However, some states require a live video consultation. But not to worry, there is perfectly legal alternative that you have most certainly heard of: Viagra. These medicines are called PDE5 inhibitors. You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. So, what is the difference between these two and how do you know your medication is the real deal?However, Kamagra is illegal to sell or purchase in the UK and it is highly unadvisable that you take it. Table of comparison. Viagra: Sildenafil: Cialis: Levitra: Spedra: Active Ingredient: Sildenafil: Sildenafil: Tadalafil: Vardenafil: Avanafil: Time to take effect: mins: mins: mins: mins: 15 mins: Duration of effect: 4. Abstract. Because sildenafil citrate is a treatment, not a cure, for erectile dysfunction (ED), many men may choose to use it for an extended period. Men with ED who had previously completed 1 of 4 double-blind trials with short-term open-label extension (combined duration, – years) were eligible for this 4-year, open-label, extension. AdGet your ED medication shipped in an unmarked package within 4 hours at $0 delivery fee. Asking for help is hard. Living with ED is harder. Finding affordable treatment? Easy.