Granule Manufacture

The ingredients of a tablet differ from one drug to another, and the different compositions will be reflected in the tablets therapeutic effectiveness. Variations in particle size will be reflected in a tablets physiochemical properties. A tablet will contain, primarily, the active ingredient, i. e. the drug that is being delivered. The tablet will also contain other ingredients that are necessary to formulate a satisfactory tablet, these ingredients are called excipients, and common excipients include: Binders: such as polyvinylpyrrolidin (PVP).

These exert an effect by holding particles together; they induce the formation of granules. Diluents: such as lactose and microcrystalline cellulose. Diluents are used to increase the mass of the powder, for example if the over all mass of a tablet needed to be increased to 50mg, a diluent would be ideal to o this. Glidants: such as colloidal silica. These act by reducing interparticulate friction. This allows the powder particles to flow better, which is an advantage during the mixing process. Lubricants: such as magnesium stearate.

This is a useful excipient which has two major effects. It helps to reduce the friction between granules and the tablet machinery and also improve the flow properties of the granules. Disintegrants: such as maize starch. These are essential as they improve the capability of the tablets to break apart in water. Once the tablet enters the body, it begins to disintegrate, the better the disintegrant, the faster dissolution will occur. The table disintegrates into smaller particles with a large surface area. This increased surface area increases the rate of dissolution.

When deciding on what excipients a product will include we look at the following properties, the dose of the drug, particle size, particle shape, solubility, stickiness and powder flow of drug material. The diluent that will be used is also chosen on the basis of these properties. We try to mix in diluents of similar shape and size to the drug particles and try to mix in a soluble diluent. Lactose increases the hydrophilicity of the formulation allowing water to come in and penetrate the formulation. One method of aiding flow properties and improving the efficacy of the overall tabletting process is by the formation of granules.

The granulation process involves combining smaller particles to from larger agglomerates. Granulation has many advantages such as increasing particle size which helps to improve flow properties. Also the dispersion and solubility properties of a powder will be improved. There are two methods for granulation, wet and dry granulation. In this practical wet granulation was used. Wet granulation was advantages over dry granulation, it is better at improving cohesiveness and compressibility. IQCS values lie between -1 and +1. A value of zero indicates a symmetrical size distribution.

Our vale of  indicates a shift away from a normal particle size distribution. This is also reflected on the shape of our histogram, a negatively skewed distribution. However one must remember that a large number of samples is ideally needed. Discussion: From looking at graph 1, it can be seen that a large number of particles are within the size range 250-350? m, but the majority of particles exist are large than this. According to a definition of particle size grades, particles of this size are classified as corse powders (? 300? m) The histogram has a typical left-shifted distribution.

This is a negative distribution, it shows that the majority of particles are in the lower size range. This is turn tells us that the granules contain more fine particles, than course particles for example. Graph 1 also shows us that there is quite a wide variation in the different particle sizes that would be present in the granules. Having different sized particles in a powder, will have an effect on its flow and packing properties. Different amounts of powder will be compressed into each table, possibly causing irregularities in the dose reaching the patient.

In an ideal tablet formulation, the distribution would be normal and uniform. Therefore there would be more regularity in the size of particles in the tablet. Graph two represents the different particle sizes present in our powder. If we read across at 50%, we see the two lines representing oversized and undersized particles intercept. Reading off this value on the x-axis tells us that our mean particle size is 500 m. This graph again shows a very large amount of particle size variation occurring.

Ideally we would like a uniform, continuous particle size, which is normally distributed, because have particles of the same size makes mixing easier and improves the flow and packing properties of powders. When particles of a range of different sizes, the volume of powder compressed into a tablet is not as controlled/ accurate as it would be if they were all the same size. This means may lead to varying dose from tablet to tablet. Error did occur during our manufacturing process, as can be seen from table 1, the amount of magnesium state that was used in preparation of granules using Ac-di-sol (2%) was much higher than other groups.

This value should have been 3. 568g. The results of this practicle are not affected, but the results of the next practicle are likely to be affected as magnesium stearate is very hydrophobic drugs release will be affected. Experimental errors are likely to have occurred. Especially as four different groups were working individually. Variation between the turning and mixing techniques by different groups are probable. Loss of material may also have occurred between transfers (from beakers into mixers and through sieves), such that we do not end up with the amounts that had been accurately measured.

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