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Before taking this medicine

Do not take sildenafil if you are allergic to sildenafil or any tablet ingredient, use nitrates or nitrites in any form, even occasionally, or take a guanylate cyclase stimulator such as riociguat. These combinations can increase the blood-pressure-lowering effect. After taking sildenafil, it is not known when nitrates can safely be given. Sildenafil should not be used if sexual activity is inadvisable because of your heart condition. Medical assessment and caution are needed if you have: • Had a heart attack, stroke or life-threatening abnormal heart rhythm within the past six months. • Very low or very high resting blood pressure, heart failure, or coronary artery disease with unstable angina. • Obstruction of blood flow out of the heart or severely impaired control of blood pressure. • A deformity of the penis, sickle cell anaemia, multiple myeloma or leukaemia, which may increase the risk of a prolonged erection. • Previous non-arteritic anterior ischaemic optic neuropathy (NAION), a condition that can cause permanent vision loss, a “crowded” optic disc, or retinitis pigmentosa. • A bleeding disorder or an active stomach or intestinal ulcer; safety in these conditions is unknown. Older adults and people with severe kidney impairment or liver impairment also need prescribing consideration. Alpha-blockers and other blood pressure medicines can increase the risk of dizziness, lightheadedness or fainting from low blood pressure. Strong CYP inhibitors, such as ritonavir, can increase sildenafil exposure and the risk of adverse effects. Combining sildenafil with other PDE5 inhibitors, other sildenafil-containing treatments or other erectile dysfunction treatments is not recommended. Seek emergency treatment for an erection lasting longer than four hours. Stop sildenafil and seek medical attention for sudden loss of vision in either eye or a sudden decrease or loss of hearing.