Abstract Since herbal supplements are not evaluated for interactions with other drugs, there are concerns about their interactions with conventional drugs, which are mostly used as multiple drug treatment approach. The present study aims to evaluate the effects of long-term use of Ginkgo biloba (GK) extract on the intestinal absorption of orally administered, single doses of fluoxetine and venlafaxine in rats. AUC calculations and cumulative diffused calculations are utilized for evaluation of physicochemical interactions in vitro. Rats administered 100 and 200 mg/kg of GK extract, and oral bioavailability of single doses of fluoxetine and venlafaxine were evaluated using HPLC method. The results showed that GK extract has no significant effects on the bioavailability of fluoxetine and venlafaxine. Fluoxetine and venlafaxine serum levels are not affected by 100 mg/kg GK extract, while 200 mg/kg significantly increases venlafaxine level, with no effect on that of fluoxetine. In conclusion, GK extract shows no physicochemical interactions with fluoxetine or venlafaxine. Long-term administration of a low dose of GK extract (100 mg/kg) had no significant effect on serum levels of fluoxetine and venlafaxine, while lager dose (200 g/kg) increases significantly only the serum level of venlafaxine, while that of fluoxetine was not affected.