Advanced Biopharmaceutics and Pharmacokinetics.pptx

Alternate Methods of Dissolution Testing
Problems of Variable control in Dissolution Testing
Meeting Dissolution Requirments
Stability Testing

1. Advanced Biopharmaceutics and Pharmacokinetics Presented by, Jayanth D M.Pharm I Year II Sem Department of Pharmaceutics College of Pharmacy Madras Medical College, Chennai - 03

2. Contents Alternate Methods of Dissolution Testing Meeting Dissolution Requirements Problems of Variable Control in Dissolution Testing Stability Testing Shelf Life Determination

3. Alternate Methods of Dissolution Testing Alternative dissolution methods are often used during drug development to better understand the relationship of the formulation components and manufacturing process on drug release. There are four major alternate methods for dissolution testing. Rotating Bottle Method Intrinsic Dissolution Method Peristalsis Method Diffusion cells

4. Rotating Bottle Method The rotating bottle method was suggested in NF-XIII (National Formulary) but has become less popular since. The rotating bottle method was used mainly for controlled-release beads. For this purpose the dissolution medium may be easily changed, such as from artificial gastric juice to artificial intestinal juice. The equipment consists of a rotating rack that holds the sample drug products in bottles. The bottles are capped tightly and rotated in a 37°C temperature bath. At various times, the samples are removed from the bottle, decanted through a 40-mesh screen, and the residues are assayed.

5. An equal volume of fresh medium is added to the remaining drug residues within the bottles and the dissolution test is continued. A dissolution test with pH 1.2 medium for 1 hour, pH 2.5 medium for the next 1 hour, followed by pH 4.5 medium for 1.5 hours, pH 7.0 medium for 1.5 hours, and pH 7.5 medium for 2 hours was recommended to simulate the condition of the gastrointestinal tract. The main disadvantage is that this procedure is manual and tedious.

6. Intrinsic Dissolution Method The dissolution of a drug powder by maintaining a constant surface area is called intrinsic dissolution. Intrinsic dissolution is usually expressed as mg/cm2/min. In one method, the basket method is adapted to test dissolution of powder by placing the powder in a disk attached with a clipper to the bottom of the basket. New drug or substance may be tested for dissolution without the effect of excipients or the fabrication effect of processing. Two types are available, Rotating Disk method and Fixed Disk method .

7. Rotating Disc Method

8. Fixed Disk Method

9. Peristalsis Method The peristalsis method attempts to simulate the hydrodynamic conditions of the gastrointestinal tract in an in vitro dissolution device. The apparatus consists of a rigid plastic cylindrical tubing fitted with a septum and rubber stoppers at both ends. The dissolution chamber consists of a space between the septum and the lower stopper. The apparatus is placed in a beaker containing the dissolution medium. The dissolution medium is pumped with peristaltic action through the dosage form.

10. Diffusion Cells Static and flow-through diffusion cells are commercially available to characterize in vitro drug release and drug permeation kinetics from topically applied dosage form (e.g., ointment, cream) or transdermal drug product. The Franz diffusion cell is a static diffusion system that is used for characterizing drug permeation through a skin model. It consists of a donor and receptor compartments in between the diffusion membrane is attached. In flow through cell the medium in the receptor compartment is constantly changed creating a perfect sink condition.

11. Non sink Methods Natural Convection Methods Klein Solvometer Method Nelson Hanging Pellet Method Levy Static Disk Method Forced Convection Methods Tumbling method Levy or Beaker method Rotating disk method Particle size method

12. Sink Methods Forced Convection Methods Wuster Pollies adsorption method Partition method Dialysis method Rotating disk apparatus Continuous Flow Methods Pernarowski method Langdenbucher method Buan and Walker method Tingstad and Riegalman method Modified column apparatus Takenaka method

13. Klein Solvometer Method In this method density difference is utilised for replacing the Dissolution medium. It consists of a carrier device immersed in dissolution medium. When dosage form is placed in the boat the bar moves and as a dosage form it moves upwards. Height of the bar movement is directly proportional to the amount of dosage form dissolved.

14. Nelson Hanging Pellet Method It consists of an aluminium strip for holding dosage form which inturn is connected to an balance arm of strip. Dosage form is placed on aluminium strip with the help of wax, this method is used to determine intrinsic dissolution rate.

15. Wuster Pollies Adsorption Method As the drug dissolves from the dosage form, it is continuously adsorbed onto the added adsorbent. This continuous removal of the dissolved drug from the solution prevents its concentration from building up to saturation levels. By effectively keeping the concentration of free, dissolved drug low in the bulk medium, the method helps to maintain sink conditions, thereby allowing for a more accurate assessment of the drug’s intrinsic dissolution rate without solubility limitations.

16. Partition Method In this method organic phase is employed to remove the dissolved drug such that the drug would partition between hydrophilic and lipophilic phases. By introducing an organic layer (e.g., octanol, dodecane , or another oil phase) on top of the aqueous dissolution medium, the system mimics the partitioning of the dissolved drug from the aqueous luminal fluid into the lipid-rich membranes of the GI tract.

17. Dialysis Method Dialysis Sac Method/Traditional Dialysis The drug delivery system (e.g., nanoparticles suspended in a small volume) is placed inside a dialysis bag (sac). This dialysis bag is then immersed in a larger volume of dissolution medium (the acceptor medium) in a vessel. The system is typically agitated (e.g., using a shaking water bath or magnetic stirrer) at a controlled temperature. Samples are withdrawn from the acceptor medium at predetermined time intervals and analyzed for the released drug.

18. Reverse Dialysis Sac Method The drug delivery system is directly added to the release medium outside the dialysis sacs. Samples of the release medium inside the dialysis sacs are taken and analyzed for released drug content. Modified USP Apparatus (e.g., using a dialysis membrane as a basket bottom) In some cases, the dialysis membrane can be integrated into standard USP dissolution apparatus. For example, a glass basket with its bottom sealed by a dialysis membrane can replace the regular basket in USP Apparatus 1. This allows for standard agitation while still separating the drug carrier from the dissolved drug.

19. Rotating Flask Apparatus In this method, a flask containing dissolution medium is rotated around its horizontal axis in a water bath kept at 37° C.

20. Meeting Dissolution Requirements For the acceptance of dissolution acceptance criteria, the following points should be considered, The dissolution profile data from the pivotal clinical batches and primary stability batches should be used for setting of the dissolution acceptance criteria for the product. Specifications should be established based on average in vitro dissolution data for each lot under study equivalent to stage 2 USP testing (n=12). For immediate release dosage form the last time point should be the time point where at least 80% of the drug has been released.

21. If the maximum amount of drug released is less than 80%, the last time point should be the time when the pleatue of the release profile has been reached (proper justification is needed). For extended release formulations, a minimum three points is recommended to set the specifications i.e. early, middle and late stages of release profile. The last time point is the point where 80% of the drug is released. If the maximum amount of drug released is less than 80% than the last point should be the point where the pleatue of the drug release profile has been reached. The term Q means the amount of drug dissolved within a given time period established in the drug product specification table and is expressed as a percentage of label content.

22. Immediate Release Dosage Form

23. Immediate Release Pooled Sample

24. Extended Release Dosage Form

25. Delayed Release Dosage Form Acid Stage

26. Delayed Release Dosage Form Buffer Stage

27. Setting Specifications as per EMA If dissolution of the biobatch is larger than or equal to 95% in 15 minutes, the specification may be set to Q=85% after 15 minutes. If dissolution of the biobatch is less than 95% but larger than or equal to 85% in 15 minutes, the specification (Q) may be set to 75%, 80% or 85% whichever is closer to Q=biobatch result -10% at 15 minutes. If dissolution of the biobatch is larger than or equal to 85% only after 30 minutes, the specification (Q) may be set to 75%, 80% or 85% whichever is closer to Q=biobatch result -10% at 30 minutes. If dissolution of the biobatch is larger than or equal to 85% only after 45 minutes, the specification may be set to 75%, 80% or 85% after 45 minutes.

28. Problems of Variable Control in Dissolution Testing The source of deviation from the accurate results of dissolution methods can be broadly classified into the following categories, Equipment related factors Process related factors Drug substance properties related factors Drug product properties related factors Miscellaneous factors: Personnel errors and cleaning

29. Equipment Related Factors Dissolution test vessel: It should have a hemispherical bottom and perfect cylindrical in shape to achieve a perfectly balanced hydrodynamic environment.

30. The dissolution calibration was carried out using USP Prednisolone tablets in two different dissolution vessels. The results widely varied between vessels used and between positions in the dissolution tester. The mean values of prednisolone dissolution percentage obtained from six positions differed significantly among vessels (P<0.05). Vessel Manufacturing process Description Vessel A (Takao, Japan) New glass processing technology Cylinder and Hemispherical inner surface Vessel B (USA) Manual blowing of molten glass into moulds Distortion and uneven inner surface

31. Paddle /Basket Shaft: Shafts must be straight Two types of basket shaft are available, O-Ring shaft Clips shaft Higher dissolution rates are reported in clipped basket shafts and it is the official USP design. Paddles are coated with teflon which sometimes peel and partially shed from paddle causing hydrodynamic flow of disturbances. It can also become rusted, nicked and dented.

32. Paddle Dimensions as per USP

33. Vibrations: Addition of energy from external source can alter the results of dissolution evaluation. Use of Filters: The filter material should have little or no tendency to absorb the drug since it will result in out of specification results. Example: Hydrophilic PTFE Nylon Polyether sulfone (PES)

34. Process Related Factors Sample Introduction: The dissolution rate of product is position dependent. Sampling: Greater disturbances of fluid hydrodynamics due to the additional insertion and residence of the sample probe into the dissolution vessel during multi-point sampling which causes variations in dissolution rate. Tablet Position Dissolution Rate Off centre High Dissolution Rate due to shear force Centre Low Dissolution Rate due to Coning

35. Deareation of Media: Dissolved air can slow down dissolution by creating a barrier either adhering to tablet surface or to the basket screens or particles can cling to bubbles on the glass surface of the vessel shafts. Drug substance and Drug Product related factors influencing Dissolution Rates Drug substance Drug Product Precipitation of drug as a change in pH of test medium. Super saturation of the test medium due to dissolution of drug. Film coating may cause sticking of tablet to vessel surface. Hardening or softening of tablet due to presence of certain excipients may cause variations in disintegration time.

36. Dissolution Profile Comparison A model independent method for comparison of two dissolution profile is based on determination of difference factor f1 and similarity factor f2.

37. Where, n is the number of Dissolution points Rt is the dissolution value of reference drug product at time t Tt is the dissolution value of test product at time t Interpretation Table F1 factor ≤15 Dissolution profiles are identical and similar. F2 factor ≥50

38. Points to be Considered Enter dissolution mean value of 12 units each (Minimum 6 units).
The dissolution measurements of the test and reference batches should be made under exactly the same conditions.
The dissolution time points for both the profiles should be the same (e.g., 15, 30, 45, 60 minutes).
Only one measurement should be considered after 85% dissolution of both the products.
To allow use of mean data, the percent coefficient of variation (%RSD) at the earlier time points (e.g., 15 minutes) should not be more than 20%, and at other time points should not be more than 10%.
Most countries recommend that where more than 85% of the drug is dissolved for both the test and reference products within 15 min, dissolution profiles may be accepted as similar without further mathematical evaluation.

39. Stability Testing The purpose of stability testing is to provide evidence of how the quality of an API or FPP varies with time under the influence of a variety of environmental factors such as temperature, humidity and light. The stability testing programme also includes the study of product-related factors that influence its quality, for example, interaction of the API with excipients, container-closure systems and packaging materials. As a result of stability testing, a retest period for the API (in exceptional cases, for example, for unstable APIs, a shelf life is given) or a shelf life for the FPP can be established and storage conditions can be recommended. Guidelines: ICH Q Guidelines.

40. Storage conditions for Stability Testing

41. Stress Testing Test name Test condition Hydrolytic degradation Drug is refluxed in 0.1N HCl or in 0.1N NaOH at pH 1-2 or pH 6-9. Oxidative stress testing Hydrogen peroxide can be used in the concentration of 3–30% at a temperature not more than 40˚C for 2–8 days.

42. Test name Test condition Thermal degradation studies Effect of temperature is studied in increments of 10°C and above for routine accelerated stability testing and relative humidity should be kept at 75% or greater . Photo degradation Samples of drug substance, and solid/liquid drug product, should be exposed to a minimum of 1.2 million lux hours (300-800nm) and at 200 watt hours per square meter.

43. Shelf life determination It is defined as the time taken by the drug to decay 90% of its original concentration. T90 = 0.105 / k

44. Drug products are stored at different temperature and RH. Samples are withdraw at different time intervals and the rate of degradation is determined. Plot graph concentration of drug remaining (a-x in case of first order) vs time. K values are calculated for all temperatures from the slope of the lines. Log K values are plotted against reciprocal of absolute temperature in kelvin units (Arrhenius equation). The straight line is extrapolated to room temperature (K25) and the corresponding log k value is determined. The K25 value is further substituted in the appropriate reaction order equation to predict the shelf life of product under normal storage conditions.

45. References Leon Shargel & Andrew BC Yu, Applied Biopharmaceutics and Pharmacokinetics seventh edition, McGrawn Hill Education ebooks , 2016. Vivian Gray , Mary Beggy , Robert Brockson , Nancy Corrigan and John Mullen, A Comparison of Dissolution Results Using O-ring vs Clipped Basket Shafts, Dissolution Technologies 2001. United States Pharmacopeia, Stage 6 Harmonization, Dissolution, 2011. European Medicines Agency, Reflection paper on the dissolution specification for generic solid oral immediate release products with systemic action, 2017. Parachi Pandey & Rahul Pal, In-Vitro Dissolution and Alternative Methods Involving in the Dissolution Rate Determination, ResearchGate , 2023.

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