OBJECTIVE To study the
pharmacokinetic effects of erythromycin to phenobarbital.METHODS 6 rabbits were divided to 2 groups.The
first group ig erythromycin 50 mg·kg -1 d in 5 days.The other was dealt with NS.A week later,the 2 groups were exchanged
administration.1 hour after the third administration,the rabbits im phenobarbital 6 mg·kg -1 .The drug concentrations of phenobarbital were assayed by FPIA method and the
pharmacokinetic parameters were calculated after 0.25,0.5,1,2,4,8,12,24,72 hours.RESULTS The main pharmacokinetic parameters after im phenobarbital in rabbits were: T max =1.41±0.41 h, C max = 16.11 ±1.25 μg·ml -1 ,CL/F=0.009±0.0002 mg·min -1 ,AUC= 661.52 ±53.88 μg·ml -1 ·h, T 1/2 ( K a)=0.20±0.067 h, T 1/2 ( K e)=27 54±2.35 h;coadministration erythromycin and phenobarbital were: T max =1.97±0.59 h, C max =17.40±1.10 μg·ml -1 , CL/F= 0.006±0.0006 mg·min -1 ,AUC=925.82±87.59 μg·ml -1 ·h, T 1/2 ( K a)=0.28±0.10 h, T 1/2 ( K e)=35.51±2.76 h.Erythromycin could decrease the CL/F and increase the AUC and T 1/2 ( K e) of phenobarbital significantly( P <0 05),but it have no significant influence to the absorption of phenobarbital.CONCLUSION It is necessary to detect the serum concentration of phenobarbital in time to avoid the phenobarbital toxicity when coadministrating erythromycin and phenobarbital.