In vivo phase
In the dog pharmacokinetic study 24 young healthy male and female Beagle (age 12–17 months; weight 7.4–12.1 kg) dogs were kept indoors in pens with sealed floors and individually housed for 5 weeks following topical fluralaner administration to avoid potential cross contamination between animals. After this 5-week period, dogs were penned in groups of 3 of the same treatment group and sex. In the cat pharmacokinetic study 24 young healthy male and female European short hair cats (age 9–11 months; weight 2.2–4.8 kg) were kept in individual cages to avoid potential cross contamination between animals.
During the time where animals were single housed, they had individual social contact with the caretaker, daily outside their pens/cages. Room environment was monitored continuously in both studies, with a temperature of 15–21 °C, relative humidity of 40–70 %, 10–20 air changes per hour and a 12-h fluorescent light/12-h dark cycle. Dogs and cats were fed once daily in the morning with a standard diet and had ad libitum access to water.
Dogs and cats were randomized to four treatment groups in each study (3 animals per sex per group), within sex, and blocked by body weight to ensure a balanced distribution.
One group of six animals was treated i.v. with a constant rate infusion over 5 min using an automatic injection system (KDS Model 200, KD Scientific Inc., Holliston, USA) at a fluralaner dose of 12.5 mg/kg BW. The perfusion rate per hour (mL/hr) was approximately 12 times higher than the respective dose volume to ensure complete administration within 5 min (dog i.v. data was previously published in Kilp et al. [4]).
All topical doses were calculated using individual body weights and the nominal content of fluralaner. In the dog study fluralaner (Bravecto™ Spot-on Solution) was administered topically to three groups of dogs at doses of 12.5, 25 or 50 mg/kg BW and was administered in one or several spots dorsally along the dogs’ back. The first spot was administered between the shoulder blades and the following spots, if necessary due to the treatment volume required, were administered approximately 5–10 cm caudal of the previously administered spot. In the cat study fluralaner (Bravecto™ Spot-on Solution) was administered topically at doses of 20, 40 or 80 mg/kg BW and was administered in one or several spots dorsally along the cat’s back. The first spot was administered at the base of the skull and the following spots, if necessary, were administered approximately 5–10 cm caudal of the previously administered spot.
Blood samples were collected from the jugular vein into sodium-citrate tubes before and at 1, 3, 5, 7, 10, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105 and 112 days after topical administration and 15 min, 2, 4 and 8 h, and 1, 2, 3, 4, 7, 14, 21, 28, 35, 49, 63, 77, 91 and 112 days after i.v. dosing. Plasma was harvested by centrifugation and subsequently stored frozen (-75 °C?±?15 °C) in sterile plastic vials until analysis. The animals were closely observed for 1 h after dosing and once daily thereafter.