Pharmacy insights

Flibanserin (Addyin) in the UK

In this post, I will be looking at FDA approved Flibanserin (Addyin) drug with the emphasis on the effectives behind the treatment and its availability in the UK.

Flibanserin available under the branded name of Addyi is FDA approved (USA) drug for the treatment of premenopausal women (women who have not gone through menopause) with hypoactive (low) sexual desire disorder (HSDD).

Flibanserin (Addyin) has been wrongly named as ‘pink Viagra’ after drug used for erectile disfunction in men, Viagra (Sildenafil). More about this in one of the further paragraphs.

What is hypoactive (low) sexual desire disorder (HSDD)?

HSDD I characterised by a low or absent interest in sexual activity (‘low libido’). There is no UK guide or official information on HSDD and its diagnosis. Some of the following symptoms may be experienced by women with HSDD (Meston & Stanton, ND):

  • absent or reduced interest in sexual activity
  • absent or reduced sexual thoughts or fantasies
  • no or reduced initiation of sexual activity
  • lack of response to a partner’s attempts to initiate
  • absent or reduced sexual excitement or pleasure in most or all sexual encounters (e.g. regardless or partner)

Addyi.com provides a simple questionnaire which may help with the diagnosis of HSDD.

Numbers of factors contribute to HSDD including psychological and physical. Imbalance of chemicals in the areas of the brain responsible for the sexual drive may also be responsible for symptoms of HSDD.

Flibanserin (Addyi) indications of use

As described above Flibanserin (Addyi) is licensed for premenopausal women who experience low sexual desire that causes distress and interpersonal difficulties. This indication does not include similar symptoms caused by (FDA, 2015):

–    medical condition or being diagnosed with a psychiatric condition

–    use of medication

–    relationship problems

Addyi is not used to enhance sexual performance.

Flibanserin (Addyi) mechanism of action

It is thought that flibanserin controls serotonin and dopamine activity in certain parts of the brain, improving their balance and therefore is responsible for the regulation of sexual response (Allers et al, 2010).

Is Flibanserin (Addyi) available in the UK? Is it available on NHS?

Flibanserin (Addyi) is not available in the UK. If Flibanserin becomes available in the UK it would be available to a limited number of patients due to the high cost of this medication. Almost certainly it would not be available on NHS due to cost-benefit ratio.

Is Flibanserin (Addyi) effective?

In 2010 Flibanserin (Addyi) failed to get a license due to inadequate risk-benefit ratio; mainly due to concerns about side effects associated with the treatment. 5 years later and with additional information from further studies FDA approved Addyi.

A systemic review on Efficacy and Safety of Flibanserin for the Treatment of Hypoactive Sexual Desire Disorder in Women analysed information from five published and three unpublished studies including a total of 5914 women.

Key findings from a systemic review on effectiveness of Addyi (Jaspers et al, 2016):

  • on average women who were treated with flibanserin experienced one-half additional satisfying sexual event per month
  • treatment with flibanserin was associated with statistically and clinically significant increased risk of side effects including the risk of dizziness, somnolence, nausea, and fatigue. In other words, clinical benefits of the treatment are marginal with a significant risk of side effects.
  • Quality of outcome evidence from studies was graded as low by two independent researchers (Cochrane Collaboration)

Flibanserin (Addyi) cost

Cost of Addyi in the USA for 30 days supply is around $426 (£331). When covered by insurance in the USA the cost is around $25 / month (Addyi.com, ND).

Why Flibanserin (Addyi) is not a ‘pink Viagra’

As I discussed in one of the above paragraphs, Addyi affects changes in certain parts of the brain. In contrast mechanism of action of Viagra (sildenafil), a drug used in the treatment of erectile disfunction in men works in a completely different way. Sildenafil’s mode of action involves smooth muscle relaxation which causes vasodilation and increased blood inflow into the penis. Sildenafil does not have any actions on the brain.

To sum up, the evidence behind the effectiveness of Flibanserin (Addyi) is of low quality. Flibanserin (Addyi) is not available in the UK and it is unlikely we will see it being prescribed in the UK.

References:

Addyi.com (ND). About Addyi. Available at: https://addyi.com/addyi/ Accessed on 16/05/2019

Allers K, Dremencov E, Ceci A, et al. (May 2010). “Acute and repeated flibanserin administration in female rats modulates monoamines differentially across brain areas: a microdialysis study”. J Sex Med. Available at: https://www.ncbi.nlm.nih.gov/pubmed/20163532 Accessed on 16/05/2019

FDA (2015). ADDYI (flibanserin): highlights of prescribing information. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/022526lbl.pdf Accessed on 16/05/2019

Jaspers Leos MD; Frederik Feys, MSc, Ph.D.; Wichor M. Bramer, BSc; et al (2016). Efficacy and Safety of Flibanserin for the Treatment of Hypoactive Sexual Desire Disorder in Women. Available at: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2497781 Accessed on 16/05/2019

Meston Cindy, Amelia Stanton (ND). Female Sexual Interest/Arousal Disorders. Available at: https://labs.la.utexas.edu/mestonlab/?page_id=1432 Accessed on 16/05/2019

I am a community pharmacist working in UK. I blog about drugs, health and pharmacy.

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