Sildenafil: uses, dosage and side effects
Sildenafil is a PDE-5 inhibitor used for erectile dysfunction. Most products are prescription-only in Ireland, while a few 50 mg products are authorised as non-prescription medicines that a pharmacist can supply after a consultation; a separate product with the same substance is used in specialist care for pulmonary arterial hypertension. This page explains what it is used for, how it is taken, its side effects, the combinations that are dangerous and how existing treatment is renewed.
What sildenafil is used for
Sildenafil is used to treat erectile dysfunction, meaning difficulty getting or keeping an erection sufficient for sexual activity. It belongs to the group called PDE-5 inhibitors: it increases blood flow into the penis in response to sexual stimulation. It does not create desire and it does nothing without arousal, which is the point people are most often surprised by. A different product containing the same substance, at different strengths and under specialist supervision, is used for pulmonary arterial hypertension; that is not the same treatment and not the same prescription. Erectile dysfunction is worth taking seriously as a signal, not only as a symptom. It is associated with cardiovascular disease, diabetes, high blood pressure, high cholesterol, low testosterone, depression, alcohol and some prescribed medicines, and it can be the first noticeable sign of an arterial problem. A GP assessment, including blood pressure, blood glucose and lipids, is worth having rather than treating the symptom alone.
Side effects of sildenafil
The effects reported most often are headache, flushing, indigestion, a blocked or runny nose, dizziness and disturbed vision such as a blue tinge or increased sensitivity to light. They follow from the way the medicine widens blood vessels, and they usually pass as the dose wears off. Three situations need urgent care. An erection that is painful or lasts more than four hours needs emergency assessment, because prolonged erection can permanently damage the penis; go to an Emergency Department or call 112 or 999. Sudden loss or reduction of vision in one or both eyes, and sudden hearing loss or ringing in the ears, both mean stopping the medicine and seeking urgent medical help. Chest pain during or after sex is an emergency, and it is important to tell the treating team that you have taken sildenafil, because that changes which medicines they can safely give you.
Dosage and how to take sildenafil
Sildenafil for erectile dysfunction is taken by mouth before sexual activity, commonly about an hour beforehand, and no more than one dose in any 24 hours. The prescriber sets the strength, usually starting in the middle of the range and adjusting according to how well it works and how well it is tolerated. It needs sexual stimulation to work; taking a tablet and waiting passively will do nothing. A heavy meal, and particularly a fatty one, slows absorption and delays the onset, and alcohol makes erection harder to achieve, so both are worth avoiding on the occasion. If it does not work the first time, do not double the dose on your own: several attempts are often needed to find the right conditions and dose, and that judgement belongs to the prescriber. Do not combine it with another PDE-5 inhibitor or with products bought online claiming to be herbal, which have repeatedly been found to contain undeclared prescription substances.
Is sildenafil available without a prescription in Ireland?
That depends on the strength. A small number of 50 mg products, Viagra Connect among them, are authorised in Ireland as medicines not subject to medical prescription. They are supplied through pharmacies only, so it is a pharmacy supply and not something you pick off a shelf; for Viagra Connect the HPRA register records a consultation with a healthcare professional as a condition of supply without a prescription, and a pharmacist will in any case judge whether the medicine is suitable for you. Every 25 mg and 100 mg product, and most 50 mg brands, remain prescription-only; the HPRA register of authorised medicines states the status of each individual product. The distinction is not bureaucratic. Sildenafil interacts fatally with nitrates, it is unsuitable after a recent heart attack or stroke, and erectile dysfunction can itself be the first sign of cardiovascular disease that needs investigating, which is precisely what the pharmacist's questions, or a prescriber's assessment, are there to catch. Our own service is not an alternative to that pharmacy route: it exists for someone whose treatment a doctor has already assessed and whose prescribed strength needs to be continued. Products offered online outside a pharmacy are a well-documented counterfeiting target, and unregulated tablets have been found to contain the wrong dose or a different substance entirely. Sildenafil is not a controlled drug, so it is not among the substances excluded from cross-border prescriptions under Article 11(6) of Directive 2011/24/EU, and a prescription issued by a prescriber elsewhere in the EU or EEA can be presented in an Irish pharmacy. The Pharmaceutical Society of Ireland has published guidance for pharmacists on dispensing such prescriptions. The pharmacist still applies professional judgement and may decline where anything is unclear, so the document must carry the fields required by the Annex to Implementing Directive 2012/52/EU and name the active substance.
Renewing an existing sildenafil prescription
If a doctor has already assessed you, prescribed sildenafil and your treatment needs to be continued, you can request a repeat prescription through our medical questionnaire. A doctor reviews what you write and, where continuation is appropriate, issues a cross-border prescription as a PDF document by e-mail; you bring it and photo identification to any pharmacy. There is no PIN code, and there is no video consultation, no telephone appointment and no live chat, because the review is asynchronous. Documents are issued by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. Answer the questions about heart disease, chest pain, nitrates and other medicines completely and honestly: those answers are the whole safety check, and leaving something out puts you at risk rather than the service. If your erectile dysfunction is new, or has changed, or you have not had a cardiovascular check, see your GP: the symptom deserves an assessment of the cause. The fee of 19,90 € covers the medical consultation, not the issuing of a document. If the doctor declines on medical grounds, the fee is returned. If you do not send documentation the doctor asks for, the consultation counts as carried out and the fee is not refunded.
Cost and reimbursement in Ireland
What sildenafil costs at the counter depends on the strength, the number of tablets in the pack, the manufacturer and the pharmacy, and it is set by the pharmacy rather than by us. Generic sildenafil has been available for years and is considerably less expensive than the original brand. We do not sell medicines and we do not quote prices for them; the pharmacist will tell you the cost before dispensing. On the state side, the HSE runs the medical card scheme and the Drugs Payment Scheme. Cover for treatment of erectile dysfunction can be restricted and may depend on the underlying medical reason, so ask the pharmacy rather than assuming. How a prescription written by a prescriber in another EU country is treated under those schemes is decided by the HSE and applied at the counter. Our own charge is the consultation fee described above and is separate from the price of the medicine.
Interactions and alcohol
One interaction is absolute: nitrates. Medicines such as glyceryl trinitrate sprays or tablets, isosorbide mononitrate and dinitrate, and the recreational drugs known as poppers, must never be combined with sildenafil, because together they can cause a catastrophic fall in blood pressure. The same applies to riociguat. Alpha blockers used for the prostate or for blood pressure, such as tamsulosin or doxazosin, can also drop blood pressure when combined, so the timing and dose need a prescriber's advice. The summary of product characteristics is specific here: if you already take an alpha blocker you should be settled on your regular daily dose of it before sildenafil is started, and starting sildenafil at 25 mg should be considered. The drop in blood pressure is most likely within four hours of taking sildenafil. Medicines that inhibit the liver enzyme CYP3A4, including ritonavir, ketoconazole, itraconazole and erythromycin, raise sildenafil levels and usually require a lower dose, while grapefruit juice acts in the same direction. Alcohol reduces the quality of erections and adds to dizziness and low blood pressure, so it works against the treatment. Give the prescriber a complete list of your medicines, including anything bought without a prescription.
Who should not take sildenafil
Sildenafil must not be taken by anyone using nitrates in any form, including poppers, or riociguat, and it is not suitable for anyone who has had an allergic reaction to it. It is contraindicated in severe liver impairment, in people with very low blood pressure, in those who have had a recent stroke or heart attack, and in people with the inherited eye condition retinitis pigmentosa. Anyone who has had non-arteritic anterior ischaemic optic neuropathy, a form of sudden vision loss, should not take it. Sexual activity itself carries a cardiac risk in people with significant heart disease, so a doctor will want to know whether your heart can safely tolerate exertion. Care is needed with bleeding disorders, active stomach ulcers, sickle cell disease and conditions affecting the shape of the penis. This is not a complete list; the full contraindications and warnings for your product are in its leaflet and in the summary of product characteristics published by the HPRA.
Generic and brand names
Sildenafil is the international non-proprietary name of the active substance. In Ireland it is dispensed mainly as generic sildenafil carrying the manufacturer's name, and the original brand name is Viagra; a separate branded product containing the same substance exists for pulmonary arterial hypertension at different strengths. The active substance and the strength determine the effect, so a generic authorised by the HPRA works like the branded tablet. Tadalafil, vardenafil and avanafil belong to the same class but differ in how long they act and in their interactions, so they are not interchangeable and a switch is a prescriber's decision. Be particularly careful about anything sold as a supplement for sexual performance: products of that kind have repeatedly been found to contain undeclared PDE-5 substances, which is dangerous for anyone taking nitrates. A cross-border prescription names the active substance, which lets a pharmacist in another country dispense the equivalent authorised product.
Sildenafil in pregnancy and breastfeeding
Sildenafil for erectile dysfunction is not indicated in women, so it is not prescribed in pregnancy or while breastfeeding for that purpose, and it should not be taken by a woman on the basis of a partner's prescription. Sharing a prescription medicine with anyone else is unsafe regardless of the medicine. The substance is used in a different form and setting in specialist obstetric and paediatric medicine, but that is a hospital decision entirely separate from the treatment described on this page. If a couple is trying to conceive, sildenafil taken by the man for erectile dysfunction does not treat fertility problems, and difficulty conceiving is a reason to see a GP for assessment of both partners. If your partner is pregnant, keep the tablets stored safely away from other people, as with any prescription medicine.
Where to find the patient information leaflet
Every medicine authorised in Ireland has a patient information leaflet, and the leaflet inside your own pack is the version that applies to you. The Health Products Regulatory Authority (HPRA) keeps a public database of medicines authorised here, where you can look up the leaflet and the summary of product characteristics for the exact strength and manufacturer you have been given. For centrally authorised medicines the European Medicines Agency publishes the same documents. Read the leaflet before the first dose and again if the pack you collect looks different from the last one, because generic versions can differ in their inactive ingredients even when the active substance and the strength are identical. If anything in the leaflet does not match what you were told, ask your pharmacist before taking the medicine. A leaflet is written for the whole patient population, so it lists effects that are uncommon; it is not a prediction of what will happen to you.
Do I need a prescription for sildenafil in Ireland?
Not for every strength. A few 50 mg products, including Viagra Connect, are authorised as non-prescription medicines supplied through pharmacies only, and the pharmacist judges whether the medicine is suitable before supplying it. All 25 mg and 100 mg products, and most 50 mg brands, still need a prescription. Either way there is a safety check, because sildenafil interacts dangerously with nitrates and is unsuitable after a recent heart attack or stroke. It is not a controlled drug, so it is not excluded from cross-border prescriptions under Article 11(6) of Directive 2011/24/EU.
How long does sildenafil take to work?
It is usually taken about an hour before sexual activity and needs sexual stimulation to have any effect. A heavy or fatty meal delays absorption, and alcohol makes an erection harder to achieve. No more than one dose should be taken in 24 hours.
What are the common side effects of sildenafil?
Headache, flushing, indigestion, blocked nose, dizziness and visual disturbance such as a blue tinge are reported most often. An erection lasting more than four hours, sudden loss of vision or sudden hearing loss all need urgent medical care.
Can I drink alcohol while taking sildenafil?
Alcohol reduces the quality of erections and adds to dizziness and low blood pressure, so it works against what you are trying to achieve. If you drink on the occasion, keep it modest, and never combine sildenafil with poppers or any other nitrate.
How do I get a repeat prescription for sildenafil?
If a doctor has already prescribed it, fill in our medical questionnaire and answer the questions about heart disease, chest pain, nitrates and other medicines fully, because those answers are the safety check. Where continuation is appropriate a doctor issues a cross-border prescription as a PDF by e-mail.