You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. The mechanism of action for ED pills is simple: They inhibit the PDE5 enzyme which regulates the signals responsible for the smooth muscle tissue. Tadalafil Cialis. It’s available in 25 mg, 50 mg, and mg tablets and lasts up to 18 hours. You should also call your insurance company to see if they cover erectile dysfunction medications.There is generic Viagra now. They have 20mg and mg tablets. It’s usually $/bottle depending on your pharmacy. things to consider if you’re gonna buy cialis online (or viagra though cialis is better). Reputation and Legitimacy: Look for reputable online pharmacies that have a history of . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or .