Nghiên cứu bào chế và sinh khả dụng viên nén acyclovir kết dính sinh học đường tiêu hóa tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF MILITARY MILITARY MEDICAL UNIVERSITY LE VAN THANH FORMULATION, PREPARATION AND BIOAVAILABILITY EVALUATION OF GASTRORETENTIVE FLOATING TABLET OF ACYCLOVIR Major: Pharmaceutics and Pharmaceutical Technology Code: 9720202 SUMMARY OF PHARMACEUTICAL Ph.D THESIS HA NOI – 2020 THE RESEARCH WORK ACCOMPLISHED AT MILITARY MEDICAL UNIVERSITY Scientific supervisors: Assoc.Prof Vũ Thị Thu Giang Assoc Prof Trần Cát Đông Reviewer 1: Professor Nguyễn Ngọc Chiến Reviewer 2: Doctor Nguyễn Hữu Mỹ Reviewer 3: Assoc Prof Nguyễn Văn Minh The Thesis will be defended against the Council of Military Medical University at: o’clock day month year This thesis can be referred at: National Library of Vietnam Library of Military Medical University LIST OF PUBLICATIONS RELATED TO THE RESULTS OF THE THESIS Lê Văn Thanh, Vũ Thị Thu Giang, Trần Cát Đông, Nguyễn Thị Trang (2016) Study on bioavailability of gastro-retentive floating tablet in dogs Journal of Military Pharmaco-Medicine, 41: 94 – 102 Lê Văn Thanh, Nguyễn Đức Long,Vũ Thị Thu Giang (2015): Study on the stability and biodhesivity in vivo of the acyclovir tablets Pharmaceutical journal N 0474, p 19-25 Le Van Thanh, Vu Thi Thu Giang, Tran Cat Dong, Ta Manh Hung, Nguyen Van Bach, (2020) Quantitative determination of acyclovir in dog’s plasma by high performanceliquid chromatography Journal of military pharmaco- Medicine N01: p 113-123 LIST OF ABBREVIATIONS Number Abbreviaton ACV AUC BDDS FULL FORM Acyclovir Area under the curve Bioadhesive drug delivery systems Number Abbreviaton FULL FORM 10 11 12 13 14 15 16 17 18 19 20 21 Cb Cmax DĐH FDDS GPDC GRDF GPKD HPLC HPMC IC50 KSGP KDSH LLOQ MRT RSD SD SKD T1/2 22 Tmax 23 24 25 26 TCCS BP USP VKN TW Carbopol Maximum plasma concentration Pharmacokinetics Floating drug delivery systems Release of pharmaceutical substances Gastroretentive Dosage Forms Extended release High-performance liquid chromatography Hydroxy propyl methyl cellulose Half maximal inhibitory concentration Controlled release Bioadhesive Lower limit of quantitation Mean Residence Time Relative standard deviation Standard deviation Bioavailability Half-life Time to reach the maximum plasma concentration Pharmaceutical manufacturing standards Bristish Pharmacopoeia United States Pharmacopeia National Institute Of Drug Quality Control INTRODUCTION Acyclovir (ACV) is a synthetic analog of nucleoside, guanosine with potent antiviral activity and high selective against human pathogens such as Herpes simplex viruses type and type 2, Varicella- zoster, Epstein-Barr and Cytomegalo In addition, this substance also inhibits the hepatitis B virus ACV selectively inhibits the viral DNA biosynthesis of viruses when they enter the cells Currently, ACV is still the first drug of choice for the treatment of the aforementioned diseases The need for ACV-containing medicines is huge, especially when there are epidemic outbreaks Moreover, in many cases, ACV must be used for long periods of time, for example, treatment to prevent recurrent immunity Herpes simplex must be taken for months or longer However, the drug has a low solubility in both water and oil as well as poor permeability and short half-life (2-3 hours) If using conventional drugs, it must be taken several times a day (4- times), causing much trouble for patients In treatment, many dosage forms of ACV are unable to maintain the desired drug concentration at the action site, so the effectiveness of treatment is not high Moreover, ACV is slowly and incompletely absorbed (10 to 20% of oral bioavailability), primarily at the first part of the gastrointestinal tract Therefore, prolonging residence time and controlling the release of drugs in the optimal region of the gastrointestinal tract is one of methods to improving oral absorption and bioavailability of ACV Bioadhesive drug delivery system has the ability to increase residence time of the drugs on the mucosal surface at the optimal absorption site, thereby contributing to enhance absorption of drugs through the gastrointestinal tract Development of this dosage form and extended-release for 12 hours containing acyclovir was to improve the effectiveness of treatment, reduce side effects and contributing to create a new improved dosage form to develop the domestic pharmaceutical industry Therefore, the thesis entitled "Study on preparation and bioavailability of gastro-retentive floating tablet" was conducted with the following objectives: Develop the formular and preparation process of acyclovir gastric bioadhesive tablet with dosage of acyclovir 200 mg in the laboratory scale Built a standard of the manufacturing pharmaceutical and initially evaluate the stability of the prepared bio-adhesives acyclovir tablet Evalute bioavailability of the tablet in the experimental dogs In order to solve the three objectives, the thesis had been done the following parts: Study on formulation of gastric bioadhesive tablet of 200 mg acyclovir Carry out the preparation process of gastric bioadhesive tablet of 200 mg acyclovir with the scale of 5000 tablets Built up the standards of the pharmaceutical manufacturers and assess the stability of gastric bioadhesive tablet of 200 mg acyclovir Develop and evaluate the HPLC method to determine the acyclovir concentration in human plasma Evaluate the biological adhesion and bioavailability of the prepared gastric bioadhesive tablet of 200 mg acyclovir in the experimental dogs • New contributions of the thesis: About the scientific and practical significances: – Gastric bioadhesive tablet of acyclovir has been shown to be able to increase the gastric retention time of the dosage form prior to reaching to the optimal absorption site of drug in the small intestine Therefore, the research of gastric bioadhesive tablet of acyclovir was based on scientific base and had scientifically significant result, contributing to the development of modern pharmaceutical preparation technology in Viet Nam – Formulation and preparation of acyclovir gastric bioadhesive tablet were completed successfully which helps to improve the absorption and oral bioavailability of acyclovir, leading to increase patient compliance as well as reduce the cost of treatment About new contributions of the thesis: – This study was the first one in Viet Nam to successful accomplish from drug formulation and preparation process, to quality standards to evaluation of stability, bioadhesion and in vivo bioavailability of acyclovir gastric bioadhesive tablet in the stomach – Research and evaluation models may be applied to pharmaceuticals with acyclovir-like properties such as: limited solubility, poor permeability and absorption primarily in the first part of the small intestine *Contents and new structuring thesis: The dissertation consists of 150 pages: Introduction (2 pages); Chapter Overview of the study (36 pages); Chapter Materials, equipment, subjects and research methods (17 pages); Chapter Research results (76 pages); Chapter Discussion (16 pages); Conclusions and recommendations (2 pages) There are 76 tables and 29 figures * References: The thesis cited 127 references, with 123 English documents CHAPTER 1: OVERVIEW OF THE STUDY The overview of the thesis updated the following issues: - Acyclovir: Chemical formula, physicochemical properties, pharmacological effects, indications, contraindications, caution, route of administration - Gastroretentive dosage Forms - GRDF): Definition of GRDF, advantages and disadvantages of the system (GRDF), application of the system (GRDF), factors affecting the system (GRDF) - List some controlled release drug systems in the stomach (GRDF): Figure 1.1 Classification of controlled drug release systems in the stomach - The thesis studied on the bioadhesion system and the floating system in the stomach - Overview of domestic and international research models CHAPTER MATERIALS, EQUIPMENT, SUBJECTS AND RESEARCH METHODS 2.1 Materials: - Acyclovir, Cb 934P, HPMC K100M, Natri hydrocarbonat, Lactose, Avicel pH101, Magnesi stearate, Talc, Aerosil - Experimental animals: white rabbits, mature, male, with weight between and 2.5 kg were selected for in vitro bioadhesive testing - Healthy dogs, male, weighing 12-14kg were selected to initially assess the bioadhesive ability and residence time in the stomach and bioavailability of ACV prepared tablets Experimental dogs were raised under the experimental conditions with a full and controlled diet but they are allowed to fast overnight for 10 hours before experimenting 2.2 Reagents, chemicals, solvents, research equipment - Reagents, chemicals, solvents, research equipment met the purity standards for research and development of preparation standards - Specific equipments: ERWEKA (UK) cube mixer, UV-VIS spectrophotometer, high-performance liquid chromatography system, hematology analyzer, biochemical analyser and some common reagents, chemicals, equipment and instruments 2.3 Research methods Methods included methods of preparation, quality control, stability study of ACV gastric bioadhesive tablet, evaluation of bioahesive ability and in vivo bioavailability, experimental design and data processing 2.3.1 Preparation method of gastric bioadhesive table of acyclovir ACV gastric bioadhesive tablets were prepared by the direct compression method with expected components: Active pharmaceutical ingredient ACV 200mg, adhesive polymer (sodium alginate, Carbopol 934P, Carbopol 940P, HPMC K4M, HPMC The effects of excipients on the release of acyclovir (active substance) from the dosage form, the ability of water absorb and the bioadhesive force of the gas-producing excipient to create the floating properties of the tablet In conclusion: In order to ensure that tablets have good bioadhesive ability as well as prolong the drug release process, the selected bioadhesive polymers were Cb 934P and HPMC K100M Sodium hydrocarbonate acted as a gas-forming agent in the formulation to help the tablet float and stick in the upper stomach 3.1.2 Develop formulation of the gastric-retentive floating tablet of ACV Experimental design: Choosing independent variables was carbopol 934P, HPMC K100M, NaHCO3 The constants were ACV, lactose, Magnesi stearate, Aerosil, Talc, Avicel Using Mode 8.0 program was to design để thiết kế the zygote model at the center The experimental formulars were shown in Table 3.7 Based on the results of the effects of the independent variables to the dependent variables and the optimization of the formular with INForm 3.1 software, the prediction formular was obtained as follows: 10 ACV: 200,00 mg; Cb 934P: 70,02 mg; HPMC K100M: 12,81 mg; NaHCO3: 98,74 mg; Lactose: 100,00 mg; Avicel pH101: 190,43 mg; Magnesi stearat: 14,00 mg; Talc: 7,00 mg; Aerosil: 7,00 mg Conducted preparation of batches of tablets, each batch of 200 tablets according to the optimal formulation and then evaluated the ability of drug release and biadhesive properties The obtained result was f2 = 83.2 (Figure 3.11) 3.2 PREPARATION OF ACV GASTRIC BIOADHESIVE TABLET – DRUG RELEASE IN THE SCALE OF 5000 TABLETS From the optimal formulation, preparation of 5000 tablets was examined Investigation and evaluation of technical parameters during the preparation of the batch L01, L02, L03 including: mixing of all solid ingredients, mixing of powders and mixing with lubricant and tablet compression All the parameters met the required critea In conclusion: The investigated results were successful completed with 5000 tablets 3.3 ESTABLISHING THE STANDARDS OF SEMI-FINISHED PRODUCTS AND ACYCLOVIR PREPARED TABLETS Establishment of facility standards and testing cards: These standards have been certified by testing institutes 3.4 INITIALLY STUDY ON ACV GASTRIC BIOADHESIVE TABLET STABILITY 3.4.1 Study on the stability of tablets stored in HDPE plastic jars: The results did not pass after months because the HDPE vial made the tablet hygroscopic 3.4.2 Study on stability of tablets stored in aluminum blisters 11 About the apperance: dissolution, content, other factors were all good Figure 3.14 Regression line showed the percentage variation of ACV in lots over time when stored under the room conditions In conclusion: After 12 months of storage in aluminum/ aluminum blister in the room condition and months in accelerated aging condition, the tablets still met the set criteria Initial assessment of life expectancy of tablet could reach over 24 months 3.5 STUDY ON BIOADHESIVE ABILITY AND BIOAVALABILITY OF ACYCLOVIR GASTRIC BIOADHESIVE TABLET 3.5.1 INVEATIGATION OF PUTTING A CONSTRACT INTO GASTRIC BIOADHESIVE TABLET Figure 3.15 X-ray results of the bioadhesive ability in dogs After hours of taking pills, tablet still sticked in the stomach 3.5.3 Bioavailability evaluation of gastric bioadhesive tablet of ACV 3.5.3.1 Developing quantitative method of ACV in dog plasma The ACV analysis method in plasma by high performance liquid chromatography connected to Detectot PDA was fully appraised by the Central Institute for Drug Testing 12 3.5.3.2 In vivo bioavailability of gastric bioadhesive tablet in dogs a Evaluate the quality of tablets before bioavailability testing The gastric bioadhesive tablet with ACV 200mg and Zovirax 200mg tablet were assessed the quality according to criteria before bioavailability testing: mass uniformity, qualitative, quantitative, disolution test All criteria were met b Evaluate bioavailability of ACV gastric bioadhesive tablet in dogs Figure 3.21 The curves of average concentration and time of two drugs Results: Drug release of ACV gastric bioadhesive tablet tends to have a long-lasting effect as shown by the average retention time of drug in the body and the time to maintain the plasma drug level at the level of more than IC50 were much longer than the results of the conventional Zovirax tablet In addition, the longer maintenance time of IC50 concentration also proved that the research on preparation of ACV gastric bioadhesive tablets had contributed to increase the bioactivity of Herpes virus resistance compared to conventional tablets The relative bioavailability of the formulated ACV gastric bioadhesive tablets compared to the Zovirax – the reference tablets with 90% confidence was 85.81% - 129.02% which had initially shown the ability of enhancing drug absorption In the gastrointestinal tract CHAPTER 4: DISCUSSION 4.1 GASTRIC BIOADHESIVE DRUG DELIVERY SYSTEM OF ACYCLOVIR 13 In fact, the drug is usually absorbed mainly in a certain area on the digestive tract Most drugs are absorbed relatively quickly at the beginning of the small intestine, slowly and not completely at the end of the gastrointestinal tract Therefore, controlling drug release in the optimal absorption region in the gastrointestinal tract is one of the ways to improve the absorption and bioavailability of the drug The extended-release dosage form is becoming increasingly important, in order to achieve the desired therapeutic effect by increasing patient compliance, maintaining a stable drug concentration in the body for a long time, reducing undesirable effects ACV is a typical pharmaceutical substance for the group of limited solubility and poor permeability ones along with absorption through interstitial cells and mainly at the beginning of the gastrointestinal tract Thus oral bioavailability is low and unstable (15 - 30%) ACV has a short elimination half-life, 30-90% were excreted in faeces as non-absorbed Therefore, the gatric bioadhesive system – drug release at the optimal absorption position (stomach and small intestine) were statistically significant to improve the oral bioavailability of ACV In fact, it has been proved through a number of researches on the system in the wordwide Therefore, the research orientation of the gastric bioadhesive drug system for ACV was an appropriate, helping to improve bioavailability and reduce the frequency of use for patients This is especially important in cases of treatment that last for months 4.2 PREAPRATION OF GASTRIC BIOADHESIVE TABLET OF ACYCLOVIR 4.2.1 Preparation method of tablets To choose the appropriate method of preparing AVV floating tablets, gastric bioadhesive tablets, 200 mg ACV tablets were prepared by two methods of direct compression and wet granulation But through research, the method of wet granulation was not appropriate, so we only choose the direct compression method Meanwhile, the direct compression method has many advantages, which are less stages, saving space, equipment and preparation time, avoiding the impact of temperature on the bioadhesive polymers and 14 active pharmaceuticals inredient Although, Cb 934P and sodium alginate are easily hygroscopic, affecting the flow of the powder However, when combined with direct compression excipients HPMC K100M and HPMC K4M at the appropriate rate, it could overcome the above disadvantages Therefore, the direct compression was chosen 4.2.2 Formulation of ACV gastric bioadhesive tablet In order to evaluate the influences of the input variables on the output variables and optimize the formular, the selection of bioadhesive polymers was conducted Research results showed that Cb 934P was an adjuvant with major influence on bioadhesion Increasing the amount of Cb 934P, the ability of swelling and the bioadhesive force increased significantly, but the percentage of ACV release decreased, which did not guarantee the quality of the tablets Hence, to meet the quality standards set out for the tablets, HPMC K100M was incorporated into the formulation As a result, the ability of drug release increased This result was also consistent with a number of published studies around the world Increasing viscosity of Cb would help better adhesion in the mucosa, and the gel layer created by Cb swelling would slow down the release of ACV In this study, the formulation used only 11.7% of the amount of polymers (only equal to 1/4 to 1/2 of the published formulations) compared to the weight of tablet This is an advantage in terms of stability To ensure that the ACV tablets retain the stomach for a longer period of time, we reduce the density of the tablet by adding NaHCO3 (gasforming agent) to the formula The role of NaHCO was to reduce the density of tablets, help them to float so that they can stick to the upper part of the stomach, and increase the swelling and bioadhesive activities of ACV 200mg tablets Because NaHCO created an alkaline environment to neutralize Cb 934P, and increased the viscosity of Cb 934P which created a thicker gel layer surrounding the tablet surface Through experimental design according to the zygote model at the reduced center by Modde 8.0 software, evaluation of the effects of the formula components by FormRule 2.0 software, the results showed that each excipient had a certain influence on the dependent 15 variables Combining the excipients with the appropriate proportion would ensure that the tablets met the quality standards set liên kết có ảnh hưởng đến khả KDSH Cb 934P was the major adjuvant that affected the bioadhesive force due to its ability to bind to glycoprotein mucous membranes by hydrogen bonds and van der Waal force, the main influences on the bioadhesive ability Within the scope of investigation, the HPMC K100M was a bioadhesive polymer that had a major influence on the percentage of ACV release About floating capacity of the tablet, both Cb 934P and HPMC K100M showed the greater influence than NaHCO The reason was that the gel formed by the bioadhesive polymer played a crucial role in capturing CO Without this gel layer or non-thick gel layer, the CO2 generated did not reduce the density of the tablet as the main effect was to break the structure of the tablet, resulting in rapid disintegration Optimizing the formula with InForm 3.1 software, we have selected the optimal formula with excipients Cb 934P, HPMC K100M, NaHCO3, lactose, Avicel PH101, Aerosil, talc, magnesium stearate to meet the requirements of tablets which controlling drug release in the stomach The most important criteria in choosing the optimal formula was biological adhesion, floating in the stomach environment and releasing ACV over time The results of the study also proved that the research design was suitable to the experiment 4.2.3 Scale up the preparation of ACV 200 mg tablets When scaling up the size of the preparation, there was no difference in the quality of mixed powder, and the quality criteria such as the mass uniformity, content uniformity, and dissolution, bioadhesion, floating ability before tablet compression among the batches Thus, it could be initially confirmed that the process of preparing ACV bioadhesive floating tablets had some advantages when it comes to scaling up later In the process of upgrading the scale of ACV tablet preparation, we realized that the tablet compression speed was one of the important parameters to be controlled The flow ability of the powder mixture depended on the polymers in the formula and the lubricant excipients On the other hand, the flow of powder depended on the moisture of the environment This was especially noticeable because 16 Cb was a highly hygroscopic polymer in the formula Therefore, the moisture limit of powders prior to tablet compression should be set to a low level (below 3%) compared to the normal limit of granulation (below 5%) and the humidity of the laboratory to be within allowed limits and should be controlled and maintained throughout the compression process In addition to the above-mentioned notes, the results of scaling up the ACV gastric bioadhesive tablet size showed the feasibility of conducting preparation of the tablets on a large scale The preparation process was not complicated and quite the same as the conventional tablet preparation process The pharmaceutical manufacturers could take advantage of existing tablet production equipment without having new equipment 4.2.4 Methods of evaluating a number of tablet quality criteria for ACV 200mg gastric bioadhesive tablet with drug release during 12 hours About quality standards of ACV bioadhesive floating tablets In the pharmacopoeia, there is no specific parts on this dosage form, as well as no ACV gastric bioadhesive tablet on the market Therefore, the proposed standard for dosage tablets was mainly based on the research documents and general standards of licensed drugs Norms of uniformity of mass, related impurities, guanine, quantitative according to ACV tablet parts in Vietnamese Pharmacopeia IV and refer to ACV capsule parts in USP 32 In general, the analytical methods were highly accurate and easy to apply in the conditions in Viet Nam The spectroscopyscan of placebo sample which had excipients with the same proportions as in tablets showing no UV absorption at the wavelength of 252 nm in determination of active pharmaceutical ingredient In-vitro bioadhesive ability testing: Currently, in Viet Nam, there is no specialized equipment for assessing adhesion ability, so we have 17 consulted foreign studies and self-made adhesive assessment equipment from Roberval scale Rabbit gastric mucosa was treated and evaluated the bioadhesive ability of the tablet Compared with previous studies, 200mg ACV tablet had high bioadhesive force, ensuring the ability to retain drugs in the stomach Cb 934P was the adjuvant that had the greatest influence on the adhesive capacity of the tablet due to the ability to bind to the mucous membrane glycoprotein by hydrogen bonds and van der Waal forces Method for evaluation of in vitro floating ability of the tablet: The floating mechanism of the tablet was the reaction between NaHCO3 and HCl of the medium, bubbling CO The released gas would be trapped in a gel layer formed by swelling polymers, reducing the density of the system and the system would float in the stomach Therefore, the evaluation method was quite simple, putting the tablet into a cup containing 100ml HCl 0.1M, then determining the lag and floating time The in vitro floating capacity of the prepared tablet according to the optimal formula: the lag time was 25 ± 2.82 minutes, the floating time was more than 12 hours and there was no disintegration during floating process From the research results, it can be seen that the tablet had a relatively long lag time compared to other studies on the stomach floating system (usually a few minutes) So we decided to use only one gas generating agent was NaHCO3 Long Tlag would be overcome with combination of floating and bioadhesive dosage form When the tablet went down, the bioadhesive polymer would exert its effects, attaching to the stomach lining That time was enough for NaHCO3 to react with HCl in the stomach, reducing the density of the tablets Kết thử nghiệm sinh học chó chứng minh cho giả thuyết Mặc dù thời gian tiềm tàng 25 phút, hình chụp x-quang cho thấy sau 1h viên trương nở sau 3h viên dày The results of a biological test on dogs also supported this hypothesis Although the lag time was 25 minutes, but the X-ray picture showed that after hour, the tablet had swolen and after hours, the tablets were remained in the stomach Water absorption capacity of the tablet was assessed by gravimetric method by determining the amount of water absorbed into the tablet The research results also presented a positive 18 correlation between the ability of water absorbtion and bioadhesive force of the dosage form This was explained by the ability to absorb swollen water and bioadhesive force due to the nature of Cb 934P It can be seen that the ability of the tablet to absorb water over time was an important parameter because this is the stage when gel barrier layers were formed with water penetration Therefore, in order to be simple but still effective in controlling the quality of the tablets, the swolen water absorption criteria was included in the evaluation criteria of ACV tablets Regarding the solubility criteria of tablets, the dosage form of bioadhesive tablet had no specific standards in the pharmacopoeia and there is no reference tablet on the market The solubility of the studied tablet increased over time, in which, the percentage of active pharmaceutical ingredient released in each time interval was 17.7% in the first hour, then hour of further release 13%, from the second to fourth hours, liberated average 11.5% per hour; from the fourth to sixth hours, average liberation of 8.83% per hour Thus, every hour active pharmaceutical ingredient released about 17.66 mg to 35.4 mg ACV The solubility of ACV in the gastric environment was over mg/ ml, so the amount of ACV released would dissolve completely quickly for easy absorption through the mucosa The drug release rate of ACV tablets complied with KP's law: (R = 0.9982) This showed that ACV was released mainly by diffusion mechanism via gel membrane In terms of AUC results, Zovirax tablets only lasted for 10 hours, while the studied tablets lasted up to 17 hours, so while only dog test results were currently available, showing potential for reducing medication use This would help avoid usage errors, especially using with Zovirax when the number of times of this tablet used up to times a day and hours apart between these doses Further bioavailability studies on humans should be conducted to determine the number of doses and the interval between doses 4.2.5 Stability study The purpose of the stability study was to provide evidence of changes in the quality of drugs under the impact of environmental factors as well as factors of drug preparations as a basis for determining the shelf life of drugs The factors included temperature, 19 humidity and light, physicochemical properties of pharmaceutical substances and excipients, dosage form, composition of drug formulations, manufacturing process, tightness and nature of packaging direct packing In addition, the stability of the excipients might also be related to drug degradation reactions, so it should be considered The stability study of ACV 200 mg capsules was conducted on the basis of references to the regulations of WHO, FDA and ASEAN guidelines on drug stability research However, due to limited equipment to ensure the research conditions, the stability of the drug was studied in two conditions of accelerated aging testin g(temperature: 40 ± oC, humidity: 75 ± 5%) and the room conditions For the purpose of storage and convenience of storage, distribution and use, we had conducted research on the stability of the prepared ACV tablet on two types of packaging: HDPE plastic jars and aluminum/ aluminum blisters Aluminum/ aluminum blister packaging was the best moisture-proof packaging, so with a polymer formula, for example Cb 934P would be the best fit The results also demonstrated that the appropriate packaging for the tablet was aluminum/ aluminum blister due to its good moisture resistance Extrapolation had been applied to predict shelf life of the drug Based on the results of monitoring quality indicators, it was possible to predict that the tablet would have a shelf life of over 24 months when was stored in the room conditions in aluminum/ aluminum blisters However, in order to draw conclusions about the real expiration date, further studies were needed to monitor the long-term stability of the drug under the room conditions (temperature: 30 ± °C, humidity: 75 ± %) 4.3 EVALUATION OF BIOADHESIVE ABILITY In the stomach, the tablet was not in a static state but moved continuously and was under the influence of many forces in different directions, not only affected by a force from the top down The contact time with the gastric mucosa also greatly affected the bioadhesive ability, the longer the exposure time, the better the adhesive tablet, while the in vitro bioadhesive test fixed the exposure time to minute Besides, the position in contact with mucous 20 membranes also affected the retention time in the stomach With many uncontrollable influences, there had been many cases where the tablets were well adhered in invitro tests, but the fact that they did not last as long as the originally effectiveness intended At present, there have not been any published or research works in the world that have been correlation in in vitro - in vivo evaluation of bioadhesive Therefore, to ensure the feasibility of the study, we determined the drug sites after taking it by an X-ray picture For the X-ray method, the optimal sample was mixed with 100 mg of barium sulfate contrast, the other excipients remained unchanged In dogs test, all dogs took X-ray after taking the tablet and the first hour and hours showed that the ACV tablets were in the stomach, at hours the drug began to desintegrate This showed that the gastric bioadhesive tablets could be able to adhere in the test animal species 4.4 BIOAVAILABILITY EVALUATION OF ACYCLOVIR GASTRIC BIOADHESIVE TABLETS 4.4.1 Development and validation of ACV quantitative methods in plasma by HPLC method About the sample processing method: From literature reviews we found that perchloric acid was commonly used in the studies to extract ACV from plasma with a very simple procedure Moreover, ACV was a substance with relatively good chemical stability After conducting the investigation, we decided to select 20% perchloric acid as a protein precipitation solvent to separate ACV from the plasma samples, with the advantage of fast (only through swirling, centrifuging steps), the recovery rate was high (from 103.1% to 104.3% with RSD between samples ≤ 3.4%), much simpler than the method using acetonitrile About the method of determination of ACV in plasma: The HPLC method with the advantages of fast, simple, high sensitivity was selected by most studies Through reference to the literature, we conducted a trial of a number of mobile phase systems such as methanol - phosphate buffer with different ratios on the C18 chromatographic column The results showed that the mobile phase system: methanol: buffer pH 3.0 (ratio 8:92) (pH 3.0 buffer phase prepared as follows: 0.43g sodium octansulfonate + 1000 mL water, 21 adjusted to pH 3.0 with acid phosphoric) had the best separation ability, ACV peaks were not mixed with the mixed peaks, the peak response rate at the LLOQ concentration was 12.1% < 20% as required The lower quantitative limit of the method was 0.1 µg / mL, lower than previous studies of 0.5 µg / mL Be sure to quantify the beginning and the end of the sampling process Therefore, this system was selected as the mobile phase in the analysis of plasma samples Evaluation of quantitative methods: The norms of the method of quantifying ACV in dog plasma had been verified according to FDA regulations and ASEAN guidelines, including specificity and specificity criteria; lower quantitative limit; linear range, regression line in dog plasma and response function; accuracy and precision; prcentage of retrieval of method and stability 4.4.2 In vitro Bioavailability evaluation of the ACV gastric bioadhesive tablets on dogs Preparations for bioavailability comparison: Zovirax tablet was the conventional tablets, of the inventors, which are the most reputable drugs on the market today This is a reference drug prescribed in documents on bioequivalence assessment of Asean as well as Viet Nam Experimental subjects: Dogs were selected as an experiment animals for initial study because dogs have a similar gastrointestinal tract with human and using dogs in the in vivo bioavailability study was to avoid dangers for humans, reducing costs Bioavailablity evaluation: The study results showed that with the confidence of 90%, the relative bioavailability of ACV 200 mg tablets compared to conventional Zovirax tablets 200 mg reached 85.81% - 129.02%, surpassing limited by 80% - 125% according to FDA regulations, initially showing the ability of improving absorption of oral medications Although Zovirax has higher C max, time to reach Tmax faster than the prepared ACV tablet, ACV tablets had a longer effect, up to 18 hours of drug concentration in dogs plasma was still greater than IC 50 ( µg/ mL) while conventional Zovirax tablets could only remain above the concentration level for up to 10 hours It was proved that the preparation of ACV tablets in the gastrointestinal tract - prolonged release had contributed to 22 improve absorption, increase activity and extend the duration of the drug's effect The obtained results can be preliminarily affirmed that the preparation of ACV tablet had achieved the goal of improving oral bioavaialbility and prolonging the drug effect in 12 hours as originally designed However, the evaluation results in animals was a prerequisite for further clinical research on volunteers Clinical trials on volunteers are expensive and require a lot of time and effort The results of AUC in animals suggested the times of taking human blood to obtain a more accurate AUC concentration curve In addition, for human trials, it was important to note that the food and gastrointestinal motility will affect the adhesion of the tablets, so it is necessary to study the conditions with and without food CONLUSIONS From the research results, the thesis had drawn some following conclusions: Formulation and preparation process of 200 mg acyclovir gastroretentative foating tablet has been developed using the floating and bioadhesion mechanism by direct method - Investigating the preparation process has been carried out, thus, acyclovir gastro-retentative foating tablet could release the active ingredient within 12 hours - Developing the preparation process of acyclovir gastro-retentative foating tablet with 12 hour- active ingredient release for 5,000 tablets/ lot The standard for ACV tablets stored in the stomach has been developed and validated based on the 12-hour floating mechanism and biological adhesion and initially evaluated the stability of lots of prepared tablets in the room conditions and accelerated aging is 12 months of research The research results show that when stored in aluminum foil - aluminum tablets are stable in both the room conditions and accelerated aging during the study period The standard for ACV tablets stored in the stomach has been developed 23 and validated based on the 12-hour floating mechanism and biological adhesion and initially evaluated the stability of lots of prepared tablets in the room conditions and accelerated aging is 12 months of research The research results show that when stored in aluminum foil - aluminum tablets are stable in both the room conditions and accelerated aging during the study period.The pharmaceutical manufacturer’s standards for ACV bioadhesive tablet in the stomach had been developed and validated based on the 12hour floating mechanism and bioadhesion; and initially evaluated the stability of lots of prepared tablets in the room conditions and accelerated aging of 12 months The research results presented that when stored tablets in aluminum - aluminum blisters, tablets were stable in both room conditions and accelerated aging during the study period The bioavailability of ACV 200 mg tablets in dogs compared with conventional Zovirax 200 mg tablets of GlaxoSmithKline was studied The results have determined the pharmacokinetic parameters of Cmax, Tmax, , Lamdaz, MRT of ACV tablets and Zovirax tablets The research results showed that ACV tablets prolonged the average drug retention time in the body much higher than conventional tablets (equivalent to 1.5 times) and the time to maintain the drug concentration in the plasma of > IC 50 was 1.8 times longer compared to conventional tablets Reccomendations - Continuing to monitor the stability of the drug in room conditions to be able to confirm the shelf life of the drug - Deploying pilot production of tablets at pilot and industrial scale - Continue to evaluate bioavailability of tablets on a larger scale to confirm the results ... exert its effects, attaching to the stomach lining That time was enough for NaHCO3 to react with HCl in the stomach, reducing the density of the tablets Kết thử nghiệm sinh học chó chứng minh... 102 Lê Văn Thanh, Nguyễn Đức Long,Vũ Thị Thu Giang (2015): Study on the stability and biodhesivity in vivo of the acyclovir tablets Pharmaceutical journal N 0474, p 19-25 Le Van Thanh, Vu Thi... following objectives: Develop the formular and preparation process of acyclovir gastric bioadhesive tablet with dosage of acyclovir 200 mg in the laboratory scale Built a standard of the manufacturing