Pharmacokinetic Studies On Octohydroaminoacridine Succinate And Iptakalim Hydrochloride

Octohydroaminoacridine succinate (9-amino-1,2,3,4,5,6,7,8-octohydroaminoacridine succinate), has recently been developed by Changchun Hua-yang High-tech Biopharm Company Ltd. (Changchun, PR China), which was identified as a new drug for the treatment of Alzheimer's disease in China. It is structurally designed from tacrine (9-amino-1,2,3,4-octohydroaminoacridine), a reversible acetylcholinesterase inhibitor, and it is the first drug licensed for the treatment of mild to moderate Alzheimer's disease involved in cholinergic system, which evidently brings harmful side effect down. In the present, it is possible that the compound is the most prospective drug for treatment of senile dementia as the acetylcholinesterase inhibitor for cholinergic system. octohydroaminoacridine succinate is now undergoing preclinical trials in China. Until now, there are few reports on the pharmacokinetic study on arotinoid because of its lability and the lower dosage used in the preclinical. A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of octohydroaminoacridine succinate in animal samples and the prediction for the process of it in human exactly in order to estimate its effectiveness and toxicity reasonably. Iptakalim hydrochloride (N-(1-methylethyl)-1,1,2-trimethylpropylamine hydrochloride), a novel cardiovascular ATP-sensitive potassium channel opener, shows antihypertensive and neuroprotective effects in a variety of in vivo and in vitro preparations. It is promising antihypertensive drug with the abililty to protect against endothelial dysfunction through activating ATP-sensitive potassium channels in endothelial cells. The compound is now undergoing extensive clinical trials in China. Iptakalim hydrochloride is a small molecular weight compound without a significant chromophore. This limits its detection by UV or fluorescence spectroscopy such that pharmacokinetic studies in rat have been based on assay of GC-MS. However, the GC-MS method require a derivatization step, arduous sample preparation, and long chromatographic run times. This paper presents a sensitive LC-MS/MS method for the determination of Iptakalim hydrochloride in plasma involving sample preparation by liquid-liquid extraction and sildenafil as internal standard. The method has been successfully applied to a clinical pharmacokinetic study involving a single 5 mg,10mg and 20mg oral dose.1. Pharmacokinetics study on Octohydroaminoacridine succinate in animals.The objective of this study was to establish an accurate and simple method in order to estimate the pharmacokinetics of octohydroaminoacridine succinate in animals (rats and dogs) for the first time. The method is optimized by the study on spectral condition, chromatography condition, pre-processing for sample and internal standard. Chromatography was performed using hypersil C18 column (150 mm×4.6mm I.D., 5μm; Jiangshen Dalian, China) as stationary phase and acetonitrile-10 mmol?L-1 ammonium acetate -formic acid (75:25:2, v/v/v) as mobile phase in the isocratic mode at a flow-rate of 1.4 mL?min-1. An ESI source was used as detector in the multiple-reaction-monitoring (MRM) mode. The results were shown as below:After ooctohydroaminoacridine succinate was administered to rats at a single dose of 0.4, 0.8 and 1.6 mg?kg-1, respectively, by gastrogavages, the main pharmacokinetic parameters were fitted with two-compartment model and not varied with the increase of dose, therefore, linear pharmacokinetic characteristics were found(r>0.708, P<0.05). The absolute bioavailability of octohydroaminoacridine succinate was estimated to be 41.8±18.3% for the dose of 0.8 mg?kg-1. After octohydroaminoacridine succinate was administered to dogs at an oral dose of 0.12, 0.24 and 0.48 mg?kg-1, respectively, the main pharmacokinetic parameters were fitted with two-compartment model and not varied with the increase of dose, therefore, linear pharmacokinetic characteristics were found(r>0.708, P<0.05). The absolute bioavailability of octohydroaminoacridine succinate was estimated to be 86.7±33.1% for the dose of 0.24 mg?kg-1.2. Tissue distribution study on octohydroaminoacridine succinate in rats.A sensitive and selective LC/MS/MS method was developed for the quantification of octohydroaminoacridine succinate in rat tissues and comparison the difference of it in rats. The results were shown as below:Octohydroaminoacridine succinate was distributed to tissues extensively in rats after an oral administration of 0.8 mg?kg-1. It was eliminated quickly from most tissues, and the concentration of octohydroaminoacridine succinate in tissues at 24 h post-dose except for spleen, fat, heart, smooth muscle and didymas was lower than 5% of that at 0.25 h post-dose. Little amount of octohydroaminoacridine succinate was detected in tissues, which meant no accumulation.The plasma protein binding ratio was tested and a higher plasma binding ratio (about 70%) was found.3. Metabolism and excretion studies on octohydroaminoacridine succinate in rats. The [3H]-labeled method was applied to investigated the excretion of octohydroaminoacridine succinate and its metabolite.Octohydroaminoacridine succinate was lessly excreted from urine after an oral gastrogavages of 0.8 mg?kg-1, and the cumulative amount within 120 h reached to 21.41±6.07 % of the dose whereas the unchanged cumulative amount in fecal within 120 h reached to 0.56±0.68 % of the dose. In the all, 21.97±6.33 % of the dose excreted from urine as octohydroaminoacridine succinate. It was indicated that the extensive metabolism was carried out in rats and the metabolite was mainly excreted from kidney. The result shows that the content of original drugs in urine, fecal and kidney is low after gastrogavages. Therefore, the [3H]-labeled method was applied to investigated the excretion of octohydroaminoacridine succinate and its metabolite. The average cumulative amount in urine and fecal reached to 83.37±4.49 % of the dose. It was indicated that the extensive metabolism was carried out in rats and the metabolite was mainly excreted from kidney. Its hydroxylation metabolite was found in urine.4. The effect of octohydroaminoacridine succinate on P450 enzymes in rat liver microsomesThree LC/MS/MS methods were developed to evaluate the effect of octohydroaminoacridine succinate on CYP 1A2, CYP2D6 and CYP3A4 activities in rat liver microsomes, respectively. The data showedscutellarin neither inducted nor inhibited the activities of CYP 1A2, CYP2D6 and CYP3A4 in rat liver microsomes.5. Pharmacokinetic and method study on Iptakalim hydrochloride in healthy volunteers.The concentration at different time in 12 healthy volunteers after oral administration of Iptakalim hydrochloride tablets (5mg, 10mg and 20mg) was determined by a validated LC/MS/MS method. The pharmacokinetic parameters were calculated based on the concentration time curve. The method developed can be used for the therapeutic drug monitoring.Conclusions:The pharmacokinetic evaluations on succinate octohydroaminoacridine succinate in animals was carried out in this thesis, base on which the drug development was promoted for this compound. The effect of octohydroaminoacridine succinate on P450 enzymes in rat liver microsomes was evaluate this thesis.A fully validated LC/MS/MS method for the determination of Iptakalim hydrochloride was developed and applied to the pharmacokinetic study in 12 healthy volunteers.