Purpose
To evaluate the in vitro impact of ritalinic acid (RA), a major metabolite of methylphenidate (drug to treat attention-deficit hyperactivity disorder), on sperm motility, vitality and oxidative stress.

Materials and Methods
Semen samples (n=13) were collected from healthy donors and a semen analysis was performed according to World Health Organization. Density gradient centrifugation was performed to isolate motile sperm. Samples were incubated with different concentrations (0, 1, 10, 100, and 1,000 ng/mL) of RA. The non-exposed group (0 ng/mL) was defined as the control group. Samples were analyzed for motility at different time points (0, 60, 150, 240, and 300 minutes) and for vitality and oxidation reduction potential (ORP) (at 0, 240, and 300 minutes). Sperm motility was assessed manually and motion kinetic parameters were recorded by computer aided semen analysis.

Results
RA at any tested concentration significantly increased sperm motility compared to the control in a time-dependent manner with a maximum increase after 240 minutes. Motion kinetic parameters were not comparable. For sperm vitality, supplementation with RA significantly maintained survival at higher levels, while non-treated sperm gradually died. These higher levels of vitality were maintained with rising RA concentrations of up to 1,000 ng/mL. A non-significant trend of increased ORP was observed in all study groups.

Conclusions
RA increases sperm motility and maintains vitality at any concentration tested. Therefore, RA might be utilized to improve sperm quality in asthenozoospermic specimens. However, further investigation is ongoing to evaluate the effect of RA on other sperm parameters.