EXPERIMENT 1TABLET FORMULATION & POWDER CHARACTERIZATIONSAFETYThis experiment involves use of a moving machine which is potentially dangerous. Ensurehands are dry before equipment is switched on/off. Take great care when compressingpowders to produce tablets. Avoid your fingers, clothes or hair getting caught anywhere onthe machine.All the materials used are in powder form and most are from everyday food substances whichare not toxic. Do not however, taste any material as it may not be food grade and minimizecontact with bare skin. Avoid inhaling the powders. Clean up any spillage of powderimmediately.Dispose of all used materials in designated waste containers / areas. Clean and replaceequipment after use. Wash all glassware after useINTRODUCTIONTablets are the most common dosage forms employed for oral administration of drugs. Asingle tablet will under normal circumstances contain different excipients each performing aspecific function, for example, bulking agents (or fillers), binding agents, disintegratingagents, lubricants, and active pharmaceutical agents.Different mixtures of these constituents will affect the final properties of the finished dosageform and their ultimate performance in the body. The properties of the tablets produced arealso affected by manufacturing process variables such as the force used to compress thepowdered excipients. Various tests need to be performed in order to characterise theproperties of tablets. These tests provide information on the effects of the differentformulation and manufacturing variables used. Such information will aid the decision for thebest formulation and set of conditions for producing an ideal tablet that will be safe, effectiveand durable. Common tests include size (thickness and weight uniformity), hardness,friability, disintegration time and tablet dissolution.The main aims of this experiment are the preparation (formulation) of tablets by directlycompressing the constituent materials using a tablet press and investigating the effects of19_JU.,varying the tablet constituents and the manufacturing process on the properties of the tabletproduced.METHODPlease follow these instructions carefully and check the diagrams overleaf for details of thetablet press and to familiarise yourself with the various parts and its operational principles. Itis also of UTMOST importance, that all mixtures put through the press contain a minimum of1.0 % magnesium stearate. This acts as a lubricant for the press, without which the lowerpunch will seize up and the die does not fill with mixture, which results in the tabletproduction coming to a stop.20l1. Preparation of powdered/ granular mixture (Mixing)Follow the formulations shown in table 1below to prepare the mixtures as follows:1.1 Weigh out the powders separately. Mix thoroughly lactose, starch and talc in a mortar.1.2 Add all of the excipients on a 2S0µm mesh and pass them through the mesh gently andpure the powder in a plastic container. Mix the powders well for Smin and label eachformulation as Batch A or Batch B.Table 1.· Tablet formulations Ingredient/FormulaFormulation/Wei!?htsA(2)B(2)Lactoseso37.SHPMC12.Sg25.0Talc1.251.25Magnesium stearate0.6250.625 2. Production (compression) of tablets2.1 Place the powder in hoper No I and compress the tabl~ts as ·ndicated in Table 2. The. . I, • · oo-1oespec1ficat10ns for each tablet should be-ttmrrn diameter an mg weight. The first twogroups should carry out the compression studies for batch AI and the rest two for batch A2,respectively. As it depicted in Table 2 the tablet compression force and dwell time are thevariables for the powder studies.2.2 Tablet characterizationa. Weigh together S tablets fromeach Batch (now Al – A20) andrecord the total weight.b. From this total weight of 5tablets, calculate the meanI(average) weight per tablet/ andthe standard deviation (SD).c. Determine tablet hardness bymeasuring the force required tofracture a sample batch of 5tablets using the Hardness Testerprovided. Calculate the mean hardness (force) and the SD for each batch.21Id. Detennine the thickness of each tablet using the calliper provided and calculate the SDfor each batch.e. Provide three Tables including the average weight, hardness and thickness of each batch.Table 2: Setting of compression force and dwell time for studying the compression behaviourofBatches 1&2. Tablet Compression Force a)Dwell Time(msec)3ot,Je8-‘-l C:-lee-.)-0f59-bOi6Cr70J/5v 10Al/BlA2/B2A7/B7A3/B3A4/B4A5/B5A6/B6AS/BSA9/B9AIO/BIO.,SR-All/Bl IAl2/Bl2Al3/Bl3Al4/Bl4Al5/Bl5Al6/Bl6Al7/Bl7AIS/BISAl9/Bl9A20/B20 kN*The tablet press settings will be adjusted by the demonstrators responsible for the practical.3.1. Tablet weight uniformity and hardnessThis is an official method and described in the Tablet Monograph (p459) and Appendix (pA21 l) of the British Pharmacopoeia (BP 2000). The specification is dependent on the weightof tablet.QuestionsThe BP specification states that for tablets weighing more than 250mg, not more than two outof 20 tablets should deviate by more than 5%. In addition, not more than I tablet shoulddeviate by more than 12.5% from the mean.a. How many tablets had deviations> 5%?b. Did your batch pass the unifonnity test?c. How useful is your experimental test on IO tablets as far as the BP specification isconcerned.3.2 Tablet hardnessQuestionsa. What is difference in hardness between Al and A2? Give a reason for the differenceb. What effect does increasing the compression pressure (or force) have on tablet hardness(Fl and F2)?22c. What are the implications of having too soft or too hard tablets?3.3. Heckel PlotsMany methods have been used over the decades to study the volume reduction mechanismand bond formation of pharmaceutical powders. The most frequently used method forstudying the powder volume reduction process is the Heckel equation, or the porositypressure function, which is based on the assumption that the process of pore reduction duringcompression follows a first-order kinetic · (Heckel, 1961). The parameters concerningcompressibility characteristics can be obtained from the porosity-pressure plot. Yieldpressure (Py) is a measure of the plasticity of materials and can be used for relativecomparisons between different material compression characteristics. A Heckel plot can beused to study plain materials, but it can also be used to study powder mixtures whosecharacteristics are usually a combination of plain material characteristics.Questionsa. Use the Heckel equation to provide the plot for each formulations A and B (one plotfor each dwell time).b. Calculate constants K and A and discuss the powder properties based on the Heckelplots.c. See APPENDIX A for Heckel plot equations.ReferencesM.E. Aulton. Pharmaceutics: The Science of Dosage Form Design. Churchil Livingstone Ed,New York, 2003.23APPENDIX Aa. The Heckel equation is widely used for relating a powder bed’ 1 t’d. . h s re a 1vedensity (D) unng compression to t e applied pressure (P). The equation iswritten as follows:ln [1 / (1- D)] =KP+ Ab. The relative densities D, of the tablets can calculated from the equation:V= D wlps [2]where Vt is the volume of tablet (cm3) and Psis the particle density of the solidmaterial (g/cm3). The ps values for formulations A and B are 1.19 g/cm3 and 1.57g/cm3, respectively.38
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