Cialis is approved to treat erectile dysfunction (ED) in adults. Doctors can prescribe Cialis for daily use or as needed before sexual activity. CialisтАЩs recommended daily dosage for ED is as follows. Dosage range: 2.5 mg to 5 mg ivermectin dewormer for horses Key takeaways: Viagra (sildenafil) is a prescription medication that treats erectile dysfunction (ED). Viagra is an oral medication. It s available as 25 mg, 50 mg, and 100 mg tablets.