Azidin (Berenil, Intervet) is a protisticide drug based on diminazene aceturate. It is widely used in veterinary medicine for the treatment and prophylactics of piroplasmosis, babesioses, and teileriosis. Azidin is not used in clinical practice because of the probability of serious side effects, in particular initiation of seizure activity. We examined the effect of Azidin on evoked GABAergic postsynaptic currents (PSTs) in cultured hippocampal neurons using a patch clamp technique. As was found, Azidin in a concentration equivalent to 40 µM diminazene aceturate provides a more than twofold drop in the amplitude of evoked GABAergic PSTs; the effect develops in 3 to 4 min after application. The diminazene concentration in blood serum after its injection into animals can reach 45 µM; this is why the seizure side effect of Azidin can probably be explained mostly by suppression of GABAergic transmission. A combination of Azidin with positive modulators of GABA receptors can be considered an approach allowing one to minimize its side effect.