Sildenafil, widely recognised for treating erectile dysfunction in men, is a phosphodiesterase type 5 (PDE5) inhibitor that increases blood flow by relaxing smooth muscle in blood vessels. Whilst licensed in the UK for male sexual dysfunction and pulmonary arterial hypertension, sildenafil is not approved by the MHRA for female sexual health concerns. Research into its effects on women has produced inconsistent results, with limited evidence of clinically meaningful benefit. Female sexual function involves complex psychological, hormonal, and vascular factors that a blood-flow medication alone cannot adequately address. This article examines what sildenafil does in females, the current evidence base, potential risks, and alternative treatment approaches for women experiencing sexual health difficulties.

What Is Sildenafil and How Does It Work?

Sildenafil is a prescription medication primarily licensed in the UK for treating erectile dysfunction in men and pulmonary arterial hypertension in both sexes. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. The drug works by blocking the enzyme PDE5, which normally breaks down cyclic guanosine monophosphate (cGMP) in smooth muscle cells. When PDE5 is inhibited, cGMP levels increase, leading to relaxation of smooth muscle and dilation of blood vessels.

In men with erectile dysfunction, this mechanism enhances blood flow to the penis during sexual stimulation, facilitating an erection. The medication does not cause arousal itself but rather supports the physiological response to sexual stimulation. Sildenafil typically begins working within 30 to 60 minutes of oral administration and its effects can last for approximately four to five hours.

Whilst sildenafil is well-established for male sexual dysfunction, it is not currently licensed by the MHRA for treating female sexual dysfunction. It's worth noting that Viagra Connect, available over-the-counter in UK pharmacies, is authorised for adult men with erectile dysfunction only and will not be supplied to women.

The drug's mechanism of action—increasing blood flow through smooth muscle relaxation—has led researchers to investigate whether similar benefits might occur in women experiencing sexual difficulties. However, female sexual function is considerably more complex than male erectile function, involving intricate interactions between psychological, hormonal, neurological, and vascular factors.

The genital tissues in women, including the clitoris and vaginal walls, contain smooth muscle and vascular structures that theoretically could respond to increased blood flow. This has prompted clinical trials examining whether sildenafil might improve arousal, lubrication, or sensation in women, though results have been mixed and the medication remains unlicensed for this indication in the UK.

Effects of Sildenafil in Women: Current Evidence

Research into sildenafil's effects on female sexual function has produced inconsistent and limited evidence. Several clinical trials have investigated whether the drug improves sexual arousal, desire, lubrication, orgasm, or satisfaction in women, but findings have been variable and often disappointing compared to its efficacy in men.

Some small studies have suggested that sildenafil may increase genital blood flow and physiological arousal in women, as measured by vaginal photoplethysmography. However, this increased blood flow does not consistently translate into improved subjective sexual satisfaction or desire. A significant challenge in this research is that female sexual dysfunction often has substantial psychological and relational components that a medication targeting blood flow alone cannot address. Clinical trials have also shown high placebo response rates in female sexual dysfunction studies, making it difficult to determine true drug effects.

Certain subgroups may experience more benefit than others. Some evidence suggests women with sexual dysfunction related to antidepressant use (particularly selective serotonin reuptake inhibitors) might experience modest improvements in arousal and orgasm when taking sildenafil. Additionally, women with sexual dysfunction secondary to medical conditions affecting blood flow may theoretically benefit, though robust evidence remains limited.

Post-menopausal women have been studied specifically, as declining oestrogen levels can affect genital blood flow and tissue health. Results in this population have been mixed, with some trials showing minimal benefit over placebo. The Medicines and Healthcare products Regulatory Agency (MHRA) has not approved sildenafil for female sexual dysfunction, reflecting the insufficient evidence base for efficacy and safety in this population.

It is important to note that there is no robust, consistent evidence of clinically meaningful benefit across the general female population. Women considering this medication should discuss the limited evidence and off-label nature of such use with their GP or specialist.

Potential Risks and Side Effects for Female Users

Although sildenafil has been studied in women, its safety profile in females is less well-established than in men, as most clinical trials and post-marketing surveillance have focused on male users. Women taking sildenafil may experience similar adverse effects to those reported in men, though the frequency and severity may differ.

Common side effects reported in clinical trials involving women include:

• Headache – the most frequently reported adverse effect, occurring due to vasodilation of cerebral blood vessels

• Facial flushing – resulting from peripheral vasodilation and increased blood flow to facial tissues

• Nasal congestion – caused by vasodilation of nasal mucosa

• Dyspepsia and gastrointestinal discomfort – affecting the digestive system

• Visual disturbances – including altered colour perception (blue tinge) or increased light sensitivity, due to mild PDE6 inhibition in the retina

• Dizziness – particularly when standing, related to blood pressure changes

Sildenafil is absolutely contraindicated with nitrate medications (used for angina) and nitric oxide donors (including 'poppers'), as this combination can cause dangerous drops in blood pressure. It is also contraindicated with soluble guanylate cyclase stimulators such as riociguat. Alpha-blockers (used for hypertension or prostate conditions) require caution and haemodynamic stability before use, but are not absolutely contraindicated.

Important interactions include potent CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, clarithromycin) which can increase sildenafil levels, and grapefruit juice which may enhance side effects. Sildenafil can also have additive blood pressure-lowering effects with antihypertensive medications.

Women with cardiovascular disease, uncontrolled hypertension, recent myocardial infarction or stroke (within 6 months), severe hepatic impairment, hypotension (BP <90/50 mmHg), hereditary retinal disorders, previous non-arteritic anterior ischaemic optic neuropathy (NAION), or active peptic ulceration should not use sildenafil without specialist assessment.

Sildenafil should not be used during pregnancy or breastfeeding for sexual dysfunction. The MHRA advises against using sildenafil for fetal growth restriction outside clinical trials, and it should only be used in pregnancy for pulmonary arterial hypertension under specialist supervision.

When to seek medical attention:

• Call 999 or attend A&E for chest pain, sudden vision loss, or severe allergic reactions

• Seek urgent care for sudden hearing loss

• Contact your GP for severe or persistent headache, prolonged dizziness or fainting

Suspected adverse reactions should be reported via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

Alternative Treatments for Female Sexual Health Concerns

Given the limited evidence for sildenafil in women, clinical practice emphasises a holistic, individualised approach to female sexual dysfunction that addresses physical, psychological, and relational factors.

Psychological and behavioural interventions form the cornerstone of treatment for many women. Cognitive behavioural therapy (CBT) and psychosexual counselling can address anxiety, negative thought patterns, relationship difficulties, and past trauma that may contribute to sexual problems. These interventions are often more effective than pharmacological approaches for female sexual dysfunction, particularly when desire or arousal difficulties have psychological origins. Your GP can consider referral to NHS psychosexual services, sexual health clinics, or private psychosexual therapists.

Hormonal treatments may benefit women whose sexual difficulties relate to hormonal changes, particularly during menopause. According to NICE guideline NG23 (Menopause: diagnosis and management), vaginal oestrogen (creams, pessaries, or rings) can improve vaginal dryness, atrophy, and discomfort during intercourse without significant systemic absorption. Systemic hormone replacement therapy (HRT) may improve overall wellbeing and indirectly benefit sexual function in peri-menopausal and post-menopausal women. Testosterone therapy is sometimes considered for post-menopausal women with hypoactive sexual desire disorder, though it is not licensed for this indication in the UK. The British Menopause Society advises that testosterone can be prescribed off-label by clinicians with expertise in menopause or sexual medicine.

Non-pharmacological approaches include:

• Vaginal moisturisers and lubricants – for dryness and discomfort

• Pelvic floor physiotherapy – for pain, tension, or weakness affecting sexual function

• Lifestyle modifications – addressing fatigue, stress, alcohol consumption, and relationship quality

• Treatment of underlying conditions – managing depression, anxiety, diabetes, or cardiovascular disease that may impact sexual health

Flibanserin is a medication licensed in some countries for hypoactive sexual desire disorder in pre-menopausal women. It works on neurotransmitter systems rather than blood flow. However, it is not licensed in the UK or EU and is not available on the NHS. Evidence for its efficacy is modest and it carries risks of hypotension and sedation, particularly with alcohol.

Women experiencing persistent sexual health concerns should consult their GP for comprehensive assessment. This should include discussion of medical history, medications (particularly antidepressants, antihypertensives, and hormonal contraceptives), relationship factors, and psychological wellbeing. Referral to gynaecology, menopause clinics, or specialist sexual health services may be appropriate depending on the underlying cause. A multidisciplinary approach addressing all contributing factors typically offers the best outcomes for female sexual dysfunction.

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