The US has approved the first pill for postpartum depression.

The Food and Drug Administration (FDA) said zuranolone, sold under the brand name Zurzuvae, has been approved as a once-daily pill taken for two weeks.

Until now, treatment for postpartum depression (PPD) was available only as an intravenous injection, the FDA said.

Drug manufacturers Sage Therapeutics and Biogen said the pill is expected to be available later this year. No price has yet been announced.

Similar to other forms of depression, symptoms of postpartum depression (PPD) can include sadness, loss of energy, suicidal thoughts, decreased ability to feel pleasure, or cognitive impairment, according to the FDA.

It is estimated that one in seven women experience symptoms of PPD in the US, research has found.

"Postpartum depression is a serious and potentially life-threatening condition in which women experience sadness, guilt, worthlessness—even, in severe cases, thoughts of harming themselves or their child," said Tiffany Farchione, head of psychiatry in the FDA's Center for Drug Evaluation and Research.

"And, because postpartum depression can disrupt the maternal-infant bond, it can also have consequences for the child's physical and emotional development."

Access to an oral medication will be beneficial for many women "coping with extreme, and sometimes life-threatening, feelings", she added.

Clinical trials showed the pill helped to significantly reduce depressive symptoms within three days. The effect of the medication was maintained at four weeks after the last dose, the FDA said.

It noted that the most common side-effects from taking Zurzuvae can include drowsiness, dizziness, diarrhoea, fatigue, the common cold, and urinary tract infection.

The agency said labelling contains a boxed warning noting that Zurzuvae can affect a person's ability to drive and perform other potentially hazardous activities. It recommends patients should not drive or operate heavy machinery for at least 12 hours after taking it.

Sage Therapeutics and Biogen had also sought approval to use zuranolone for major depressive disorder (MDD), or clinical depression. However, the FDA said the medication did not provide substantial evidence of effectiveness and said an additional study or studies would be needed.

The companies said they were evaluating their next steps.

Sage Therapeutic said it was "highly disappointed for patients, particularly amid the current mental health crisis and millions of people with MDD struggling to find symptom relief."