Study On The Preparation And Pharmacokinetic Of The Sustained-release Pellets Of Pyridostigmine Bromide

Pyridostigmine bromide is a cholinesterase inhibitor, by inhibiting the activity of acetylcholinesterase,to reduce the destruction of acetyl choline which is released by cholinergic nerve,and accumulate acetyl choline in the synaptic cleft,and activate muscarinic receptor and nicotinic acetylcholine receptor,then improving the muscular tone of gastrointestinal smooth muscle,bronchisl smooth muscles and skeletal muscle inthe body. It has been mainly used for myasthenia gravis in clinical therapeutics,and has been applicable to uroschesis,postoperative abdominal distension and supraventri--culartachycardia. Because of the t1/2 of PB is 2.6 ~ 3.5h, it came into effect after half an hour, but it is fast to elimination, Although it can improve the symptoms, but short duration, it needed to be given once per 4 ~ 6. The high frequency of drug use and blood drug concentration fluctuation lead to the obvious side effects such as muscle tremors. The issue intends to develop Pyridostigmine bromide sustained-release pellets which were taken once per 12 hours, to decrease the peak value of blood drug concentration and improve blood trough concentration in vivo.thus reduce the frequency of administration and side effects that caused by blood drug concentration fluctuation.Objective To develop pyridostigmine sustained-release pellets per 12 hours administration,reduce the side effects that caused by blood drug concentration fluctuation, improve patients compliance with medication and provide a basis for the development of pyridostigmine formulation.Materials and Methods 1、To prepare white pellets which use suger sphere as its carrier, alcohol as its solvent and low viscosity ethyl cellulose as adhesion agent,then coat the pellets with ethyl cellulose,PEG and diethyl phthalate separated as Sustained Release coating material, the hole-maker and the plasticizer, to prepare Pyridostigmine bromide film-controlled sustained-release pellets.2 、Prepared the pyridostigmine bromide white pellets and film-controlled sustainedrelease pellets by fluidized bed bottom spray, Use the cumulative release as the relevant data, a preliminary Screening condition of the film coating process has been performed By changing the coating flow rate, air flow rate and air inlet temperature.3、Through the preliminary studies, determined the formulation and process parameters,Use the cumulative release as the relevant data,and investigate the effcet of the using amount of plasticizer, porogen and coating weight on dissolution; On this foundation,using the similarity factor(f2)between the test preparation and control preparation as selection standard,and the best coating prescription was selected by uniform design.then made model fit on the release of the optimized prescription.4、To develop a method for the determination of PB sustained-release pellets.5、To establish a method for the determination of the release rate, using the content,release degree, appearance character and related substance as selection standard, the effects of high temperature, high humidity and light on the stability of PB sustained-release pellets were investigated.6、To establish a LC/ MS method for determination of pyridostigmine bromide in rat plasma. SD rats were selected as the experimental animals, made PB pellets and PB sustained-release pellets as the control group and experimental group separately,oral administration, blood samples were taken at different time points, and plasma samples were treated with LC-MS. analyze the pharmacokinetic parameters by DAS 3.0program.Results 1、Results of prescription screening; The circularity and appearance of the prepared pellets were both better.2 、 Results of process; there were no adhesion,electrostatic phenomenon and the circularity of the pellets is better when the nozzle diameter is 0.5mm, the inlet air volume is 22±1 m3·h-1,the air inlet temperature is 50℃, the atomization pressure is 0.7Mpa, the coating flow rate is 1.5ml·min-1, and the material temperature is 36.3、The results of prescription optimization; with the increase of the dosage of plasticizer and coating weight the release rate of pellets was obviously slowed down, and the release rate of pellets was accelerated with the increase of the dosage of the pore forming agent.When PEG was 12.8%,DEP was 22.7% and weight gain 21.6%,the release characteristics of prepared PB sustained-release pellets and Foreign commercial sustained-release tablets were similar in vitro,and the similarity factor(f2) was 85.7.4、The results of determination methods of content and release;the maximum absorptionwavelength of PB is 269 nm, there were no absorption of blank accessories at 269nm;The linear range was 12.66 ~ 44.31μg·ml-1;better accuracy and precision; PB keeps stable in 24h; The recovery rate of the method was 96.75%~101.63%.5 、 The results of preliminary quality and stability research; The release rate was determined by using the paddle method and the water as the dissolution medium, and the stirring speed was 50 rpm. the drug release profiles in vitro followed first order kinetics, The drug release by diffusion and followed the release mechanism of film-controlled pellets. The influencing factors test results showed that the content,release degree, appearance character and related substance were not sensitive to high temperature and light but sensitive to high humidity, the pellets should be stored in dry.6、The results of pharmacokinetics of pyridostigmine bromide sustained-release pellets in experimental rat;PB selected ion mass spectral : m/z 181.0→m/z 72.1; Linear range of plasma samples of PB: 7.80~ 250.00ng/ml; Endogenous substance does not interfere with the determination of PB; Good precision, method recovery rate and extraction recovery rate is in line with the requirements; Plasma samples remained stable when frozen for 3 times and for 24 hours. The phannacokineties parameter of test preparation are AUC0-t:714±333.55 ug/L*h, Cmax :155.27±35.11ug/L,Tmax:2.1h,t1/2:4.42h;the phannacokineties parameter of reference preparation AUC0-t :507.55±181.19 ug/L*h,Cmax 125.94±47.32ug/L,Tmax:1.3h,t1/2:2.39 h.Conclusion 1、The release model of pyridostigmine bromide sustained-release pellets accord with a kinetic model, it release by insoluble membrane diffusion.2 、 PB sustained-release pellets were sensitive to humidity and unstable under high humidity conditions, which need to be stored under dry conditions.3 、 Compared with the pill, the blood concentration of PB sustained-release pellets declined slowly, and have the function of controlled release.