In the United Kingdom, Viagra (sildenafil) is classified as a Prescription Only Medicine (POM) and cannot legally be supplied without a prescription from a qualified healthcare professional. However, some online pharmacies offer an online consultation that serves as a digital prescription process, allowing you to buy or order generic Viagra without visiting a clinic in person. At Elstree Pharmacy, we require a completed medical questionnaire reviewed by a registered prescriber before dispatching Viagra to ensure safety and appropriateness of treatment.
It is important to distinguish between regulated online pharmacies that dispense Viagra under a valid clinical assessment and entirely unregulated websites claiming to supply Viagra without prescription. Only pharmacies registered with the General Pharmaceutical Council (GPhC) and operating under UK regulations are authorised to supply POM medicines such as Viagra.
The UK classifies medicines into three main categories: Prescription Only Medicine (POM), Pharmacy medicine (P), and General Sales List (GSL). A Pharmacy medicine (P) can be sold only under the supervision of a pharmacist, without a prescription, whereas a POM requires a valid prescription.
Viagra is a POM, which means you cannot legally purchase Viagra tablets over the counter or via general retail. Any supplier offering Viagra without a prescription must provide an online clinical consultation that meets the MHRA and GPhC standards, effectively issuing a prescription after reviewing your medical details.
Sildenafil is the active ingredient in Viagra and is classified as a phosphodiesterase type 5 (PDE5) inhibitor. It works by enhancing nitric oxide–mediated relaxation of smooth muscle in the corpus cavernosum, resulting in increased penile blood flow and facilitating erection during sexual stimulation.
Viagra is the original brand name for sildenafil citrate developed by Pfizer. Generic Viagra contains the same active ingredient and must meet the same quality, safety and efficacy standards set by regulatory authorities.
Film-coated tablets improve handling, stability and patient acceptability. The coating may also mask the taste of sildenafil and protect the active ingredient from moisture.
No. Viagra does not increase sexual desire. It facilitates the physiological process of erection when sexual arousal is already present.
Onset of action is typically within 30–60 minutes. Factors such as food intake, particularly high-fat meals, can delay absorption and reduce peak plasma levels.
The duration of action is around 4 to 5 hours, although individual response varies. This window represents the period during which improved erectile response is most likely.
Generic Viagra contains the same sildenafil citrate at equivalent doses and must adhere to the same pharmacological and regulatory requirements. Differences may exist in excipients, tablet shape, colour and packaging.
PDE5 is an enzyme that breaks down cyclic guanosine monophosphate (cGMP), a messenger that mediates smooth muscle relaxation in the penis. Inhibition of PDE5 increases cGMP concentrations, leading to vasodilation and increased blood flow into the corpora cavernosa.
Sildenafil binds selectively to PDE5, preventing cGMP breakdown. Elevated cGMP levels result in relaxation of penile blood vessels and erection in the presence of sexual stimulation.
No. Viagra enhances the mechanical process of erection but does not affect libido or sexual desire directly. Psychological factors play a separate role in sexual interest.
Yes. Without sexual arousal and neurovascular signalling that generate nitric oxide release, PDE5 inhibition alone will not produce an erection.
Sildenafil is also licensed at different doses for pulmonary arterial hypertension under the brand name Revatio, but that indication is separate from erectile dysfunction treatment.
Prices for Viagra vary depending on dose, pack size, brand versus generic and the retailer’s pricing strategy. Online pharmacies often offer competitive rates, and generic Viagra can be substantially cheaper than branded tablets. Below is an example comparison for information only. Contact Elstree Pharmacy for live pricing and stock availability.
| Example | Strength | Pack Size | Price | Status | Note |
|---|---|---|---|---|---|
| Example A | 50 mg | 4 tablets | £29.99 | In Stock | Generic sildenafil, cheaper option |
| Example B | 100 mg | 8 tablets | £49.95 | In Stock | Branded Viagra, premium price |
Pricing is influenced by brand or generic status, dose, pack quantity, distribution costs and retailer margin. Purchasing generic Viagra online can often yield cheaper prices without compromising quality.
Sildenafil for erectile dysfunction is commonly available in 25 mg, 50 mg and 100 mg film-coated tablets. The 50 mg dose is typical starting strength for most patients.
Packs of 4, 8 and 12 tablets are usual. Some pharmacies may offer larger multipacks or multi-dose blister cards.
Pack size affects cost per tablet and ensures sufficient supply for short-term assessment of response. Excess supply without follow-up can increase risk of misuse.
| Feature | Why it matters |
| Strength | Determines dose-response and efficacy |
| Pack size | Ensures appropriate course length |
| Brand vs generic | Affects price, but not active ingredient |
| Coating | Improves stability and swallowability |
Some manufacturers offer rapidly disintegrating tablets or oral films designed to dissolve on the tongue for faster onset and ease of administration.
ED is the inability to attain or maintain an erection sufficient for satisfactory sexual performance. It can stem from vascular, neurological, hormonal or psychological causes.
Persistent ED lasting more than six months, ED in younger men without apparent cause, or ED associated with cardiovascular risk factors warrants medical evaluation.
Yes. Occasional performance difficulty is common and may relate to stress, fatigue, alcohol consumption or transient health issues.
Lifestyle modifications such as weight loss, regular exercise, smoking cessation and reduction of alcohol intake can improve erectile function.
Goals include restoring satisfactory sexual function, improving quality of life and addressing underlying health conditions that contribute to ED.
A Prescription Only Medicine requires a prescription or an online clinical assessment that results in the issue of a prescription. Viagra is POM in the UK.
Pharmacy medicines (P) can be supplied without a prescription but only under pharmacist supervision. Viagra does not fall into this category.
GSL medicines are those permitted for general sale in non-pharmacy retail outlets. ED treatments are not GSL.
Reclassification would require regulatory approval by the MHRA, based on safety data for unsupervised use. To date, sildenafil for ED remains POM.
Penile injection therapy (alprostadil), vacuum erection devices, hormone therapy for testosterone deficiency and surgical implants for refractory cases.
Sildenafil has a shorter half-life (4–5 hours) while tadalafil lasts up to 36 hours. Tadalafil allows greater spontaneity but may increase risk of prolonged effects.
Vardenafil has similar onset and duration to sildenafil but may be preferable for some due to individual metabolic differences and side effect profiles.
| Feature | Sildenafil (Viagra) | Tadalafil (Cialis) | Vardenafil (Levitra) |
| Class | PDE5 inhibitor | PDE5 inhibitor | PDE5 inhibitor |
| Onset | 30–60 min | 30–120 min | 25–60 min |
| Duration | 4–5 hrs | 24–36 hrs | 4–5 hrs |
| Food effect | Delayed by high-fat meal | Minimal effect | Reduced by high-fat meal |
| Typical OTC | No (POM) | No (POM) | No (POM) |
No. Choice depends on personal preference, desired duration, side effect profile and cost. Generic sildenafil is often the cheapest option for short-term use.
High-fat meals can delay absorption and reduce peak levels of sildenafil, potentially delaying onset of effect. A light meal or empty stomach is recommended for optimal onset.
Excess alcohol impairs erectile function and may increase side effects such as dizziness or headache when combined with sildenafil.
Smoking can damage blood vessels and reduce nitric oxide availability, worsening ED. Quitting smoking may enhance responsiveness to PDE5 inhibitors.
Regular aerobic exercise enhances cardiovascular health and nitric oxide production, potentially improving erectile function even without medication.
Yes. Common side effects include headache, flushing, dyspepsia, nasal congestion, dizziness and visual disturbances. Most are mild and transient.
| Area | Examples |
| Head | Headache, dizziness |
| Face | Flushing, warmth |
| Digestive | Indigestion, dyspepsia |
| Vision | Blue tinge, sensitivity to light |
| Serious | Priapism, severe hypotension (rare) |
Priapism is a prolonged, painful erection lasting >4 hours. It is a medical emergency requiring immediate treatment to prevent permanent tissue damage.
Rarely, sildenafil can cause temporary visual disturbances including blurred vision, increased light sensitivity or changes in colour perception.
Serious hypersensitivity reactions are rare but can include rash, difficulty breathing or facial swelling. Immediate medical attention is required.
Viagra may be used as needed for erectile function. There is no strict limit on cumulative use if medically appropriate, but regular review is advised for chronic users.
Long-term sildenafil use in ED has a well-established safety record. Monitoring is recommended for cardiovascular status and visual function in frequent users.
Some users report reduced effect over time, possibly due to underlying vascular disease progression rather than pharmacological tolerance.
Regular review ensures continued appropriateness of therapy, correct dosing and timely identification of new contraindications or interactions.
Yes. Significant interactions occur with nitrates (contraindicated), alpha-blockers (risk of hypotension), HIV protease inhibitors (increase sildenafil levels) and certain antifungals or macrolide antibiotics.
Combined use of sildenafil and nitrates can cause profound hypotension, syncope and risk of cardiovascular events.
Sildenafil is metabolised via CYP3A4 and CYP2C9. Inhibitors of these enzymes can elevate sildenafil levels; inducers can reduce efficacy.
Sildenafil is not indicated for use in women attempting conception or during breastfeeding for ED. Its use in pregnant women is limited to investigational pulmonary hypertension therapy under specialist care.
Generic Viagra contains sildenafil citrate, the same active ingredient as branded Viagra, in an equivalent dose. It meets rigorous regulatory requirements for quality, safety and efficacy.
Different manufacturers may use distinct excipients, coatings, tablet colours, shapes and packaging. Each product has its own patient information leaflet and expiry date.
Store at room temperature away from moisture and heat. Keep in original packaging to protect from light and humidity.
Regulation applies to each authorised product. Always consult the enclosed patient leaflet or the electronic Medicines Compendium for details on indications, dosing, contraindications and warnings.
Reliable sources include the MHRA website, electronic Medicines Compendium (eMC), BNF and qualified healthcare professionals including pharmacists and GPs.
No. This page is general guidance provided by Elstree Pharmacy (The Corner Shop B, High Street, Elstree, WD6 3BY). For personalised advice on purchasing, dosing, side effects and interactions, please consult our pharmacy team or your doctor.
