How does Viagra work?
Viagra is a well-known erectile dysfunction medication with a proven track record.
The introduction of Viagra was a major milestone in sexual medicine, providing an effective treatment for erectile dysfunction at a time when options were limited. Sildenafil citrate, the active ingredient in Viagra, was originally researched as a cardiovascular drug and was found to have a notable effect on penile blood flow. This led to the development of Viagra as the first prescription tablet for erectile dysfunction. Since its approval, Viagra has been widely used to help men achieve and maintain erections by increasing blood flow during sexual arousal.
Viagra tablets belong to a group of medicines known as PDE-5 inhibitors. PDE-5 inhibitors are the first-line medications for erectile dysfunction in men. The active ingredient sildenafil blocks the PDE-5 enzyme, which normally breaks down cGMP — a chemical that helps relax blood vessels in the penis.
By slowing this breakdown, Viagra increases blood flow to the penis during sexual stimulation. This helps you achieve and maintain a firm erection.
Viagra onset of action: 30–60 minutes
Viagra duration of action: around 4–6 hours
Important
Viagra only works when a man is sexually stimulated, as it does not cause an erection on its own but enhances the natural blood flow response that occurs during arousal.
What dosages and dosage forms of Viagra are available?
While the conventional film-coated tablet remains the most widely prescribed formulation of Viagra in the UK, several alternative dosage forms have been developed to address specific patient needs and preferences. These innovations aim to improve convenience, speed of onset, and ease of administration of erectile dysfunction medication, particularly for patients who have difficulty swallowing tablets.
Traditional film-coated tablets
The standard Viagra formulation consists of blue, diamond-shaped, film-coated tablets, which are available in strengths of 25 mg (lowest dose), 50 mg and 100 mg.
The usual starting dose is 50 mg, but the optimal Viagra dosage should be determined by a doctor based on effect and tolerability.
Orodispersible tablets of sildenafil
Orodispersible tablets (ODTs) or melting tablets are designed to dissolve rapidly on the tongue without requiring water, making them particularly suitable for patients with dysphagia or those seeking greater discretion and convenience.
Sildegra is one example available in European markets. Orodispersible sildenafil tablets typically contain the same active ingredient in equivalent doses (25mg, 50mg, or 100mg) but are formulated with excipients that promote rapid disintegration when placed on the tongue.
Viagra oral films and melting strips
Oral thin films or "melting strips" represent an even more portable and discreet alternative. These postage-stamp-sized strips contain sildenafil citrate incorporated into a thin polymer matrix that adheres to the tongue or buccal mucosa and dissolves within seconds to minutes.
Viagra films offer rapid disintegration and enhanced convenience. The thin film format also allows for more discreet storage and administration.
Viagra Connect: over-the-counter access
In the UK, sildenafil is also available as Viagra Connect, a 50 mg film-coated tablet that can be purchased without a prescription following a pharmacy consultation. Viagra Connect is intended for men with erectile dysfunction who meet specific suitability criteria and provides a regulated, over-the-counter option under pharmacist supervision.
Viagra Connect tablets are the same blue, diamond-shaped film-coated tablets as prescription Viagra, but are available in pack sizes of 4 or 8 tablets.
Viagra Manufacturer
Viagra is manufactured by Pfizer, the original producer of sildenafil. Pfizer (or its subsidiaries) is also the manufacturer of Viagra Connect and its authorised generic version, sildenafil citrate.
Various generic sildenafil products are available, but they cannot be sold under the brand name Viagra (at least without proper legal authorisation).
Can you get Viagra without a prescription?
It is important not to take erection problems and erectile dysfunction treatment carelessly.
To buy Viagra in the UK, you need a prescription from a doctor. Viagra is not sold over the counter, except for Viagra Connect, which is a pharmacy-only version.
A prescription ensures the correct dose, reduces risks of side effects and prevents harmful interactions — also when you purchase Viagra online.
What should be considered before taking Viagra?
Viagra tablets are not vitamins or everyday supplements. This medication for erectile dysfunction is serious; it affects blood flow and other bodily functions. Speak to a doctor before buying and using Viagra if you:
- have heart or circulation problems;
- have blood disorders such as sickle cell anaemia, leukaemia, or multiple myeloma;
- have Peyronie’s disease or anatomical penile deformities;
- have stomach ulcers or bleeding disorders.
Should you experience sudden vision changes, stop using Viagra and seek immediate medical advice.
How to use Viagra correctly for the best results
Clinicians developed a clear administration protocol to ensure success for erectile dysfunction treatment with Viagra:
- Take one tablet with water 30–60 minutes before sexual activity.
- The effect of Viagra lasts for around 4 to 6 hours.
- Heavy, high-fat meals may delay the effect of Viagra. Taking sildenafil on an empty stomach enhances its effect.
- Viagra and alcohol do not mix well — alcohol can reduce erection quality and increase side-effect risk. If you take Viagra to help with erectile dysfunction, drink alcohol in moderation, or avoid it altogether.
- Take no more than one dose of Viagra in 24 hours.
- Viagra only works by improving blood flow with sexual stimulation and does not increase libido.
If Viagra does not seem to work, the reason may be: incorrect timing, unsuitable dosage, lack of arousal, interactions with other medicines or an underlying medical cause. Discuss this with your doctor.
When should Viagra not be taken?
As with other erectile dysfunction medications, it is essential to strictly observe the clear contraindications.
Do not take Viagra tablets if you:
- are taking nitrates or nitric-oxide donors;
- have severe heart disease or have recently had a heart attack or stroke;
- have severe liver failure;
- if your blood pressure is very low (below 90/50 mm Hg);
- are allergic to sildenafil.
Viagra is not intended for women.
What are the possible side effects of Viagra?
Sildenafil is generally well-tolerated when used to treat erectile dysfunction under medical supervision. Most potential side effects are either mild or short-lived. Nevertheless, the following adverse effects should be taken into account:
Very common (≥10%)
- Headache
Common (1–10%)
- Facial flushing
- Indigestion
- Nasal congestion
- Visual disturbances
Uncommon (0.1–1%)
- Dizziness
- Skin rash
- Sleep disturbances
- Tinnitus
Rare (0.01–0.1%)
- Heart attack
- Stroke
- Low blood pressure
Very rare (<0.01%)
- Sudden hearing loss
- Priapism (painful erections)
A full list of Viagra side effects is available in the patient information leaflet.
Seek urgent medical help if you experience severe or worrying side effects. Always take Viagra at the prescribed dosage. Taking more than the prescribed dose increases the risk of serious complications of this erectile dysfunction treatment.
Is it possible to take Viagra along with other medications?
Since Viagra influences blood flow, it can interact with specific medicines, which is why medical advice is important before use. Viagra tablets can interact with:
- Nitrates – must never be combined with Viagra
- Certain antibiotics (erythromycin, clarithromycin)
- Cimetidine
- Antifungal medicines (ketoconazole, itraconazole)
- HIV medicines (ritonavir, saquinavir)
- Alpha-blockers for prostate problems or high blood pressure
Always tell your doctor about all prescribed medicines, over-the-counter products and supplements before taking Viagra. Read the patient information leaflet carefully before starting this ED treatment.
How can you buy Viagra safely in the UK?
At a local pharmacy
With a valid prescription, you can purchase Viagra safely at any UK pharmacy, with professional advice from the pharmacist.
Order Viagra online
Trusted online providers offer online consultation with licensed doctors. You complete a medical questionnaire, a doctor reviews it, and if suitable, you receive a prescription and Viagra delivery direct to your home.
Ordering online also lets you compare Viagra price options and look for offers.
Warning about illegal suppliers
Never try to get Viagra without a prescription from unregulated websites. Counterfeit Viagra pills often contain untested or harmful ingredients.
Is Viagra covered by health insurance in the UK?
NHS prescriptions for Viagra for men are only available under specific medical conditions (e.g., diabetes-related ED, spinal cord injury). Most men will need a private prescription and pay for the blue pill themselves.
