Answer
They are different salt forms of diclofenac. In this gel, diclofenac diethylammonium content is expressed as an equivalent amount of diclofenac sodium.
Sources for this answer
- Voltarol Osteoarthritis Joint Pain Relief 1.16% Gel — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.