Bayer’s legal team attempted to derail efforts to consolidate lawsuits over alleged Mirena IUD pseudotumor cerebri and idiopathic hypertension side effects into a single coordinated legal action in June. Bayer is already facing a separate legal action over the Mirena birth control device.

The Mirena birth control device is an intrauterine device (IUD), a type of birth control implant. It is designed to be inserted into the uterus by a doctor, where it remains for up to five years. However, Mirena lawsuits have alleged that the Mirena IUD may cause serious IUD side effects.

In May, a group of plaintiffs filed a motion to group all of the Mirena pseudotumor cerebri lawsuits into a single coordinated legal action called a multidistrict litigation, or MDL.

The U.S. court system can group similar lawsuits into MDLs to help coordinate evidence and avoid duplication of efforts in nearly identical lawsuits. MDLs have some similarities to the more familiar class action lawsuit in that both involve a group of plaintiffs making similar allegations against the same defendant.

The Mirena lawsuits in question all relate to an alleged group of related Mirena IUD side effects. This includes pseudotumor cerebri (PTC) and idiopathic intracranial hypertension (IIH).

In idiopathic intracranial hypertension, the blood pressure in the skull is higher than normal, risking a number of serious complications. Similarly, pseudotumor cerebri involves a buildup of pressure in the brain.

However, in the case of PTC, the buildup of fluid and pressure on the brain causes symptoms that mimic brain tumors. In fact, the name “pseudotumor cerebri” is a scientific Latin for “fake tumor of the brain.”

PTC can cause symptoms like blurred vision, tunnel vision, blindness, headache, and other neurological problems.

These Mirena PTC lawsuits allege that the Mirena IUD caused their complications and that Bayer has not done enough to protect the public from this risk.

However, Bayer has countered that there are not enough Mirena lawsuits over PTC and IIH to warrant a MDL. At the time, there were only roughly 10 Mirena lawsuits related to PTC and IIH.

Bayer is already facing a separate MDL over other alleged Mirena IUD complications, including perforation of the uterus by the birth control device. This separate group of Mirena lawsuits includes over 800 individuals alleging perforation and other complications.

The Mirena lawsuits over PTC and IIH would form a second, separate MDL against Bayer over alleged Mirena IUD side effects.