The mechanism of action for ED pills is simple: They inhibit the PDE5 enzyme which regulates the signals responsible for the smooth muscle tissue. People taking nitrates like nitroglycerin Nitrostat or isosorbide mononitrate Imdur should not take PDE5 inhibitors, as doing so could result in a dangerous drop in blood pressure. First and foremost, be sure that whichever online pharmacy you choose is legitimate, safe, and secure. You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Levitra vardenafil : This medication is taken one hour before sex and can last up to 24 hours. They require a prescription for any controlled substance and have a licensed pharmacist to answer questions rather than support staff.Although Cialis and Viagra are both PDE5 inhibitors that boost nitric oxide in your body to help with ED, they’re different medications. Cialis comes in a lower dose than Viagra . $ medication_outlined Availability Available See GoodRx coupons warning Are you looking for information on Adcirca (tadalafil) instead? What is Tadalafil (Cialis)? Drug . MNT ‘s review At Hims, Cialis is available as: Daily tadalafil: or 5 mg daily pill Tadalafil: 5 mg, 10 mg, or 20 mg, taken as needed Cialis: mg, 5 mg, 10 mg, and 20 mg, taken .