Sildenafil (Pfizer)

Sildenafil Pfizer is the branded form of sildenafil citrate. Pfizer makes it, and Pfizer first developed the active ingredient. It is sold under the trade name Viagra.

The medicine is a PDE5 inhibitor (a type of drug that relaxes blood vessels). Doctors prescribe it to treat erectile dysfunction (ED) in adult men.

Sildenafil blocks an enzyme called PDE5. This enzyme works in the corpus cavernosum, the spongy tissue inside the penis. When you are sexually aroused, your body releases nitric oxide there.

Nitric oxide switches on a substance called guanylate cyclase. This raises levels of cyclic guanosine monophosphate (cGMP).

cGMP relaxes the smooth muscle, so more blood can flow into the erectile tissue. Sildenafil stops cGMP from breaking down. This makes the erection stronger and longer-lasting.

You need sexual stimulation for sildenafil to work. It does not cause an erection on its own. The medicine usually starts to work 30 to 60 minutes after you take it by mouth.

The effect lasts about four to six hours.

Sildenafil Pfizer comes as 25 mg, 50 mg, and 100 mg tablets. The branded product matches generic sildenafil in quality, safety, and how well it works.

Some patients still prefer the brand because it feels familiar and they trust it.

Take one tablet about 30 to 60 minutes before you plan to have sex. Swallow the tablet whole with water. You can take sildenafil with or without food.

A large or high-fat meal may make it start working more slowly.

Do not take more than one tablet in any 24-hour period. You need sexual stimulation for the medicine to work. If you do not have sex, you will not notice any effect.

Do not drink grapefruit juice while you take sildenafil. It can raise the level of the drug in your body. Never combine sildenafil with nitrate medicines or recreational nitrate substances (poppers).

The usual starting dose is 50 mg. Take it about one hour before sex. Your doctor may raise the dose to 100 mg or lower it to 25 mg, depending on how well it works and how you tolerate it.

Some people should start at 25 mg. This includes elderly patients (over 65), people with liver problems, and people with severe kidney problems (GFR below 30 mL/min).

You may also need a lower dose if you take sildenafil with CYP3A4 inhibitors, such as erythromycin or ritonavir. These are drugs that slow down how your body clears sildenafil.

Headache is the most common side effect. It happens in about 10 to 15 per cent of users.

Facial flushing (a warm, red face), a blocked nose, indigestion (dyspepsia), and dizziness each happen in roughly 5 to 10 per cent of men.

Some men notice changes in their vision, mainly at higher doses. These can include a blue-green tinge to what they see, more sensitivity to light, and blurred vision.

These changes are short-lived and go away as the drug wears off.

Back pain and muscle aches (myalgia) happen now and then. Priapism is rare but serious. This is an erection that lasts longer than four hours.

It is a medical emergency and needs treatment straight away.

In rare cases, men have reported sudden hearing loss and a condition called non-arteritic anterior ischaemic optic neuropathy (NAION), which can affect sight.

It is not fully clear whether sildenafil causes these problems. Even so, get medical help at once if your vision or hearing changes suddenly.

Do not take sildenafil with nitrate medicines. These include glyceryl trinitrate, isosorbide mononitrate, and isosorbide dinitrate. The same goes for recreational nitrates (poppers).

Mixing them can cause a severe and possibly fatal drop in blood pressure.

Take care if you have heart or blood vessel disease, especially if sex is not safe for you. Some men should not use sildenafil at all.

This includes men who have had a heart attack or stroke in the last six months. It also includes men with unstable angina, an uncontrolled irregular heartbeat, or low blood pressure.

Tell your prescriber if your penis has an unusual shape, such as in Peyronie's disease.

Also tell them if you have a condition that raises the risk of priapism, such as sickle cell disease or leukaemia.

Do not take sildenafil if you use nitrate medicines. Also do not take it if you have a severe heart or blood vessel condition that makes sex unsafe.

Avoid it if you are allergic to sildenafil or to any other ingredient in the tablet.

Do not take sildenafil if you have had a stroke or heart attack in the last six months. Avoid it if you have severe liver problems or low blood pressure (below 90/50 mmHg).

Also avoid it if you have an inherited eye disorder that damages the retina, such as retinitis pigmentosa.