Bioavailability and Disposition Kinetics of Amoxicillin

.. OBJECTIVE: The study was planned to observe the bioavailability and disposition kinetics of amoxicillin in adult rabbits (irrespective of sex) under healthy and dehydrated conditions. Design: Comparative. Place and duration of study: The study was conducted at the department of pharmacology, University of Veterinary and Animal Sciences, Lahore from April 2013 to October 2013. Methodology: Initially all rabbits were weighed and their packed cell volume (PCV) and other biochemical parameters were observed under normal conditions. Bioavailability and disposition kinetics of amoxicillin (10mg/kg body weight) were studied in normal rabbits following oral and intravenous route of drug administration. After 10 days washout period, these rabbits were made dehydrated by keeping the animals off water but not food. The animals with 10% decrease in body weight were declared dehydrated. Their parameters were again measured. Treated rabbits were administered amoxicillin orally and intravenously (10mg/kg body weight). Samples were drawn at prescribed time. Amoxicillin was assessed in plasma by using microbiological assay method. Plasma concentration was analyzed using non compartmental method. Results: The water deprived or dehydrated rabbits showed a significant increase in the packed cell volume, blood glucose and plasma globulins as compared to the normal rabbits. However, there was a significant (p<0.05 & p<0.01) decrease in body weight, total proteins, albumins and albumin globulin ratio of the dehydrated rabbits. The peak plasma concentration, volume of distribution and rate constant of elimination was lower in the dehydrated rabbits as compared to the normal rabbits. The plasma concentration of amoxicillin after intravenous administration in dehydrated rabbits had a significant (p<0.05 & p<0.01) larger area under curve, area under 1st moment curve, a longer half life and a larger mean residence time. Conclusions: The study in the dehydrated rabbits indicated the need of modification of dosage regimen.