Viagra sildenafil citrate is a prescription medicine that treats erectile dysfunction in adult men by improving blood flow to the penis during sexual stimulation. At ADR Clinic a GPhC-registered UK men’s health service sildenafil citrate is prescribed online by GMC-registered doctors after a free 5-minute consultation, dispensed by a UK pharmacy, and delivered discreetly next day. Choose from 25mg, 50mg or 100mg, priced from £[X] per tablet. Branded Viagra and generic sildenafil are clinically identical same active ingredient, same dose strengths, same effect.
What Is Viagra Sildenafil Citrate?
Sildenafil citrate is the active ingredient in Viagra the original prescription medicine for erectile dysfunction, developed by Pfizer and first licensed in the UK in 1998. When Pfizer’s patent expired in 2013, sildenafil citrate became available as a generic medicine. Branded Viagra and generic sildenafil are pharmacologically identical: same molecule, same dose strengths, same effect only the price differs.
ADR Clinic supplies only MHRA-approved sildenafil citrate, dispensed through our GPhC-registered pharmacy partner. We do not sell, import, or recommend grey-market or overseas sildenafil under any circumstances.
At-a-glance facts
- Drug class: PDE5 inhibitor
- Available strengths: 25mg, 50mg, 100mg
- Onset of action: 30–60 minutes
- Duration of effect: up to 4 hours
- Available as: branded Viagra (Pfizer) or generic sildenafil
- Legal status in UK: Prescription-Only Medicine (POM). Viagra Connect 50mg is the only sildenafil product available over the counter, and only after a pharmacist consultation.
How Sildenafil Citrate Works
When you’re sexually aroused, your body releases nitric oxide in the penis. That triggers a chemical called cGMP, which relaxes the smooth muscle in the blood vessels and lets blood flow in — which is how an erection happens.
In men with erectile dysfunction, an enzyme called PDE5 breaks cGMP down too quickly. Sildenafil citrate blocks PDE5. cGMP sticks around longer. Blood flows in.
An erection becomes possible.
Two things this means in practice:
- Sildenafil does not push blood into the penis. It removes the brake that was stopping a normal erection from happening.
- Sexual stimulation is still required. A tablet without arousal does nothing.
Timing and food
- Take 30–60 minutes before sexual activity
- Works fastest on an empty stomach
- Heavy or fatty meals can delay onset by up to an hour
- Maximum one tablet per 24 hours
- Small amounts of alcohol are safe; heavy drinking blunts the effect
Sildenafil Citrate vs Branded Viagra: Side-by-Side
Feature
Active ingredient
Dosage strengths
Onset of action
Duration of effect
MHRA-approved
Prescription required
Typical UK private price
Manufacturer
Generic Sildenafil
Sildenafil citrate
25mg, 50mg, 100mg
30 – 60 minutes
Up to 4 hours
Yes
Yes*
From £ [X] per tablet
Multiple licensed UK
Viagra (Pfizer)
Sildenafil citrate
25mg, 50mg, 100mg
30 – 60 minutes
Up to 4 hours
Yes
Yes*
From £ [X] per tablet
Pfizer
Want to Save 70–90% with Generic Sildenafil?
Same active ingredient, same UK-licensed manufacturers, same MHRA standard. Most ADR Clinic patients choose generic for the price and stay on it.
Which should you choose?
- Generic sildenafil same clinical effect, usually 70–90% cheaper. The right
- choice for most patients.
- Branded Viagra for patients with a strong preference for the Pfizer original
- or who have a long history of responding well to it.
Both are available through ADR Clinic following a free online consultation.
At ADR Clinic, sildenafil citrate is prescribed by UK-licensed doctors and dispensed through our GPhC-registered pharmacy partner. We supply MHRA-approved tablets only never grey-market imports.
Sildenafil Citrate Doses: 25mg, 50mg or 100mg?
Sildenafil citrate is licensed in three strengths. Your prescriber will recommend a starting dose based on your age, medical history, current medicines, and the severity of your symptoms. Never adjust your dose without clinical advice.
| Dose | Typical Use | Price |
| 25mg | Men over 65, on certain blood pressure medicines, or sensitive to side effects at 50mg | From £[X] |
| 50mg | Standard starting dose for most adult men new to ED treatment | From £[X] |
| 100mg | Maximum licensed daily dose. Used when 50mg is not effective and the lower dose was well-tolerated | From £[X] |
Not Sure Which Strength Is Right for You?
A 5-Minute Clinical Questionnaire Is Enough For Our Prescriber To Recommend The Correct Starting Dose.
Rules that don’t change:
- Maximum one tablet in any 24-hour period
- Take 30–60 minutes before sex
- Try a dose at least 6–8 times before deciding it doesn’t work effectiveness often improves with familiarity
Side Effects and Who Should Not Take Sildenafil
Sildenafil citrate is one of the most extensively studied medicines in the world. Most side effects are mild and short-lived — usually a direct consequence of the same blood-vessel relaxation that makes the medicine work.
Common side effects (more than 1 in 100 men)
- Headache
- Facial flushing
- Indigestion
- Blocked or runny nose
- Mild dizziness
- Temporary visual disturbances (blue tinge, light sensitivity)
Do NOT take sildenafil citrate if you:
- Take nitrate medicines for chest pain (e.g. GTN spray, isosorbide)
- Take riociguat for pulmonary hypertension
- Use recreational poppers (which contain nitrates)
- Have had a recent heart attack or stroke
- Have severe liver disease
- Have very low blood pressure (below 90/50 mmHg)
Speak to your prescriber before taking sildenafil citrate if you:
- Take alpha-blockers for blood pressure or prostate symptoms
- Have a heart condition or angina
- Have sickle cell disease, leukaemia, or myeloma
- Have a stomach ulcer or bleeding disorder
- Have an inherited eye condition (e.g. retinitis pigmentosa)
Why UK Men Choose ADR Clinic for Sildenafil Citrate
- GPhC-registered UK pharmacy. Every order is dispensed legally under General Pharmaceutical Council oversight.
- GMC-registered prescribers. Your consultation is reviewed by a doctor on the General Medical Council register — never an algorithm, never an overseas pharmacist.
- Genuine MHRA-approved sildenafil citrate only. Sourced through regulated UK supply chains. We do not import grey-market product.
- Free, confidential online consultation. Five minutes to complete, no upfront charge. You pay only if a prescription is approved.
- All three licensed strengths available. 25mg, 50mg, and 100mg sildenafil citrate, prescribed at the dose clinically right for you.
- Discreet next-day UK delivery. Plain, signed-for packaging with no clinical markings. Free standard delivery on orders above £[X].
- Aftercare without subscription. Your prescriber stays available for follow-up, dose adjustment, and ongoing support. No auto-renewals, no lock-in.
How to Get Sildenafil Citrate Online – 4 Steps
Step 1 — Complete a free online consultation (5 minutes) Answer questions about your medical history, current medications, and ED symptoms. No payment at this stage.
Step 2 — UK doctor reviews your case A GMC-registered prescriber assesses whether sildenafil citrate is safe and appropriate for you.
Step 3 — Prescription issued (if clinically appropriate) If approved, your prescription is sent electronically to our partnered GPhC-registered pharmacy. If sildenafil citrate isn’t suitable, we’ll explain why and suggest alternatives like tadalafil or vardenafil.
Step 4 — Discreet next-day delivery Your sildenafil citrate is dispatched in plain, signed-for packaging — no clinical or pharmacy markings on the outside.
What a First Prescription Looks Like – A Patient Example
Mark is 52, lives in Leeds, and has been losing erections during sex for around eighteen months. He doesn’t want to book a GP appointment about it.
Thursday evening, he completes ADR Clinic’s free online consultation in seven minutes. He’s honest about everything mild high blood pressure, a single ramipril 5mg in the morning, no nitrates, no heart history. Friday morning, an ADR Clinic GMC-registered doctor reviews his answers and approves a starting dose of sildenafil 50mg. He pays at this stage not before. The prescription is sent electronically to the GPhC pharmacy partner the same morning.
Saturday morning, a plain signed-for envelope arrives. No “Viagra” on the outside, no clinic logo. That evening, Mark takes one 50mg tablet with a glass of water forty minutes before sex. Around the thirty-minute mark he notices a faint warmth in his face the well-documented flushing side effect and a slightly stuffy nose. With his partner, he gets a firmer and longer-lasting erection than he has in a year and a half.
Three months later, he’s still on 50mg, takes it on planned evenings only, and spends roughly the same amount each month as a single takeaway. ED hasn’t disappeared but it no longer runs his life.
About ADR Clinic – Our Clinical Governance
ADR Clinic is a UK-based men’s health clinic specialising in prescription erectile dysfunction treatment. Our service is built on four regulatory pillars:
- Pharmacy: dispensed through our GPhC-registered pharmacy partner
- Prescribers: every consultation reviewed by a doctor on the GMC register
- Medicines: MHRA-approved sildenafil citrate only
- Standards: CQC-registered service standards
Our prescribing principles
- We will say no when sildenafil is not clinically appropriate
- We will recommend alternatives (tadalafil, vardenafil) or onward referral where needed
- We will never auto-renew a prescription without clinical review
Ready to Start? Speak to a UK Doctor Today
Ready to Take Back Control?
You don’t need to book a GP appointment, sit in a waiting room, or risk your health on an unregulated overseas site. A UK GMC-registered doctor can review your case today and genuine MHRA-approved sildenafil citrate can be at your door tomorrow.
Genuine Sildenafil Online UK — Frequently Asked Questions
Yes. Sildenafil citrate is the active ingredient in Viagra. Branded Pfizer Viagra and generic sildenafil contain the same medicine at the same dose strengths and work in identical ways. The clinical effect is the same; only the price and the manufacturer differ.
Sildenafil citrate typically starts working in 30 to 60 minutes. It works fastest on an empty stomach; heavy or fatty meals can delay onset by up to an hour. The effect lasts up to 4 hours from when it begins.
At ADR Clinic, sildenafil citrate starts from £[X] per tablet for the 50mg strength. Prices vary by dose and pack size. The online doctor consultation and prescription are included free — there is no separate prescription fee.
No. Only Viagra Connect 50mg can be sold over the counter in UK pharmacies, and only after a pharmacist consultation. All other strengths of sildenafil citrate require a prescription. ADR Clinic provides this through a free 5-minute online consultation with a UK GMC-registered doctor.
The NHS prescribes generic sildenafil citrate for men with specific medical conditions including diabetes, multiple sclerosis, prostate cancer, spinal injury, and after radical pelvic surgery. Men who don’t meet these criteria use a private prescription through a regulated clinic such as ADR Clinic.
Up to 4 hours from the moment it starts working. Sildenafil does not give you a 4-hour erection — it creates a 4-hour window during which sexual arousal can produce an erection.
No. Sildenafil citrate is licensed for use as needed, with a maximum of one tablet in any 24-hour period. If you need daily ED treatment, low-dose tadalafil (Cialis) is usually a better option — your prescriber can advise.
The most common side effects are headache, facial flushing, indigestion, a blocked or runny nose, mild dizziness, and short-lived visual changes such as a blue tinge or light sensitivity. These usually resolve within a few hours. Rare but serious side effects include priapism, sudden vision loss, and sudden hearing loss seek immediate medical help if these occur.
Do not take sildenafil citrate if you take nitrates for chest pain, take riociguat for pulmonary hypertension, use recreational poppers, have had a recent heart attack or stroke, have severe liver disease, or have very low blood pressure. Always disclose your full medical history during your consultation.
Yes in healthy men, sildenafil citrate has been in clinical use since 1998 and is one of the most studied medicines in the world. It has not been linked to tolerance, dependence, or organ damage. Annual prescriber review is recommended for men on ongoing treatment.
No. They are pharmacologically identical. A 50mg generic sildenafil tablet has the same active ingredient at the same dose and the same regulatory standard as a 50mg Pfizer Viagra tablet. Any perceived difference is usually placebo or formulation preference, not pharmacological strength.
Orders approved before [cut-off time] are dispatched the same day for signed-for next-day UK delivery. Packaging is plain and discreet — no clinical or pharmacy markings on the outside. Standard delivery is free on orders above £[X].
About ADR Clinic + Clinical Governance
ADR Clinic is a UK-based men’s health clinic specialising in prescription erectile dysfunction treatment, including sildenafil citrate (Viagra).
We are committed to safe, evidence-based prescribing. Where sildenafil citrate is not clinically appropriate, our doctors will say so – and recommend alternatives or onward referral where needed.
What Our Patients Say About ADR Clinic
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