Many men prescribed sildenafil for erectile dysfunction wonder what physical sensations to expect when taking this medication. Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, works by enhancing blood flow to the penis during sexual arousal. Importantly, the medication does not produce a distinct 'feeling' in the way some drugs might. Most users notice no immediate physical awareness until sexually stimulated, when achieving and maintaining an erection becomes easier and more reliable. Some men may experience mild side effects such as facial flushing, headache, or nasal congestion, which result from the medication's effects on blood vessels throughout the body. Understanding what to expect helps ensure safe, effective use of this commonly prescribed treatment.

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. Sildenafil is also prescribed under different brand names for pulmonary arterial hypertension, though this article focuses on its use for erectile dysfunction.

The mechanism of action centres on improving blood flow to the penis during sexual stimulation. When a man becomes sexually aroused, the body releases nitric oxide in the erectile tissue of the penis. This triggers an enzyme called guanylate cyclase, which increases levels of cyclic guanosine monophosphate (cGMP). The cGMP relaxes smooth muscle cells in the blood vessels of the penis, allowing increased blood flow and facilitating an erection.

Naturally, an enzyme called PDE5 breaks down cGMP, which can limit erectile function. Sildenafil works by inhibiting PDE5 , thereby preventing the breakdown of cGMP and maintaining higher levels in the penile tissue. This allows the blood vessels to remain dilated for longer, supporting the ability to achieve and maintain an erection when sexually stimulated.

It is crucial to understand that sildenafil does not cause automatic erections. Sexual stimulation is still required for the medication to be effective. The drug typically begins to work within around 1 hour of taking it orally, with effects lasting approximately 4 hours. The usual starting dose is 50mg, which may be adjusted between 25mg and 100mg based on effectiveness and tolerability. Sildenafil should only be taken once daily.

In the UK, sildenafil is available on prescription and as Viagra Connect 50mg from pharmacies following a pharmacist assessment. It is not indicated for women or people under 18 years of age. Sildenafil must not be taken with nitrate medications (including GTN), amyl nitrite ('poppers'), or riociguat, as this combination can cause dangerous drops in blood pressure. Heavy meals or high fat foods may delay the onset of action, and alcohol can worsen erectile dysfunction and increase the risk of side effects.

Physical Sensations When Taking Sildenafil

Many men wonder what physical sensations to expect when taking sildenafil. It is important to clarify that sildenafil itself does not produce a distinct 'feeling' or sensation in the way some medications might. Most users report no immediate physical awareness that the medication is working until they become sexually aroused.

When sildenafil is effective, men typically notice that achieving an erection becomes easier and more reliable during sexual stimulation. The erection may feel firmer and be maintained for longer compared to attempts without the medication. Some men describe a sense of increased confidence knowing the medication is supporting their erectile function, though this is psychological rather than a direct physical sensation from the drug.

A small proportion of users report subtle physical sensations that may be attributed to the medication's effects on blood vessels. These can include:

• A feeling of warmth or flushing, particularly in the face, neck, or chest

• Mild nasal congestion or a feeling of stuffiness

• A slight awareness of heartbeat or pulsing sensations

• Occasional light-headedness, especially when standing up quickly

• Headache, which is a very common side effect

These sensations, when present, are generally mild and temporary. They result from sildenafil's vasodilatory effects (widening of blood vessels) occurring throughout the body, not just in the penis. The medication affects blood vessels more broadly because PDE5 enzymes are present in various tissues.

It is worth emphasising that the absence of noticeable sensations does not mean the medication is not working. Sildenafil's effectiveness should be judged by its ability to support erectile function during sexual activity, not by whether you 'feel' the tablet working.

To optimise effectiveness, avoid heavy meals and limit alcohol consumption before taking sildenafil. If you experience pronounced palpitations, chest discomfort, faintness, or persistent light-headedness, stop sexual activity and seek medical advice. If you have concerns about whether sildenafil is effective for you, discuss this with your GP or prescribing clinician rather than increasing the dose independently.

Common Side Effects and How They Feel

Like all medications, sildenafil can cause side effects, though not everyone experiences them. Understanding what these feel like can help you distinguish between normal responses and situations requiring medical attention. According to clinical data, the most frequently reported side effects are generally mild to moderate and often diminish with continued use.

Headaches are among the most common side effects, categorised as 'very common' in the medicine's information. These typically feel like tension headaches—a dull, pressing sensation across the forehead or temples. They usually develop within a few hours of taking the medication and resolve within 24 hours. Staying well-hydrated and taking a standard dose of paracetamol (if appropriate) can help manage this.

Facial flushing creates a sensation of warmth and redness, particularly across the cheeks, neck, and upper chest. This feels similar to the flush some people experience after alcohol consumption or during embarrassment. It results from blood vessel dilation and typically subsides within a few hours.

Nasal congestion can make breathing through the nose feel more difficult, similar to having a mild cold. Some men describe a 'stuffy' sensation without actual mucus production. This occurs because sildenafil affects blood vessels in the nasal passages.

Indigestion or dyspepsia may cause discomfort in the upper abdomen, a burning sensation, or mild nausea. Taking sildenafil with a light meal may help reduce this effect, though be aware that fatty meals can delay the medication's onset of action.

Visual disturbances are less common but can include:

• A blue tinge to vision

• Increased sensitivity to light

• Slightly blurred vision

These visual effects are usually mild and temporary, resolving within a few hours. They occur because sildenafil has a slight effect on PDE6 enzymes in the retina.

Dizziness may occur, particularly when standing up quickly, due to temporary blood pressure changes. This feels like light-headedness or a brief sensation of unsteadiness. If you experience dizziness or visual disturbances, do not drive or operate machinery until these effects have completely resolved.

Most side effects are transient and do not require treatment cessation, but persistent or severe symptoms warrant medical review. If you experience any concerning side effects, you can report them through the MHRA Yellow Card scheme.

When to Seek Medical Advice About Sildenafil

While sildenafil is generally well-tolerated, certain situations require prompt medical attention. Understanding these warning signs is essential for safe medication use.

Seek immediate emergency care (call 999 or attend A&E) if you experience:

• Chest pain or discomfort during or after sexual activity—this could indicate cardiovascular problems. Importantly, if you have taken sildenafil, do NOT use GTN spray or tablets, and inform emergency services when you last took sildenafil

• Sudden vision loss in one or both eyes, which may signal non-arteritic anterior ischaemic optic neuropathy (NAION), a rare but serious condition

• Sudden hearing loss or decrease, sometimes accompanied by tinnitus or dizziness

• Priapism—an erection lasting more than four hours, which requires urgent treatment to prevent permanent damage to penile tissue

• Severe allergic reactions, including difficulty breathing, swelling of the face, lips, tongue, or throat, or severe skin rashes

Contact your GP or prescribing clinician within 24-48 hours if:

• Side effects are persistent, worsening, or significantly affecting your quality of life

• You experience severe or recurrent headaches that do not respond to standard pain relief

• You notice irregular heartbeat or palpitations

• Sildenafil appears ineffective after trying it on several occasions as prescribed

• You develop new symptoms that concern you after starting sildenafil

Routine review is appropriate when:

• You wish to discuss dose adjustment—never alter the dose without medical guidance

• You are starting new medications, as drug interactions can occur (particularly with nitrates, alpha-blockers, or certain antifungals and antibiotics)

• Your underlying health conditions change, such as developing cardiovascular disease, liver or kidney problems

• You experience psychological concerns related to erectile dysfunction that medication alone does not address

According to NICE Clinical Knowledge Summary on erectile dysfunction, men with erectile dysfunction should receive holistic assessment and management. This often includes blood tests to check for diabetes, cholesterol levels, and testosterone, along with blood pressure monitoring. Some men may need referral to urology, endocrinology, or psychosexual therapy services depending on their specific situation.

Sildenafil is one component of comprehensive care, and ongoing dialogue with healthcare professionals ensures safe, effective treatment tailored to individual needs. Never obtain sildenafil from unregulated sources, as counterfeit medications pose serious health risks.

Frequently Asked Questions