The classification of powders is as follows:

1. Aerosol powders: Medicated powders that are taken or administered by inhalation with the help of a dry powder inhaler are aerosol powders. The products delivered by this route are intended for the treatment of asthma or bronchial disorders. The particle diameters, which are delivered by this route, are in the range of 1–6 µm. These products also contain inert propellants and pharmaceutical diluents to protect the powder from humidity, to aid in flow property and for the metering uniformity.
2. Bulk powders: Medication in bulk powder forms is limited to non-potent substances. Examples of powders taken in the bulk forms are medicated topical anti-infectives such as polymyxin B sulfate, tolnaftate, etc., douche powders for vaginal use such as Massengill powder, reconstituted antacid preparation such as sodium bicarbonate, laxative such as psyllium, etc.
3. Divided powders: These are properly blended by using geometric dilution method and then based on the amount to be taken at a single time are divided as single dosing units. The divided powders are packed in small piece of paper folded to enclose the medication. Examples: Powdered laxatives, douche powder and analgesic powders.
4. Effervescent powders: These powders when mixed with water shows effervescence with the liberation of carbon-di-oxide. The effervescence also helps in masking the bitter taste of active ingredients. The usual content of these powders are sodium bicarbonate, organic or inorganic acids such as citric acid, tartaric acid, etc.
5. Explosive powders: Substances such as an oxidizing agent and reducing agent when triturated in a mortar and pestle there are chances of explosion, which may occur due to the heat generation and may lead to serious consequences. To handle such type of powders each ingredient should be separately triturated and lightly mixed without applying any pressure. Alternatively the powders can be individually triturated and can be separately packed and dispensed with suitable directions to the patient regarding its use.Some of the oxidizing and reducing agents are listed in Table 5.6. Table 5.6 List of Oxidizing and Reducing AgentsOxidizing AgentsReducing AgentsPotassium chlorateCharcoalPotassium dichromateSulfurPotassium nitrateSulfidesPotassium permanganateTannic acidSilver nitrate
6. Medicated powders for internal use: These powders are available to be used both internally and externally. Internally used powders are added in water or directly taken internally. Internal medicated powders can also be inhaled for both local such as analgesics and systemic use such as laxatives. Medicated powders taken systemically will have faster rate of dissolution and absorption when compared to any other SDFs. These powders are also available in reconstituted form.
7. Insufflations: These powders are usually applied with an applicator known as insufflators. Insufflations are finely divided powder form introduced into different body cavities such as nose, ear, vagina, tooth sockets, etc. When the insufflator is compressed, a current of air distributes the powder particles in a stream of gas through the nozzle into the delivery site. Uniform dose delivery may not be obtained by insufflations.
8. Dusting powders: Dusting powders are used externally for local application, not intended for systemic action. The desirable characteristics of dusting powders are non-irritability, homogeneity, free flow, good spreadability and covering capability, fine state of subdivision, and capacity to protect the skin from chafing and irritation caused by friction, moisture, and chemical irritants. The formulation usually contains substances such as kaolin, talc, zinc oxide, starch, and boric acid. These powders are micronized by passing through sieves #85 or 120. It should be preferably dispensed in sifter-top containers. Such containers provide the protection from air, moisture, and contamination as well as convenience of application. It should contain a label as “FOR EXTERNAL USE ONLY.” The categories of drugs dispensed are lubricants, protectives, adsorbents, antiseptics, antipruritics, astringents and antiperspirants. Dusting powders can be classified into the following two types:
   1. Medicated dusting powders: These are the bulk SDFs, which are intended to be applied on the intact skin for local action.
   2. Surgical dusting powders: These are the bulk SDF, which are intended to be applied into the deep layers of the skin. These preparations need to be sterile as it comes in contact with open wounds and deep layers of the skin.
9. Dentifrices: Dentifrices are bulk powders for external use to clean teeth. They mainly contain an abrasive agent such as precipitated calcium carbonate or hydrous dibasic calcium phosphate. It also contains a surfactant, mild soap or detergent and sweetening agents.
10. Douche powders: These powders are most commonly used for vaginal use and intended for the action of cleansing agents or used as an antiseptic. They may also be used for nasal or ophthalmic route. The main criteria for these preparations are to ensure complete mixing and to maintain the micronized particle size by passing through sieve #85.