Example: Drug-Excipient Compatibility with DSC

DSC measurements were carried out with the DSC 204 F1 Nevio on:

• Diclofenac sodium (drug)
• Magnesium stearate (excipient)
• Physical mixture of both (weight ratio: 1:1)

Diclofenac sodium (blue curve): The peak at 280.6°C (onset) results from melting of diclofenac. Decomposition occurs immediately after melting (ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermal effect).

Magnesium stearate (orange curve): The endothermal effect with 3 maxima at 76.0°C, 89.1°C and 114.9°C is due partly to melting of the sample and partly to evaporation of surface and bound water.

Mixture diclofenac sodium + magnesium stearate (green curve): The peak of magnesium stearate is detected. However, melting and Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. decomposition of diclofenac are shifted to lower temperatures. This indicates an interaction between the drug and excipient.

--> Hint for possible incompatibility

Example: Drug-Excipient Incompatibility with TGA

TGA measurements were carried out with the TG 209 F1 Nevio on: 

• Diclofenac sodium (drug)
• Magnesium stearate (excipient)
• Physical mixture of both (weight ratio: 1:1)

Diclofenac sodium (blue curve): The sample begins losing mass at 303.1°C. This indicates the Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. decomposition of diclofenac.  

Magnesium stearate (orange curve): The mass loss of 3.9% is due to the release of surface and bound water. The Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. decomposition begins at 351°C.

Mixture of diclofenac sodium + magnesium stearate (green curve): Evaporation of the water present in magnesium stearate occurs in the same temperature range. However, Decomposition reactionA decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products. decomposition of the mixture begins at lower temperature (279°C) than with the single components. This indicates an interaction between the drug and excipient.

--> Hint for incompatibility