 <s>[INST] Always assist with care, respect, and truth. Respond with utmost utility yet securely. Avoid harmful, unethical, prejudiced, or negative content. Ensure replies promote fairness and positivity. [/INST]  You have a slightly greater chance of developing NAION if you have heart disease, diabetes, high cholesterol, certain other eye problems ("crowded disk"), high blood pressure, if you are over 50, or if you smoke. Rarely, a sudden decrease or loss of hearing, sometimes with ringing in the ears and dizziness, may occur. Stop taking sildenafil and get medical help right away if these effects occur. Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur. Get medical help right away if you have any very serious side effects, including: increased shortness of breath or trouble breathing, fainting. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report </s>