A one-time dose of 300 mg of sildenafil is an overdose of the drug and increases the incidence and severity of adverse drug use events. The recommended dose of sildenafil is 50mg, and the maximum recommended dose is 100mg. A one-time dose of 300mg has severely exceeded the maximum recommended dose and is considered an overdose of the drug. Adverse reactions can occur when the drug is taken at the regular recommended dose, including headache, flushing, dyspepsia, occlusion, urinary tract infection, visual abnormalities, diarrhea, dizziness, and rash. Adverse reactions at overdoses are similar to those at lower doses, but with increased incidence and severity. When overdose occurs, symptomatic supportive therapy is indicated. Renal dialysis does not increase clearance of sildenafil due to its high plasma protein binding and non-urinary clearance. Those who do need to take the drug should do so under the supervision of a physician and seek medical attention if there is any discomfort to avoid delaying treatment.