Online medical consultation for Viagra.

Sildenafil is the active ingredient in Viagra and many generics authorised in the EU. It belongs to the PDE-5 inhibitor family alongside tadalafil, vardenafil and avanafil. Each molecule differs in onset, duration and selectivity over secondary receptors.

Its effect is facilitatory, not inductive: it requires sexual stimulation to produce a response — it does not cause an erection on its own.

During sexual stimulation, the nervous system releases nitric oxide in erectile tissue. Nitric oxide activates guanylate cyclase, raising cGMP levels and relaxing the smooth muscle of penile arteries, increasing blood flow.

Sildenafil blocks PDE-5, the enzyme that degrades cGMP. By inhibiting it, cGMP stays elevated longer and the erectile response is prolonged.

Onset of action is 30–60 minutes after intake; duration is 4–6 hours. Absorption is slowed by fatty meals.

The EMA indication is for adult men with erectile dysfunction. The licensed doctor reviews your cardiovascular history, current medication and risk factors. Erectile dysfunction is often an early marker of subclinical cardiovascular disease — ruling that out is part of the evaluation.

It is contraindicated with nitrates (severe hypotension risk), riociguat and specific antiretroviral combinations. The questionnaire is designed to flag these cases.

Sildenafil is taken on demand, about an hour before planned sexual activity. The standard starting dose is 50 mg, adjustable to 25 or 100 mg based on response and tolerance. It should not be taken more than once a day.

In studies, satisfactory clinical response exceeds 70 % in adequately selected patients — the outcome depends on the underlying cause, the dose, and concurrent cardiovascular factors.

The most common side effects are headache, facial flushing, nasal congestion, dyspepsia and transient visual changes (light sensitivity, blue-tinged perception).

Absolute contraindications include concomitant nitrates (nitroglycerin, isosorbide), a history of NAION (non-arteritic anterior ischaemic optic neuropathy) and specific riociguat combinations. The doctor reviews the full questionnaire before prescribing.

Seek emergency care if you experience chest pain, priapism (erection > 4 h) or sudden vision loss.