> ## Documentation Index > Fetch the complete documentation index at: https://docs.hi-doctor.ai/llms.txt > Use this file to discover all available pages before exploring further. # Side effects: sexual health medicines > Reported side effects of the PDE5 inhibitors and dapoxetine, the frequencies in the EU product information, and the interactions that rule them out. The tablets used for erectile dysfunction all work the same way — they block the PDE5 enzyme so the blood vessels in the penis stay relaxed during arousal — and they share a side-effect pattern that follows from that: headache, flushing, indigestion, a blocked nose. Dapoxetine, used for premature ejaculation, is a different class of medicine with a different profile. **Nitrates are an absolute contraindication for every PDE5 inhibitor on this page.** Nitrate medicines and nitric-oxide donors, including recreational "poppers", must never be combined with them: blood pressure can fall dangerously. This is one of the checks the consultation runs before anything is prescribed — see [Safety](/essentials/safety). ## Sildenafil | Reported effect | EU frequency | | ---------------------------------------- | ---------------------------------- | | Headache | Very common — at least 1 in 10 men | | Flushing | Common — 1 in 100 to 1 in 10 | | Dyspepsia (indigestion) | Common — 1 in 100 to 1 in 10 | | Nasal congestion | Common — 1 in 100 to 1 in 10 | | Visual disturbance | Common — 1 in 100 to 1 in 10 | | NAION (sudden loss of vision in one eye) | Rare — 1 in 10,000 to 1 in 1,000 | In the pivotal trial, headache, flushing and dyspepsia were the most common effects, occurring in 6% to 18% of men. Visual colour distortion, visual disturbance and blurred vision are all listed as common. A dedicated study found mild, temporary blue/green colour-discrimination changes 1 hour after a 100 mg dose, with no effect remaining 2 hours after the dose. Sildenafil is contraindicated in men who have already lost vision in one eye from NAION. ## Tadalafil | Reported effect | EU frequency | | ----------------------- | ---------------------------- | | Headache | Common — 1 in 100 to 1 in 10 | | Back pain | Common — 1 in 100 to 1 in 10 | | Myalgia (muscle pain) | Common — 1 in 100 to 1 in 10 | | Dyspepsia (indigestion) | Common — 1 in 100 to 1 in 10 | | Flushing | Common — 1 in 100 to 1 in 10 | | Nasal congestion | Common — 1 in 100 to 1 in 10 | Frequency rises with higher doses. With once-daily dosing, most headaches occur in the first 10 to 30 days of treatment. Tadalafil is contraindicated in men who have lost vision in one eye because of NAION, whether or not the episode was linked to a PDE5 inhibitor. It is also contraindicated with nitrate medicines and with guanylate cyclase stimulators, and after a recent heart attack (within 3 months) or stroke (within 6 months). ## Vardenafil | Reported effect | EU frequency | In the at-home pivotal trial | | -------------------------------------------------------- | ------------------- | ---------------------------- | | Headache | Very common | 7% to 15% of men | | Flushing | Common | 10% to 11% of men | | Dyspepsia or rhinitis | Common | up to 7% of men | | Dizziness | Common | — | | Visual disturbance, ocular hyperaemia, colour distortion | Uncommon | — | | NAION | Frequency not known | — | Vardenafil is contraindicated in men who have already lost vision in one eye from NAION, with nitrate medicines and nitric-oxide donors, and in men with severe cardiovascular disease. It can lower blood pressure and has specific precautions for QT prolongation and rhythm medicines. Film-coated and orodispersible tablets are not interchangeable dose for dose. ## Avanafil | Reported effect | EU frequency | | ---------------- | --------------------------------- | | Headache | Common — 1 in 100 to 1 in 10 | | Flushing | Common — 1 in 100 to 1 in 10 | | Nasal congestion | Common — 1 in 100 to 1 in 10 | | Back pain | Uncommon — 1 in 1,000 to 1 in 100 | | Sinus congestion | Uncommon | | Dizziness | Uncommon | | Blurred vision | Uncommon | Headache is named as one of the most frequently reported reactions across a safety database of 2,566 exposed subjects. Back pain sits in the uncommon band of the adverse-reaction table, although the safety summary names it among the most frequently reported reactions. Avanafil is contraindicated with nitrate medicines and nitric-oxide donors, and in men with serious cardiovascular conditions such as recent heart attack, stroke or unstable angina. ## Dapoxetine Dapoxetine is a short-acting serotonin reuptake inhibitor used on demand for premature ejaculation. | Reported effect | 30 mg | 60 mg | | --------------- | ----- | ----- | | Nausea | 8.7% | 20.1% | | Headache | 5.9% | 6.8% | | Diarrhoea | 3.9% | 6.8% | | Dizziness | 3.0% | 6.2% | Figures are from the phase 3 trials. **Fainting.** EU regulators reviewed severe fainting episodes with the 60 mg tablet. The European Commission decision of 20 January 2012 requires treatment to start at 30 mg and allows a move to 60 mg only if 30 mg was not enough and no moderate or severe reactions occurred. The EU product information contraindicates dapoxetine in the presence of: * significant heart disease — heart failure (NYHA II–IV), conduction disorders such as AV block or sick sinus syndrome, ischaemic heart disease or significant valve disease * any history of fainting * a history of mania or severe depression * moderate or severe liver impairment * treatment with an MAO inhibitor or with thioridazine now or in the last 14 days * treatment with any other serotonergic medicine — SSRIs, SNRIs, tricyclics, tramadol, triptans, linezolid, lithium, tryptophan or St John's wort — now or in the last 14 days * treatment with a strong CYP3A4 inhibitor such as ketoconazole, itraconazole, ritonavir, saquinavir, telithromycin, nefazodone, nelfinavir or atazanavir * hypersensitivity to dapoxetine or any of the tablet's ingredients Dapoxetine is authorised in EU countries including Spain, but Hi-Doctor does not prescribe it: it needs a doctor who can first check your heart history, your mood history and your other medicines, because fainting is a recognised risk. ## Seek urgent care for * an erection lasting 4 hours or longer * sudden loss of vision or hearing * chest pain, collapse, or a severe allergic reaction * fainting, severe dizziness, mood changes, or thoughts of self-harm on dapoxetine Call your local emergency number. Do not take another dose, and do not wait for a reply to a message. ## And tell your doctor if * the prescribed dose does not give a satisfactory response after several correctly timed attempts — do not increase the dose yourself * you have marked dizziness, palpitations, or a headache that is severe or persistent * any new heart, chest-pain, blood-pressure, rhythm, prostate, antifungal, antibiotic or HIV medicine is started Related: [sildenafil](/library/medicines/sildenafil) · [tadalafil](/library/medicines/tadalafil) · [dapoxetine](/library/medicines/dapoxetine) · [treatment areas](/essentials/treatments) ## Start a consultation Answer the sexual health questionnaire and a registered doctor reviews it. They decide whether treatment is appropriate, which one, and at what dose — and declining is a normal outcome. See [what it costs](/essentials/pricing) and [how the review works](/essentials/how-it-works). This page is reference information, not medical advice and not a prescription. Whether a medicine is appropriate for you is decided by a registered doctor after reviewing your consultation.