2. Comparative dissolution testing and applications
WHO workshop on
Quality, good manufacturing practice and bioequivalence with a focus on antituberculotics
Jiaxing, China
5 to 9 November 2007
Comparative dissolution testing and applications
Theo Dekker, D.Sc.
Research Institute for Industrial Pharmacy
North-West University, Potchefstroom, South Africa

3. What is dissolution testing? Tablets and capsules (conventional IR)
It measures the portion (%) of the API that
has been released from tablets/capsules and
has dissolved in the dissolution medium during controlled testing conditions within a defined period
The tablet thus first disintegrates
Then the API will be able to dissolve
Slow disintegration ➜ slow dissolution
The % API dissolved is determined with an appropriate validated method: UV/VIS, HPLC, AA, GC, etc

4. Oral suspensions & powders for oral suspensions
Dissolution also applicable to the following oral preparations
Oral suspensions
Use unit dose (e.g. 5 ml) of well mixed suspenion
Example: Ibuprofen Oral Solution USP
Powders for oral suspensions
Sample: reconstituted suspension
Using unit dose of well-mixed reconstituted suspension
Principle
No disintegration (like tablets) - only rate of API dissolution
Important for APIs of low solubility (BCS)

5. Glossary Solid oral dosage forms
Immediate release (IR) typically means that 75% of the API is dissolved within 45 minutes
Rapidly dissolving: ≥ 85% in ≤ 30 minutes
Very rapidly dissolving: ≥ 85% in ≤ 15 minutes
Modified-release dosage forms (consult IntPh, PhEur/BP, USP)
Formulation deliberately changes release (slows down)
Extended-release (prolonged-release)
Slower release throughout the gastro-intestinal tract
Delayed-release (enteric coated tablets)
Resists gastric fluid & disintegrates in intestinal fluid
Not part of presentation

6. What is multi-point dissolution?
In multipoint dissolution
multiple (≥ 3) samples are withdrawn from the dissolution medium during dissolution testing
at pre-determined time points (intervals) and
each sample is analysed for the % API dissolved
A graph of % API dissolved against time
= the dissolution profile

7. Multi-point dissolution Example of dissolution profile

8. Comparative dissolution testing The principle
Two or more products or batches containing the same API are compared
by means of multipoint dissolution
The strength of products / batches may or may not be the same (depending on purpose of test)
The dissolution conditions are similar, e.g.
Apparatus, medium, volume, rotation speed & temperature
Minimize possible experimental differences in conditions
Samples are taken at the same time points and the data (dissolution profiles) compared
Calculations: correct for volume change of dissolution medium

9. Comparative dissolution testing Example

10. Comparative dissolution testing
When are dissolution profiles similar?

11. Comparative dissolution testing Profile similarity determination
If both the test and reference product show more than 85% dissolution within 15 minutes,
the profiles are considered to be similar
No calculations are required
If this is not the case, apply point 2
Calculate the f2 value (similarity factor):
If f2 ≥ 50
the profiles are regarded similar

12. Comparative dissolution testing Similarity factor f2
n = number of time points
Rt = % API dissolved of reference product at time point x
Tt = % API dissolved of test product at time point x
Minimum of 3 time points (zero excluded)
12 units (one / vessel) for each batch (for “official” purposes)
Only one measurement should be considered after the comparator product has reached 85 % dissolution (or asymptote is reached)
RSD: ≤ 20% at early time point & ≤ 10% at higher time points

13. Comparative dissolution testing f2 calculation – spread-sheet design

14. Comparative dissolution testing Dissolution conditions (study design)
Apparatus
(choice)
Paddle, 75 (or 50) rpm or
Basket, 100 rpm
Dissolution media
(All three media for full comparison)
pH 6.8 phosphate buffer
pH 4.5 acetate buffer
Buffer pH 1.2 or 0.1 M HCl
Volume of media
900 ml or less
Temperature
37°C ± 0.5°C
Sampling points
10, 15, 20, 30, 45, (60, 120) min. (short intervals)
Units (individual)
12 for “official” studies

15. Typical time points Immediate release tablets (capsules)1 10 2 15 3 20 4 30 5 45
Rationale:
Condition 1
≥ 85% dissolution of both products within 15 min.
15 minute time point thus essential
Condition 2, for calculation of f2
a minimum of 3 points are required
Only one measurement should be considered after 85 % dissolution
20 minute time point thus first possible one (if 15 minute fails 1st condition)

16. Comparative dissolution testing Comparison of products
When are the dissolution properties of two products (batches) regarded similar?
When the dissolution profiles are similar
in all three media
Statements of instability or insolubility are not acceptable, but should be demonstrated / justified (literature?)

17. Example 1 Determination of similarity of profiles
Example 1-A
% API dissolved
Time (min)
Tablet A (Ref)
Tablet B (Test) 10 87 94 15 96 99 20 30
100 45
101 60
f2 required?
No, ≥ 85% in 15 min
f2 (n = N/A ?)
profiles similar
Example 1-B
% API dissolved
Time (min)
Tablet D (Ref)
Tablet E (Test) 10 55 57 15 72 78 20 85 91 30 97
100 45
102 60
101
f2 required?
Yes
f2 (n = 3 ?)
64 (similar)

18. Example 1 Determination of similarity of profiles (cont.)
Example 1-C
% API dissolved
Time (min)
Tablet X (Ref)
Tablet Y (Test) 10 29 34 15 38 41 20 47 50 30 63 64 45 80 79 60 95 91
f2 required?
Yes
f2 (n = 6 ?)
74 (similar)
Example 1-D
% API dissolved
Time (min)
Tablet D (Ref)
Tablet A (Test) 10 55 87 15 72 96 20 85 99 30 97
100 45
102
101 60
f2 required?
Yes
f2 (n = 3 ?)
31 (not similar)

19. Example 2 Ciprofloxacin: two batches of same product
Manufacturer
Batch Nr
Expiry date
Status
Cipro 500
ABC Ltd
xxx
06/2008
Test
zzz
07/2008
Reference
Apparatus paddle at 50 rpm
Media: 1 pH 1.2 HCl solution (900 ml)
2 pH 4.5 acetate buffer (900 ml)
3 pH 6.8 phosphate buffer (900 ml)
Temp.: 37°C ± 0.5°C (start, middle, end)
Units: Twelve tablets per medium, each batch
Sampling: Manual, through in-line filter (0.45 μm PVDF) at 10, 15, 20, 30 and 45 minutes
Analysis: HPLC

20. Example 2 Ciprofloxacin: two batches (cont.)
Medium►
pH 1.2
Buffer pH 4.5
Buffer pH 6.8
% dissolved
Time (min)
b/n xxx
b/n zzz 10 83 80 93 96 28 31 15 95 92 97 99 34 36 20
100 38 39 30
102
101 40 45 41
similarity ? n = 5 ?
≥ 85% in 15 min.
f2 = 83 (≥ 50)
Conclusion: The profiles in all three media can be regarded similar / not similar, since …………

21. Example 2 Ciprofloxacin: two batches (cont.)
pH Acetate buffer pH 6.8

22. Example 2 Ciprofloxacin: two batches (cont.)
Phosphate buffer pH 6.8
Why is only
40% dissolution
reached in
buffer pH 6.8?

23. Ciprofloxacin (cont.) Solubility is pH dependent:
“Highly soluble” at pH < 6
100% dissolution obtained in pH 4.5 and pH 1.16
At pH 6.8 and 40°C the solubility is about 0.2 mg/ml
this explains 40% dissolution for 500 mg dose !!
40°C ▼
Questions:
May change in particle size affect the dissolution rate at pH 6.8?
What dissolution level should ciprofloxacin 250 mg tablets be able to reach in pH 6.8 medium?
X. Yu et al. Pharm. Research, 11, (1994)

24. Example 3 Clarithromycin tablets – Proportional formulations
2 strengths prepared from same granulate
f2 = 31
Profiles not similar !
Solubility of the API in buffer pH 6.8 “low” according to BCS
Do you expect that particle size or polymorphism may have effect on the profiles?

25. Example 4 Isoniazid/Ethambutol tablets
Purpose of study
Part of quality testing according to PhInt monograph
Samples studied
Note that the Product A is double strength
(though it has fastest dissolution rate !)
Isoniazid / Ethambutol 2HCl
Product
300mg / 800mg A
150mg / 400mg B C D

26. Example 4 Isoniazid/Ethambutol tablets
Conditions and requirement according to
Monograph for Isoniazid and Ethambutol hydrochloride tablets in
International Pharmacopoeia (PhInt)
Apparatus
Paddle, 75 rpm
Dissolution medium
pH 6.8 phosphate buffer
Volume of medium
500 ml
Degassed?
No (undegassed)
Temperature
37°C ± 0.5°C
Sampling points
10, 15, 20, 30, 45, an 60
Requirement
≥ 85% of label claim dissolved in 30 min

27. Isoniazid/Ethambutol tablets (1) Medium: pH 6.8 phosphate buffer

28. Isoniazid/Ethambutol tablets (2) Medium: pH 6.8 phosphate buffer
fails requirement: <85%

29. Isoniazid/Ethambutol tablets (3) Medium: pH 6.8 phosphate bufferC D

30. Isoniazid/Ethambutol tablets (4) Discussion of results
The dissolution profiles of the 2 APIs in a particular product are similar (this is true for all 4 products)
Both APIs are highly soluble (BCS definition)
The products show different dissolution rates
Dissolution rate A > B ≈ C >> D
Disintegration (min)
Dissolution rate related to disintegration time
f2 values show that B & C have similar profiles
Dissolution method discriminating
Typical type of results during pharmaceutical R&D

31. Example 5 4FDC TB tablets Dissolution conditions (USP)
Rifampicin/Isoniazid/Pyrazinamide/Ethambutol 150mg/75mg/400mg/275mg
Dissolution conditions (USP)
900 ml pH 6.8 phosphate buffer (not degassed)
paddle, 100 rpm
37°C ± 0.5°C
Sampling points: 10, 15, 20, 30 and 45 minutes
USP requirement: 75% (Q) in 45 minutes (all APIs)
Rifampicin stability
Good in pH 6.8 buffer (reason for choice)
Poor at lower pH

32. Example 5 4FDC TB tablets (2)
Similar dissolution profiles
Isoniazid, pyrazinamide & ethambutol hydrochloride
high solubility (BCS) – expected to be similar
Rifampicin shows slower dissolution rate
Low solubility (BCS)

33. Example 5 4FDC TB tablets (3)
WHO Technical Report Series 937, page 8:
The Expert Committee “agreed that rifampicin should serve as the marker for dissolution testing in the relevant FDCs, as it was the least soluble substance.”
This data supports the decision

34. Example 6 Rifamicin powder
Rifampicin exist in 3 solid state forms:
Polymorph I
Polymorph II
Amorphous form
Commercial material contains:
Polymorph II (predominantly) or
Mixture of polymorph II and amorphous form
Five commercial samples (A to E) tested
Samples A, B & E: Form II
Samples C & D: Form II + amorphous form

35. Example 6 Rifamicin powder (2)
Medium: Water
Profiles A, B & E are similar (f2 ≥ 50)
Profiles C & D are similar (f2 ≥ 50) - dissolution incomplete
Profiles A, B, E dissimilar from profiles C,D (f2 < 50)
A, B, E (form II)
C, D (form II + amorph)

36. Example 6 Rifamicin powder (3)
Presence of amorphous form slows down dissolution of raw material powder at higher pH (f2 test)
Reason: Agglomeration / wettability
Comparative powder dissolution powerful tool for
selection of API manufacturer and
even in-house specification ?
Dissolution method for API powders
overcome floating on medium see reference below
Reference:
S.Q Henwood et al. Drug Dev. & Ind. Pharm. 26, (2000) (RIIP)
amorphous form

37. Applications
Comparative dissolution: basic tool for selection of the formulation during product development
By comparison of the dissolution profiles of comparator product with those of development batches
Optimise, to get similar profiles
Hint: start with comparator product before development
To get dissolution profiles required for the generic product
Disintegration testing can aid in the early phases
Maximize the chances of bioequivalence
Integral part of development report
dossier and PQIF

38. Applications (cont.)
Scale up from development (pivotal) to production batches
To demonstrate in vitro similarity of such batches
This is considered essential for retention of efficacy and quality
Note that bioequivalence studies are done normally only once on a bio-batch during development
It must be demonstrated that the product retains the dissolution characteristics up to production scale
The studies should be submitted in dossier as part of the FPP development report

39. Applications (cont.)
Selection of the dissolution specifications for product release & stability purposes
Conditions and acceptance criteria to be set
The dissolution profiles of the bio-batch should be used for this purpose
A dissolution specification should be able to detect inadequate release properties of the commercial batches
A “generous” dissolution limit has no quality selectivity
Example: Isoniazid/Ethambutol hydrochloride tablets

40. Applications (cont.)
Demonstration of in vivo bioequivalence of one or more of the lower strength(s) of an FPP may be waived based on
an acceptable in vivo BE study of the highest strength against the comparator product
demonstration of similarity of dissolution profiles between the higher (bio-batch) and lower strength
if the lower strength is proportionally similar in formula to the higher strength (bio-batch)
if all pharmacokinetic requirements are met
Consult the bio-guideline, also for reverse situation

41. Applications (cont.) Post-approval amendment application
A requirement of a particular change may be to demonstrate that the profiles of the amendment batch and the current batch are similar
Consult guideline on variations

42. Reporting Comparative dissolution data
Full report, including
Purpose of study
Products / batches information
Batch number, manufacturing/expiry date, packaging, etc.
CoA & size for “own” batches (and BMR for bio-studies report)
Dissolution conditions and method
Analytical method or reference to part of dossier
Results (% API dissolved)
Tabulated
Graphically
Similarity determination / calculation
Conclusion

43. Comparative dissolution testing Guidelines
Multisource (generic) pharmaceutical products: guidelines on registration requirements to establish interchangeability
Paragraph 9: In vitro testing (dissolution)
WHO Technical Report Series 937, Annex 7 (2006)
Dissolution testing. Supplement 1 to
Guideline on Submission of Documentation for Prequalification of Multi-source (Generic) Finished Pharmaceutical Products (FPPs) Used in the Treatment of HIV/AIDS, Malaria and Tuberculosis
(Generic guideline)

44. Comparative dissolution testing Relevant training material
WHO/FIP Training Workshop on Dissolution, Pharmaceutical Product Interchangeability and Biopharmaceuticals Classification System (BCS)
Kiev, Ukraine, June 2007
On WHO Prequalification website
Strongly recommended

45. Closing remarks Comparative dissolution plays an important role in:
product development
up-scaling from development to production
setting of quality dissolution specifications
waiving of BE studies in proportionally similar formulations
post-approval changes (variations)
Manufacturers should
understand the basic requirements of conducting comparative dissolution testing
know how and where to apply it
be able to determine similarity of profiles
All data in presentation generated at the RIIP

46. Multipoint dissolution Example of (fast) manual sample pulling