The U.S. Justice Department is in the process of organizing the hundreds of testosterone drug lawsuits into a single legal proceeding. However, drug giant Pfizer Inc. is arguing that lawsuits over its drugs should be treated separately.

There has been a recent wave of concern over low testosterone, a condition in which the level of androgens, or “male hormones,” decreases in men as they age. While decreasing levels of testosterone are a normal part of aging, an excessively sharp decline can produce a variety of symptoms including lethargy, irritability, and reduced libido. Testosterone-replacement drugs, also called androgen-replacement drugs (androgens are a family of hormones that include testosterone), are designed to alleviate these symptoms by replacing the declining hormones. However, concerns have arisen about the possible risk of side effects.

Androgen-replacement drugs have been allegedly linked to an increased risk of blood clot-related complications. While blood clots are an important part of human physiology, they can cause medical emergencies, including strokes, pulmonary embolism, and certain types of heart attacks. It has been alleged that androgen-replacement drugs are linked to an increased risk of these complications.

At present, the various androgen replacement lawsuits are in the process of being organized into a type of group lawsuit called multidistrict litigation or MDL. MDLs are similar to class action lawsuits in that they allow a group of individuals to take legal action against the same defendant over similar alleged harms. At present, the U.S. Judicial Panel on Multidistrict Litigation (JPML) is coordinating individual cases into a single MDL.

The proposed testosterone MDL against the makers of androgen replacement drugs currently includes several different companies, including AbbVie Inc., Abbott Laboratories, Eli Lilly and others. All of these companies make various androgen replacement drugs including gels and creams. The motion to create a testosterone lawsuit MDL came in response to a motion that was filed by plaintiffs in several individual cases in March of 2014. Similar motions have also been filed by other plaintiffs. However, most of the companies involved have agreed to the MDL, including AbbVive, the company that makes Androgel. Androgel has a 60 percent share of the market on low-T drugs, and makes up a comparable percentage of the cases in the proposed MDL. However, Pfizer has argued that they should not be included in the consolidated testosterone product lawsuit.

While Pfizer does produce a testosterone drug, the company has filed a motion arguing that its product and the circumstances surrounding its testosterone drug are different enough that they do not belong in the MDL. The bulk of testosterone-based drugs are creams or gels, designed to be absorbed through the skin. However, Pfizer’s product is designed to be injected. Additionally, most of the individual cases in the proposed MDL involve the allegation that low-T drugs are aggressively advertised on television. However, Pfizer contends that since it never advertised their low-T drugs, the lawsuits against Pfizer are distinct from the other cases in the proposed MDL.