Two pharmaceutical companies have been warned over the packaging and marketing of some pain relievers.

The Commerce Commission has issued warnings to Glaxosmithkline Consumer Healthcare New Zealand Limited and AFT Pharmaceuticals Limited that some products were likely to have breached the Fair Trading Act.

Some Voltaren, Panadol and Maxiclear "twin" products contained the same active ingredients as single products but were marketed and packaged differently, the commission claims.

Claims the twin products could treat specific pain like osteoarthritis, back and neck pain, or sinus pain and congestion were found to be untrue, and they were no more effective as a single product treatment option.

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The commission says it's satisfied with the changes the companies have made, or are in the process of making after the warnings were issued.

No further action will be taken at this stage, and the commission expects other companies to take the warnings into account, it said.

In Februrary, the makers of four Nurofen products were fined $1.08 million over the packaging and adverts.

Claims Nurofen Migraine Pain, Nurofen Tension Headache, Nurofen Period Pain and Nurofen Back Pain targeted different pain were false when it was found all contained the same ingredients.