Pharmaceutics Lecture 1 - 3 PDF

Pharmaceutics -3 LECTU RE 1 1 DR/ OMNIA SARHAN  Powders DR/ OMNIA SARHAN 2  Powders The term "powder" describes a formulation in which a drug powder has mixed with other powdered excipients (f lavoring, coloring and sweetening a...

Pharmaceutics -3 LECTU RE 1 1 DR/ OMNIA SARHAN  Powders DR/ OMNIA SARHAN 2  Powders The term "powder" describes a formulation in which a drug powder has mixed with other powdered excipients (f lavoring, coloring and sweetening agents) to produce the final product. Pharmaceutical formulas: 1- Bulk powder or granules intended for internal use, 2- Divided powder or granules for internal use, 3- Dusting powders for external use, 4- Insufflations for administration to ear, nose, or throat, 5- Antibiotic syrups to be reconstituted before use, 6-Powders for reconstitution into injection or dry powder inhalations DR/ OMNIA SARHAN 3  Properties of Powders 1- Porosity Bulk volume (Vbulk); The total volume occupied by the powder True volume (V); The volume occupied by the powder minus the void volume (volume of space) Vbulk = true volume + volume of spaces between particles (Vv) Vv = bulk volume (Vbulk) – True volume (V) DR/ OMNIA SARHAN 4  Properties of Powders b- Densities of particles ( weight per unit volume, W/V) Three types of densities: a- Bulk density (B ) or apparent density ( a ) It is a characteristic of a powder rather than individual particles and determined from the bulk volume and the weight of a dry powder W bulk = -------- Kg m-1 Vbulk Bulk density of the powder is always less than true density, and so, the powder has single true density and many different bulk densities depends on the way in which the particles are packed and the bed porosity. Bulk density  true density Bulk density = k x true density Bulk density (bulk ) Packing fraction (K) = ------------------- True density ( ) DR/ OMNIA SARHAN 5  Properties of Powders b- Densities of particles ( weight per unit volume, W/V) b- True density of the material itself, is exclusive of the voids and intra-particle pores larger than molecular or atomic dimensions. c- Granular density as determined by the displacement of mercury, which does not penetrate at ordinary pressures into pores smaller than about 10 μm When a solid is nonporous, true and granular density are identical c- Bulkiness= Specific bulk volume = reciprocal of bulk density * It is an important consideration in the packaging of powders ** Bulkiness increases with a decrease in particle size (light powder). *In mixture of materials of different sizes, the smaller particles sift between the larger ones and tend to reduce bulkiness. DR/ OMNIA SARHAN 6  Mixing of Powders Three mechanisms by which powder mixing occurs: a- Convective mixing arises when there is transfer of relatively large amount of particles from one part of the powder bed to another, as might occur when a mixer blade moves through the mix. This type of mixing contributes mainly to the macroscopic mixing of powder mixtures and tends to produce a large degree of mixing fairly quickly and needs extended time to achieve random mix. b- Shear mixing occurs when a 'layer' of material moves or flows over another 'layer'. c- Diffusion mixing, in which true random mix and movement of individual particles through the air space or void between them. DR/ OMNIA SARHAN 7  Factors affecting the f low properties of powders a- Particle size *Relatively small particles (less than 10 μm) flow through an orifice (cohesive forces between particles = magnitude of gravitational forces) *As the particle size increase gravitational forces (A maximum f low rate is reached after which the f low decreases as the size of the particle approach that of the orifice. (large particles clogging orifices). *If a powder contains a reasonable amount of small particles: the powder’s flow properties improved by (1) removing the “fines” or (2) adsorbing them onto the larger particles (granules) DR/ OMNIA SARHAN 8  Factors affecting the f low properties of powders b- Porosity increas of voids leading to increases bulk volume and decrease density, that decreases flow of powders. c- Moisture: Poor f low may result from the presence of moisture. Drying the particles will reduce the cohesiveness and improve the flow properties. d- Density: Low density= high internal porosity= decrease flow= increase bulkiness e- Shape and Surface Texture Elongated or flat particles tend to pack, albeit loosely, to give powders with a high porosity= low density. Particles with a high density and a low internal porosity tend to possess free-flowing properties. In general; good f low properties can be achieved by optimizing particle size, high density, low porosity, spherical shape, no roughness and decrease the moisture contents DR/ OMNIA SARHAN 9  Pharmaceutical preparations of powders a- Bulk powders The mixed ingredients are packed into a suitable bulk container, such as a wide-mouthed glass jar. Because of the disadvantages of this type of preparation the constituents are usually relatively non- toxic medicaments with a large dose. b- Divided powders Divided powders are similar formulations to bulk powders but individual doses are separately wrapped in packaging materials of foil and plastic laminates. All powders and granules should be stored in a dry place to prevent deterioration due to increase of moisture. c- Bulk granules One disadvantage of bulk powders is that, because of particle size differences, the ingredients may segregate, either on storage in the f inal container or in the hoppers of packaging machines. If this happens the product will be non-uniform and the patient will not receive the same dose of the ingredients on each occasion. This can be prevented by granulating the mixed powders. DR/ OMNIA SARHAN 10  Pharmaceutical preparations of powders d- Divided granules These are granulated products in which, one dose is individually wrapped. Effervescent granules can be formulated and presented in this manner. e- Dusting powders Dusting powders contain ingredients used for therapeutic, prophylactic or lubricant purposes and are intended for external use. Only sterile dusting powders should be applied to open wounds. Such preparations should be prepared using materials and methods designed to ensure sterility and to avoid the introduction of contaminants and the growth of microorganisms. f- Dry-powder inhalers The use of dry-powder systems for pulmonary drug delivery is now extensive. This dosage form has developed m into one of the most effective methods of delivering active ingredients to the lung for the treatment of asthma and chronic obstructive pulmonary disease. g- Oral antibiotic syrups h- Powders for injection DR/ OMNIA SARHAN 11  Pharmaceutical preparations of powders i- Insufflations They are medicated powders which are blown into regions such as the ear, nose and throat using an insuf flator. The use of traditional insuf flations declined because they were not very acceptable, and no uniform dose was obtained. To enhance convenience and ensure that a uniform dose is delivered on each occasion, devices have been developed to replace the traditional insuf flator. Suf ficient drug for one dose may be presented in a hard gelatin capsule diluted with an inert, soluble diluent such as lactose. The capsule is placed in the body of the insuf flator and is broken and the drug is inhaled by the patient as a fine powder. DR/ OMNIA SARHAN 12 DR/ OMNIA SARHAN 13