Powders: Advantages and limitations as dosage form, powders as dosage form and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

Powders: Advantages and limitations as dosage form, powders as dosage form and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

The term “powder” has more than one connotation in pharmacy. It may be used to describe the physical form of a material, that is, a dry substance composed of finely divided particles. Or, it may be used to describe a type of pharmaceutical preparation, that is, a medicated powder intended for internal (i.e., oral powder) or external (i.e., topical powder) use. A powder is defined as a dosage form composed of a solid or mixture of solids reduced to a finely divided state and intended for internal or external use.

Advantages of powders:

  1. Unlike a standardized capsule or tablet powders enable a primary care provider to easily alter the quantity of medication for each dose.
  2. Powders can also aid in clinical studies of drug preparations because the dose can be so readily adjusted.
  3. Doses can be individually weighed and placed in powder papers, envelopes, or small vials/bottles.
  4. Infants and young children who cannot swallow tablets or capsules will accept powders that can be mixed with a formula or sprinkled in applesauce or some other appropriate food.
  5. If a drug is too bulky to be prepared as a capsule or tablet, it may be suitable for a powder dosage form.
  6. Powders provide a rapid onset of action because they are readily dispersed, have a large surface area, and usually require only dissolution, not disintegration, before.

Limitations of powders:

  1. Powders are not the dosage form of choice for drugs with unpleasant taste. This is because masking of unpleasant tastes may be a problem with this type of preparation.
  2. Drugs that deteriorate rapidly with exposure to atmosphere or acidic pH should not be dispensed as powders. For example, ferrous iron salts are easily oxidized and should not be administered as powders.
  3. Powders are bulky and inconvenient to carry.
  4. 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.
  5. Dispensing potent drugs requiring low doses as powders (e.g., bulk powders) may not be appropriate. This is because individual doses are usually extracted from the bulk using a 5 ml spoon, which is subject to variation in spoon fill (e.g., level or heaped spoonfuls).
  6. Powders are not well suited for dispensing hygroscopic or deliquescent drugs.

Powders as dosage forms: There are a variety of powdered dosage forms commercially available, such as bulk powders, divided powders, dusting powders, insufflations, and
dry powder inhalers.

Bulk Powders – Bulk powders refer to a mixture of all the materials, packed into a properly designed bulk container, such as a glass or plastic bottle. The major problem of bulk powders is the inaccuracy of dose. Drugs present in the bulk powders are better suited, if they have a wider therapeutic window, a large dose, and pleasant taste. Effervescent powders are a special type of bulk powder. In addition to drugs and other excipients, effervescent powders contain an effervescent couple (i.e., sodium bicarbonate and citric acid), which react and effervesce when in contact with water. The effervescent dosage form is helpful to cover the unpleasant taste of salty or bitter drugs. For drugs that are not stable when dissolved in an aqueous pharmaceutically acceptable diluent, such as water, sterile liquid can be added to sterile powders contained in ampoules to form the solution just prior to use.

Divided Powders – Divided powders are bulk powders in which the individual dose has been packed separately. The traditional packing of divided powders is in wrapped paper. However, many problems are involved in this, when the materials are volatile, hygroscopic, or deliquescent. Therefore modern packing methods are developed to replace the use of paper wrapping, such as foil and plastic laminates. Effervescent powders can be packed into individual doses, because the plastic laminates can protect powders from moisture adsorption. The powdered product should always be protected from exposure to moisture.

Dusting Powders – Dusting powders are designed for external use, acting as a therapeutic, lubricant, or protective. Dusting powders act locally and are intended to have no systemic absorption. Dusting powders are usually dispensed in a relatively fine state (micronized) to increase efficacy and decrease irritation. Dusting powders can be packed in glass or metal containers with a perforated lid to allow the powders to be dusted to the effective area. Excellent flowability is necessary for this dosage form. Pressure aerosols are another delivery form that can generate dusting powders. They are more expensive than the sifter-container, but several advantages are realized, such as convenient operation, and protection from moisture, air, and contamination.

Insufflations and Dry Powder Inhalers (DPI) – Insufflations are fine powders of drugs, which are dosed into the nose, ear, or throat by the use of an insufflator. The use of conventional insufflators has declined, due to poor patient compliance and dose non-uniformity. Some newly developed devices have been introduced to replace the traditional insufflators. In these devices, drugs are usually dispensed with a carrier excipient, such as lactose, and placed into a hard gelatin capsule. When the device is operated, the capsule is broken and the fine powder is inhaled into the patient’s body.

Pulmonary delivery of dry powder formulations is a popular approach to deliver the drug to the lung locally, for the treatment of such diseases as asthma and chronic obstructive pulmonary disease (COPD).

Multiple choice questions:

1.A dry substance composed of finely divided particles is known as

a)tablet

b)capsule

c)powders

d)all of these

2.A medicated powder intended for internal use is

a)oral powder

b)topical powder

c)both of these

d)none of these

3.A medicated powder intended for external use is

a)oral powder

b)topical powder

c)both of these

d)none of these

4.Which of the following are advantages of powders?

a)Doses can be individually weighed and placed in powder papers, envelopes, or small vials/bottles

b)Powders are bulky and inconvenient to carry

c)Powders are not well suited for dispensing hygroscopic or deliquescent drugs

d)all of these

5.Infants and young children who cannot swallow tablets or capsules will accept ____ that can be mixed with a formula or sprinkled in applesauce or some other appropriate food.

a)pills

b)lozenges

c)powders

d)all of these

6.If a drug is too bulky to be prepared as a capsule or tablet, it may be suitable for a _____ dosage form.

a)parenteral

b)opthalmic

c)powders

d)suspensions

7.Powders provide a rapid onset of action because they

a)are readily dispersed

b)have a large surface area

c)usually require only dissolution not disintegration

d)all of these

8.Powders are not the dosage form of choice for drugs with unpleasant taste. This is because masking of unpleasant tastes may be a problem with this type of preparation.

a)true

b)false

9.Powders are not a suitable dosage form for the administration of drugs that

a)deteriorate rapidly with exposure to atmosphere or acidic pH

b)are inactivated in the stomach

c)can cause damage to the stomach

d)all of these

10.Powders are not well suited for dispensing 

a)hygroscopic

b)deliquescent drugs

c)both of these

d)none of these

11.A mixture of all the materials, packed into a properly designed bulk container, such as a glass or plastic bottle is known as

a)Bulk powders

b)Divided powders

c)Dusting powders

d)Insufflations

12.Drugs present in the bulk powders are better suited, if they have

a)wider therapeutic window

b)a large dose

c)pleasant taste

d)all of these

13.Bulk powders in which the individual dose has been packed separately is known as

a)Bulk powders

b)Divided powders

c)Dusting powders

d)Insufflations

14.Powders that are designed for external use, acting as a therapeutic, lubricant, or protective are known as

a)Bulk powders

b)Divided powders

c)Dusting powders

d)Insufflations

15.Insufflations are fine powders of drugs, which are dosed into

a)nose

b)ear

c)throat

d)all of these

Solutions:

  1. c)powders
  2. a)oral powder
  3. b)topical powder
  4. a)Doses can be individually weighed and placed in powder papers, envelopes, or small vials/bottles
  5. c)powders
  6. c)powders
  7. d)all of these
  8. a)true
  9. d)all of these
  10. c)both of these
  11. a)Bulk powders
  12. d)all of these
  13. b)Divided powders
  14. c)Dusting powders
  15. d)all of these

References:

  1. Remington Essential of Pharmaceutics, 1st edition 2013, page no. 443.
  2. Ansels Pharmaceutical Dosage Forms and Drug Delivery systems, 10th edition, page no. 214-215.

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