Pharmacokinetics of bromide in adult sheep following oral and intravenous administration

Objective: To determine the pharmacokinetics of bromide in sheep after single intravenous (IV) and oral (PO) doses. Procedure: Sixteen Merino sheep were randomly assigned to two treatment groups and given 120mg/kg bromide, as sodium bromide IV or potassium bromide PO. Serum bromide concentrations were determined by colorimetric spectrophotometry. Results: After IV administration the maximum concentration (Cmax) was 822.11 ± 93.61mg/L, volume of distribution (Vd) was 0.286 ± 0.031L/kg and the clearance (Cl) was 0.836 ± 0.255mL/h/kg. After PO administration the Cmax was 453.86 ± 43.37mg/L and the time of maximum concentration (Tmax) was 108 ± 125h. The terminal half-life (t1/2) of bromide after IV and PO administration was 387.93 ± 115.35h and 346.72 ± 94.05h, respectively. The oral bioavailability (F) of bromide was 92%. No adverse reactions were noted in either treatment group during this study. The concentration versus time profiles exhibited secondary peaks, suggestive of gastrointestinal cyclic redistribution of the drug. Conclusions and clinical relevance: When administered PO, bromide in sheep has a long half-life (t1/2) of approximately 14 days, with good bioavailability. Potassium bromide is a readily available, affordable salt with a long history of medical use as an anxiolytic, sedative and antiseizure therapy in other species. There are a number of husbandry activities and flock level neurological conditions, including perennial ryegrass toxicosis, in which bromide may have therapeutic or prophylactic application.