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

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

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)

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

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 In multipoint dissolution multiple (≥ 3) samples are withdrawn from the dissolution medium during dissolution testing at pre-determined time points (intervals) and each sample is analysed for the % API dissolved A graph of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

Multi-point dissolution Example of dissolution profile

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

Comparative dissolution testing Example

Comparative dissolution testing When are dissolution profiles similar?

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

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

Comparative dissolution testing f2 calculation – spread-sheet design

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

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)

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?)

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)

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)

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

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 …………

Example 2 Ciprofloxacin: two batches (cont.) pH 1.2 Acetate buffer pH 6.8

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

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, 522-527 (1994)

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?

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

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

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

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

Isoniazid/Ethambutol tablets (3) Medium: pH 6.8 phosphate buffer C D

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) 7 11 11 21 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

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

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)

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

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

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)

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, 403-408 (2000) (RIIP) amorphous form

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

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

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

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

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

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

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)

Comparative dissolution testing Relevant training material WHO/FIP Training Workshop on Dissolution, Pharmaceutical Product Interchangeability and Biopharmaceuticals Classification System (BCS) Kiev, Ukraine, 25 - 27 June 2007 On WHO Prequalification website Strongly recommended

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

Multipoint dissolution Example of (fast) manual sample pulling