US pharmaceutical giant Pfizer is seeking to introduce an over-the-counter version of its top-selling heart drug Lipitor, The Wall Street Journal reported on Wednesday, citing unnamed sources.US regulators would need to approve the company\'s plan to sell the popular anti-cholesterol drug without a prescription, though, and such approval is uncertain, the newspaper said in an article published on its website.Selling an over-the-counter version of Lipitor could help Pfizer\'s bottom line as the company faces a \"patent cliff\" that threatens to erode profits during the next few years.Lipitor will lose patent protection and face competition from cheap generic copycats in the United States starting in November. Pfizer has already lost exclusive rights to sell the drug in Canada, Spain, Brazil and Mexico.The company reported on Tuesday that its revenues in the second quarter fell one percent from a year ago to $17.0 billion.Pfizer\'s shares were up 0.3 percent in after-market trading following the release of The Wall Street Journal\'s report.