Drug giants GlaxoSmithKline and Novartis are being taken to court by Australia's consumer watchdog over "false or misleading" claims in the marketing of pain relief products, it was announced Wednesday.

The case by the Australian Competition and Consumer Commission centres around their Voltaren Osteo Gel and Voltaren Emulgel lines.

It claims they represented Osteo Gel on its packaging and online as specifically formulated for treating osteoarthritis and was more effective than Emulgel, when they had identical formulas.

Both products contain the same active ingredient, diclofenac diethylammonium gel 11.6mg/g, which acts in a non-specific manner to reduce local pain and inflammation wherever it is applied.