The magnitude of side effects should be patient-specific; both tadalafil and sildenafil have similar side effects, but the side effects of tadalafil may last longer due to a larger window of action. Both tadalafil and sildenafil are prescription medications that are commonly used to treat erectile dysfunction, and both share similar side effects; common adverse reactions to both include headache, back pain, myalgia, nasopharyngitis, and facial flushing. Tadalafil is a long-acting medication and sildenafil is a short-acting medication, so the adverse effects of tadalafil may last relatively longer depending on the potency of the medication. Contraindications for both Tadalafil and Sildenafil include patients who are taking any form of nitrates, guanylate cyclase stimulators, women, children, etc. Patients who need to treat erectile dysfunction are advised to do so under the supervision of a doctor, and should not use the medication on their own to avoid adverse consequences.