Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. Insurance: If you plan to use insurance, make sure the online provider accepts it. This is important for your overall health and safety, as certain medications can negatively interact with each other or cause existing conditions to worsen. It works for up to 36 hours. Its effects might last longer if you have mild to moderate ED. The mechanism of action for ED pills is simple: They inhibit the PDE5 enzyme which regulates the signals responsible for the smooth muscle tissue.Brand-name Viagra is also available through Optum Store in , , mg pills starting at $80 per dose if purchased in bulk. Pros & cons Free online consultation and free shipping on medications.  · Do not take Viagra more than once per day. Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon). Viagra can help you have an erection when sexual stimulation occurs. An erection will not occur just by taking a pill. Follow your .  · For treatment of erectile dysfunction: For oral dosage form (tablets): Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. Your doctor may adjust your dose if needed.