In Vitro Tests Other Than Dissolution for Bioequivalence Assessment

While dissolution testing is a primary tool for predicting bioequivalence, several other in vitro methods contribute critical insights, especially for BCS Class II/IV drugs or complex formulations. Below is a list

1. Solubility Studies

• Determine the solubility of the API in various pH buffers (e.g., pH 1.2, 4.5, 6.8) and biorelevant media (FaSSIF, FeSSIF).
• Supports BCS classification and predicts absorption potential.

2. Permeability Assays

• Common models include Caco-2 cell monolayers and PAMPA (Parallel Artificial Membrane Permeability Assay).
• Used to estimate passive transport across intestinal cells and support BCS classification.

3. Precipitation Kinetics and Supersaturation Studies

• Evaluates the risk of drug precipitation upon exposure to intestinal conditions.
• Essential for amorphous or supersaturating drug delivery systems.

4. Dynamic Gastrointestinal Simulation Models

• Examples include TIM-1, USP Apparatus IV (flow-through cell).
• Simulate pH, transit time, and bile salt dynamics to predict bio-performance.

5. In Vitro Lipolysis

• Used for lipid-based formulations to assess digestion and drug solubilization under simulated GI conditions.
• Provides insight into drug release and absorption from self-emulsifying or lipid matrix systems.

6. IVIVC

• Establishes a mathematical relationship between in vitro dissolution and in vivo absorption.
• Useful for scaling up, biowaiver applications, and post-approval changes.

7. PSD Testing

• Determines size and uniformity of API particles.
• Affects dissolution, absorption rate, and content uniformity.

8. pH-Shift Dissolution Studies

• Simulate transition from gastric (acidic) to intestinal (neutral) environment.
• Useful for weakly basic drugs with pH-dependent solubility.

9. In Vitro Diffusion Testing

• Utilizes Franz diffusion cells or synthetic membranes.
• Relevant for semi-solid, transdermal, or topical dosage forms to assess drug permeation.

10. Mucoadhesion and Mucus Penetration Studies

• Evaluate formulation residence time on mucosal surfaces.
• Important for buccal, vaginal, nasal, or rectal dosage forms.

11. Rheological Testing

• Measures viscosity, thixotropy, and shear behavior of suspensions, gels, and emulsions.
• Influences dose uniformity and drug delivery behavior.

12. Gastric Emptying and GI Transit Simulation

• Uses models like BioGIT to mimic GI transit, gastric emptying, and drug mixing.
• Useful for drugs with narrow absorption windows or significant food effect

13. Powder Flow and Compaction Testing

• Evaluates flowability, compressibility, and compactibility.
• Influences tablet uniformity, disintegration, and ultimately bio-performance.

14. Physiologically Based Pharmacokinetic (PBPK) Modeling

• Tools like GastroPlus, Simcyp, and NONMEM use in vitro data to simulate in vivo PK profiles.
• Supports bioequivalence predictions, formulation optimization, and virtual BE studies.

Read also:

• Developing the Formula | Laying the Scientific Foundation
• Key Challenges in Bioequivalence (BE) Studies

Resource Person: Moinuddin Syed. Ph.D, PMP®