WOODCLIFF LAKE, N.J., July 26 /PRNewswire-FirstCall/ -- Par Pharmaceutical Companies, Inc. (NYSE: PRX - News) today announced it has begun shipping metoprolol succinate extended release 100 mg and 200 mg tablets. As previously announced, in November 2006 Par entered into a supply and distribution agreement with AstraZeneca in the U.S. to distribute metoprolol succinate extended release tablets, which is substitutable for AstraZeneca’s TOPROL-XL® extended release tablets. Par began shipping 25 mg tablets of generic Toprol-XL at that time.