Sildenafil Patient Information Leaflet Explained

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Understanding Your Sildenafil Patient Information Leaflet

Published: 7 November 2026

The sildenafil patient information leaflet (PIL) is the official document packed with every box of sildenafil tablets, providing essential information about how to take the medicine, what to expect, possible side effects, and important safety warnings [3]. Every PIL is approved by the UK medicines regulator and written to help you use sildenafil safely and effectively. This page explains what you'll find in your sildenafil patient information leaflet and answers common questions to help you get the most from your treatment.

What Is Included in the Sildenafil Patient Information Leaflet?

The sildenafil patient information leaflet is a comprehensive guide that accompanies every pack of sildenafil tablets, whether you receive generic sildenafil or branded Viagra [12]. It is a legal requirement in the UK and across Europe, and the content is standardised to ensure every patient receives the same essential information about their medicine.

Your PIL is divided into clear sections: what sildenafil is and what it is used for; what you need to know before you take it (including who should not take it and warnings about other medicines); how to take sildenafil (dosage and timing); possible side effects (common, uncommon, and rare); how to store the tablets; and what the pack contains [12]. The leaflet also includes the name and contact details of the manufacturer and the date it was last revised.

Reading your sildenafil patient information leaflet before you take your first dose is important, even if a doctor or pharmacist has already explained how to use the medicine. The PIL contains detailed safety information, including interactions with other medicines, conditions that may make sildenafil unsuitable, and what to do if you experience side effects [3]. Keep the leaflet in a safe place so you can refer back to it if you have questions later.

How to Take Sildenafil: Key Instructions from the Patient Information Leaflet

The sildenafil patient information leaflet explains that sildenafil is taken as needed, approximately one hour before you plan to have sexual activity [3]. The usual starting dose for most men is 50 mg, though your prescriber may recommend 25 mg if you are over 65, have liver or kidney problems, or take certain other medicines. If 50 mg works but causes side effects, your dose may be reduced; if it does not work well enough, it may be increased to a maximum of 100 mg [3].

Sildenafil should be swallowed whole with water and can be taken with or without food, though a large, high-fat meal may delay how quickly it works [12]. You should take sildenafil no more than once in any 24-hour period. The medicine only works when you are sexually aroused; it does not cause an automatic erection and is not an aphrodisiac [1][3].

If you accidentally take more than your prescribed dose, contact your doctor or go to your nearest accident and emergency department straight away, even if you feel well. Taking too much sildenafil increases the risk of serious side effects, including dangerously low blood pressure, fainting, prolonged erection, and visual disturbances [12]. If you forget to take a dose, simply take it when you remember (if you still plan sexual activity), but never take a double dose to make up for a missed one.

Timing and Effectiveness

Sildenafil typically starts to work within 30 to 60 minutes, though it can take up to two hours in some men [3]. The effect usually lasts for about four to five hours, during which time it may be easier to get and keep an erection when you are sexually stimulated. This does not mean you will have an erection for four hours; rather, the medicine remains active in your system and can help you respond to sexual stimulation during that window [9]. Plan to take your tablet with enough time before sexual activity, and remember that sexual arousal is still necessary for the medicine to work.

Important Safety Warnings in Your Sildenafil Patient Information Leaflet

The sildenafil patient information leaflet contains critical safety warnings that you must read and understand before taking the medicine [12]. Sildenafil must never be taken if you are using nitrate medicines for chest pain (such as glyceryl trinitrate spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl nitrite or alkyl nitrites). Combining sildenafil with any of these can cause a sudden, dangerous drop in blood pressure that may be life-threatening [3].

You should not take sildenafil if you have severe heart or liver problems, have recently had a stroke or heart attack, have low blood pressure, have certain rare inherited eye conditions (such as retinitis pigmentosa), or have ever had non-arteritic anterior ischaemic optic neuropathy (NAION), a condition that causes sudden vision loss [3][12]. Sildenafil is also not suitable if you have been advised by your doctor to avoid sexual activity because of heart problems.

Tell your prescriber about all medicines you take, including those bought without a prescription, herbal remedies, and supplements. Sildenafil can interact with alpha-blockers (used for prostate problems or high blood pressure), some antifungals and antibiotics, HIV medicines, and other treatments [3]. Your prescriber will check whether sildenafil is safe for you and may adjust your dose or timing to reduce the risk of interactions. Never take sildenafil together with another medicine for erectile dysfunction.

Sildenafil Patient Information Leaflet: Side Effects to Be Aware Of

The sildenafil patient information leaflet lists possible side effects, grouped by how common they are [12]. Very common side effects (affecting more than 1 in 10 men) include headache. Common side effects (up to 1 in 10 men) include flushing (redness or warmth in the face, neck, or chest), indigestion, dizziness, visual disturbances such as blurred vision or a blue tinge to vision, and nasal congestion [3]. These side effects are usually mild and temporary, often improving as your body adjusts to the medicine.

Uncommon and rare side effects include nausea, vomiting, skin rash, eye redness or discomfort, back pain, muscle aches, nosebleeds, feeling drowsy, and changes in blood pressure [12]. Very rarely, sildenafil has been associated with serious side effects such as sudden loss of vision in one or both eyes (which may be a sign of NAION), sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), seizures, irregular heartbeat, chest pain, and priapism (a painful erection lasting more than four hours) [3][12].

If you experience chest pain during or after sex, do not use nitrate medicines to treat it; instead, seek medical help immediately and tell the healthcare professional that you have taken sildenafil [12]. If you have an erection that lasts longer than four hours, go to accident and emergency straight away, as priapism can cause permanent damage if not treated promptly. If you notice sudden vision or hearing loss, stop taking sildenafil and contact a doctor urgently. Most men tolerate sildenafil well, but it is important to know when to seek help.

Reporting Side Effects

If you experience any side effect that bothers you or does not go away, talk to your doctor or pharmacist [12]. You can also report side effects directly via the UK Yellow Card Scheme at www.mhra.gov.uk/yellowcard or by searching for MHRA Yellow Card in the Google Play or Apple App Store. Reporting side effects helps the medicines regulator monitor the safety of medicines and can contribute to protecting other patients.

Where to Find and How to Read Your Sildenafil Patient Information Leaflet

Your sildenafil patient information leaflet is folded inside the medicine box or blister pack [12]. If you have misplaced your leaflet, you can find an electronic copy on the Electronic Medicines Compendium (eMC) website at www.medicines.org.uk/emc, where PILs for all UK-licensed medicines are published. Simply search for the brand name (such as Viagra or the manufacturer's name for generic sildenafil) and select 'Patient Information Leaflet' from the documents available.

The PIL is written in plain language and organised into numbered sections to make it easy to find the information you need [12]. Section 1 explains what the medicine is for; section 2 covers what you need to know before taking it (contraindications, warnings, and interactions); section 3 describes how to take the medicine; section 4 lists possible side effects; section 5 explains how to store it; and section 6 provides details about the contents and manufacturer.

If you find any part of the sildenafil patient information leaflet difficult to understand, ask your pharmacist or doctor to explain it. Do not rely solely on information from unofficial websites or forums; the PIL is the authoritative source approved by the UK regulator. If you receive sildenafil from Cured Pharmacy, our pharmacist-led team is available to answer questions about your treatment and help you understand your leaflet during your online consultation and afterwards.

Sildenafil Patient Information Leaflet and Your Online Consultation

When you request sildenafil through Cured Pharmacy, a UK-registered prescriber reviews your online consultation to ensure the medicine is safe and suitable for you, taking into account your medical history, current medicines, and any conditions listed in the sildenafil patient information leaflet as contraindications or warnings [2][3]. This clinical review is a legal requirement for all prescription medicines and ensures you receive the same standard of care as you would from your GP or a face-to-face consultation.

During your consultation, you will be asked about conditions such as heart disease, high or low blood pressure, liver or kidney problems, blood disorders, stomach ulcers, and eye conditions, as well as any medicines you take regularly or occasionally [3]. This information is cross-checked against the safety warnings in the sildenafil patient information leaflet to identify any risks or interactions. If sildenafil is not suitable, the prescriber may suggest an alternative treatment or advise you to see your GP for further assessment [2].

Once your treatment is approved and dispensed, you will receive the sildenafil patient information leaflet with your medicine. Reading it carefully before your first dose ensures you understand how to take sildenafil correctly, what side effects to watch for, and when to seek medical help [12]. If you have new symptoms or your health changes after starting treatment, contact your GP or our pharmacy team for advice. Erectile dysfunction can be an early warning sign of cardiovascular disease or diabetes, so it is important to have regular health checks with your doctor [1][10].

Accessing Treatment at Cured Pharmacy

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering convenient access to sildenafil and other erectile dysfunction treatments after a clinical consultation. You can request sildenafil from £0.45 per tablet (or £0.36 with first-order code Ednew), with your medicine and patient information leaflet delivered discreetly to your door. All prescriptions are reviewed by UK-registered prescribers, and our pharmacy team is available to answer questions about your treatment and help you use your medicine safely.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 7 November 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 7 November 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 7 November 2026]
4. Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral sildenafil in the treatment of erectile dysfunction. New England Journal of Medicine, 338(20), 1397–1404. https://pubmed.ncbi.nlm.nih.gov/9580646/ [accessed 7 November 2026]
5. Feldman, H. A., Goldstein, I., Hatzichristou, D. G., Krane, R. J., & McKinlay, J. B. (1994). Impotence and its medical and psychosocial correlates: Results of the Massachusetts Male Aging Study. Journal of Urology, 151(1), 54–61. https://pubmed.ncbi.nlm.nih.gov/8254833/ [accessed 7 November 2026]
6. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 7 November 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.