Formulation and Evaluation of Floating Microspheres of Captopril - IJPI

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031Formulation and Evaluation of Floating Microspheresof CaptoprilPrasanth V.V 1 , Suman Rawat 2* , Sourav Tribedi 1 , Rinku Mathappan 1 , Sam T Mathew 31 Gautham College of Pharmacy, Sultanpalya, R.T. Nagar, Bangalore- 560032, Karnataka,2 Dept. of Pharmaceutics, Gautham College of Pharmacy, Bangalore- Karnataka,3 Associate Manager, Regulatory affairs and Medical writing, Biocon Pvt Ltd, BangaloreABSTRACTFloating microspheres of Captopril were prepared by Non-aqueous solvent evaporationtechnique using Ethyl cellulose, Eudragit RS-100, Eudragit RL-100 polymers in varyingconcentration. Captopril is an angiotensin converting enzyme inhibitor, widely used inmanagement of hypertension with a short half life of 2hr and oral bioavailability of 70%.Formulations were evaluated for percent yield, particle size, entrapment efficiency, in vitrobuoyancy and in vitro drug release studies. The optimized formulation F3 and F9 complyingwith all evaluations parameters of floating microsphere and found to be satisfactory.Formulations F3 and F9 follows zero order, non fickian diffusion mechanism. Acceleratedstability study was carried out for the optimized formulations F3 and F9 and results showedthat there were no significant changes in percentage drug entrapment efficiency, particle size,percentage buoyancy and in vitro controlled release of Captopril. The surface morphologyanalysis formulations F3 and F9 showed a hollow spherical structure with a smooth surfacemorphology.Keywords: Captopril, Floating microsphere, Floating drug delivery system, Ethyl cellulose,Eudragit RS- 100, Eudragit RL-100.INTRODUCTIONThe oral route is considered as the mostpromising route of drug delivery due to theease of administration, patient complianceand flexibility in formulation [1] . However,this approach has several physiologicaldifficulties such as inability to restrain andlocate the controlled drug delivery systemwithin the desired region of the GIT due tovariable GET and motility. Furthermore,the relatively brief GET in humans whichnormally averages 2-3hr through the majorabsorption zone, i.e, stomach and upperpart of the intestine can result inincomplete drug release from the drugdelivery system leading to reducedefficacy of the administered dose [2] .Gastro retentive dosage form can remain inthe gastric region for several hours and*Corresponding AuthorSuman RawatVolume 3, Issue 2, March − April 201341 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031hence significantly prolong the gastricresidence time of drugs. It is also suitablefor local drug delivery to the stomach andproximal small intestine[3] . Gastroretention helps to provide betteravailability of new products with suitabletherapeutic activity and substantial benefitsfor patients [4] .Gastro retentive floating drug deliverysystem have a bulk density lower than thatof gastric fluids and thus remains buoyantin the stomach without affecting GER for aprolonged period of time [5] . While thesystem is floating on gastric contents, thedrug is released slowly at a desired ratefrom the system. Gastro retentive floatingmicrospheres have emerged as an efficientmeans of enhancing the bioavailability andcontrolled delivery of many drugs.Microsphere are characteristically freeflowing powders consisting of protein orsynthetic polymers, which arebiodegradable and biocompatible in natureand ideally having a particle size less than200µm [6] . Microspheres aremultiparticulate drug delivery systemswhich are prepared to obtain prolonged orcontrolled drug delivery to improvebioavailability, stability and to target thedrug to specific site at a predetermined rate[7] . They are made from polymeric waxy orother protective materials such as natural,semi synthetic and synthetic polymers.Floating microspheres are gastro-retentivedrug delivery systems based on noneffervescentapproach. The floatingmicrospheres have been utilized to obtainprolonged and uniform release in thestomach for development of a once dailyformulation. When microspheres come incontact with gastric fluid the gel formers,Volume 3, Issue 2, March − April 2013polysaccharides, and polymers hydrate toform a colloidal gel barrier that controlsthe rate of fluid penetration into the deviceand consequent drug release [8-9] .Captopril is an orally active inhibitor ofangiotensin converting enzyme and it iswidely used in the treatment ofhypertension and congestive cardiacfailure. The bioavailability of Captopril isapproximately 70% and has relativelyshort half-life of 2hr and requires frequentadministration of dose 25-50 mg, 2 to3times daily. Captopril is freely watersoluble drug and has site specificabsorption from GIT and on other hand,the drug is unstable in the alkaline pH ofthe intestine, where as stable in acidic pHand specifically absorbed from stomach[10] . The main purpose of the present workwas to formulate and evaluate floatingmicrospheres of Captopril to prolongedgastric retention time, improvesbioavailability, reduces drug waste andimproves solubility of drug.MATERIAL AND METHODSCaptopril was obtained as a gift samplefrom Caplin Point Laboratories Ltd,Puducherry, India. Ethyl Cellulose,Eudragit RS100 and Eudragit SL100 wereprocured from S.D Fine Chemicals,Bangalore, India. All other reagents usedwere of analytical grade.MethodsFormulation of floating microspheres ofCaptoprilThe compositions of different floatingmicrospheres of Captopril are shown inTable 1. Microspheres containing antihypertensivedrug as a core material wereprepared by a Non-aqueous Solventevaporation method. The drug and42 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031different ratio of polymers (Ethylcellulose, Eudragit-RL100 and Eudragit-RS 100) were mixed in cooled mixture ofethanol: dichloromethane at roomtemperature (1:1). The slurry was slowlyintroduced into 30ml of liquid paraffinwhile being stirred at 500 rpm by amechanical stirrer equipped with a threebladed propeller at room temperature. Thesolution was stirred for 2hr to allow thesolvent to evaporate completely and themicrospheres were collected by filtration.The microspheres were washed repeatedlywith petroleum ether. Microspheres weredried for 1hr at room temperature andsubsequently stored in a desicator forfurther studies [11] .Table 1. Compositions of various captopril floating microspheresFormulationCodeDrug(mg)EthylCellulose(mg)Eudragit RS100 (mg)Eudragit RL100 (mg)RatioF1 400 400 200 - 2:1F2 400 800 400 - 2:1F3 400 1200 600 - 2:1F4 400 300 300 - 1:1F5 400 600 600 - 1:1F6 400 900 900 - 1:1F7 400 400 - 200 2:1F8 400 800 - 400 2:1F9 400 1200 - 600 2:1F10 400 300 - 300 1:1F11 400 600 - 600 1:1F12 400 900 - 900 1:1EvaluationsPercentage yieldThe prepared microspheres were collectedand weighed. The measured weight wasdivided by the total amount of all nonvolatilecomponents which were used forthe preparation of the microspheres [12] .Wact.% yield = x 100WtWact. = Actual weight of ProductWt = Total weight of excipient & drugParticle size analysisVolume 3, Issue 2, March − April 2013The particle size of the microspheres wasdetermined by using optical microscopymethod. Approximately 10 microsphereswere counted for particle size using acalibrated optical microscope [12] .Drug content and drug entrapmentefficiencyMicrospheres equivalent to 50 mg of thedrug were taken for evaluation. Theamount of drug entrapped was estimatedby crushing the microspheres andextracting with aliquots of 0.1N HClrepeatedly. The extract was transferred to a43 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-103150 mL volumetric flask and the volumewas made up using 0.1N HCl. The solutionwas filtered and the absorbance wasmeasured after suitable dilutionspectrophotometrically at 212 nm againstappropriate blank. The amount of drugentrapped in the microspheres wascalculated by the following formula [12] .Wact.% DEE = x 100WtWact.= Amount of drug actually presentWt =Theoretical drug load expectedIn vitro buoyancyThe in vitro buoyancy was carried outusing simulated gastric fluid USPcontaining 1% Tween 80 as a dispersingmedium. Microspheres were spread overthe surface of 900 mL of dispersingmedium at 37±0.5 o C. A paddle rotating at100 rpm agitated the medium. Eachfraction of microspheres floating on thesurface was collected at a predeterminedtime point (24 hr). The collected sampleswere weighed after drying [13] .W% Buoyancy = x100W Int.W = weight of floating microspheresW Int. = Initial weight of floatingmicrospheresIn vitro drug release studyIn vitro drug release studies were carriedout in USP type II dissolution testapparatus. Microspheres equivalent to 50mg of the pure drug were used fordissolution study. 1 mL of the aliquot waswithdrawn at predetermined intervals andfiltered. The required dilutions were madewith 0.1N HCl (Simulated gastric fluid)and the solution was analyzed for the drugcontent spectrophotometrically at 212nmagainst suitable blank. Equal volume of thedissolution medium was replaced in thevessel after each withdrawal to maintainsink condition. Three trials were carriedout for all formulations. From thispercentage drug release was calculated andplotted against function of time to studythe pattern of drug release. The similarityof dissolution profile of the preparedformulations was compared with that ofthe predicted theoretical value to arrive atthe optimum profile [14-15] .Release kineticsIn order to understand the mechanism andkinetics of drug release, the results of thein vitro drug release study were fitted withvarious kinetic equations namely zeroorder (% drug release vs. time), first order(log% unreleased drug vs. time), andHiguchi matrix (% drug release vs. squareroot of time). In order to define a modelwhich will represent a better fit for theformulation, drug release data furtheranalysed by Peppas equation, Mt/M∞=kt n ,where Mt is the amount of drug released attime t and M∞ is the amount released attime ∞, the Mt/M∞ is the fraction of drugreleased at time t, k is the kinetic constantand n is the diffusion exponent, a measureof the primary mechanism of drug release.Regression co-efficient (r 2 ) values werecalculated for the linear curves obtained byregression analysis of the above plots [16] .Accelerated stability studiesVolume 3, Issue 2, March − April 201344 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031Accelerated stability studies were carriedout on most satisfactory formulation as perICH guidelines Q1A at 40±2 °C (75±5%RH). The most satisfactory formulationstored and sealed in aluminium foil for 90days. After 30, 60 and 90 days interval %drug entrapment efficiency, Particle size,% Buoyancy of most satisfactoryformulation was determined. In vitrorelease study was also carried out of bestformulation [17] .Scanning Electron MicroscopyThe surface morphology of themicrospheres was examined by ScanningElectron Microscopy. The scanningelectron photomicrograph was taken at theacceleration voltage of 20 kV, originalmagnifications × 500.RESULTS AND DISCUSSIONPercentage yield and Particle sizeanalysis of microspheresThe percentage yield and particle size ofmicrosphere of all formulations were in therange of 78.09±2.06% to 95.13±1.37%(Table 2). It was found that whenconcentration of Ethyl cellulose increased,the percentage yields also increased. Theformulation F12 showed maximumpercentage yield of 95.13±1.37% compareto other formulations. The particle size offloating microspheres varied between45±0.05 to 116±0.12 μm. The lowerparticle size obtained when Eudragit RS-100 was used with Ethyl cellulose andhigher particle size was due to EudragitRL-100 with Ethyl cellulose.Drug content and drug entrapmentefficiencyDrug content of the prepared formulationsranged between 39.55±0.99 and 44.95±1.2mg and drug entrapment efficiency variedVolume 3, Issue 2, March − April 2013from 79.10±0.09 to 89.30±0.05% (Table3). This result indicated that, the drugcontent and drug entrapment efficiencyincreased with increasing concentration ofEthyl cellulose with the combination ofEudragit RS-100.In vitro buoyancyPercentage of in vitro buoyancy of variousfloating microspheres formulations areshown in Figure 1. As the amount ofhydrophobic polymer Ethyl cellulose isincreased, the % of buoyancy also found tobe increased. Among all the formulations,F3 batch showed maximum in vitrobuoyancy of 96±0.25 and F10 showedlowest in vitro buoyancy of 85± 0.09.In vitro drug release studyIn vitro drug release of different floatingmicrospheres of captopril is shown inFigure 2. The result of cumulativepercentage drug release of all formulationsF1, F2, F5, F6, F7, F8, F11 and F12 after22hr was found to be 97.60%, 98.52%,97.99%, 95.85%, 99.94%, 98.97%,98.98%, 97.54%) and for F4, F10 after 20hr was found 92.17%, 96.34% and for F3,F9 after 24 hrs was found 99.28%, 99.82%respectively. Drug release study of all theformulations was performed in simulatedgastric fluid (pH 1.2) at 37±0.5 °C. Drugrelease form these microspheres wereslow, extended and dependent on the typeof polymer and concentration of polymerused. When viscosity of polymer increasedin the formulation, the release of drug fromformulation was decreased, this may bedue to increase in strength of gel matrix ofthe polymer. The polymer, Eudragit RS-100 has high viscosity which showed theleast drug release from the microsphere.Thus it would have swell and hold water45 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031inside its microgel network and theseproperties might have retarded the drugrelease. The formulation containingEudragit RS-100 along with increase inEthyl cellulose showed slow and longestrelease and this combination madeformulations more effective. Theformulation prepared with Eudragit RL-100 showed the faster drug release fromthe formulation due to its lower viscosity.Among all the formulations F3, F9,selected as optimized formulations basedon drug entrapment efficiency, in vitrodrug release and buoyancy property.Release kineticsDissolution data of the optimizedformulations (F3 and F9) was subjected toregression analysis and were fitted tokinetic models, visualized Zero order, Firstorder, Higuchi square root andKorsemeyer- peppas (Table 4). The r 2 -value of zero order was found as 0.9958and 0.9964 for F3 and F9 respectively andthe r 2 - value of first order was found as0.6524 and 0.6712 for F3 and F9respectively. This result suggests that thedrug released by zero order for bothformulations. Further to ascertain the exactmechanism of drug release the dissolutiondata of the optimized formulations (F3 andF9) was subjected to Korsemeyers-peppasand Higuchi’s diffusion equation. The r 2value for Korsemeyers-peppas andHiguchi’s diffusion equation for F3 and F9was obtained as 0.9834, 0.9713 and0.9135, 0.9136 respectively. It shows thatthe best fit model for both the formulationis Korsemeyers-peppas model. The slopevalue (n) in Korsemheyers-peppasequation for both the formulations (F3 andF9) got values 0.8386 and 0.7990 whichVolume 3, Issue 2, March − April 2013suggests that release of captopril frommicrospheres followed the non fickiantransport.Accelerated stability studiesThe optimized formulations, F3 and F9was wrapped and sealed in an aluminumfoil. Results of stability studies are shownin Table 5. The % drug entrapmentefficiency, % buoyancy, particle size, Invitro release study of most satisfactoryformulation was determined and resultshowed that there was no significantchanges occurs during storage.Scanning electron microscopyScanning electron microscopy ofoptimized formulation F3 and F9 is shownin Figure 3. The view of the microspheresshowed a hollow spherical structure with asmooth surface morphology. The outersurface of the microspheres was smoothand dense, while the internal surface wasporous. The shell of the microspheres alsoshowed some porous structure.CONCLUSIONFloating microspheres of Captopril wereprepared by Non-aqueous solventevaporation technique. From among all theformulations, F3 and F9 selected as bestformulation, showed no significant changein particle size, percentage drug content, invitro drug release, percentage buoyancyduring and at the end of the acceleratedstability studies. The SEM analysisformulations F3 and F9 showed a hollowspherical structure with a smooth surfacemorphology. The outer surface of themicrospheres was smooth and dense, whilethe internal surface was porous. The shellof the microspheres also showed some46 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031porous structure. From the above study itwas concludes that Captopril can beformulated in the form of floatingmicrospheres using hydrophobic waterimpermeable polymer hydrophobic waterpermeable polymer and in vitro drugrelease studies indicated that it is apotential drug delivery for Captopril.REFERENCES1. Singh BN, Kim KH “Floating DrugDelivery Systems: An Approach ofOral Controlled Drug Delivery viaGastric Retention” Journal ofControlled Release. 2000;63:235-59.2. Rouge N, Buri P, Doelker E. Drugabsorption sites in thegastrointestinal tract and Dosageforms for site specific delivery. Int.J. Pharm. 199;136:117-39.3. Ali J, Arora S, Khar RK. Floatingdrug delivery System. A Review.AAPS Pharm Sci Tech.2005;06:E372-E390.4. Deshpande AA, Shah NH, RhodesCT, Malick W. Development of anovel controlled-release system forgastric retention. Pharm Res.1997;14:815-19.5. Singh BN, Kim KH. Floating drugdelivery systems: an approach tooral controlled drug delivery viagastric retention. J. ControlRelease. 2000;63:235-39.6. Vyas SP, Khar. “Targeted andControlled Drug Delivery NovelCarrier System”. 1 st ed. CBSPublishersn and Distributors, NewDelhi. 2002;417-54.7. Gholap SB, Banarjee SK,Gaikwad DD, Jadhav SL, ThoratVolume 3, Issue 2, March − April 2013RM. Hollow microsphere: areview. 2010; 1:1-15.8. Shivkumar HG, Vishakanta GD,PramodKumar TM. Formulationand evaluation of mucoadhesivedrug delivery system for some antiasthmaticdrugs. IJPE 2004;38:22-26.9. Sweetman SC. Martindale, Thecomplete drug reference 33 rd ed.Pharmaceutical press. 2002.10. Oates JA. Antihypertensive agentsand the therapy of hypertension.In.Hardman JG, Limbard LE,Molinoff PB, Ruddon RW GilmanAG, editors. Goodman andGilman’s the pharmacologicalbasis of therapeutics. 9 th ed. NewYork: McGraw Hill. 1996;781.11. Jain SK, Awasthi AM, Jain NK,Agrawal GP. Calcium silicatebased microsphere ofrepaglinide for gastroretentivedrug delivery system:Preparation and in-vitrocharacterization. J Control Rel.2005;107:300-09.12. Joseph NJ, Lakshmi S,Jayakrishnan. A floating typeoral dosage form for piroxicambased on hollow polycarbonatemicrospheres: In-vitro and invivoevaluation in rabbits. JControl Rel. 2005;71-79.13. Iannuccelli V, Coppi G,Bernabei MT, Cameroni R. Aircompartment multiple unitsystem for prolonged residence.Part I. formulation study. Int JPharm 1998;174:47-54.47 | P a g ehttp://www.ijpi.org

INTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-103114. Costa P, Modeling andcomparision of dissolutionprofile. Eur J Pharm Sci.2001;13:123-33.15. Patel Asha, Ray Subhabrata,Thakur Ram, In-vitro evaluationand optimization of controlledrelease floating drug deliverysystem of Metforminhydrochloride. DARU.2006;14:57-64.16. Yadav KS, Satish CS, ShivkumarHG. Preparation and evaluation ofchitosan-Poly (Acrylic acid)Hydrogels as Stomach specificdelivery for amoxicillin andMetronidazole. Indian J.Pharm Sci.2007;69:91-95.17. Note for guidance on stabilitytesting. Stability testing of newdrug substances and products 2003.Available from URL:http://www.tga.gov (Cited 12 NOV2012).Table 2. Percentage yield of floating microspheres of CaptoprilFormulation code Percentage yield* (%) Particle size* (µm)F1 86.25± 1.21 97 ± 0.53F2 88.29 ± 1.30 70 ± 0.79F3 94.88 ± 1.31 110.± 0.25F4 79.24 ± 1.24 93 ± 0.24F5 86.78 ± 1.56 64± 0.78F6 95.13 ± 1.37 45 ± 0.05F7 84.15 ± 1.87 82 ± 0.15F8 86.96 ± 1.09 106 ± 0.95F9 93.15± 2.10 116 ± 0.12F10 78.09 ± 2.06 93 ± 0.09F11 85.10 ± 2.54 106 ± 0.4F12 92.50 ± 1.01 108 ± 0.49Volume 3, Issue 2, March − April 201348 | P a g ehttp://www.ijpi.org

Percentage BuoyancyINTERNATIONAL JOURNAL OFRESEARCH ARTICLEPHARMACEUTICAL INNOVATIONS ISSN 2249-1031Table 3. Drug content and drug entrapment efficiency of all formulationsFormulation code Drug content* (mg ) Drug entrapment efficiency*(%)F1 42.20 ± 0.40 84.40 ± 0.7F2 43.70 ± 1.05 87.40 ± 0.01F3 44.95 ± 1.2 89.30 ± 0.05F4 40.55 ± 0.79 81.10 ± 0.01F5 41.10 ± 1.09 82.20 ± 1.03F6 43.60 ± 1.8 87.20 ± 0.05F7 42.55 ± 1.47 85.10 ± 1.04F8 39.55± 0.99 79.10 ± 0.09F9 44.10 ± 1.06 88.20 ± 1.2F10 41.35 ± 0.56 82.70 ± 0.09F11 41.60 ± 1.90 83.20 ± 1.21F12 43.45 ± 0.23 86.90 ± 0.77* Average of three determinations9896949290888684828078Formulation codeF1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12Figure 1. In vitro buoyancy of different floating microspheres of captoprilVolume 3, Issue 2, March − April 201349 | P a g ehttp://www.ijpi.org