Available now: A 'female Viagra', but it comes with a warning

The first drug to treat low sexual desire in premenopausal women, dubbed "female Viagra", has been approved in the United States, but with a warning about potentially dangerous side effects such as severe low blood pressure and fainting.

The US Food and Drug Administration on Tuesday approved Addyi (flibanserin) to treat acquired, generalised hypoactive sexual desire disorder in premenopausal women.

Prior to Addyi's approval, there were no FDA-approved treatments for sexual desire disorders in men or women.

"Today's approval provides women distressed by their low sexual desire with an approved treatment option," said Janet Woodcock, director of the FDA's Centre for Drug Evaluation and Research.

HSDD is characterised by low sexual desire that causes marked distress or interpersonal difficulty and is not due to a co-existing medical or psychiatric condition, problems within the relationship, or the effects of a medication or other drug substance, FDA said.

HSDD is acquired when it develops in a patient who previously had no problems with sexual desire. HSDD is generalised when it occurs regardless of the type of sexual activity, the situation or the sexual partner.

"Because of a potentially serious interaction with alcohol, treatment with Addyi will only be available through certified health care professionals and certified pharmacies," said Woodcock.

"Patients and prescribers should fully understand the risks associated with the use of Addyi before considering treatment," she said.

Addyi can cause severely low blood pressure (hypotension) and loss of consciousness (syncope). These risks are increased and more severe when patients drink alcohol or take Addyi with certain medicines (known as moderate or strong CYP3A4 inhibitors) that interfere with the breakdown of Addyi in the body.

Because of the alcohol interaction, the use of alcohol is contraindicated while taking Addyi. Health care professionals must assess the likelihood of the patient reliably abstaining from alcohol before prescribing Addyi, FDA said.

Addyi is being approved with a risk evaluation and mitigation strategy (REMS), which includes elements to assure safe use.

Addyi is a serotonin 1A receptor agonist and a serotonin 2A receptor antagonist, but the mechanism by which the drug improves sexual desire and related distress is not known.

Addyi is taken once daily. It is dosed at bedtime to help decrease the risk of adverse events occurring due to possible hypotension, syncope and central nervous system depression (such as sleepiness and sedation).

Patients should discontinue treatment after eight weeks if they do not report an improvement in sexual desire and associated distress, FDA said.

The effectiveness of the 100 mg bedtime dose of Addyi was evaluated in three 24-week randomised, double-blind, placebo-controlled trials in about 2,400 premenopausal women with acquired, generalised HSDD.