The first federal trial over the bleeding risks of Xarelto, Johnson & Johnson and Bayer’s blockbuster anticoagulant, kicks off next week, with 18,000 more cases stacked up behind it. It will be the initial indicator of whether juries are likely to side with the drugmakers, ruling that their med is safe and effective, or patients, who claim the two companies hid the real risks of the blood thinner.

The case in New Orleans was brought by Joseph Boudreaux, who took the drug to cut his stroke risk but claims it caused internal bleeding that caused heart problems and resulted in a visit to intensive care unit for a week, the Chicago Tribune reported.

RELATED: Sources: Bayer, J&J's Xarelto faces first U.S. lawsuits

In their defense, J&J and Bayer point out that the FDA has deemed the drug safe and effective and that the risks it holds are clearly laid out on its label.

"The allegations made in the Xarelto lawsuits contradict years of data on the medicine and the FDA's determination of its safety and efficacy," William Foster, a spokesman for J&J's Janssen unit, told the newspaper.

According to the Tribune, court documents indicated that lawyers for the companies are likely to argue that the plaintiffs also can’t prove their doctors would have chosen not to prescribe the drug even if the labels read like the plaintiffs suggest.

The so-called bellwether case is important for the drugmakers, which generate significant revenue from Xarelto. It was Bayer’s top seller last year at $3.24 billion, and ranked third for J&J, with $2.5 billion in sales.

J&J actually saw sales of Xarelto fall 9.3% Q1 as payers squeezed deeper discounts out for Xarelto and rival drugs, Eliquis from Bristol-Myers Squibb and Pfizer, and Pradaxa from Boehringer Ingelheim.

RELATED: J&J's Remicade sees 'very little' biosim erosion, but payers are sticking it to Xarelto

While Xarelto continues to lead the market for new generation anticoagulants, Boehringer’s Pradaxa enjoys one advantage over the others: A reversal agent approved for it can be taken in case of uncontrolled bleeding.

J&J and Bayer, like Pfizer and BMS, had hoped to be able to offer their own bleeding antidotes last year but that effort was stymied when its developer, Portola, got an FDA complete response letter for AndexXa, delaying its entry into the market.

Related: Portola touts new data on recently rejected Xarelto, Eliquis antidote

Coumadin, which was the go-to blood thinner for years before these new, more tolerated, drugs were approved, also has an antidote. The lack of an antidote for Xarelto is likely to play into the trial.

How the jury receives and weighs all of these arguments in the decision it reaches is particularly important in these early cases. It provides bargaining leverage to one side of the other to potentially arrive at settlements for the thousands of cases waiting in the wings.

As law professor David Logan explained to the newspaper, "Once the results are in, the parties may feel more confident about whether to settle the remaining claims."