The Effect of Dextromethorphan on the Testes of Adult Sprague-Dawley Rats

Dextromethorphan (DM) is a dextro-rotatory isomer of levophanol and a major constituent of over 125 over the counter (OTC) cough syrups. In-vivo and ex-vivo studies have shown that DM has pain suppressive properties comparable to ketamine via its N-methyl-D-Aspartate (NMDA) receptor antagonism. There is a wide spread abuse of Cough syrups in Nigeria particularly amongst adolescent males. NMDA receptor antagonists have been reported to have anti-fertility properties. Pure samples of DM constituted in normal saline was administered orally to twenty mature male adult Sprague-Dawley rats of weight 177.75 ± 7.68 g daily for 8 weeks. The animals were divided randomly into 4 groups; A, B, C, D (n=5). DM-HBr was administered at the following dosages: group A: Normal saline (control); group B: 0.214 mg/ kg b.w; group C: 0.571 mg/ kg b.w; group D: 4.285 mg/ kg b.w. At sacrifice; Routine histology, semen analysis, serum and intra-testicular levels of male reproductive hormones and testicular oxidative stress markers were assayed. Groups C and D showed a significant difference (p < 0.05) in sperm count, sperm motility and abnormal morphology as well as reduction in the intra-luminal spermatozoa population compared to the control. Furthermore, a significant increase (p < 0.05) in testicular oxidative stress markers and a reduction in mean values of reproductive hormones were observed. DM may induce oxidative stress which could lead to a decline in reproductive function following chronic administration. These effects are dose dependent.