Cialis is the trade name of tadalafil tablets and Viagra is the trade name of sildenafil citrate tablets, and it is impossible to compare which one has more side effects. 1. Tadalafil tablets: adverse reactions include headache, dyspepsia, back pain, nasopharyngitis, upper respiratory tract infection, influenza, cough, nasal congestion, limb pain, gastroesophageal reflux disease, hypersensitivity reactions, epilepsy, and visual field loss. 2. Sildenafil Citrate Tablets: Adverse reactions include headache, flushing, dyspepsia, nasal congestion, back pain, myalgia, nausea, dizziness, rash, epilepsy, anxiety, transient generalized amnesia, epistaxis (nosebleed), prolonged erection, hematuria, abnormal erection, diplopia, decreased visual acuity, ocular congestion, eye swelling, retinal edema, and periplacental macular edema, among other adverse reactions. Tadalafil tablets are mainly used to treat erectile dysfunction in men, which requires sexual stimulation to take effect, and cannot be used in women. Sildenafil is mainly used for the treatment of erectile dysfunction, also can not be used for women. It is recommended that patients who are not feeling well go to a regular hospital and follow the doctor’s instructions for symptomatic treatment.