Mild dosage forms accompany a person from birth. The first meeting with them occurs even in infancy, when the mother smears the delicate skin of the child with baby cream. From this moment we become inseparable with a variety of ointments, gels and pastes.
Soft dosage forms, the classification and characteristics of which will be presented below, are used in dermatology, ophthalmology, surgery, gynecology and other areas of medicine. They are very popular among doctors of various specialties because of the ease of application, ease of preparation and long shelf life. The cosmetic industry is also poorly presented without all kinds of creams and ointments.
Ointments
It is best to start a story about soft dosage forms with ointments, since this association first comes to mind for an average citizen. Ointments are medicines used for external use that contain less than a quarter of the dry matter of the total amount of the drug. They are obtained by mixing medicinal substances with bases with a characteristic consistency.
Soft dosage forms on modern ointment bases (petrolatum, lanolin, pork fat, wax, oil paraffin, etc.) are produced both on an industrial scale and in the form of piece, unique recipes. When choosing the basis, the nature of the application, the therapeutic effect that must be achieved, as well as the ability of the material to dissolve the drug, are taken into account. So, for example, petroleum jelly only covers the skin, and lanolin is also absorbed into it.
Since ointments are used mainly for the treatment of dermatological diseases, then in their manufacture they focus on local action. The doctor may prescribe these drugs in an abbreviated or expanded form. The abbreviated form is used for finished drugs, and also when the ointment contains only one medicinal component and is mixed with petroleum jelly.
Creams
It is impossible to imagine soft dosage forms without creams. A cream is a dispersed system that contains two or more components. Such a system, while observing the necessary thermal characteristics, retains a characteristic - less viscous than cream - consistency.
The oil-in-water emulsion can contain up to 90% water and is designed to moisturize the skin. If the composition “water in oil” is used, then the components are taken in approximately equal proportions. This cream is necessary to soften and nourish the skin. The composition may include fats, waxes, mineral oils, silicones, alcohols and other substances.
The mixture for the manufacture of cream is selected in accordance with its intended use. It can have a warming or, conversely, cooling effect, relieve inflammation or contribute to the healing of a skin defect. Abbreviations are used for prescribing cream, and the basis and amount of water are never indicated, leaving this issue to the discretion of the pharmacist.
Gels
A gel is a mild dosage form that can be used not only externally, but also subcutaneously and even orally. It has a jelly-like consistency and, as a rule, is colorless or transparent. At the moment, this is the most common and popular form of release of medicinal substances.
There are hydrophilic and hydrophobic gels. They are obtained by combining water, polymer powder (usually acid) and a neutralizer (soda, ammonia, carbonate, etc.). After thorough mixing, the mixture thickens and a gel is obtained. The viscosity of the resulting substance is measured in poises or centipoises.
The variety and popularity of gels is explained by the fact that they are close in their characteristics to the hydrogen index to the skin, they are quick and easy to prepare, they are evenly distributed and do not clog pores. In addition, almost any drug substance can be added to the gel.
Pastes
Pasta is one of the varieties of ointment, which has more powdered substances (about 65%) and, as a result, a denser consistency. Due to this property, it stays on the skin for a long time and absorbs excess fluid in itself, which makes it indispensable for achieving an anti-inflammatory effect.
In most cases, in order to achieve the desired consistency of the paste, neutral substances, such as zinc powder, talc or starch, are added to it. Recipes for pastes are written out only in expanded form. An exception is made only for finished drugs manufactured in the factory. As a rule, after indicating the main ingredients and the base in the right proportions, they write: "Mix to make a paste." Official pastes are written out, indicating the trade name.
Liniment
When listing soft dosage forms in pharmacology, we also mean liquid ointments or liniments. In fact, these are thick or jelly-like liquids that melt at a temperature of 37 degrees, so they must be rubbed into the skin on the damaged area. This type of medicine can include any creams, ointments, gels or pastes that have characteristic features.
The shelf life of liniment is short, so they are most often prepared directly in the pharmacy. For cooking use a liquid base (sunflower, olive, linseed or liquid paraffin). After all the ingredients and their proportions are indicated, the recipe must indicate: “Mix to make liniment.” This is important, as the ointment, paste and liniment may have the same composition.
Suppositories
Soft dosage forms in pharmacy production are also represented by candles. They, like liniment, melt at body temperature, but at the same time under normal conditions are able to maintain a solid form. Cocoa butter or alloys made of paraffin and other inert substances are used as the basis for this type of medicine.
There are rectal and vaginal suppositories. The first, as a rule, have a bullet-shaped or cone-shaped and weigh an average of up to three grams. Vaginal suppositories can be in the form of balls, ellipses or have a flat shape (pessaries). They also weigh three to four grams.
Rectal suppositories are used both for the treatment of local processes in the rectum, and for the general effect on the body, because good blood supply to this part of the digestive canal allows substances to be rapidly absorbed from the mucous membrane and have a systemic effect.
When extracting suppositories of simple composition, the active substance and its amount are indicated. In the case of the appointment of candles with a complex composition, only the commercial name and the number of units of the medicine are written.
Gelatin capsules
If a pediatrician or gerontologist needs to prescribe medication in a soft dosage form to the patient, the prescription begins with the word: “capsules”. The shell in such medicines consists of edible gelatin. It is necessary for the active substance to get unharmed to the place of use. For example, not all drugs tolerate the acidic environment of the stomach well, therefore, they must be protected from such an effect and at the same time the necessary properties must be preserved.
According to the method of application, capsules are:
They can have different contents: powders, granules, capsules, pellets, tablets, ointments, or even live bacteria.
Patches
Adhesives close the list of soft dosage forms. Recipes and their characteristics are quite simple. Patches are attached to the skin in order to have a local or general effect on the body. At a temperature of 20 degrees, this medicine is solid and is a mixture of rubber, fats, oils, antioxidants and the active substance.
Some patches do not carry a therapeutic load, but are used to fix the edges of the wound, tighten the skin in a certain direction (in traumatology, cosmetology, dermatology) or to hold bandages and bandages in place.
Since most medicinal plasters have official names and are produced in a factory way, when writing a prescription, an abbreviated form is used, indicating only the trade name and size.
Soap
Cosmetic and medical soaps are slightly different in composition. The latter is obtained after heating alkali and fat, while glycerin and other fatty acids are released from fats. In order to catalyze the reaction, sodium hydroxide or potassium is used.
When water is added, the soap begins to foam and mechanically cleanses the skin. If the composition contains sedatives or disinfectants, then in addition to the main effect, it relieves inflammation, dries rashes or disinfects.
The official medical soap is an odorless white powder that can dissolve in water or alcohol. Allocate another "green soap" - a translucent brown or greenish mass with a faint odor.