What Are the Symptoms of Erectile Dysfunction? Others may find that it takes Cialis closer to eight hours to work and take the medication well before sexual activity. While this effect should not be of consequence in most patients, prior to prescribing CIALIS, physicians should carefully consider whether their patients with underlying cardiovascular disease could be affected adversely by such vasodilatory effects. As with other PDE5 inhibitors, tadalafil has mild systemic vasodilatory properties that may result in transient decreases in blood pressure. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. Maximum effects can be seen between 30 minutes and eight hours. An erection results from an increase in blood flow to the penis.5 mg 10 mg 20 mg At 20 mg, both drugs are also approved to treat symptoms of benign prostatic hyperplasia (BPH), such as difficulty urinating. They work by relaxing the muscle cells in the prostate, allowing urine to flow out of the bladder. As a side note, there’s another medication that uses tadalafil as its active ingredient: Adcirca. Cialis comes in several different strengths, including: milligrams (mg) 5 mg. 10 mg. 20 mg. The cost for these different strengths depends on whether you have insurance, your individual plan. What is generic Cialis? Generic Cialis is called tadalafil, which is the active ingredient in Cialis. Cialis is Food and Drug Administration (FDA) approved to treat erectile dysfunction (ED).