Viagra cannot be used:

• with any other oral or local treatments for erectile dysfunction
• with treatments for pulmonary arterial hypertension (PAH) containing Sildenafil or any other PDE5 inhibitors
• if you do not have erectile dysfunction
• if you are a woman
• if you are under the age of 18
• if you are allergic to Sildenafil or any of the other ingredients in this medicine
• if you are taking medicines called nitrates, the combination may lead to a dangerous fall in your blood pressure. Tell your doctor if you are taking any of these medicines which are often given for relief of angina pectoris (or “chest pain”). If you are not certain, ask your doctor or pharmacist
• if you are using any of the medicines known as nitric oxide donors such as amyl nitrite (“poppers”), the combination may also lead to a dangerous fall in your blood pressure
• if you are taking riociguat. This drug is used to treat pulmonary arterial hypertension (i.e. high blood pressure in the lungs) and chronic thromboembolic pulmonary hypertension (i.e. high blood pressure in the lungs secondary to blood clots). PDE5 inhibitors, such as Viagra have been shown to increase the hypotensive effects of this medicine. If you are taking riociguat or are unsure tell your doctor
• if you have a severe heart or liver problem
• if you have recently had a stroke or a heart attack, or if you have low blood pressure
• if you have certain rare inherited eye diseases (such as retinitis pigmentosa)
• if you have ever had loss of vision due to non-arteritic anterior ischaemic optic neuropathy (NAION)

Please tell your doctor if you are using, have recently used or might use any other medicines, including medicines obtained without a prescription. Some medicines may cause problems, especially these:

• Nitrates, medicines for angina, or nitric oxide donors, such as amyl nitrite. Taking these medicines with Viagra could seriously affect your blood pressure. Talk to a doctor without taking Viagra
• Medicine for the treatment of arrhythmias, such as quinidine, procainamide, amiodarone or sotalol
• Ritonavir or indinavir, medicines for HIV. Talk to a doctor without taking Viagra
• Ketoconazole or itraconazole, anti-fungal medicines
• Erythromycin, or clarithromycin, macrolide antibiotics
• Alpha-blockers, a type of medicine used to treat high blood pressure and enlargement of the prostate (as benign prostatic hyperplasia)
• Riociguat

Your doctor must take special care before starting you on Viagra if you:

• have sickle cell anaemia (an abnormality of red blood cells), leukaemia (cancer of blood cells), multiple myeloma (cancer of bone marrow)
• have a deformity of your penis or Peyronie’s Disease
• have problems with your heart (your doctor should carefully check whether your heart can take the additional strain of having sex)
• currently have a stomach ulcer or a bleeding problem (such as haemophilia)
• experience sudden decrease or loss of vision (stop taking Viagra and contact your doctor immediately)
• have kidney or liver problems (your doctor may decide on a lower dose for you)
• are taking medicines known as protease inhibitors, such as for the treatment of HIV, your doctor may start you on the lowest dose (25mg) of Viagra

Other considerations:

• You can take Viagra with or without food, but preferably not after a heavy or high-fat meal as this may delay the effect
• Alcoholic drinks can make erection difficulties worse
• Viagra might make some people feel dizzy or affect their vision. If you feel dizzy or if your vision is affected, after taking Viagra, don’t drive or operate any tools or machines