Study On The Determination Of Artemisinin/naphthoquine Phosphate In Human And Pharmacokinetics

AIM: To develop a rapid and sensitive assay for simultaneousdetermination of artemisinin and naphthoquine in human plasma andurine samples by liquid chromatography-mass spectrometry(LC-MS/MS). Then measure the concentrations and study the clinicalpharmacokinetics of artemisinin and naphthoquine in healthvolunteers' plasma and urine samples after an oral administrated atfour dosage levels of the Compound Complex NaphthoquinePhosphate Tablets.STUDY METHOD: Artemisinin, naphthoquine and the internalstandard, telemisartan, were extracted from plasma and urine usingdiethyl ether-dichloromethane (60:40 v/v), and separated on a Zorbaxextend C18 column using methanol-10 mM ammonium acetate (80:20v/v). Detection was carried out by multiple reaction monitoring(MRM) on a Q-trapTM LC-MS/MS system with an ESI interface inthe positive ion mode. MRM was performed at unit resolution usingthe mass transition ion-pairs m/z 283.3→ m/z 209.1,m/z 410.3→m/z 337.1 and m/z 515.20 → m/z 276.10 for artemisinin,naphthoquine and telemisartan, respectively. The linearity, specificity,precision, accuracy, recovery and stability were estimated for thevalidations of both assays for plasma and urine.The concentrations of artemisinin and naphthoquine in healthvolunteers' plasma and urine samples after administrated an oraldosage at low, medium, high and postprandial levels of theCompound Complex Naphthoquine Phosphate Tablets weremeasured, respectively. After the plasma concentration–time profilewas shown, the area under the curve (AUC0-t) was determined by thelinear trapezoidal rule. The terminal elimination half-life (T1/2) wasestimated with least-squares regression of values in the terminallog-linear region of plasma concentration-time curves. Other mainpharmacokinetics parameters were described and estimated.RESULTS: Highly selective, sensitive, rapid and reproducibilitymethods for the simultaneous determination of artemisinin andnaphthoquine in human plasma and urine using LC-MS/MS havebeen developed and validated in this paper.The standard curve of artemisinin was linear over a working range of4-1000 ng/ ml with the limit of quantitation (LOQ) of 4 ng/ ml andthe limit of detection (LOD) of 2 ng/ ml. The standard curve ofnaphthoquine was linear over a working range of 0.5-500 ng/ ml withthe limit of quantitation of 0.5 ng/ ml and the limit of detection of0.05 ng/ ml. In the range of the standard curve, there is no co-elutingendogenous substances significantly influenced the determination ofartemisinin and naphthoquine in human plasma and urine. Theaccuracy was in the range 92.3%-106.5% and the intra-and inter-dayprecision was <10.6%. It was shown high and stable recovery for theextraction procedure. Both plasma and urine samples were stable inthree freeze-thaw cycles test, in the autosampler at room temperaturefor 8 h and in storage at ?20 °C for 40 days. The methods, whichwere certified the conformance to relevant standards ofPharmacopoeia of People's Republic of China, were ideally suited forthe study of clinical pharmacokinetics of artemisinin andnaphthoquine after an oral dosage of the Compound ComplexNaphthoquine Phosphate Tablets.After administrated an oral dosage at concentrations of 700,1400, 2100 and postprandial 1400 mg/ml of the Compound ComplexNaphthoquine Phosphate Tablets, the results of parameters forartemisinin were as follows: 4.12, 3.38, 5.18 and 4.25 h of the t1/2;2647, 4729, 6108 and 8084 ng·h/mL of the AUC0-t;189, 211, 246and 124 L/h·individual of the total body clearance (TBCL, CL);1123, 1170, 1835 and 758 L/ individual of the apparent volume ofdistribution (Vd). The results of parameters for naphthoquine wereshown as follows: 192, 242, 191, and 158 h of the t1/2;412, 828, 1632and 394 ng·h/mL of the AUC0-t;486, 483, 368 and 1016L/h·individual of the CL;134195, 168452, 101430 and 231045 L/individual of the Vd.A comparison of postprandial and preprandial parameters of anoral administration of 1400 mg of the Compound ComplexNaphthoquine Phosphate Tablets showed: artemisinin, thepostprandial AUC0-t was 171% of preprandial AUC0-t, thepostprandial Cmax was 268% of preprandial Cmax, the postprandial CLwas 58.5% of preprandial CL, and the postprandial Vd was 64.8% ofpreprandial Vd. The bioavailability and Cmax of artemisinin could besignificantly increased by postprandial administration. On the otherhand, bioavailability and Cmax of naphthoquine were shownsignificant degradation. Naphthoquine, the postprandial CL was211% of preprandial CL, the postprandial Vd was 137% ofpreprandial Vd, the postprandial AUC0-t was 47.5% of preprandialAUC0-t, and the postprandial Cmax was 52.4% of preprandial Cmax.The results of pharmacokinetics of the Compound ComplexNaphthoquine Phosphate Tablets showed: Comparing an oraladministration of the Compound Complex Naphthoquine PhosphateTablets with an oral administration of artemisinin or naphthoquine,the t1/2 and mean residence time (MRT) were increased, theconcentrations for the drugs in plasma could maintain high levels ofeffective concentrations for a long time. It was beneficial for thetherapy of impaludism. Furthermore, postprandial administrationcould significantly increase the bioavailability and Cmax ofartemisinin and curative effect. The tolerance of Compound ComplexNaphthoquine Phosphate Tablets was moderate.