Tadalafil may cause side effects. BPH is caused by an enlarged prostate. It is recommended to take up to 10mg for as-needed use, though some men find a lower or higher dosage works better for them. When using this medicine for erectile dysfunction, the ability to have sexual activity may be improved for up to 36 hours after taking the tablet. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. If you are taking tadalafil for erectile dysfunction on a regular schedule, take the missed dose as soon as you remember it. However, its counterpart Tadalafil or Cialis is also effective and best known for its long-lasting effects.Tadalafil is in a class of medications called phosphodiesterase (PDE) inhibitors. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. . It is the brand name for tadalafil, a medication also used to treat ED. Tadalafil is in a class of drugs called phosphodiesterase-5 (PDE5) inhibitors and is .  · Adults—5 milligrams (mg) once a day, taken at the same time each day, without regard for the timing of sexual activity. Children—Use is not recommended. For .