Glossary

Pharmaceutical Development

is the process of developing a pharmaceutical product that contains one or more specific active pharmaceutical ingredients (APIs) in a specific dosage form. It involves:

  • selecting appropriate excipients;
  • determining the appropriate administration route(s) and dosage form(s); and
  • designing the manufacturing process in order to achieve a drug product that is stable, safe, effective, and convenient for the patient to use. 

Pharmaceutical development involves:

  • physicochemical and biological characterization of the API;
  • evaluating the potential effect of the API’s physicochemical properties on the performance of the final product;
  • choosing suitable excipients, defining their concentrations and their influence on stability, and determining the bioavailability of the final formulation; and finallyestablishing the compatibility of the API with excipients and with any other APIs that may be present in the formulation.

Different techniques are needed to perform the physicochemical characterization of APIs and excipients; these include thermal analysis and rheology.

Thermal analysis is crucial for understanding the physical and chemical stability, compatibility, PolymorphismPolymorphism is the ability of a solid material to form different crystalline structures (synonyms:  forms, modifications).polymorphism, and processing characteristics of pharmaceutical compounds. Key thermal analysis methods include Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Thermomechanical Analysis (TMA); see table 1.

Rheology helps develop and optimize the formulation, processing, stability, and delivery of pharmaceutical products. It provides insights into the viscosity, viscoelasticity, and texture of formulations (table 1) that are essential for ensuring consistent quality, efficacy, and patient acceptability.

Pharmaceutical development is guided by ICH* guidelines, particularly ICH Q8 (R2) (Pharmaceutical Development), which provides a comprehensive framework for a systematic approach to drug development. Other guidelines such as ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System) complement ICH Q8 (R2). The first provides principles and examples of tools for quality risk management and the second establishes a comprehensive quality system for the entire lifecycle of a pharmaceutical product.

*ICH: International Council of Harmonization

Table 1: Thermal analysis and rheology applied in pharmaceutical development.

 DSCTGATMARheology
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Temperature

x

 

 

x

Glass transition

x

 

x

 
PolymorphismPolymorphism is the ability of a solid material to form different crystalline structures (synonyms:  forms, modifications).Polymorphism

x

 

x

 
Thermal stability

x

x

 

 
Oxidative stability

x

x

 

 
Compatibility

x

x

  
Release of volatiles

x

x

 

 

Hygroscopicity 

x

  
Expansion behavior 

 

x

 
Dynamic viscosity 

 

 

x

Flow behavior  

 

x

Yield StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress  

 

x

ThixotropyFor most liquids, shear thinning is reversible and the liquids will at some point in time gain their original viscosity when a shearing force is removed.Thixotropy   

x

Viscoelastic properties   

x

Texture analysis  

 

x