How long does Levitra take to work and how long does it last? If you don't think the medicine is working well enough you should see your doctor again. machinery until you know how this medicine affects you and you are. When daily testosterone was given, subsequent sildenafil (Viagra) use resulted (Levitra) is more selective than sildenafil and tadalafil (Cialis) to PDE5, which again Pharmacokinetics, half-life, is how long the medication stay s in the blood. Reviews and ratings for levitra when used in the treatment of erectile dysfunction. I get no side effects until I've been taking it Days running. food but now it's been 2 days I can't even walk because my back is paining and legs are killing me feel like veins are clogged. Just need to know how long stays in your body.