Question from practice: diclofenac salts: potassium or sodium?

Oral formulations of diclofenac are formulated as either the sodium or potassium salt. The sodium salt is found in the original prescription-only formulation of Voltarol (enteric coated) 25mg and 50mg tablets and its generic equivalents that account for most oral diclofenac preparations currently used in the UK. The potassium salt is contained in POM Voltarol Rapid 25mg and 50mg products and their generic equivalents; as well as in the over-the-counter products such as Voltarol Joint Pain, Voltarol Pain-eze, and Actavis’s Double Action Pain Relief tablets, which are also marketed as Boots Diclofenac Potassium Tablets. All these OTC diclofenac potassium products contain 12.5mg per tablet and share the adult dose regimen of two tablets initially, followed by one or two tablets every four to six hours as needed, with no more than six tablets (ie, 75mg) to be taken in any 24-hour period. They are indicated for short-term relief of headache, dental pain, period pain, rheumatic pain, muscular pain and backache and the symptoms of colds and influenza, including fever; with a recommendation not to exceed three days’ treatment. The OTC tablets can be used by people over 14 years of age.