<p>Caution should be exercised if patients have any allergies to any other medicines or any other substances such as foods, preservatives or dyes, heart or blood vessel problems, sudden loss of eyesight in one or both eyes. Caution should be taken if patients have any of the following medical conditions such as diabetes, kidney or liver problems, leukaemia, multiple myeloma, any disease or deformity of penis, any bleeding disorder such as haemophilia, stomach ulcer, sickle cell anaemia, color vision problems, sudden decrease or loss of hearing or receiving any other treatment for impotence.</p>