Zulresso, also known as brexanolone, has just been approved to treat postpartum depression by the U.S. Food and Drug Administration (FDA). This is the first drug ever approved to specifically assist women suffering from this mood disorder and the second new antidepressant treatment passed by the FDA this month, after the landmark approval of esketamine.

It has been decades since an antidepressant agent with a new mechanism of action was approved for clinical use by the FDA. Earlier this month a ketamine-like nasal spray was finally approved to target treatment-resistant depression, and now a second novel antidepressant has been approved by the agency, this time designed to treat women suffering from postpartum depression.

Zulresso has a novel mechanism of action that is unlike any other approved antidepressant drug. When a woman is pregnant her body releases a compound called allopregnanolone, which is known to activate GABA receptors in the brain. In order to counteract this, a woman's GABA receptors go dormant during pregnancy, but after a woman gives birth her allopregnanolone levels return to normal, and her GABA receptors reactivate.

It has been hypothesized that in some women those GABA receptors do not effectively, or quickly, reactivate, and this is what can trigger postpartum depression. Zulresso is a synthetic form of allopregnanolone designed to rapidly activate a woman's GABA receptors and reduce acute symptoms of depression in the days after giving birth.

Across multiple human trials leading up to the eventual FDA approval, Zulresso was found to be effective in reducing symptoms of depression, however, the drug was not without side effects. It was found to occasionally result in severe sedation and possible sudden loss of consciousness during administration. This caused the FDA to approve the drug through what is called a Risk Evaluation and Mitigation Strategy.

The restricted approval means the drug can only be administered by certified heath care providers in health care facilities. The safest way to administer Zulresso was found to be through a slow intravenous infusion lasting 60 hours. This makes the drug reasonably onerous and difficult for many patients to obtain, so at this stage the treatment is only recommend for patients suffering from severe postpartum depression.

Alongside the time-consuming administration protocol, Zulresso is also not cheap. It has been reported a single treatment will cost around US$34,000, and that is before hospital costs for three days are included.

Despite these limitations the FDA approval offers women suffering from the devastating effects of postpartum depression an important new treatment option developed specifically for this mental health condition.

Source: FDA