It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Summary Cialis and Viagra are both pills for treating erectile dysfunction. The patent on Revatio indicated for pulmonary arterial hypertension rather than erectile dysfunction expired in late Tadalafil can be synthesized starting from D – tryptophan methyl ester and piperonal via a Pictet—Spengler reaction. You should only be treated with one of these products at a time. What side effects can this medication cause?The recommended starting dose for Cialis intended for once daily use is mg, take at the same time each day, without regard to timing of sexual activity. This may be increased to 5mg/day based on need and tolerability. May be taken with or without food. Cialis is available as a generic, under the name tadalafil. 3. Cialis is available in a generic version. Cialis ED dosage for occasional use. The normal dosage of Cialis for occasional use in treating ED is 10 mg taken before sexual activity. If you have. Tadalafil is a medicine used to treat erectile dysfunction (ED, also called impotence) and problems with urination caused by an enlarged prostate (benign prostatic hypertrophy or BPH). It is sometimes known by its generic name tadalafil, and sometimes known by its trade name, Cialis. There are also other brands of this medicine available.