Flupirtine (FLU) is a non-opiod analgesic drug belonging to the class of N-methyle-D- aspartate. In human medicine FLU is recommended for the treatment of a wide range of pain states, but no study been performed in Pets. The aim of this study is to evaluate the pharmacokinetic profiles (PK) of FLU in healthy dogs and cats after different routes of administrations. Six healthy Labrador breed adult dogs and six healthy mixed breed adult cats were used in two different experiments. Dogs: single dose, four-group and four-treatment (Intravenous IV, Oral immediate release POIR, per rectum [5 mg /kg]; oral prolonged release POPR [200 mg /subject], cross over design. Cats: single dose, two-groups, two treatments (IV and POIR [5 mg /kg]), cross over design. The wash out period between trails was 1 week. Blood samples were collected at assigned times and plasma was analyzed by a validated HPLC method. Some adverse effects, rapidly resolved, were noted only in dogs after IV treatment. The FLU plasma concentration was detectable in all groups up to 36 h. The bioavalability (F %) value after POIR, POPR and RC in dogs were 41.9, 36.8 and 29.3%respectively, while oral F% in cat was 39.3+9.7%. Oral bioavailability in dogs and cats was similar, but about two times smaller than that found in the human (90%). This large differences demonstrated that PK values derived in pets shouldn`t be extrapolated to human and vice versa. This study represents the first step that should pave the way for use of this active ingredient in Pet animals.