Something else worth swallowing
Christopher Yates talks about the new drug touted as a female viagra
Dubbed ‘Female Viagra’, the drug Lady Prelox has gone on sale in the UK this week, marketed as being ‘clinically proven’ to improve female sexual dysfunction. Whether or not it works is another matter.
Despite the marketing, Lady Prelox is not related to Viagra, but is a new version of Prelox, a combination of L-arginine and a pine bark extract called pycnogenol. Prelox has been used to treat erectile dysfunction (ED) and has shown some effectiveness.
The main differences between the male and female version of Prelox are a lower dose of L-arginine and the colour of the pills – in a stunning display of gender stereotyping, Lady Prelox is pink and Prelox is blue.
Blood flow to the penis is the driving force behind an erection. To increase flow, blood vessels within the penis dilate, allowing more blood in. This vasodilatation is due to the action of nitric oxide (NO), which is produced from L-arginine. Viagra works downstream of NO by blocking the effects of an enzyme that switches off the pathway turned on by NO.
L-arginine supplements have been shown to improve the symptoms of ED, but in a weak and highly dose-dependent way. Assuming vasodilatation is important for female sexual function, the lower dose present in Lady Prelox (200 mg versus 700 mg) could render it less effective.
The other ingredient in Prelox, pycnogenol, stimulates e-NOS, the enzyme responsible for producing NO from L-arginine. This leads to a synergistic effect between the two ingredients, with pycnogenol increasing the activity of e-NOS and the L-arginine giving the enzyme the substrate it needs. In a very small (21 people) clinical trial, there is an improvement in male sexual function compared to placebo, measured by responses to a questionnaire.
Unfortunately, this trial and all others investigating the effects of Prelox on ED have been small in size (under 50 patients). Some of the trials did not compare the effects of Prelox to anything else, meaning the improvement could simply be thanks to the placebo effect.
In a clinical trial of Lady Prelox on 100 women aged 37-45, all patients were given a management plan, consisting of changes to lifestyle, diet, exercise and stress control. Half the women were also given Lady Prelox. Both groups showed increased sexual function, with a larger increase in the group taking Prelox. As the control group were not given anything in place of Prelox, this difference could once again simply be down to the placebo effect.
Another trial, on post-menopausal women, gave an improvement in sexual function compared to placebo. However, this trial was only single-blind, meaning that whilst the patients did not know which treatment they were getting, the doctors running the trial did.
Not only that, but unlike the causes of male ED, the causes of female sexual dysfunction are unclear. Whilst there is an increase in genital blood flow during arousal, whether improving this flow leads to an improvement in sexual function is not known.
If sexual dysfunction is psychological, improving blood flow will not help. Prelox, like Viagra, requires the user to be aroused and so as Dr Graham Jackson, chairman of the Sexual Advice Association, told the Daily Mail, “if you’re not turned on by your partner, no amount of tablets will help.”
The results of the trials of this supplement have been covered in the Daily Mail, the Telegraph, and on websites around the world. As with many science articles in the news, there is an acceptance of the results of the clinical trials without critically appraising the methods. This problem is by no means unique to this pill or these articles, which do point out that the biology behind female sexual dysfunction is still unclear.
Overall, this supplement seems to be a weaker, pink version of a pill that may help treat erectile dysfunction, being marketed to treat something with an unknown biological basis in women based on two small, unreliable clinical trials. If you’d like some, it costs £37.95 for a month’s supply, and get in touch with Felix Science, as we would love to hear all about it.
