During the last week of August, PharMerica Corp. adopted what it called a “poison pill measure” to halt an unwanted buyout from Omnicare Inc.

The poison pill measure, also known as a shareholders’ rights plan, was created to dissuade Omnicare from following through on its attempt to buy PharMerica by diluting the value of any shares that Omnicare can get its hands on.

According to PharMerica, the plan goes into effect when an individual or group takes hold of 15 percent of more of PharMerica stock without approval of PharMerica’s Board of Directors. Also, the plan goes into effect if an individual or group begins a tender offer that provides the offering party at least 15 percent of the stock of PharMerica. If the plan is triggered, stockholders other than the person or group acquiring stock will be able to exercise the options of PharMerica for twice the exercise price of $45.

The options will trade with the company stock and expire after the annual 2012 meeting of PharMerica should the shareholders not approve the stockholder rights plan. If the stockholder rights plan is approved the options will have a life of 10 years.

San Diego shareholders’ rights attorneys note that Omnicare is a drug distributor to nursing homes and other kinds of long-term care providers. They have made public an offer to buy PharMerica for $457 million that calculates to $15 per share. PharMerica responded by stating that the offer was not only too low but would likely be barred by antitrust authorities.

Source: Bloomberg Businessweek “PharMerica adopts shareholder rights plan” Aug. 25, 2011