Chronic administration of gabapentin and a gabapentin-carbamazepine combination reversibly suppress testicular function in male Wistar rats (Rattus norvegicus).

The effect of chronic administration of gabapentin, carbamazepine or a gabapentin-carbamazepine combination on testicular function in male rats was investigated to determine the effect of combining reduced doses of anti-epileptic drugs on the management of seizures, particularly with respect to the testis sequellae of chronic anti-epileptic administration. Male rats were randomized into four groups (n=10). Each group received daily intraperitoneal (i.p.) injections for 28days as follows: Group I, normal saline 0.1mL/day; Group II, gabapentin (GBP) 16mg/kg/day; Group III, carbamazepine (CBZ) 20mg/kg/day; and Group IV, sub-therapeutic doses of both GBP (8mg/kg) and CBZ (10mg/kg)/day. Twenty-four hours after the last treatment, five rats from each group were sacrificed and the remaining rats were allowed to recover for another four weeks. Sperm characteristics, serum testosterone, and histological integrity of the testis was assessed 24h after treatment and after 28days of drug withdrawal. GBP, CBZ, and GBP-CBZ combination significantly reduced the absolute weight of the testis, epididymis, and seminal vesicle (p<0.05). Moreover, epididymal sperm count and morphology were significantly decreased (p<0.05) in GBP, CBZ, and GBP-CBZ groups. Reduction in serum levels of testosterone for all of the treated groups was statistically significant (p<0.05). The cytoarchitecture of the testicular tissue in the testis of CBZ and GBP-CBZ groups showed disorganization. The altered testicular function were almost restored in GBP treated rats. CBZ and GBP-CBZ combination have delayed but reversible antifertility in the rats. Hence, chronic administration of GBP, CBZ, and GBP-CBZ combination reversibly reduced testicular function in male rats.