It works for up to 36 hours. With real medication, you know exactly what you are getting, safely prescribed by a physician and used by many others to great effects. Place the tablet in your mouth and allow it to dissolve without chewing. Allow 24 hours to pass between doses. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir.Levitra is a medication used to treat erectile dysfunction in men. Our page provides detailed information on how Levitra works, its dosage, potential side effects, and precautions to take before using it. Whether you’re a first-time user or looking to switch to a new medication, our comprehensive guide can help you make an informed decision about using Levitra. In general, a lower dose (5mg) that’s meant for daily use can cost around $20 to $32 per dose, and a higher dose (10mg and 20mg) meant for “as-needed” use can cost around $80 – $85 per dose. It contains the same active ingredient as Levitra and can begin working in about 15 minutes. Viagra takes around 30 minutes to become effective and lasts about 4 hours. Cialis lasts much longer.