This document discusses drug excipient interactions, which can be either physical or chemical in nature. Physical interactions affect the dissolution of the drug, such as between cationic drugs and anionic superdisintegrants which can delay release. Chemical interactions are always detrimental and include hydrolysis, oxidation, isomerization, and Maillard reactions. These interactions can be characterized using thermal, spectroscopic, chromatographic, and microscopic methods as well as accelerated stability studies and radiolabelled techniques.

1. Drug excipient interactions
Mr Santosh S Sarnaik
MS Pharmaceutics
NIPER Guwahati

2. Introduction
Proper design of formulation
Physical interaction
Chemical interaction
Beneficial or detrimental

3. Types
Drug interactions
Drug- excipient Drug – drug Drug packaging

4. Drug excipient interactions
There are two types:
Physical
Chemical

5. Physical interaction
• Affect dissolution of drug
• Example-
1. Cationic drug and anionic superdisintegrants – delayed release
2. Cyclodextrin class ii drug- increase dissolution

6. Chemical interaction
• Always detrimental
• Various types of chemical interactions:
1. Hydrolysis- amide and ester group e.g lactic acid(increases pH)
2. Oxidation- alcohol and aldehyde e.g. benzocaine(silicified)
3. Photooxidation- sunlight or artificial light(Riboflavin)
4. Isomerization- dextro to levo and vice versa(Adrenaline)
5. Mailard reaction- between primary amine and reducing
sugar(isoniazid and lactose)

7. Characterization
• Thermal – DSC, TGA, isothermal microcalorimetry
• Spectroscopic method-FT-IR, ssNMR
• Chromatographic method- TLC, HPLC, HPTLC
• Microscopy- SEM
• Accelerated stability study
• Radiolabelled techniques
• Vapour pressure osmometry