In vitro dissolution testing methods

useful for all the Pharmacy graduates

1. In vitro Dissolution
Testing Methods
P.N.Mallikarjun
Associate Professor,
VignanInstitute of Pharmaceutical Technology
Duvvada,Visakhapatnam.A.P .

2. Definition-

Dissolution: is a process in which a solid
substance solubilizes in a given solvent i.e. mass
transfer from the solid surface to the liquid
phase.
DissolutionRate:is the amount of drug substance
that goes in solution per unit time under
standardized conditions of liquid/solid interface,
temperature and solventcomposition.

3. SOLUBILITY DISSOLUTION RATE
Absolutesolubilityisdefined
asthemaximumamountof
solutedissolvedinagiven
solventunderstandard
conditionsoftemperature,
pressureandpH.
Dissolution rate is defined
as the amount ofsolid
substancethat goes into
solution per unit time
under standard
conditions of temperature,
pH, solvent composition
and constant solid surface
area.
It is a staticprocess. Itis a dynamic process.

4. It is a system to differentiate the drugs on the basis of their solubility
and permeability.
The drug substances are classified as:
Class I -High permeability, High solubility. Ex:-Metoprolol.
Class II -High permeability, Low solubility. Ex:-Ezetimibe.
Class III -Low permeability, High solubility. Ex:-Cimetidine.
ClassIV-Lowpermeability,Lowsolubility.Ex:-Hydrochlorothiazide

5. Dissolution and drug release tests are in-vitro tests that measurethe
rate and extent of dissolution or release of the drug substance from
a drug product, usually aq.medium under specifiedconditions.
It is an important QC procedure for the drug product and linkedto
product performancein-vivo.
NEED FOR DISSOLUTIONTESTING:
Evaluation ofbioavailability.
Batch to batch drug releaseuniformity.
Development of more efficacious and therapeutically optical
dosageforms.
Ensures quality and stability of theproduct.
Product development, qualitycontrol,researchandapplication.

6. DISSOLUTION PROCESS OF SOLID DOSAGE FORMS

7. 1.Theinitialstepinvolvesthebreakingofatabletinto
granules(disintegration).
2.Sometimes,thesegranulesfurtherbreaktoyieldfine
particles(deaggregation)
3.The next step involves the releasing of the drug into solution
(dissolution)
4.Absorption.
Essential steps in Dissolution of a Tablet

8. FACTORS RELATING TO THE DISSOLUTION APPARATUS
Design of thecontainer
Size of thecontainer
Shape of thecontainer
Nature ofagitation
Speed ofagitation
Performance precision of the apparatus
FACTORS RELATING TO THE DISSOLUTION FLUID
1.Volume
2.Temperature
3.Deaeration of dissolutionmedium
4. pH
5.Composition

9. IN VITRO DISSOLUTION METHODS
Various classification of Dissolution methods are there
Based on type of system
1.Basic methods
Based on sink condition
2.Sink and non sink methods
3.Official / Compendialmethods and
4.Unofficial/Alternative methods

10. 
1.BASIC METHODS
1.Beakermethods(Closed compartment system)
2.flow-through (Open compartmentsystem)
3.DialysisMethod

11. 2.NON SINK SINK
1) NATURAL CONVECTION
a)Klein solvmetermethod
b)
c)
Nelson hanging pellet method
Levy static diskmethod
2)FORCEDCONVECTION (NS)
a)Tumblingmethod
b)Levy or Beakermethod
c)Rotating diskmethod
d)Particle sizemethod
e) USP Rotating basketapparatus
f) USP Paddleapparatus
a)Wursterpollisadsorption
b)
c)
d)
Partition method
Dialysismethod
Rotatingdiskapparatus
3) FORCED
CONVECTION(SINK)
4) CONTINOUSFLOW:
a)Pernarowskimethod
b)Langenbuchermethod
c)Baun andWalker
d)Tingstad andReigelman
e)Modified columnapparatus
f)Takenakamethod

12. 3.COMPENDIAL/OFFICIAL METHODS
Compendialor Official tests are standardised methods
and specification testing for generic pharmaceutical
material and finished products.
They are utilised as basic requirements needed for
most regulatory submission around the world

13. I.P U.S.P B.P E.P
TYPE1 Paddle
apparatus
Basket
apparatus
Basket
apparatus
Basket
apparatus
TYPE2 Basket
apparatus
Paddle
apparatus
Paddle
apparatus
Paddle
apparatus
TYPE3 Reciprocating
cylinder
Flowthrough
cell
Flowthrough
cell
TYPE4 Flowthrough
cell
TYPE5 Paddleover
disk
TYPE6 Rotating
cylinder
TYPE7 Reciprocating
disk

14. USP.APPARATUS DESCRIPTION ROT.SPEED DOSAGEFORM
TYPE1 Basketapparatus 50-120rpm IDR,DR,ER
TYPE2 Paddleapparatus 25-50rpm IDR,DR,ER
TYPE3 Reciprocating
cylinder
6-35rpm IDR,ER
TYPE4 Flow throughcell N/A ER,Poorlysoluble
API
TYPE5 Paddle overdisk 25-50rpm TRANSDERMAL
TYPE6 Rotatingcylinder N/A TRANSDERMAL
TYPE7 Reciprocating
holder
30rpm ER

15. APPARATUS-1(ROTATINGBASKET)
DESIGN:
Vessel: -Made of borosilicate glass.
-Semi hemisphericalbottom
-Capacity1000ml
Shaft:-Stainless steel316
-Rotates smoothly without
significance wobble(100rpm)
-Speedregulator
Water bath:-Maintained at37±0.5ºC
USE: Tablets, capsules, delayed release
suppositories, floating dosageforms.

16. METHOD(Rotatingbasket):
Place the stated volume of the dissolution medium(±1 %) inthe
vessel and equilibrate dissolution medium to37±0.5°C.
Place 1 tablet or capsule in the apparatus ,taking care to excludeair
bubbles from the surface of the dosage form unit and immediately
operate the apparatus at the ratespecified(100rpm).
Withdraw a specimen from a zone midway between the surface ofthe
dissolution medium and the top of the rotating basket,not less than
1cm from the vessel wall at each timesstated.
Replace the aliquots withdrawn for analysis with equal volumesof
fresh dissolution medium at37°C.
Keep the vessel covered for the duration of the test and verifythe
temperature of the mixture under test at suitabletimes.
Perform the analysis as directed in individual monograph andrepeat
the test with additional dosage formunits.

17. Apparatus 1 -Basket

18. Advantages
Full pH change during thetest
Can be easily automated
which is important forroutine
investigations.
Disadvantages
Basket screen is cloggedwith
gummyparticles.
Hydrodynamic „dead zone“
under thebasket
Degassing isparticularly
important
Mesh gets corroded by HClsolution.

19. APPARATUS-2(ROTATING PADDLE)
DESIGN:
Vessel: -Same as basketapparatus
Shaft: -The blade passes through the shaft so that the bottom ofthe
blade fuses with bottom of theshaft.
Stirringelements:-Made oftefflon
For laboratorypurpose
-Stainless steel316
Water-bath: -Maintains at37±0.5°C
Sinkers : -Platinum wire used toprevent
tablet/capsule fromfloating

20. METHOD
It consists of a special coated paddle formed from a blade anda
shaft that minimizes turbulence due tostirring.
The coated material isinert.
The paddle is attached vertically to a variable -speed motorthat
rotates at a controlledspeed.
The tablet or capsule is placed into a round-bottom dissolution
flask and the apparatus is housed in a constant temperaturewater
bath maintained at37°C.
Most common operating speeds are 50rpm for solid oraldosage
forms and 25 rpm forsuspensions.
A sinker ,such as few turns of platinum wire may be usedto
prevent a capsule or tablet fromfloating
Used for film coated tablets that stick to the vessel walls orto
help to position tablet/capsule under thepaddle.

21. Advantages
Easy touse
Robust
pH changepossible
Can be easily automated which is importantfor
routineinvestigations
Disadvantages
pH/media change is often difficult
Hydrodynamics are complex, they vary with site of the dosage
form in the vessel (sticking,floating) and therefore may
significantly affect drugdissolution
Sinkers for floating dosageforms

22. Paddleapparatus:

24. SinkerTypes:

25. APPARATUS-3(RECIPROCATING CYLINDER)
DESIGN:
Vessel: -Set of cylindrical flat bottom glassvessels
-Set of reciprocatingcylinders
-stainless steel fittings(SS316)and
screens made of nonsorbingor
non-reactivematerials.
Agitation type:-Reciprocating
-5-35rpm
Volume of dissolutionmedium:-200-250ml
Water bath:-Maintain at37±0.5°C
USE: Tablets, beads, controlledand
extended releaseformulations

26. METHOD(Reciprocatingcylinder):
Place the stated volume of dissolution medium in each vessel ofthe
apparatus, assemble the apparatus, equilibrate the dissolution
medium to 37±0.5 and remove thethermometer
Place one dosage form unit in each of the cylinders taking careto
exclude the air bubbles from the surface of each dosage unit and
immediately operate the apparatus as specified in themonograph.
During the upward and downward stroke, the reciprocatingcylinder
moves through a total distance of 9.9 to10.1cm.
Within the time interval specified raise the cylinders and withdrawa
portion of the solution under test from a zone midway between the
surface of the dissolution medium and bottom of eachvessel.

27. Advantages
Easy to change thepH
pH-profiles
Hydrodynamics canbe
directly influenced by
varying the diprate
Disadvantages
Small volume (max. 250ml)
Littleexperience
Limiteddata

29. APPARATUS-4 (FLOW THROUGHCELL)
DESIGN:
Reservoir : -For dissolutionmedium
Pump : -Forces dissolution medium throughcell
-Holding asample
-Flow rate10-100ml/minor 240-960ml/h
-Laminar flow ismaintained
-Peristaltic/centrifugal pumps are notrecommended
Water bath:-Maintain at37±0.5°C
USE:
Low solubility drugs ,micro particulates ,implants,suppositories
controlled releaseformulations

30. METHOD(Flow throughcell):
The flow through cell is transparent & inert mountedvertically
withfilters.
Standard cell diameters are 12 & 22.6mm.
The bottom cone usually filled with glassbeadsof1mm
diameter.
Tablet holder used for positioning special dosage form e.g.inlay
tablets.
Place the glass beads into the cell as specified in themonograph.
Place one dosage unit on top of the beads or on a wirecarrier.
Assemble the filter head and fix the parts together by means ofa
suitable clampingdevice.
Introducebythepumpofthedissolutionmediumwarmedto
37±0.5throughthebottomofthecelltoobtaintheflowrate
specifiedandmeasuredwithanaccuracyof5%.
Collecttheeluatebyfractionsateachofthetimesstated.

31. d.
Advantages
easy to change mediapH
pH-profilepossible
Sink conditionsmaintaine
differentmodes
a)opensystem
b)closedsystem
Disadvantages
Deaerationnecessary
high volumes ofmedia
laborintensive

32. Celltypes:
Tablets 22.6mm Powders /GranulesImplantsTablets 12mm
Suppositories/
Soft
gelatincapsules

33. Flow-ThroughCell:

35. APPARATUS-5(PADDLE-OVER-DISK)
DESIGN:
Vessel
Shaft
Stirring elements-rotating speed 25-50rpm
Sample holder:-disk assembly that hold a product in such away
that release surface is parallel withpaddle
-Paddle is directly attached over diskassembly
-Samples are drawn between surface off the medium
and top of the paddleblade
Volume:900ml
Temperature:32°C

36. USE: Transdermal patches, ointments, floaters ,emulsions.
Modification: Disk design andvolume
Advantages:
Easy tohandle
Sink conditions aremaintained.
Membrane effect isminimum.
i.e. drug is placed on a disc at thebottom.
Disadvantages:
Disk assembly restricts the patchsize
Borosilicateglass
17 mesh is standard(othersavailable)
Accommodates patches up to90mm.

37. This method is used for testing the release of drugsfrom
transdermalproducts.
The apparatus consists of a sample holder or disc assemblythat
holds theproduct.
The entire preparation is placed in a dissolution flask filledwith
specified medium maintained at32ºC.
The paddle is placed directly over the discassembly.
The disk assembly holds the system flat and is positioned suchthat
release surface is placed parallel with the bottom of the paddle
blade. Vessel is covered to minimize evaporation duringtest.
Samples are drawn midway between the surface ofdissolution
medium and the top of the paddle blade at specifiedtimes.

38. APPARATUS-6(CYLINDER)
DESIGN:
Vessel:-In place of basket, cylinder isused.
Shaft :-Stainless steel316
Sample :-Mounted to cuprophan (inner porous cellulosicmaterial)
an entire system adheres tocylinder.
-Dosage unit is placed in cylinder and release from sideout.
Water-bath: maintained at32±0.5°C
USE:
Transdermal patches cannot be cut into smallsize.
Solid dosage forms, pH profile , smallvolumes

39. METHOD( cylinder):
Use the assembly from apparatus 1 except to replace the basketand
shaft with a stainless steel cylinder stirringelement.
The temperature is maintained at32±0.5°C.
The dosage unit is placed on the cylinder with side out.
The dosage unit is placed to the exterior of the cylinder such that
long axis of the system fits around the circumference of thecylinder
and removes trapped airbubbles.
Place the cylinder in the apparatus and immediately rotate at therate
specified in the individualmonograph.
Samples are drawn midway between the surface of thedissolution
medium and the top of the rotating cylinder foranalysis.

40. cylinder:
Advantages: -Equipment (apparatus 1)available with the
manufacturers can be used with modification as apparatus6.
Disadvantages:-Large volume of medium isrequired.
-Drug gets diluted & causes difficulties inanalysis
-Difficult to clean thecylinder.

41. APPARATUS-7(RECIPROCATING-DISK)
DESIGN:
Vessel:-Flat bottomed cylindricalvessel
-Volume of dissolutionmedium
Shaft:
Sample : -Placed on disk shapedholders
Agitation:-Reciprocation
-Reciprocating frequency 30
cycle/minute
Water-bath:-Maintain at32±0.5°C
USE:
Transdermalpatches
shaft
disk
dissolutionmedium
constanttemp
waterbath

42. METHOD(Reciprocatingdisk):
Theassemblyconsistsofasetofvolumetricallycalibratedsolution
containersmadeofglassorsuitableinertmaterial,amotor,adrive
assemblyusedtoreciprocatethesystemvertically.
Thesamplesareplacedonthediskshapedholdersusingcuprophan
supports
Thetestiscarriedoutat32°C.
The reciprocating frequency is30cycles/min.
Advantages:-Convenient method for selecting the volume of the
medium.
-sink conditions can bemaintained.
-more sensitivity
Disadvantages: -Investment is high because the design is totally
different from standard equipment already available inindustry.

45. 4.ALTERNATIVE METHODS
1.ROTATING/STATIC DISKMETHOD
Developed by late Eino Nelson and described by Levy andSahli.
In this method ,the drug is compressed in a non-disintegratingdisc
withoutexcipients.
The disc is mounted in a holder so that only one face of the discis
exposed to the dissolutionmedium.
The holder and disc are immersed in medium and held in afixed
position as in static disc method and rotated at a given speed in
rotating discmethod.
Samples are collected at predeterminedtimes.
Surface area of the drug through whichdissolution
occurs is kept constant –intrinsic dissolutionrate.

46. 2.BEAKERMETHOD:
Reported by Levy andHayes(1960).
Dissolution medium, 250ml of 0.1N HCl at 37°Cplaced
in a 400mlbeaker.
Agitation by three blade polyethylene stirrer,5cm diameterand
rotates at 60rpm.
Stirrer immersed to a depth of 2.7 cm in medium and in thecenter.
Tablets are placed in a beaker and test was carriedout.
Samples are removed and assayed for thecontent.
3.FLASK STIRRERMETHOD
Developed by Poole(1969).It includes RBF and a stirringelement
similar to that of beakermethod.
RBF used to avoid the formation of moulds of particles indifferent
positions on the flat bottom of abeaker.

47. 4.PERISTALSISMETHOD:
To stimulate hydrodynamic condition of GIT tract in an in-vitro
dissolutiondevice.
It consists of rigid plastic cylindrical tubing fitted with septumand
rubber stopper at bothends.
Dissolution chamber consists of a space between septum andlower
stopper.
Dissolution medium is pumped with peristaltic action throughthe
dosageform.
5.ROTATING BOTTLEMETHOD:
It consists of rotating rack to hold sample drug products inbottles
and they are capped tightly & rotated in 37°C temperaturebath.
Sample are decanted through a 40 mesh screen and residueare
assayed.

48. 6.DIALYSISMETHOD:
Cell consist of 32mm inflatedmembrane.
Plugged at the lower end by tight fitting cylindrical perspexbox.
Upper end of the tube held by thin perspex ring inserted intothe
tube and secured by an elasticband.
The cell suspended , from the arm of the tablet disintegration
apparatus and containing the dosage form in 150ml ofdistilled
water at37°C.
The cell is raised or lowered 30times a min, into 150ml ofdistilled
water at sametemperature.
Agitation by slight flexing and stretching of the dialysismembrane
as it enters and leaves the bath. Rotated at60rpm.
.

50. 7.DIFFUSIONCELL
Static or flow through diffusion cells are used to characterize in-
vitro drug release and drug permeation kinetics from a topicaldrug
product eg: Ointment, cream or transdermal drugproduct.
The Franz diffusioncellisstatic diffusion system usedto
characterize drug permeation through skinmodel.
The skin is mounted on the Franz diffusion cell and thedrug
product is placed on the skinsurface.
The drug permeates across the skin into a receptorfluid
compartment that may be sampled at varioustimes.
This system is used for selection of appropriate formulationthat
has optimum drugdelivery.

51. Diffusioncell

52. 12/08/12
39

53. Dissolution Testing methods Forsome
Drug Delivery Systems
A number of methods are used to conductin-vitro evaluation
of controlled ocular drug delivery systems.
(a) Bottlemethod
In this method, dosage forms are placed in the culture
bottles containing phosphate buffer at pH 7.4.
The culture bottles are shaken in a thermostatic water bath
at37°C.A sample of medium is taken out atappropriate
intervals and analyzed for drugcontents.
40
Ocular DrugDelivery Systems

54. 41
b) Modified rotating basketmethod
In this method,dosage form is placed in a basket
assembly connected to astirrer.
The assembly is lowered into a jacketed beaker
containing buffermedium.
The temperature of system is maintainedat 37°C. A
sample of medium is taken out at appropriatetime

55. Beakermethod
The dosage form in this method is made to adhere at the bottom of the
beaker containing the medium and stirred uniformly using over head
stirrer.
Volume of the medium used for the studies varies from 50-500 ml and
the stirrer speed form 60-300rpm.
Modified Keshary ChienCell
A specialized apparatus was designed in thelaboratory.
It comprised of a Keshary Chien cell containing distilled water (50ml) at
37
0
c as dissolutionmedium.
TMDDS (Trans Membrane Drug Delivery System) was placed in a glass
tube fitted with a 10# sieve at the bottom which reciprocated in the
medium at 30 strokes permin.
Samples are removed at appropriate time intervals and analyzed for
drug content.
Particulate Drug Delivery systems(MICROSPHERES)

56. DISSOLUTION ACCEPTANCE CRITERIA
Q –Value
Definedas a percentage of drug content
dissolved in a giventime period.

57. DISSOLUTION ACCEPTANCE CRITERIA
STAGE Acceptancecriteria
S1
No. of Dosageunits
tested
6 No Dosage unitis
less thenQ+5%
S2 6 Average Of12
dosage units(S1+S2)
and no dosage unitis
S3 12(6+6+12=24)
less thenQ-15%
Average of 24
dosageunits>-And
not more than two
dosage units areless
than Q-15% and No
dosage unit is less
46
thanQ-25%

58. COMPARISON OF DISSOLUTION PROFILE
Difference factor (f1 Value)-
Define as calculate the % Difference between 2
curves at each time point and is a measurement of
the relative error between 2curves.
f1= {[Σ t=1n |Rt-Tt|] / [Σ t=1n Rt]} ×100.
Values range from 0 to 15
47

59. Similarity Factor (f2 value)-define as
measurement of similarity in % Dissolution
between twocurve.
Where R
t and T
t =
cumulative %dissolved
for reference andtest
Values range from 50(similar)to 100(Identical)

60. CONCLUSION:
By studying various factors influencing therateofdissolution,we
can optimize type of dissolution method and the different
properties of theformulation.
To predict drug product performance it is essential to select
suitable dissolution method.
By conducting dissolution studies we can know the batch tobatch
reproducibility.
In vitro Dissolution profile is used toestimate the In vivo behaviour of
thedrugproduct.
The best available tool to atleast quantitatively assure about the
biological availability of drug from itsformulation is its invitro
dissolution.

61. REFERENCES
D.M.Brahmankar, Biopharmaceutics and
pharmacokinetics-A Treatise; Vallabh Prakashan,
page no.20–31.
Leon Shargel, Applied Biopharmaceutics &
Pharmacokinetics; 4
th
edition, page no.132-136.
The Indian Pharmacist, February 2008,Page
no.10-12

62. United States Pharmacopoeia –24, page no.:1942
–1951.
“Current perspectives in dissolution testing of
conventional and novel dosage forms”, by Shirazad
Azarmi, Wilson Roa, Raimar Lobenberg, Int.jou.
Of pharmaceutics 328(2007)12 –21.
Alton’s pharmaceutics “ The design and
manufacturing of medicines”, by Michael E. Alton,
page no.: 21 –22.