Pharmacokinetics Of L-carnitine And Its Acyl Esters In Chinese Healthy Volunteers

Subject:To develop specific,sensitive and simple HPLC methods to determine L-carnitine(LC) and its acyl esters Acetyl-L-cainitine(ALC) and Propionyl-L-cainitine(PLC) levels in human plasma and urine.And HPLC method was used in pharmacokinetic study of L-carnitine and its acyl esters after single oral administration of L-carnitine oral solution in Chinese healthy volunteers.METHODS HPLC-UV:The analytes were extracted by protein precipitation and then precolumn derivatization with 2,4'-Dibromoacetophenone(PBPB) were performed. The fluorescent derivatives were separated on a Hypersil SiO₂ column,and the mobile phase consisted of acetonitrile-citrate buffer solution(10:90),the flow rate was 1.2 ml·min^-1,the derivatives were monitored with a UV detector set at 260nm.HPLC-FL:The analytes were extracted by protein precipitation and then precolumn derivatization with 1-aminoanthracene(1-AA) were performed.The fluorescent derivatives were separated on a Hypersil C₁₈ column,and the mobile phase consisted of acetonitrile-0.1mol·L^-1 ammonium acetate(34:66),the flow rate was 1.0ml·min^-1.The derivatives were monitored with a fluorimetric detector set at 248 nm(excitation wavelength) and 418 nm(emission wavelength).After single oral administration of 2g L-carnitine oral solution in 12 Chinese healthy volunteers,the plasma was collected at Oh,0.5h,1.0h,1.5h,2h,2.5h,3.0h,3.5h,4.0h,5.0h, 6.0h,8.0h,12.0h,24.0h,and the urine was collected at Oh,0～2h,2～4h,4～8h,8～12h, 12～24h.The concentration of LC,ALC and PLC in plasma and urine were measured by HPLC-FL and the pharmacokinetics parameters were calculated by DAS software.RESULT:The good linearity of the assay were observed over the concentration ranges investigated,2.5～500μmol·L^-1 in plasma and 2～1000μmol·L^-1 in urine for LC by HPLC-UV and 2～500μmol·L^-1 for LC,0.5～50μmol·L^-1 for ALC,0.1～20μmol·L^-1 for PLC in plasma and 2～1000μmol·L^-1 for LC,1～500μmol·L^-1 for ALC,0.2～50μmol·L^-1 for PLC in urine by HPLC-FL.The recoveries,precision and stability test of LC,ALC and PLC correspond the requirement in plasma and urine.The methods were proved to be stable,accurate and convenient to study the concentrations of LC,ALC and PLC in clinical plasma and urine.After single oral administration of 2g L-carnitine oral solution, the main pharmacokinetic parameter of LC Cmax is(84.73+25.23)μmol·L^-1,t_1/2β is (60.33+14.97)h,AUC_(0-t) is(2676.41+708.33)μmol·L^-1·h,Tmax is(3.4+0.46)h.ALC: t_1/2α:(6.33+6.39)h,t_1/2β:(35.90±28.86)h,AUC_(0-t):119.54±55.84μmol·L^-1·h,AUC_(0-∞): 166.20±77.41μmol·L^-1·h,Tmax:(2.4±0.66)h,Cmax:(12.89±5.52)μmol·L^-1,and PLC:t_1/2α:(3.10±3.93)h,t_1/2β::(25.74±30.33)h,AUC_(0-t):(57.98±48.52)μmol·L^-1·h, AUC_(0-∞):(155.57±264.22)μmol·L^-1·h,Tmax:(3.8±0.79)h,Cmax:(5.08±3.08)μmol·L^-1. The accumulated excretion of LC,ALC and PLC were(613.47±161.72)μmol, (368.25±134.77)μmol,(61.29±37.75)μmol in 24h,respectively and the accumulated excretion rate of LC was 6.05%in 24h after administration.CONCLUSION:The specific,sensitive and simple HPLC-UV and HPLC-FL methods were developed to determine L-carnitine(LC) and its acyl esters Acetyl-L-cainitine(ALC) and Propionyl-L-cainitine(PLC) levels in human plasma and urine.The HPLC-FL method was successfully used in pharmacokinetic study of L-carnitine and its acyl esters after single oral administration of L-carnitine oral solution in Chinese healthy volunteers.