Sildenafil Online UK

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor, a medicine that helps relax blood vessels. It was first developed and licensed for erectile dysfunction (ED) under the brand name Viagra.

During sexual stimulation, your body releases nitric oxide, which relaxes blood vessels. Sildenafil blocks PDE5 in the corpus cavernosum, the spongy tissue in the penis.

This stops the breakdown of cyclic guanosine monophosphate (cGMP), a chemical messenger. As a result, blood vessels stay relaxed for longer.

This boosts blood flow to the penis and helps you get an erection. Sildenafil was the first PDE5 inhibitor on the market. It is still one of the most studied ED treatments.

It works across many causes of ED. These include psychogenic (linked to the mind), organic (vascular, neurogenic, or hormonal), and mixed causes.

In clinical trials, sildenafil improved erections in about 70-80% of men. It starts to work quickly, in 30-60 minutes, and lasts about 4-6 hours.

Since the patent expired, generic sildenafil has become the most cost-effective PDE5 inhibitor. NICE recommends PDE5 inhibitors as the first-line medicine for ED.

Sildenafil only works if you are sexually aroused. It does not raise your sex drive on its own.

Take one tablet about 1 hour before you plan to have sex. You can take sildenafil with or without food. A high-fat meal can delay how fast it works by about 1 hour.

It can also lower the peak level in your blood by about 29%. Do not take more than one dose in 24 hours. Swallow the tablet whole with water. Avoid drinking too much alcohol.

Alcohol can affect erections on its own and may raise the risk of low blood pressure (hypotension).

Grapefruit juice can raise sildenafil levels in your blood by blocking the CYP3A4 enzyme that breaks the drug down. So use it with care.

The tablet does not produce an erection without sexual arousal.

The usual starting dose is 50 mg, taken about 1 hour before sex. Your doctor may adjust it based on how well it works and how you tolerate it.

The dose can go up to a maximum of 100 mg or down to 25 mg. A 25 mg starting dose is advised for some people.

This includes those aged over 65, those with liver problems, and those with severe kidney problems (creatinine clearance below 30 mL/min).

It also includes people taking CYP3A4 inhibitors, medicines that slow down how the body clears sildenafil, such as erythromycin or cimetidine.

If you also take ritonavir, the most you should take is 25 mg in 48 hours. Take sildenafil no more than once a day.

Side effects are grouped by how often they happen, based on clinical trial data from the product information (SmPC).

Very common (≥1/10): Headache (reported in 12-16% of patients), flushing (10-12%).

Common (≥1/100 to <1/10): Indigestion (dyspepsia), blocked nose, dizziness, changes to vision (a colour tinge, more sensitivity to light, or blurred vision, caused by mild blocking of PDE6 in the retina), and nausea.

Uncommon (≥1/1,000 to <1/100): Vomiting, rash, eye pain, sensitivity to light (photophobia), fast heartbeat (tachycardia), palpitations, low blood pressure (hypotension), muscle pain (myalgia), nosebleeds (epistaxis), and drowsiness.

Rare (≥1/10,000 to <1/1,000): Priapism (a long-lasting erection), non-arteritic anterior ischaemic optic neuropathy (NAION, a type of vision loss), sudden hearing loss, and seizures.

Vision symptoms are usually mild and pass quickly. If you get priapism, an erection lasting more than 4 hours, get emergency medical help. This prevents lasting damage to the tissue.

The MHRA advises that you report any sudden loss of vision or hearing while taking a PDE5 inhibitor.

Never take sildenafil with nitrates or nitric oxide donors. Together they can cause a severe drop in blood pressure. Wait at least 24 hours after sildenafil before you take a nitrate.

(For tadalafil the wait is 48 hours.) Take care if you have a heart condition that makes sex risky.

This includes unstable angina, a recent heart attack (MI) within the last 6 months, a recent stroke, severe heart failure, or blood pressure that is too high or too low and not controlled.

Taking sildenafil with alpha-blockers, such as doxazosin or tamsulosin, may cause low blood pressure with symptoms.

You should be stable on your alpha-blocker before you start sildenafil, and start at the lowest dose. Sildenafil has not been studied in inherited retinal disorders such as retinitis pigmentosa.

Take care if you have a penis that is bent or shaped differently (Peyronie's disease or marked curvature).

Also take care if you have a condition that raises the risk of priapism, such as sickle cell disease, multiple myeloma, or leukaemia.

Do not take sildenafil if any of the following apply to you. You are allergic to sildenafil or any of its ingredients. You take organic nitrates or nitric oxide donors in any form.

You have severe liver problems. You have had a recent stroke or heart attack (myocardial infarction). You have very low blood pressure (below 90/50 mmHg).

You have a condition where widening blood vessels or having sex is unwise. You also must not take more than 25 mg of sildenafil in 48 hours if you take ritonavir.

Do not take sildenafil with guanylate cyclase stimulators, such as riociguat.