In single dose studies in healthy volunteers, when administered with up to 400 mg of Zydena once daily, no serious adverse reactions were observed. The adverse events (headache, facial flushing, etc.) showed an increase in frequency as the dosage increased, but most of them were minor reactions that were resolved without treatment. In case of an overdose, symptomatic therapy should be initiated in general. As Zydena has a high plasma protein binding rate and is not excreted in urine, its clearance rate is not increased by dialysis.