Many men wonder whether sildenafil, commonly known as Viagra, can boost sexual desire or make them feel hornier. Whilst sildenafil is highly effective for treating erectile dysfunction (ED), it is important to understand exactly how it works and what it can and cannot do. Sildenafil belongs to a class of medicines called phosphodiesterase type 5 (PDE5) inhibitors, which enhance blood flow to the penis in response to sexual stimulation. However, it does not directly influence libido or sexual desire. This article explains the difference between arousal and erectile function, clarifies sildenafil's role, and outlines when to seek medical advice for concerns about sexual health.

What Is Sildenafil and How Does It Work?

Sildenafil is a prescription medication primarily used to treat erectile dysfunction (ED) in men. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. In the UK, sildenafil is available under the brand name Viagra, as well as generic formulations, and is regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). Viagra Connect (50 mg) is available as a pharmacy medicine without prescription, while other sildenafil products remain prescription-only.

The mechanism of action of sildenafil is highly specific to the physiological process of achieving an erection. When a man is sexually stimulated, nerve signals trigger the release of nitric oxide in the erectile tissue of the penis. This chemical messenger activates an enzyme that produces cyclic guanosine monophosphate (cGMP), which relaxes smooth muscle cells in the blood vessels of the penis, allowing increased blood flow. Sildenafil works by inhibiting the PDE5 enzyme, which normally breaks down cGMP. By blocking this breakdown, sildenafil helps maintain higher levels of cGMP, thereby enhancing blood flow to the penis and facilitating an erection in response to sexual stimulation.

It is crucial to understand that sildenafil does not work in isolation. The medication requires sexual arousal to be effective—it does not spontaneously cause erections. Sildenafil typically begins to work within 30 to 60 minutes of oral administration, with effects lasting approximately four to five hours. The typical dose for ED is 50 mg (range 25-100 mg) taken about 1 hour before sexual activity, not more than once daily. High-fat meals can delay the onset of action, and excessive alcohol may reduce effectiveness.

Sildenafil is metabolised primarily in the liver via CYP3A4/2C9 enzymes and eliminated mainly in faeces (~80%) with some urinary excretion (~13%). It is also licensed for the treatment of pulmonary arterial hypertension under the brand name Revatio at different doses.

Importantly, sildenafil must not be used with nitrate medications (including recreational 'poppers') or riociguat due to potentially dangerous drops in blood pressure. Caution is needed with alpha-blockers and in those with cardiovascular disease, hypotension, or recent heart attack or stroke.

The Difference Between Arousal and Erectile Function

Understanding the distinction between sexual arousal (libido) and erectile function is essential when considering how sildenafil works. Sexual arousal, or libido, refers to the psychological desire for sexual activity. It is influenced by a complex interplay of factors including hormones (particularly testosterone), neurotransmitters, emotional state, relationship dynamics, stress levels, and overall mental health.

Erectile function, by contrast, is the physiological ability to achieve and maintain an erection sufficient for sexual intercourse. This is primarily a vascular and neurological process involving adequate blood flow to the penis, proper nerve signalling, and healthy erectile tissue. A man can experience sexual desire without being able to achieve an erection (erectile dysfunction), or conversely, may have normal erectile function but reduced interest in sexual activity (low libido).

These two aspects of sexual health are regulated by different biological systems. Libido is largely governed by the central nervous system and hormonal factors, particularly testosterone produced by the testes and regulated by the hypothalamic-pituitary-gonadal axis. Psychological factors such as depression, anxiety, relationship stress, and past trauma can significantly impact desire.

Erectile function depends on the peripheral nervous system, adequate cardiovascular health, and local tissue responses in the penis. Conditions affecting blood vessels (such as diabetes, hypertension, or atherosclerosis) or nerve damage can impair erectile function without necessarily affecting libido. Similarly, psychological factors like performance anxiety can interfere with erectile function even when desire is present.

This distinction is clinically important because treatments targeting one aspect may not address the other. Sildenafil specifically addresses the vascular component of erectile function but does not directly influence the psychological or hormonal factors that drive sexual desire. It's worth noting that ED and low libido often coexist and may require parallel assessment by healthcare professionals.

When to Speak to Your GP About Low Libido

Low libido, or reduced sexual desire, is a common concern that can significantly impact quality of life and relationships. If you are experiencing persistent or distressing changes in your sexual desire, it is important to discuss this with your GP. There is no single 'normal' level of libido—it varies considerably between individuals and across different life stages—but a noticeable change from your usual pattern warrants medical attention.

You should consider speaking to your GP if:

• Your reduced libido is causing personal distress or relationship difficulties

• The change in desire is sudden or unexplained

• You are experiencing other symptoms such as fatigue, mood changes, weight changes, or erectile difficulties

• You suspect your medication may be affecting your libido

• You have concerns about testosterone levels or other hormonal issues

• You experience severe headaches, visual field defects, or unusual breast discharge (urgent referral needed)

Your GP will typically conduct a thorough assessment including a detailed medical and sexual history, review of current medications, and evaluation of psychological factors. Blood tests may be arranged to check hormone levels, including two separate morning testosterone measurements (between 8-11 am) to confirm any deficiency. If testosterone is low or borderline, additional tests may include luteinising hormone (LH), follicle-stimulating hormone (FSH), prolactin, sex hormone binding globulin (SHBG), thyroid function, and sometimes fasting glucose and lipids.

Many medical conditions can affect libido, including diabetes, cardiovascular disease, thyroid disorders, depression, and chronic pain conditions. Numerous medications are also associated with reduced sexual desire, including certain antidepressants (SSRIs/SNRIs), antipsychotics, beta-blockers, 5-alpha-reductase inhibitors (finasteride/dutasteride), antiandrogens, spironolactone, GnRH analogues, and opioid painkillers.

Your GP can help identify any underlying causes and discuss appropriate management options, which may include addressing lifestyle factors (such as stress, sleep, alcohol consumption, and exercise), treating underlying medical conditions, adjusting medications, or referring you to specialist services. Referrals may be made to endocrinology for consistently low testosterone or abnormal hormone levels, or to psychosexual therapy for persistent psychological factors. Early consultation allows for proper investigation and prevents unnecessary anxiety about what may be a treatable condition.

Does Sildenafil Increase Sexual Desire or Libido?

The straightforward answer is that sildenafil does not directly increase sexual desire or libido. There is no official pharmacological link between sildenafil and the psychological or hormonal mechanisms that govern sexual desire. The drug's mechanism of action—inhibiting PDE5 to enhance blood flow to the penis—does not influence the brain centres, neurotransmitters, or hormones responsible for sexual interest and motivation.

Sildenafil is specifically designed to address the physical component of erectile dysfunction, not the psychological drive for sexual activity. It will not create sexual desire where none exists, nor will it increase baseline libido in men with normal sexual interest. The medication requires sexual arousal to be effective; without stimulation and desire, sildenafil alone will not produce an erection.

However, there is an important indirect consideration. Some men who have experienced erectile dysfunction may develop secondary psychological effects including performance anxiety, reduced confidence, and avoidance of sexual situations. Over time, these psychological factors can contribute to reduced sexual desire. In such cases, successfully treating erectile dysfunction with sildenafil may help restore confidence and reduce anxiety, which could indirectly lead to improved sexual interest. This is a psychological benefit resulting from restored function rather than a direct pharmacological effect on libido.

If you are experiencing both erectile difficulties and low libido, it is essential to discuss both concerns with your GP. Low libido may require different investigations and treatments, such as:

• Evaluation and treatment of testosterone deficiency

• Review and potential adjustment of medications affecting desire

• Assessment and management of depression or anxiety

• Referral to psychosexual therapy or counselling

• Addressing lifestyle factors including stress, sleep quality, and relationship issues

Using sildenafil when the primary issue is low libido rather than erectile dysfunction is unlikely to be beneficial and does not address the underlying cause. A comprehensive assessment by your GP can help determine whether erectile dysfunction, low libido, or both are present, and guide appropriate, evidence-based treatment tailored to your specific situation.

Frequently Asked Questions