Hackensack, N.J. ? A prominent group flexed its legal muscle last week against an alleged drug industry attempt to stall access to low-cost medicines.

AARP, which represents 35 million members 50 years and older, joined three consumer lawsuits that accused several pharmaceutical companies of using various tactics to block generic drugs from reaching the market. The organization said Wednesday’s move marked the first time it was becoming directly involved in litigation against drug manufacturers.

“We’re trying to change some behavior,” said Bruce Vignery, an attorney with AARP.

AARP said it chose three cases because they involved treatments widely used by Americans 50 and over. The cases involve:

Buspar, an anti-anxiety drug. The suit alleges Bristol-Myers Squibb Co. abused patent law to prevent access to generic versions.

K-Dur 20, a potassium supplement. The plaintiffs allege Schering-Plough Corp., Upsher-Smith Laboratories, and Wyeth illegally conspired to prevent generics from reaching the market.

Tamoxifen, a breast-cancer therapy. The case alleges AstraZeneca PLC paid generic drug maker Barr Laboratories to supply the drug that was not a true “generic” in terms of price.