Before the advent of tablets, pills were the main dosage form for internal use. Currently, the share of pills in the formulation of pharmacies does not exceed 1-1.5%. However, the pills have not lost their value as a dosage form that allows for broad individualization when prescribing drugs. The main advantage of pills is that a wide variety of drugs can be combined in the pill mass, and often those that in another dosage form (for example, in solutions) may be incompatible.
Further, in the form of pills, it is possible to hide the unpleasant taste and smell of medicinal substances, especially if a shell is applied to the pills. The pills are very convenient to take: a pill that is round and slimy in the mouth is much easier to swallow than a tablet of equal weight. Pills are not inferior to tablets in terms of drug dosage accuracy and ease of storage. The slowness of action of medicinal substances in the form of pills, in comparison with other forms, should be evaluated and used as a prolonging property.
Recall that plasticity is the property of bodies to irreversibly change their shape under the influence of sufficiently large deforming forces, resisting deformation under the influence of small forces. As applied to the pill mass, plasticity should be understood as its ability to take the appropriate shape, that is, to roll out into a rod and then into balls. Simultaneously with plasticity, the pill mass should also have a definitely pronounced elasticity. If the pill mass does not possess this property, but shows some tendency to softening, then during storage, under the influence of relatively weak deforming forces, the spherical shape of the pills may change. On the other hand, if the pill mass becomes too elastic, then it is difficult to roll it into a rod and prepare round bodies of the correct shape. The ability of the pill mass to disintegrate in gastric (or intestinal) juice according to GPC refers to the ability of the pills rolled out of it to disintegrate in water or 0.5% hydrochloric acid solution at 37 ° C (with gentle shaking of the cone 1-2 times per second, avoiding shaking) within 1 hour. The specified properties of the pill mass are achieved by the appropriate selection of aids.
Herbal Viagra. Powders of licorice root, dandelion, wormwood, valerian root are always accompanied in pills with the extracts of the same name. Other plant powders, such as marshmallow powder, can also be added to the composition of the pill masses. All plant powders contain both soluble or water-swollen substances and insoluble solid particles of plant tissues. Therefore, they can be in the liquid and solid phases of the pill mass. The above applies equally to rosehip and wheat flour. Rosehip fruits (pulp) contain many pectin substances, which swell in the presence of water and bind the incoming ingredients well, resulting in a plastic and sufficiently elastic pill mass.
A high swelling capacity due to the presence of gluten in wheat flour and its high elasticity make it possible to prepare pills even from pill masses that are difficult to process.
Mineral powders (bentonite, white clay, aluminum hydroxide, aerosil). They differ in their ability to absorb liquids (water, oils). They act on the mass as drying agents, imparting greater hardness to the pills after drying. They are widely used in cases where the pills contain substances that are readily decomposed in the presence of organic substances.
It enters the mass as a solid phase. At body temperature, starch swells noticeably, so pills containing it disintegrate more easily. Starch is good to combine with glucose and sugar.
The effect of some excipients can be mixed. For example, flour contains highly hydrophilic gluten and at the same time slightly hydrophilic (at ordinary temperatures) starch. Obviously, the latter will act as a sealing substance and at the same time reduce the high elasticity of gluten. This applies equally to plant powders, since, along with substances capable of forming sticky and viscous solutions (pectins, mucus), they contain many insoluble and non-swelling particles (starch, particles of various tissues), which are typical plasticizers.
The choice of excipients for obtaining a good pill mass depends on the properties of the administered medicinal substances and their amounts. Let us explain this with a few examples.
Medicinal substances are insoluble or very slightly soluble in water or other solvent. Two options are possible here: a) medicinal substances are prescribed in very small quantities (for example, substances of list A). If these substances are mixed with a viscous liquid (for example, with a thick extract of licorice root), then due to the small amount of solid phase, the forming mass will not work.
To such a mass, it is imperative to add the optimal amount of powdery insoluble substances in order to give it the necessary plastic properties. Such substances can be vegetable powders (in the case of extracts), starch, flour; b) medicinal substances are prescribed in significant quantities. In this case, it is usually sufficient to add an optimal amount of a viscous adhesive liquid to obtain a plastic pellet mass. The more pronounced the hydrophobicity of the solid phase, the greater the sticking ability of a viscous liquid.
Medicinal substances are soluble in water, ethanol, glycerin. In this case, it is important to dissolve them in a minimum amount of water (ethanol, glycerin). Next, the resulting solution is mixed with a viscous liquid, which is then compacted by adding solids to a plastic state. In the event that a significant amount of the aqueous phase has to be introduced to dissolve medicinal substances, swellable hydrophilic substances are added to obtain a high-viscosity mass, which is then made plastic using swellable solids.
Medicinal substances are liquids that are not miscible with water. In this case, it is necessary to preliminarily emulsify them using the appropriateemulsifiers, followed by sealing of the emulsion body.
Thus, medicinal substances can be in pills in the form of a solution, suspension, emulsion. The pill mass should be considered as a plastic mass consisting of two phases: 1) a hydrophobic or low-hydrophilic solid phase; 2) hydrophilic gelatinous or highly viscous liquid phase. Medicinal substances can be in any of these phases together with excipients. The optimal quantitative ratio of these phases, as well as all the properties of the pill mass, are a complex function of the properties of medicinal and excipients. Therefore, even before the preparation of the pills, it is necessary to think over, and if necessary, check the properties and behavior of medicinal and auxiliary substances when they are combined in the pill mass.
Prescribing pills. When prescribing pills, prescriptions usually indicate only the amounts of drugs based on the total number of pills prescribed. At the same time, the amounts of excipients are not indicated (recipe 20.1) or indicated in a general formulation: quantum satis - how much is needed (recipe 20.2).
Recipes indicating the amounts of basic substances per pill are rare (recipe 20.3). The choice of aids (prescriptions 20.1-20.3) is left to the pharmacist, in the case of prescription 20.4 it is agreed by the doctor.