- Objective To assess the effect of kallikrein on sperm motility and sperm count in infertile oligozoospermie and asthenozoospermic men. Design Double-blind placebo-controlled clinical trial. Setting Multicenter trial in three andrologic clinics. Patients Infertile men with < 20 × 106 total sperm count and > 3 × 106 sperm cells/mL and/or sperm motility of < 30%. Interventions One hundred fourteen men received either placebo or 600 kallikrein units of kallidinogenase by mouth daily for 12 weeks. Semen analyses were performed before and at 6-week intervals during the trial. Compliance and incidence of adverse effects were assessed. Results The incidence of adverse effects was similar under placebo and under kallidinogenase treatment, usually mild, transient, and did not require the cessation of treatment in any patient. Kallidinogenase was not superior to placebo in improving sperm count and sperm motility. Conclusions At the doses and for the duration given, our results were disappointing. The absence of a therapeutical effect, as evidenced in the present study may be due to the very low absorption rate of kallidinogenase after oral administration. Probably a much higher dose of kallidinogenase should be used to achieve a therapeutic affect.