'Female Viagra' - a closer look at flibanserin

The first drug to treat low sexual desire in women has received US Food and Drug Administration (FDA) approval.

But the little pink tablets, to be sold under the brand name Addyi, have proven controversial. Here is what you need to know about what has been dubbed the "female Viagra".

Er, it shouldn't really be called 'female Viagra'

That flibanserin - to use its chemical name - would draw comparison to its blockbuster male equivalent was inevitable but the nickname is misleading.

While a Viagra pill treats erectile dysfunction by improving blood flow to the penis, flibanserin was developed as an anti-depressant and boosts sexual desire by balancing chemicals in the brain.

Specifically, the drug treats hypoactive sexual desire disorder (HSDD), essentially a lack of libido that causes distress and is thought to affect between 5.5 million and 8.6 million US women.

It is something of a holy grail for so-called Big Pharma

A stress ball at the offices Sprout Pharmaceuticals - the small-scale company who have made a breakthrough

By gaining approval, Addyi's makers Sprout succeeded where medical giants have failed.

Pfizer, Procter & Gamble and others have all tried to develop products treating low sexual desire in women.

While the product has its pros and cons, medical practitioners now have a new treatment available to treat a common condition.

Sprout plans to launch the product in mid-October. A rival, Palatin Technologies, has an alternative treatment for HSDD in late-stage trials.

Addyi has minimal effects, but potentially severe side-effects

Women taking the drug reported around one more sexually satisfying event a month, compared to a placebo.

But supporters say even this small benefit is worthwhile - "I want to want my husband, it is that simple,'' said Amanda Parrish, one of the women involved in trials.

The FDA's approval of Addyi comes with tough safety measures, meaning that its usage is unlikely to be as widespread as with male Viagra.

Doctors will only be able to prescribe the drug after counselling patients about potential side-effects, including low blood pressure, nausea and fainting.

Pharmacists must remind patients not to drink alcohol while taking the drug, which can make the effects more severe.

And while Viagra can be taken shortly before having sex, Addyi must be taken daily.

It is a victory for campaigners

"This is the biggest breakthrough in women's sexual health since the advent of 'the Pill' for contraception," The National Consumers League said in a statement.

Lobbying group Even the Score, which has campaigned for better treatment of women's sexual health, accused the FDA of gender bias, highlighting the numerous products available treating sexual dysfunction in men, although none of them treat low desire.

Some physicians have welcomed the approval too, such as Dr Lauren Streicher, associate professor of clinical obstetrics and gynaecology at Northwestern University.

"This is an enormous, enormous advance in women's health.

"Of all the sexual dysfunctions, this is by far the most common in every single age category and we've had no options for women up until now."

But sceptics remain

Addyi's critics argue that the FDA has approved a drug of marginal impact with potentially serious side-effects. Previous versions of the drug have been rejected by the FDA.

"Unfortunately, we haven't heard the last of this drug," warned consumer group Public Citizen.

PharmedOut, which focuses on marketing in pharmaceuticals, said the FDA has been swayed by "a clever, aggressive public relations campaign".

"This opens the way for drug companies to pressure the FDA through public relations campaigns to approve more bad drugs: It's bad news for rational drug approval," Adriane Fugh-Berman, a pharmacology professor and director of PharmedOut told the Washington Post.

The medical status of HSDD has been disputed, with some arguing that low libido in women cannot be treated in the same way as erectile dysfunction in men.

"Women's sexuality is very complicated. It's not a matter of just taking that pill, by the way, and then all of a sudden the lights go on," Judy Kuriansky, a clinical psychologist and certified sex therapist, told CNN.