class="Serp__item__snippet--34vQF">Sildenafil (Viagra) and Vardenafil (Levitra) have relatively rapid onsets compared to Tadalafil (Cialis). Sildenafil (Viagra) and Vardenafil (Levitra) can be effective in as little as 1 hour, while Cialis might not take effect for 2 hours, though for some patients...