You can take Viagra daily, but because the medication stays in your system for four to six hours, it will not be effective all day. According to the FDA, generic medications contain the same active ingredients as brand names, meaning there’s no difference in effectiveness or safety. Tadalafil will make these symptoms less severe and reduce the chance that prostate surgery will be needed. Can I trust online reviews about Cialis? Make sure to get an estimate of when you can expect your prescription in the mail. While each PDE5 inhibitor differs slightly, they’re very similar in treating erectile dysfunction. To work, it requires sexual stimulation as well.Tadalafil (Cialis). This medication is taken with or without food an hour before sex. It works for up to 36 hours. You can take it in a small dose daily or in a larger dose as needed. If you do buy medicines over the internet: Check to see if an online pharmacy is legitimate. Never order medicines from an online pharmacy that doesn’t list. Side Effects. Headache, stomach upset, back pain, muscle pain, stuffy nose, flushing, or dizziness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. To.  · Cialis; Descriptions. Tadalafil is used to treat men who have erectile dysfunction (also called sexual impotence). Tadalafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where .