Aims: Regarding to importance of Ivermectin as a clinical anti-parasite drug, identification of its interaction with other drugs is necessary. At present study, the interaction of Verapamil as an inhibitor P-glycoprotein was evaluated on Ivermectin concentration in serum and cerebrospinal fluid in dog.

Methods: In this experimental study with animal model which was done in faculty of veterinary medicine of Ahvaz in 2011 10 mixed breed dogs was randomly divided into 2 groups (5 dogs at each group). First group received 0.2mg/kg of Ivermectin for each kilo of body weight and second group received of 3mg/kg of Ivermectin for each kilo of body weight along with verapamil. The level of Ivermectin was detected by HPLC in blood samples 1, 2 and 3 hours and in cerebrospinal fluid 1.5 hours after injection. Statistical analysis was carried out by SPSS 16. Repeated measurement and T-independent test were used for comparison of sample means.

Results: In both groups, the serum concentration of Ivermectin was decreased at second hour and then increased in comparing with first hour. The Ivermectin was not detected cerebrospinal fluid of first group while it was 45.44± 10.91ng/ml in second group.

Conclusion: Serum concentration of Ivermectin increases by intramuscular injection after one hour and Verapamil increases cerebraospinal fluid concentration of Ivermectin.