Classification of Powders

Bulk Powders

Bulk powders are nonpotent and can be dosed with acceptable accuracy and safety using measuring devices such as the teaspoon, cup, or insufflator. This practically limits the use of orally administered bulk powders to antacids, dietary supplements, laxatives, and a few analgesics. Many bulk powders are used topically.

Dusting Powders

Dusting powders are fine medicinal (bulk) powders intended to be dusted on the skin by means of sifter-top containers. A single medicinal agent may be used as a dusting powder; however, a base is frequently used to apply a medicinal agent and to protect the skin from irritation and friction. Bentonite, kaolin, kieselguhr, magnesium carbonate, starch, and talc are used as inert bases for dusting powders. Powder bases absorb secretions and exert a drying effect, which relieves congestion and imparts a cooling sensation. All extemporaneous dusting powders should be passed through a 100-200 mesh sieve to ensure that they are grit free and will not further mechanically irritate traumatized areas.

Douche Powders

Douche powders are used to prepare solutions that cleanse the vagina. Most douche powders are used for their hygienic effects, but a few contain antibiotics.

Douche powders are prescribed as a matter of convenience for the patient, since a powder is more portable than a bulky solution. The formula is developed so that a teaspoonful or tablespoonful of powder dissolved in a specified volume of water provides the desired concentration. The pH usually ranges from 3.5 to 5 when the solution is prepared. Feminine bulb syringes or fountain syringes are used for vaginal irrigation. Since many of the ingredients are volatile (e.g., menthol, thymol, and volatile oils), douche powders should be packaged in glass jars with a wide mouth. Some commercial douche powders are available in metal foil packets, which contain the proper amount of powder for a single douche. Many douches are also available as prepared unit of use solutions in disposable applicators.

Insufflations

Insufflations are extremely fine powders to be introduced into body cavities. To administer an insufflation, the powder is placed in the insufflator, and when the bulb is squeezed, the air current carries the fine particles through the nozzle to the region for which the medication is intended. All extemporaneously compounded insufflations must be passed through a 100 mesh sieve. Pressurized packages provide an elegant approach to the administration of insufflations.

Powder Sprays

In contrast to dusting powders, powders dispensed under pressure will deliver targeted and uniform application at the desired site. Also, in an aerosol container medicated powders may be maintained in a sterile condition. The powder particles must be a definite size range to prevent clogging of the valve orifice and to provide uniformity of application. In general, powders that are to be packaged as powder sprays must not contain particles greater than 50 microns if they are to be sprayed successfully.