Sildenafil For Erectile Dysfunction: Guide To Dosage & Safety

Sildenafil is a medication primarily used to treat

erectile dysfunction

(ED), also known as impotence, in men. It helps by improving blood flow to the penis, enabling an erection when sexually stimulated. This article covers everything from how sildenafil works to dosage, side effects, and important safety information, mirroring the structure of authoritative patient guides.

About sildenafil tablets

**Erectile dysfunction** (sometimes called impotence) means you cannot get or maintain a proper erection for sexual activity. Sildenafil, available as brands like Viagra or generics such as Aronix, addresses this by targeting the underlying vascular issue.

Sildenafil belongs to a group of medicines called

phosphodiesterase type-5 (PDE5) inhibitors

. It works by preventing the action of a chemical called phosphodiesterase type-5, which relaxes blood vessels and improves blood flow to the penis following sexual stimulation. Without sexual arousal, sildenafil does not cause an erection—it requires physical stimulation to be effective.

Clinical studies show sildenafil is highly effective, with rapid onset (as little as 14 minutes in some men) and duration up to 12 hours. In trials, 46.5% to 87% of patients reported improved erections compared to placebo. It significantly enhances quality of life and partner satisfaction.

Before taking sildenafil

Always consult a doctor before starting sildenafil, especially if you have underlying health conditions. Inform your doctor if you:

• Have

  heart or blood vessel disease

  , such as angina, heart failure, or irregular heartbeat.
• Have recently had a

  heart attack

  (within the last 6 months).
• Have

  low blood pressure

  or high blood pressure not controlled by medication.
• Have

  ever had a stroke

  .
• A problem with the

  shape of your penis

  (such as Peyronie’s disease), or if you have

  priapism

  (painful, prolonged erections).
• Are due to have

  eye surgery

  (especially cataract surgery) in the near future.
• Have

  sickle cell disease

  ,

  multiple myeloma

  , or

  leukaemia

  .
• Have a

  stomach ulcer

  .
• Have

  liver or kidney problems

  .
• Have a

  history of bleeding disorders

  or

  retinal pigmentation

  .

Sildenafil is not suitable for everyone. It should not be taken with nitrates (used for chest pain) or certain other medications, as this can cause a dangerous drop in blood pressure. Sexual activity itself poses risks for those with heart conditions—discuss with your doctor if you’ve been advised to avoid it.

How to take sildenafil

Follow your doctor’s instructions precisely. Sildenafil tablets are taken orally, usually as needed before sexual activity.

Dosage

Available strengths: 25mg, 50mg, 100mg. The usual starting dose is

50mg

, taken 30-60 minutes before sex (up to 4 hours prior). Do not take more than once daily.

• Adults up to 65 years: 50mg as a single dose, adjustable to 25mg or 100mg based on efficacy and tolerance.
• Over 65 years or liver/kidney issues: Start at 25mg.

Swallow the tablet whole with water. It can be taken with or without food, but high-fat meals may delay absorption.

Key tips

• Be sexually stimulated for it to work.
• Effects last 4-6 hours on average, up to 12 in some.
• If no effect, do not increase dose without medical advice—counseling or dose adjustment can help non-responders.

Who can and cannot take sildenafil

Sildenafil is for adult men with ED. It is

not for

:

• Women or children.
• Men using nitrates, riociguat, or guanylate cyclase stimulators.
• Those with severe heart/liver/kidney disease, recent stroke/heart attack, or uncontrolled hypotension/hypertension.
• Men with hereditary retinal disorders or severe vision loss.

Special populations: Effective in diabetes, post-prostatectomy, but efficacy may be lower. NHS availability: Generics on prescription; branded Viagra limited to specific conditions.

Side effects of sildenafil

Common side effects are mild and short-lived.

Common side effects

These affect more than 1 in 100 people:

• Headache
• Feeling sick (nausea)
• Reddening of the skin (flushing)
• Indigestion or heartburn
• Visual disturbances (blurred vision, blue tint)
• Nasal congestion

Serious side effects

Rare but seek immediate medical help for:

• **Priapism**: Erection lasting >4 hours—emergency to prevent permanent damage.
• Chest pain, dizziness, nausea during sex.
• Sudden vision/hearing loss.
• Severe allergic reaction (rash, swelling, breathing difficulty).

Sildenafil has a favorable safety profile overall.

How to cope with side effects

• Headache/flushing: Rest, drink water, paracetamol if needed.
• Indigestion: Eat smaller meals, antacids.
• Blurred vision: Avoid driving; resolves quickly.
• For persistent issues, lower dose or switch medication.

Pregnancy and breastfeeding

Sildenafil is not indicated for women and has no relevance to pregnancy or breastfeeding in ED context. For pulmonary hypertension uses, consult a specialist.

Other medicines, food and drink, alcohol

Medicines

Avoid with:

• Nitrates (e.g., glyceryl trinitrate).
• Riociguat.
• Alpha-blockers (unless stabilized).
• Other PDE5 inhibitors or HIV protease inhibitors (dose adjustment needed).

Food and drink

Grapefruit juice may increase levels—avoid large amounts. Fatty foods delay onset.

Alcohol

Large amounts worsen ED and increase side effects like dizziness—limit intake.

Dosage and strength

Strength	Typical Use	Notes
25mg	Starting dose for elderly, liver/kidney issues	Lower risk of side effects
50mg	Standard dose for most men	Adjust if needed
100mg	If 50mg ineffective	Higher side effect risk; max once daily

Detailed clinical data: Higher doses (up to 200mg) may help non-responders but increase adverse events.

What if I take too much?

Overdose symptoms: Prolonged erection, severe hypotension. Seek emergency care immediately.

About NICE guidance

NICE recommends PDE5 inhibitors like sildenafil as first-line ED treatment for eligible men.

Common questions about sildenafil

How long does sildenafil take to work?

Usually 30-60 minutes; fastest in 14 minutes. Effects up to 4-12 hours.

Can I take sildenafil with alcohol?

Limited amounts yes, but excess impairs function.

Does sildenafil cure ED?

No, it treats symptoms; address underlying causes.

Is sildenafil safe long-term?

Yes, studies show good tolerability up to 9 months nightly.

Alternatives if sildenafil fails?

Dose adjustment, counseling, other PDE5i, or injections/implants.

This guide ensures safe, informed use. Always consult healthcare professionals.