Powders (BP103T) » PHARMACAREERS

Introduction

In pharmaceutics, a powder is defined as a dry, solid substance composed of finely divided drugs, with or without excipients, intended for internal or external use. It is a solid substance in a finely divided state. Powders represent one of the oldest and most conventional dosage forms. They were originally found to be a convenient mode of administering drugs derived from hard vegetables such as roots, barks, and woods. As synthetic drugs were introduced, powders were used to administer insoluble drugs. In this article we will classification of powders, advantages and disadvantages of powders.

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Classification of powders

Pharmaceutical powders can be broadly classified based on their use, particle size, and the way they are presented to the user.

Based on use: Powders can be for internal use (oral, nasal, or insufflation) or external use (topical application).
Based on particle size: Powders are classified into very coarse, coarse, moderately coarse, fine, and very fine based on their particle size.
Based on dispensing: Powders can be bulk powders (supplied in large quantities) or divided powders (individual doses packed separately).

In pharmaceutics, powders can be classified into simple powders and compound powders based on their composition.

Simple Powders

These are powders that contain only one or more pharmacologically active substances and may include inert excipients or diluents. They are created by blending and intimately mixing the powdered components. Simple powders can contain a single pharmacologically active substance or a mixture of active ingredients, creating a combination that serves a specific therapeutic purpose. For example, a powdered form of aspirin where aspirin is the sole active ingredient.

Compound Powders

These are powders that involve the combination of two or more ingredients, which may include active pharmaceutical ingredients (APIs), diluents, binders, disintegrants, and flavouring agents. These powders are more complex, requiring careful formulation to achieve specific therapeutic or manufacturing objectives. Compound powders can contain various components, each serving a distinct purpose in the formulation. In addition to active ingredients, they often include excipients for stability, palatability, or to achieve specific pharmaceutical characteristics. For example, a powder for oral reconstitution involves combining active ingredients and excipients designed for reconstitution into a liquid for oral administration.

Understanding the difference between simple and compound powders ensures precision in dosing, helping healthcare professionals and patients administer the correct amount of medication. The classification based on simplicity or complexity indicates whether the powder is a straightforward single-ingredient formulation or a more intricate combination designed for a specific therapeutic intent.

Pharmaceutical powders offer several advantages and disadvantages that can impact their use in various applications.

Advantages of Powders

Wide Choice of Ingredients: Powders allow for a wide choice of ingredients, and the dose can easily be achieved for patient administration.
Physicochemical Stability and Longer Shelf Life: Powders have better physicochemical stability and longer shelf life compared to liquid dosage forms.
Acceptability: Children and adults who have trouble swallowing tablets or capsules may find powders more acceptable.
Large Dose Administration: A large dose that cannot be administered in other forms can be administered as powder.
Rapid Dispersion: A rapid dispersion of drugs occurs in the stomach when given in powder forms rather than in compressed form.
Faster Dissolution Rate: Dissolution rate of oral powders containing water-soluble drugs is generally faster than tablets or capsules.
Ease of Swallowing: A powder can be dispersed in water or another liquid and more easily swallowed.
Flexibility in Compounding Solids: Powders offer a lot of flexibility in compounding solids.
Economic Manufacturing: Manufacturing of powder dosage form is economic. Hence, product cost is quite economic as compared to other dosage forms.

Disadvantages of Powders

Unpleasant Taste: Powders are not the dosage form of choice for drugs with unpleasant taste.
Stability Issues: Drugs that deteriorate rapidly with exposure to atmosphere or acidic pH should not be dispensed as powders.
Inconvenience: Powders are bulky and inconvenient to carry.
Not Suitable for Certain Drugs: Powders are not a suitable dosage form for the administration of drugs that are inactivated in the stomach or drugs which can cause damage to the stomach.

Preparation of powders

Official preparations are governed by standards set by pharmacopeias, which ensure their quality, safety, and efficacy. The preparation of the powders involves several steps.

Pulverization: The powder is created by grinding each ingredient into fine particles.
Levigation: In this procedure, a solvent is used to turn the dry powder into a paste.
Spatulation: This technique involves blending a small amount of powders by scrubbing a spatula over a small piece of paper or an ointment tile.
Tumbling: This method is used to mix powders.
Sifter Mixing: This method is used to mix powders and ensure uniform distribution of ingredients.

Dusting powders

Dusting powders are pharmaceutical formulations in powder form that are designed for external application, typically to the skin. They are finely divided, dry substances intended for topical use. The composition of dusting powders often includes active and inactive ingredients. The active ingredient could be a therapeutic agent, such as an antifungal or antibacterial substance. The inactive components often include talc, starch, zinc oxide, or other inert powders that contribute to the powder’s texture and application properties

These powders serve various purposes, which includes,

Relieving irritation
Absorbing moisture
Preventing friction
Treating certain skin conditions

Dusting powders generally fall into two categories.

Surgical Dusting Powders: These are used mainly in body cavities and on burns and umbilical cords of infants as a result of major wounds.
Medical Dusting Powders: These are used on superficial skin conditions.

Effervescent Powders

These are pharmaceutical dosage forms that contain a combination of active and inactive ingredients that effervesce when mixed with water, producing a fizzy and pleasant-tasting solution. The active ingredient in the powder can be a drug or a combination of drugs, and the inactive ingredients usually include a mixture of organic acids and carbonates. When the effervescent powder is dissolved in water, the acid and carbonate react to form carbon dioxide gas, causing the solution to fizz and bubble. This effervescence also increases the surface area of the drug, leading to faster dissolution and absorption in the body.

Efflorescent Powders

These are crystallized powders containing water of hydration or crystallization. When exposed to a low-humidity environment, this water can be liberated either through manipulation or when exposed to manipulation. This process is known as efflorescence.

Hygroscopic Powders

These powders have the property of absorbing moisture from the surrounding environment. When exposed to air, these powders can attract and retain water molecules, causing them to become damp or even dissolve. The absorption of moisture can lead to changes in the physical and chemical properties of the powder, such as altered particle size, texture, and stability.

Eutectic mixtures

Eutectic mixtures in pharmaceutical powders are two-component systems, where components are completely miscible in liquid state but immiscible in solid state. They exist as solid dispersions at a specific ratio, known as the eutectic point, which represents the lowest melting point for any mixture of the components. These mixtures can occur when two or more drug substances are combined in specific ratios. In pharmaceuticals, eutectic mixtures can impact drug formulation, stability, and bioavailability. They are innovative strategies with enhanced solubility, dissolution, and potential therapeutic efficacy. Understanding eutectic mixtures is crucial for drug development and delivery.

Geometric dilutions

Geometric dilution is a technique used in pharmaceutical compounding to ensure uniform distribution of potent or active ingredients in a powder mixture.
It involves adding equal proportions of ingredients gradually, starting with the smallest quantity, and thoroughly mixing them until a homogenous blend is achieved.
This method is particularly important when working with small quantities of potent drugs or active ingredients to achieve accurate and consistent dosages in the final product.
Geometric dilution promotes accuracy in dosing by evenly distributing small quantities of potent substances throughout a larger mixture.
It helps achieve uniformity in the final product, minimizing the risk of hotspots or areas with higher concentrations.

Summary

Pharmaceutical powders are dry, solid substances composed of finely divided drugs, with or without excipients, intended for internal or external use. They can be classified based on use (internal or external), particle size (very coarse to very fine), and dispensing (bulk or divided powders). Official preparations of pharmaceutical powders, recognized in pharmacopeias, include simple powders (one ingredient) and compound powders (mixture of substances). Each is prepared by reducing the ingredients to a fine powder, weighing properly, and packaging separately. These powders offer flexibility, stability, and ease of administration.