Diclofenac (Voltaren)

• Generic name: Diclofenac Potassium; Diclofenac Sodium
• Brand names: Voltaren, Cataflam
• Pharmacologic category: Nonsteroidal Anti-inflammatory Drug
• FDA approved: July 28, 1988
• Pregnancy risk factor: B (topical); C (oral)/D (3rd trimester)

Diclofenac is a relatively strong non-steroidal anti-inflammatory drug (NSAID) of the arylalkanoic acid family. This medicine has analgesic, anti-inflammatory, and antipyretic properties.

It is effective in cases of moderate to severe pain where quick pain relief is required. It is used to reduce inflammation and pain in the following conditions:

• Ankylosing spondylitis
• Menstrual pain (Primary dysmenorrhea)
• Rheumatoid arthritis
• Osteoarthritis
• Gout attacks
• Mild to moderate post-operative or post-traumatic pain

In the United States all diclofenac (Voltaren) formulations are classified as Rx-only.

In several countries diclofenac is available over-the-counter (OTC). OTC preparations are licensed in New Zealand, Australia, Sweden, Switzerland, Germany, South Africa.

• Duration of action: The duration of action of one single dose is much longer (6 to 8 hours) than the very short half-life of the drug indicates. This could partly be due to a particular high concentration achieved in synovial fluids.
• Onset of action: Potassium salt (Cataflam) is more rapid than sodium salt (Voltaren) because it dissolves in the stomach instead of the duodenum.
• Metabolism: Hepatic to several metabolites
• Elimination half-life: 2 hours
• Excretion: Urine (65%); feces (35%)

• Diclofenac is among the better tolerated NSAIDs
• Rather potent pain reliever
• May alleviate the discomfort associated with inflammatory infections of the throat, ear, or nose

• Hypersensitivity (anaphylactoid) reactions. Even in patients without prior exposure anaphylactoid reactions may occur.
• Cardiovascular side effects. May cause cardiovascular problems, including heart attack, stroke, and new onset or worsening of preexisting hypertension.
• Gastrointestinal side effects. Long-term use of diclofenac and similar NSAIDs predisposes for peptic ulcers. It can cause gastrointestinal bleeding, ulceration, and perforation of the stomach, small intestine, or large intestine. These serious problems can occur at any time, and often without warning signs or symptoms.

• Alzheimer's disease. Diclofenac may prevent the development of Alzheimer's disease if given daily in small doses during many years. All investigations were stopped after it was found that some of the other investigated NSAIDs (naproxen, rofecoxib) caused a higher incidence of death cases due to cardiovascular side effects and stroke compared to placebo.
• Shy-Drager syndrome. Diclofenac has been found to increase the blood pressure in patients with Shy-Drager syndrome (autonomous hypotension) often seen in diabetic patients. Currently, this use is highly investigational and cannot be recommended as routine treatment.

Inhibits prostaglandin synthesis by decreasing the activity of the enzyme, cyclooxygenase, which results in decreased formation of prostaglandin precursors. Mechanism of action for the treatment of AK has not been established.

• 1. U.S. FDA. Diclofenac Prescribing Information (PDF format)