Make sure you tell your doctor if you have any other medical problems, especially: Abnormal penis, including a curved penis or birth defects of the penis—Chance of problems occurring may be increased and this medicine should be used with caution in these patients. It is optional to have any further orders written. At the time of the study, there were 20 pharmacies and 34 drug stores in the town. Multiple answers were also reported concerning the timing of taking the drug sildenafil in which 40 It shares similarities with sildenafil in terms of effectiveness and duration of action. Check with your doctor immediately if any of the following side effects occur: Less common burning feeling in the chest or stomach burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings cloudy or bloody urine. Higher cost: Tadalafil may be more expensive than other ED medications, especially when used daily. · Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 .  · Viagra comes as an oral tablet that contains the active drug sildenafil. Sildenafil is also available in generic form. Viagra is classified as a phosphodiesterase type 5 (PDE5) inhibitor.  · 10 tips to use sildenafil (aka Viagra) effectively. A set of instructions should be given to patients on sildenafil: A minimum wait of 45 minutes to 1 hour is required between taking the tablet.