Pharmacokinetic study of paracetamol was conducted in five female buffalo calves following single i.v. injection of paracetamol @ 40 mg/kg. The drug was detected up to 2 h only in plasma, while it was detected for a longer period of 48 h in urine with a mean concentration of 1.87 ± 0.48 and 10.90 ± 1.14 mg/ml, respectively. The mean distribution half life (t1/2) of 0.11 ± 0.01 h and elimination half life (t1/2) of 0.77 ± 0.09 h indicated that the drug is rapidly distributed as well as eliminated quickly in buffalo calves. The rapid elimination of the drug is due to the higher values of rate constant of drug elimination from central compartment (Kel) of 1.471 ± 0.089 h−1 and total body clearance (ClB) of 43.67 3.39 ml/kg/min. This led to the lower value of mean residential time (MRT) of 1.00 ± 0.01 h, indicating that paracetamol remained for a shorter period only in the body of buffalo calves. A higher Vdarea of 2.34 ± 0.19 L/kg obtained in the present study suggested good distribution of paracetamol in body fluids and tissues which is further supported by the approximate tissue to plasma concentration ratio (T/P) of 0.59 ± 0.13.
