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A Novel Gastro-Retentive Floating Microsphere of Gabapentin

M. Pharm*¹, S. Kalaiyarasan², P. Jothi Mani³, S. Jothi⁴

1. Assistant Professor of Sri Vijay Vidyalaya College of Pharmacy, Nallampalli, Dharmapuri. 2, 3, 4 . B. Pharm student of Sri Vijay Vidyalaya College of Pharmacy, Nallampalli, Dharmapuri.

ABSTRACT- Gabapentin is a widely used antiepileptic and neuropathic pain drug that exhibits absorption mainly in the upper gastrointestinal tract and has a short biological half-life, which limits its oral bioavailability. To present research aimed at developing a novel gastro-retentive microsphere system gabapentin design to prolong gastric residence attain prolong sustained drug diffusion Floating microcapsule were formulated prepared utilizing sodium alginate and ethyl cellulose as polymeric carriers by the ionotropic gelation technique mediated by calcium chloride. The developed formulations were systematically evaluated for particle size distribution, surface morphology, drug loading, encapsulation efficiency, in vitro buoyancy, and in vitro drug dissolution behavior. FTIR analysis verified the absence of significant drug–polymer interaction, suggesting compatibility between gabapentin and selected excipients. The optimized formulation demonstrated good floating ability with prolonged buoyancy and sustained drug release over an extended period. In Vitro release studies demonstrated a controlled release pattern suitable for gastro-retentive delivery. Overall, the developed gastro-retentive floating microspheres of gabapentin may represent a promising approach to improve therapeutic efficacy, reduce dosing frequency, and enhance patient compliance in the management of neuropathic pain and epilepsy.

KEY WORDS: Gabapentin,gastro-retentivedrugdeliverysystem,floatingmicrospheres,sodiumalginate,ethylcellulose, sustainedrelease.

I. INTRODUCTION:

Microspheresaresmallsphericalparticlesdesignedfordrugdeliverywithdiametersintherangeof1-1000micrometers. Microspheres are also known as microparticles. They consist of microcrystalline structures or are used to encapsulate medicinal compounds in various formulations. Microspheres are designed to be synthesizedfrom a wide range of biopolymersandsyntheticpolymers.Theroleofmicrospheresiscrucial.Improvetheabsorptionoftraditionalmedicines and minimize side effects. Microcapsules are spherical, freely circulating particles made up of naturally biodegradable macromolecules.

Microspheres can be classified into two main types:

 Micrometrics:Inthesetheactivesubstanceisuniformlydispersedthroughoutthepolymermatrix.

 Microcapsules:Theseconsistofacorematerialenclosedwithinawell-definedcapsulewall.

FLOATING MICROSPHERES:

Floatingmicrospheresareatypeofdrugdeliverysystemthathasabulkdensitylowerthangastricfluid,allowingthemto remainbuoyantinthestomach regardlessofthestomachemptyingrate.Whilefloatingisatypeofdrugdeliverysystem, they release the drug for a prolonged period of gastric fluid, minimizing side effects, increasing the bioavailability, and therebyprovidingasustainedtherapeuticeffect.Whilefloatingonthestomachcontents,thedrugisreleasedgraduallyat a controlled rate, which prolongs gastric residence time and stabilizes plasma drug concentration. Thereby providing a sustainedtherapeuticeffect.

Fig 01: Floating Microspheres

Gunamathi,

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Gabapentinisananticonvulsantdrugusedprimarilytohelpcontrolacertaintypeofseizureinpeoplewithepilepsyandto treat nerve pain (neuropathic pain). The gabapentin mechanism of action decreases abnormal electrical activity in the brain,thuspreventingseizures.

Gabapentin is now widely used for other conditions such as epilepsy, neuropathic pain, and restless neuropathic syndrome.Thefloatingmicrospheresofgabapentinprovidesustainedrelease,andthesodiumalginateandethylcellulose act as the main polymers to produce extended release of the floating tablet for 12 hrs. I will be prepared by the floating microspheresofgabapentin,whichisatotalof1200mgtakenthriceinaday(TID).

The neuroprotective drug gabapentin, also known as 1-aminomethylcyclohexane acetic acid, has antiepileptic qualities. Thefloating systems arelowdensityandhavesufficientbuoyancytofloatthegastriccontentandremain buoyantinthe stomach without affecting stomach emptying for a prolonged period of time or causing inadequate drug release in the stomachattheabsorptionsite.

II MATERIALS AND METHOD:

Gabapentinisprocuredfromanapprovedsupplier.Itisusedasananticonvulsantforepilepsyandneuropathicpain.Ethyl CelluloseispreparedfromagiftsamplefromColorconAsiaPvt,Ltd,Goa.Itisusedasahydrophobicandcontrolleddrug release.SodiumalginateisbroughtfromIsoChemicals.CalciumchlorideisbroughtfromIsoChemicals.

FORMULATION OF GABAPENTIN FLOATING MICROSPHERES:

IONOTROPIC GELATION METHOD:

1. Accuratelyweighthedrug,sodiumalginate,andcalciumchloride.

2.Take5%CaCl₂(calciumchloride)dissolvedin100mlwater.

3. Thenweighed100mgofdrug,350mgofsodiumalginate,and450mgofethylcellulose.

4. Thenthesedrugmixturesandpolymeraregentlymixedwiththeuseofamagneticstirrer.

5. Calciumcarbonateisaddedtotheabovemixtureandmixeduniformlytoimpartfloatingproperty.

6. The drug-polymer dispersion is extruded dropwise through a syringe into calcium chloride solution under gentle stirring.

7. Oncontactwithcalciumions,sodiumalginatedropletsundergoioniccross-linking,forminggelledmicrospheres.

8. TheinteractionbetweencalciumcarbonateandtheacidicmediumgeneratesCO₂,whichbecomesentrappedwithinthe microspheres,therebyimpartingbuoyancy.

9. The prepared microspheres were retained in the calcium chloride solution for a predetermined duration to ensure completecross-linking.

10. Themicrosphereswerefilteredandrepeatedlywashedwithdistilledwatertoeliminateexcesscalciumions.

11.Themicrospheresaredriedatroomtemperatureorinahotairovenatlowtemperature.

Fig. no. 2: Microspheres Formulation

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Table NO: 01 Formulation Chart of Floating Microspheres

Formulation

EVALUATION OF FLOATING MICROSPHERES OF GABAPENTIN:

1) Percentage Yield:

Thedriedmicrobeadswere weighed, andthepercentageyieldofthepreparedmicrospheres wascalculatedby usingthe followingformula.(5)

Percentageyield=��+��×100

2) Size Analysis and Determination:

In size distribution analysis, the microspheres of different sizes in a batch were separated by sieving, using standard sieves.Theamountswereweighedandretainedondifferentsieves.Themeanparticlesizeofthemicrobeadsiscalculated bythisformula:

Meanparticlesize=Ʃmeanparticlesizeofthefraction×weightfraction.Weightfraction

Weightfraction

3) Swelling Index:

Theswellingindexofmicrospheresisanindicationofthecapacityofthemicrospherestoimbibethewaterandswell.For estimatingtheswellingindex,themicrosphereswereweighedinitiallyandthensuspendedin25mlofphosphatebufferat pH 7.4. The spheres were taken out at different time intervals using a stainless steel grid and blotted carefully without pressing hard to remove the excess surface liquid. The swollen beads are weighed in an electronic microbalance. The studieswereperformedintriplicate,andaveragevaluesweretakenindataanalysis.(10)

The%weightgainbybeadswascalculatedbythefollowingformula:

Swelling Index = (Wt. – W0) / W0 X 100

Where,Wt.=Massofswollenbeadsattimet

W₀=massofdrybeadsatt.

4) In Vitro Buoyancy:

Gabapentin-equipped microspheres were assessed for in vitro floating properties on a USP dissolution device 2 (paddle type). Fifty single microspheres were submerged in a vessel of 500 mL SGF from each formulation. The rotation of the paddleat50rpm,whilemaintainingthetemperatureat37±0.5°C.Thenumberofmicrospheresfloatingwasmeasuredup to eight hours at hourly periods. In vitro buoyancy was represented as a percentage, and the following equation was determined.(11) © 2026, IRJET | Impact Factor value: 8.315 | ISO 9001:2008

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Weightoffloatingmicrospheres

F%= X100

Weightofinitialmicrospheres

5) Drug Entrapment Efficiency:

Theentrapmentefficiencyofthemicrosphereswasdeterminedby extractionofdrugfromthemicrospheres.Inatypical procedure,50mgofdriedmicrosphereswasgroundinapestleandmortar,andthefinemicrospheresdissolvedinafew mLofethanolanddilutedwith50mLof0.1NHClfor24h. After24h,thesolutionwasmovedovera0.45µmfilter.The gabapentinpresentinthefiltratewasevaluatedspectrophotometricallyat210nmusingaUV-visiblespectrophotometer (Shimadzu,UV1800,Japan)using0.1NHClasablank.(8,9)

Weightofdruginmicrospheres

Drugentrapmentefficiency= X100

Weightoffeddrug

5) Determination of Drug Loading of Microspheres:

20mgofhollow-loadedgabapentinmicrospheresamplesweredissolvedatroomtemperaturebyultrasonicationin50mL ethanol to determine the load. The liquid was then purified by a Millipore (0.45 µm) filter. An ultraviolet (UV)-visible sensor (UV 1700-1800) (Shanghai Phoenix Optical Instrument Co., Ltd., Shanghai, China) was used to determine drug concentrations at 210 nm and 284 nm. The drug loading of gabapentin-loaded hollow microspheres was determined by thefollowingequation.(7)

AmountofFDinhollowmicrospheres

Drugloadingamount= X100

Numberofhollowmicrospherescontaining

7) FTIR Spectral Analysis:

AnFTIRstudywascarriedouttochecktheidentityofthedrug.Theinfraredspectrumofgabapentinwasdeterminedona Fouriertransform infraredspectrophotometerusingtheKBrdispersionmethod.The baselinecorrectionwasdoneusing dried potassium bromide. Then the spectrum of the dried mixture of drug and potassium bromide was run, followed by the drug, by using an FTIR spectrophotometer. The absorption maximums in the spectrum obtained with the substance beingexaminedcorrespondinpositionandrelativeintensitytothoseinthereferencespectrum.

III. RESULT AND DISCUSSION:

Analytical Methods:

Determination of λ max by using 0.1 N HCl:

Themaximumabsorptionforgabapentinin0.1NHClwasfoundtobe210nm,anditisshowninthefigure:

Fig. no. 3: λ max observed for gabapentin in 0.1N HCl.

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Preparation of standard curve of Gabapentin 0.1N HCl:

The UV absorption spectrum of gabapentin in 0.1 N HCl showed λ max at 210 nm. The absorbance obtained for various concentrations of gabapentin in 0.1 N HCl is given in the table. The graph of absorbanceversusconcentrationforgabapentinwasfoundtobe linear intheconcentrationrangeof20–100µg/ml The drugobeysBeer–Lambert’slawintheconcentrationrangeof2–10µg/ml.

Table No. 2: Data of absorbance vs concentration for Gabapentin

Percentage Yield:

Calibration of 0.1N HCL

y = 0.0443x + 0.0007 R² = 1

Concentration

Fig. no: 4 Standard graph of Gabapentin in 0.1N HCl

FormulaforPercentageYield X 100

Practicalyield(mg) Percentage Yield (%) =

Theoreticalyield(mg)

Theoreticalyield=Totalsolidweight=1200mg.

Practicalyield=Weightofdriedmicrospheresobtained.

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Table No: 3 Percentage Yield

SIZE ANALYSIS AND DETERMINATION:

Theparticlesizeofgabapentinmicrosphereswasdeterminedby theopticalmicroscopymethodusingacalibratedocular micrometer.

Procedure:

Asmallquantityofdriedmicrospheresfromeachformulation(F1–F6)wasdispersedinliquidparaffin. Adropofdispersionwasplacedonacleanglassslideandcoveredwithacoverslip. Themicrosphereswereobservedunderanopticalmicroscopeatsuitablemagnification. Around 100 particles weremeasuredrandomlyforeachformulation.

Table NO: 04 Size Analyses and Determination

Swelling Index: Method of Determination:

TheswellingbehaviourofgabapentinmicrosphereswasdeterminedinpH7.4phosphatebuffer.

Table No: 05 Swelling Index In Vitro Buoyancy:

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After 12 hours, the microspheres that remained floating and those that settled at the bottom were collected separately, dried,andweighed.

Table no.: 06 In Vitro Buoyancy Drug entrapment efficiency:

Thesolutionwasfilteredandsuitablydiluted,andtheabsorbancewasmeasuredusingaUV–visiblespectrophotometerat 210 nm against a reagent blank. The drug content was calculated using the previously prepared calibration curve of gabapentin.

Table no: 07 Drug Entrapment efficiency

Determination of Drug-Loading Microspheres:

Thedrugloadingofgabapentin-loadedmicrospheresrangedfrom24.1%to32.2%. Hence,formulationF6wasconsidered thebestformulationintermsofdrugloadingcapacity.

Table no: 08 Determination of Drug-Loading Microspheres

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FTIR Spectral Analysis:

IDENTIFICATION OF GABAPENTIN BY FTIR SPECTROSCOPY:

DRUG EXCIPIENT COMPATIBILITY STUDIES:

Fig no. 05: FTIR Spectrum of pure drug Gabapentin

Fig. no. 06: FTIR Spectrum of pure drug Gabapentin and Sodium Alginate

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Fig. no. 07: FTIR Spectrum of Gabapentin and sodium Alginate and Ethyl cellulose

Table No.: 09 Major Peaks Observed in the FTIR Spectrum of Gabapentin and a Drug with a Different Polymer Used in the Formulation.

Functionalgroup

N–H stretching (Primaryamine)

N–Hbending(Amine)

C–O/C–O–Cstretching

C–Hbending

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C₆H₆(O)substitution

IV CONCLUSION:

The present study successfully developed a novel gastro-retentive floating microsphere system of gabapentin using polymeric carriers to enhance gastric residence time and sustain drug release. The prepared microspheres exhibited satisfactoryphysicochemicalcharacteristics,includinggoodflowproperties,highdrugentrapmentefficiency,anduniform particlesizedistribution.Invitrobuoyancystudiesconfirmedprolongedfloatingbehavior,validatingthegastro-retentive potentialoftheformulation.

Theinvitroreleasestudiesdemonstratedacontrolledandsustainedreleaseprofile,whichisadvantageousforimproving theoralbioavailabilityofgabapentin,adrugwithanarrowabsorptionwindowandshortbiologicalhalf-life.

Overall, the developed floating microsphere system represents a promising gastro-retentive drug delivery approach for gabapentin,withthepotentialtoimprovetherapeuticefficacyandpatientcompliance.

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