Sildenafil

Generic Sildenafil: What You Need to Know

Sildenafil was the first tablet approved for erectile dysfunction (ED). It launched as Viagra in 1998 and remains one of the most widely prescribed medicines in men's health. Generic tablets contain the same active substance, sildenafil citrate, and many manufacturers now produce it since the original patent expired. The result is a thoroughly studied treatment with more than 25 years of real-world use, at a far lower cost than the brand. Specialists also use sildenafil at a lower dose for pulmonary arterial hypertension, but the products in this category are for ED.

How Sildenafil Works

When a man becomes sexually aroused, nerve endings in the penis release nitric oxide. This prompts the production of a chemical messenger, cGMP, which relaxes the smooth muscle in the penile arteries and spongy tissue so that blood can flow in. Sildenafil blocks phosphodiesterase type 5 (PDE5), the enzyme that normally clears cGMP away. The relaxing signal therefore lasts longer, and an erection is easier to achieve and maintain.

Sildenafil only works alongside sexual stimulation, so it won't produce an erection on its own. It has no effect on libido, and the erection subsides normally after sex.

Sildenafil Strengths and Formats

Standard tablets come in the three licensed strengths (25, 50 and 100 mg), alongside several other formats.

The format changes how you take the medicine, not the dose. A 100 mg jelly sachet or chewable tablet is still a 100 mg dose, so the same daily maximum applies.

How to Take Sildenafil

• The usual starting dose is 50 mg, taken about one hour before sexual activity. It can be taken anywhere between 30 minutes and 4 hours beforehand.
• Depending on the result and any side effects, a doctor may raise the dose to 100 mg or lower it to 25 mg.
• The maximum is 100 mg, taken no more than once in 24 hours. Higher-strength tablets (120–200 mg) fall outside the licensed range and are not recommended. If 100 mg doesn't give a good result, see a doctor rather than taking more.
• Most men notice an effect within 30–60 minutes, and sildenafil can help with erections for roughly 4–6 hours.
• Swallow standard tablets whole with water. For other formats, follow the pack instructions.

Food and alcohol

A heavy or high-fat meal slows the absorption of sildenafil and can delay its effect by about an hour. For the most reliable result, take it on an empty stomach or after a light meal. A drink or two is unlikely to cause problems, but heavy drinking makes dizziness and headaches more likely and reduces erection quality in its own right.

Possible Side Effects

Side effects are usually mild and fade as the medicine wears off. The most common are:

• Headache
• Facial flushing or a feeling of warmth
• Indigestion
• A blocked or stuffy nose
• Dizziness
• Visual changes, such as a blue or green tinge, blurring or sensitivity to light, caused by a weak effect on a related enzyme in the eye
• Nausea and muscle aches

Stop and get urgent medical help if you have:

• An erection lasting more than 4 hours, or one that is painful
• Sudden reduced or lost vision in one or both eyes
• Sudden hearing loss, or ringing in the ears with dizziness
• Chest pain, a racing or irregular heartbeat, or fainting during or after sex
• Signs of a severe allergic reaction, such as swelling of the face or throat, or difficulty breathing

Who Should Not Take Sildenafil

Do not use sildenafil if you

• Take any nitrate medicine (such as GTN spray, isosorbide mononitrate or dinitrate) or nicorandil, or use "poppers" (amyl nitrite). Together they can cause a dangerous drop in blood pressure. If you ever need emergency treatment for chest pain, tell the medical team when you last took sildenafil.
• Take riociguat for pulmonary hypertension
• Have been told to avoid sexual activity because of a heart problem, or have had a heart attack or stroke in the last six months
• Have very low blood pressure or severe liver disease
• Have lost vision from NAION (a type of optic nerve damage), or have an inherited retinal condition such as retinitis pigmentosa
• Already take another PDE5 inhibitor, such as tadalafil, vardenafil or avanafil

Check with your doctor first if you take

• Alpha-blockers (for example doxazosin or tamsulosin). You should be stable on the alpha-blocker first, and a 25 mg starting dose is usually advised.
• Strong enzyme inhibitors such as ritonavir and other HIV protease inhibitors, ketoconazole, itraconazole, clarithromycin or erythromycin. These can sharply raise sildenafil levels, so a 25 mg dose is usually recommended, and with ritonavir sildenafil is generally best avoided.
• Other blood pressure medicines, which can add to the lowering effect

Also tell your doctor if you have a bleeding disorder, an active stomach ulcer, or a condition linked to priapism or penile deformity (for example sickle cell disease, leukaemia, multiple myeloma or Peyronie's disease). Grapefruit juice can increase sildenafil levels and is best avoided around a dose.

Sildenafil, Tadalafil and Combination Products

Sildenafil and tadalafil are similarly effective for most men. The practical difference is timing: sildenafil is short-acting and suits planned occasions, while tadalafil works for up to 36 hours and can be taken as a small daily dose. Our sildenafil vs tadalafil guide compares them in depth, or you can browse the tadalafil range.

Some products in this category combine sildenafil with dapoxetine for men who also have premature ejaculation. They add the side effects of a second medicine, so read our dapoxetine guide and speak to a doctor before considering one.

Storage

Store below 86°F (30°C) in the original blister or sachet, away from damp, direct sunlight and children. Don't use any form after its expiry date.

Frequently Asked Questions

Is generic sildenafil the same as Viagra?

It contains the same active ingredient, sildenafil citrate, and works in the same way. The color, shape, flavor and inactive ingredients may differ between manufacturers.

Are 150 mg or 200 mg tablets more effective?

Not for most men. The labeled maximum is 100 mg once a day, and higher doses mainly increase side effects such as headache, flushing and visual disturbance. If 100 mg isn't enough, a doctor can look for underlying causes or suggest a different treatment.

Can women take sildenafil?

Sildenafil is not licensed to treat sexual problems in women, and products marketed at women contain the same medicine. Women with sexual health concerns should ask a doctor about suitable options.

The content of this page is general health information, not personal medical advice. Sildenafil is a prescription medicine and is not suitable for everyone. Check with a doctor or pharmacist that it is safe for you, particularly if you have heart problems or take nitrates, alpha-blockers or other regular medicines.