Research On The Preclinical Absorption Pharmacokinetics And Brain Distribution Of Ansofaxine Hydrochloride

AIM Liquid chromatography tandem mass spectrometry (LC/MS/MS) approach wasdeveloped for the sensitive and specific determination of ansofaxine andO-desmethyvenlafaxine(ODV) in rat plasma and brain tissue(brain andhypothalamus) simultaneously. Then the assay was used for the comparativeabsorption kinetics study of ansofaxine hydrochloride and ODV in rats anddistribution in rat brain and hypothalamus.STUDY METHOD Biological specimen of ansofaxine and ODV was extracted withN-hexane-dichloromethane-isopropanol (300:150:15, V:V:V) and The residue wasreconstituted with mobile phase solution, which was methanol:5mM ammoniumacetate (85:15, V:V), and then20μL was injected into the LC-MS/MS system..HPLC separation was performed on an Agilent SB-AQ column maintained at40°Cand the flow rate was set at1.0mL/min. Multiple reaction monitoring (MRM)detection mode was carried out with the precursor to product ion transitions foransofaxine of m/z381.8→58.1, ODV of m/z263.9→58.1and diazepam of m/z285.2→193.1.The specificity, linearity, the low limit of quantification, precision, accuracy,recovery, matrix effects and stability were evaluated for the validations of methodfor plasma, brain and hypothalamus.RESULT Rats were administrated at low (4mg/kg), medium (8mg/kg) and high (16mg/kg) doses of ansofaxine hydrochloride through oral gavage. ODV, the controldrug, was administrated at the dosage of5.04mg/kg (equivalent to8mg/kgansofaxine hydrochloride in molar unit) through oral gavage and intravenous bolusinjection. The pharmacokinetic parameters of ODV were shown in Table A. Table A Pharmacokinetic parameters of ansofaxine hydrochloride and ODV aftersingle administrationRats were administrated4,8and16mg/kg ansofaxine hydrochloride throughoral gavages (dose ratio1:2:4).The ratio of Cmaxwas1:2.6:5.8. The ratio of AUC0→twas1:2.9:7.0and the ratio of AUC0→∞was1:2.9:7.0. AUC and Cmaxwerepositively correlated with doses (P<0.05) using linear regression method. Linearpharmacokinetics was assessed using a pharmacokinetic program BAPP3.1. Theresults showed an overlap between the95%confidence interval the judgmentinterval. Thus, final conclusion on linear pharmacokinetics of ansofaxine cannot bedrawn.Rats were administrated ansofaxine hydrochloride and ODV at equivalentdosages in molar unit. Cmax, AUC0→tand AUC0→∞of ODV obtained from the ratsdosed with ansofaxine hydrochloride were respectively higher than those obtainedfrom the rats dosed with ODV, but the difference was not significant (P>0.05). Theobserved MRT, Vd/F and CL/F were not significantly different between the twogroups (P>0.05). However, T1/2was significantly different (P<0.05).Absolute bioavailability was calculated using AUC0→tfollowing oral andintravenous administration. The absolute bioavailability of ansofaxine hydrochloridewas34.8%and the absolute bioavailability of ODV was30.6%in rats.Following oral administration of8mg/kg ansofaxine hydrochloride in rats,ansofaxine was distributed in brain and hypothalamus rapidly. Ansofaxineconcentrations in hypothalamus, bladder, uterus and ovary reached peaks at1h.Following oral administration of equal ansofaxine hydrochloride and ODV inrats, at0.25,0.5,1,2, and4h, the ODV concentration of ansofaxine was muchhigher than ODV itself in both total brain and hypothalamus, which demonstratedthat the BBB permeability of ansofaxine was better than ODV. In all, based on theresults, ansofaxine is a promising prodrug of ODV with improved oralbioavailability and BBB perpeambility.