Vidalista 20 mg contains tadalafil, a prescription medicine used to treat erectile dysfunction. The 20 mg strength is generally the maximum recommended on-demand dose, taken before sexual activity and not more than once daily. Common side effects include headache, flushing, indigestion, muscle/back pain, and dizziness. Do not take tadalafil with nitrate medicines (such as nitroglycerin) or recreational “poppers,” as this can cause a dangerous drop in blood pressure; a licensed clinician or pharmacist can confirm whether 20 mg is appropriate for you.