Britian's consumer watchdog said the company offered doctors only an expensive version of the drug by withdrawing Gaviscon Original Liquid from the NHS prescription database.
Reckitt had delisted the drug so that doctors searching for the product under its brand name would fail to find the potentially cheaper generic name.
The OFT has sent a "statement of objections" to Reckitt, which gives companies notice of a proposed infringement decision under the Competition Act 1998. This can potentially lead to a fine of 10 per cent of a company's turnover if found guilty.
Reckitt has a turnover of over £7bn a year and makes many household brands such as Dettol, Clearasil, Nurofen, Finish, and Cillit Bang.
The OFT move follows an investigation by the BBC's Newsnight programme in 2008, which estimated the cost to the NHS caused by Reckitt's action could be £40m.