛 尔贴剂二者的释放行为都符合上述方程,其相关系数良好。氢化可的松乳膏的释放数据(据Sha h,1989),也可用相同的方程来描述。该方程与Higuchi方程相比较,多出一个截距 项,这可能与药物溶出特性有关。关键词Higuchi方程,Chandrasekran-P aul方程,药物由透皮给药装置骨架中的释放ASimplifiedExpressionf oraDiffusion-DissolutionCon-trolledReleaseo fDrugfromMatrixinTDDSJun-MinZheng,LiYangand You-QingHeDepartmentofPharmaceulics,Shenyan gPharmaceuticalUniversity,Shenyang110015Rec eivedDecember8,1993,AcceptedSeptember5,1994 AbstractChandrasekran-paul(1982)madeanequat ionofdrugreleasefrommatrixsystemasfollows:I nthispaperasimplifiedexpressionhasbeendeduc edfromitwithinordinaryrangeofexperimentalti meandwithappropriatevaluesofK.Thecumulative amountofdrugreleasemayvaryindirectproportio ntothesquarerootoftimewithanintercept,thati s,Thereleasebehaviourofbothnifedipinepatcha ndpropranololpatchhasfittheexpressionwithgo odcorrelationcoefficient.There0leasedataofh ydrocortisonecreams(Shah,1989)alsocanbedesc ribedbythesameexpression.ComparedwithHiguch i’sequation,thepresenceof theintercept,A〃,m ayberelativetodrugdissolutioncharacteristic s.KeywordsHiguchi’sequation;Chandrasekran-p aul’sequation;DrugreleasefrommatrixinTDDSTr ansdermaldeliveryhasbecomeanimportantmeanso fdrugadministration.Themechanismsofdrugrele asefromthematrixinTDDShavebeenputforthinman ypapers.Intheearly1960’s,thetheoryofdiffusi onreleaseofsoluteordrugfromasuspensionwasin itiallyproposedbyTHiguchi ̄(1).Ithasbeenappl iedextensivelyinthepharmaceuticalfieldwithf avorableresultsformanyyears.Butthereareseve ralcaseswhicharenotadequatelydescribedbythe model ̄(2,3).In1982,ChandrasekaranandPaul(C- P)presentedadissolutioncontrolledtransportm odelfromthedispersedmatrixtocombinethedisso lutionanddiffusionmechanisms ̄(4),itisveryfl exibletoapplytoeitherofthecontrolledmechani sms.TheC-P’sEquationreadslikethis:Thepurpos eofthispaperistomodifytheC-P’s equationinas impleway.DeductionoftheEquationReplacetheco ntentoftheparenthesesinequation(1)byY:Becau seM_tisanumberofthedrugquantiy(μg/cm ̄2),wec anbesurethattheYisapurenumberfromequation(1 ).Suppose t=1,2,4,6,8,11,14 or 24andsubstit utethemintoequation(2)andcal-culatethevalue sofYwithdifferentvaluesof K,wecanfind:Itisc orrectatK=0.1,0.09,0.08,…0.01.Thecalculatio nindetailisgivenintheap-pendix.Substituteeq uation(3)intoequation(1),wehavetheformof eq uation(4)justliketheHiguchi’sequation,butwi thanintercept. ExperimentsReleaseratedeterm ination ̄(5,6)Thepatchesofnifedipineandpropr a-nololbothweremadeofpolyacrylateadhe-sivea sreservoirandpreparedbyasolventcastingproce dure.Itcontainedabackingmembrane,aprotectiv elayerandareservoirinwhichthedrugwasdispers edordis-solved.Theprofilesofthedrugreleasea safunctionoftimeweredeterminedbyHPLCmethodu singsimplifiedFranzdiffusioncell.ResultsThe invitrodrugreleaseamounts(μg/cm ̄2)versusthe squarerootoftimeprofilesfortwokindsofpatche sareshowninthefollowingfigures(Fig1~2).Itca nbeseenthatthecumulativeamountsofdrugreleas evariedindirectproportiontothesquarerootoft imewithanintercept.Wehavetheapparentexpress ionof NifedipinePatchas:and thatofPropranol olPatchas:wecanalsodescribethemasM_t=B〃t-A〃 .ResultsandDiscussionTheC-P’sequationisbase donverygoodconsiderationofdiffusionanddisso lu-tioncontrolleddeliverymechanismwithaprec isemathematicalthermodynamicme-thod,butitis stillmorecomplexandneedstomakecomplicateope rations.Inordertoobtainthegeneralsolution,a dissolutionrateconstant,K,andadiffusioncoef ficient,D,mustbegivenandthequantitativetest ofthoseparametershassomedifficultiesinor-di narypharmaceuticallaboratories.Accord-ingto theabovededuction,undersomecon-straintcondi tions,i.e.,limitingthevalueofK andtinthegiv enrange,wecouldsimplifytheC-P’sequationinth esameformasthatofHiguchi’sequationbutwithan intercept.Inourexperimentalresultsaboveandm anypapersfromotherauthors,theinter-ceptexis tsinmostcases.In1989,Shahetalreportedasetofdatafromtwohydrocorti-sonecreams ̄(7).Whentheydeterminedthere-leaseprofile,theyusedarelativelyperme-ablemembranebetweentheformulat
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