POWDERS AND GRANULES: A TEACHER’S COMPREHENSIVE GUIDE
Welcome, future pharmaceutical scientists and manufacturing professionals!
Powder is defined as a uniform and dry mixture of one or more finely divided particulate material. In the current scenario, powder is rarely used as a dosage form but it is being employed as the starting material in the manufacture of many dosage forms. Powder is one of the oldest dosage forms which are meant for internal as well as external application. They are known to impart adequate elasticity, rapid therapeutic effect and ease in drug administration.
Granules are a type of dosage form which are composed of dried aggregates of powder solid particles containing one or more APIs (active pharmaceutical ingredients). The normal size range of granules is 4–12 sieves. Different sizes of granules can be formed according to the intended application.
As a pharmacy educator with years of experience teaching pharmaceutics, I have observed that students often find powders and granules challenging due to their diverse applications. Let me tell you: Powders and granules are the foundation of solid dosage form manufacturing—they are essential intermediates for tablets and capsules.
In this comprehensive guide, I will walk you through the fundamentals of powders and granules—their types, preparation methods, advantages, and disadvantages. I will cover insufflations, dusting powders, effervescent powders, effervescent granules, and their preparation methods. By the end of this article, you will have a thorough understanding of these essential dosage forms. Let us begin!
Dpharmguru’s exam insights:
Powders and granules are frequently tested in pharmacy exams. Remember: Powders are divided into internal use (divided and bulk) and external use (insufflations, dusting powders). Effervescent powders contain sodium bicarbonate and acids. Granules have better flowability than powders. Effervescent granules are prepared by wet, dry, fusion, or non-aqueous methods. These are classic exam questions!
5.11. POWDERS
5.11.1. Types of Powders
Depending on their use, powders are divided into:
A) Internal Use
- Divided Powders: Simple powders and Compound powders
- Bulk Powders: Effervescent powders, Antacid powders, Laxative powders
B) External Use
- Insufflations
- Dusting powders
- Snuffs
- Douche powders
- Dental powders
5.11.1.1. Insufflations
- Inhalational type of dusting powders intended to be applied into the nose, throat, ear, and vagina
- Administered with the help of insufflators
- Extremely fine powders meant for introduction into body cavities
- When the bulb is squeezed, air flow carries fine particles through the nozzle to the affected area
5.11.1.2. Dusting Powders
- Applied on the skin by dusting through sifter-top
- Fine powders possessing medicinal properties
- Inert bases used: bentonite, kaolin, kieselguhr, starch, magnesium carbonate, talc
- Base helps in preventing skin irritation and friction
- Bases absorb secretions and bring about drying effect
- No systemic action as they are not absorbed in blood circulation
- Medicated dusting powders: applied to open wounds or whole skin
- Non-medicated dusting powders: not to be used on broken skin
Preparation of Dusting Powders:
- Trituration
- Pulverisation
- Levigation
Sterilisation: Talc and kaolin sterilised by dry heat method (160°C for 2 hours) prior to use.
Example: Zinc oxide (20gm), Salicylic acid (0.2gm), Starch (78gm) – mixed and passed through No. 80 sieve.
5.11.1.3. Effervescent Powders
- Produce effervescence in the presence of water as they release carbon dioxide
- Comprised of ingredients like sodium bicarbonate, citric acid, tartaric acid
- Quantity of acids is slightly more than required for neutralising the bicarbonate
- Provides an agreeable sour taste
Ingredients: Sodium bicarbonate (dry powder) 477gm, Tartaric acid (dry powder) 252gm, Citric acid crystals 162gm
Preparation Methods:
- Heat Method: Mixed with 15–20% of acid ingredients, heated at 100°C on water bath
- Wet Method: Citric acid moistened and mixed with sodium bicarbonate; granulator used
Example Formula: Sodium bicarbonate (20.4gm), Sugar (60.0gm), Tartaric acid (10.8gm), Citric acid (7.2gm), Iron and ammonium citrate (2.15gm)
5.11.2. Advantages of Powders
- Oldest dosage form, used both internally and externally
- More stable than liquid dosage forms
- Specific amount can be prescribed depending on patient’s need
- Much less incompatibility compared to liquid dosage forms
- Easily dissolve in body fluids due to greater surface area
- Portable
5.11.3. Disadvantages of Powders
- Drugs with bitter, nauseous, and unpleasant taste cannot be dispensed
- Deliquescent and hygroscopic drugs cannot be dispensed
- Drugs affected by atmospheric conditions are inappropriate
- Time-consuming preparation process
5.12. GRANULES
5.12.1. Effervescent Granules
- Uncoated granules containing acid substances and carbonates or hydrogen carbonates
- React rapidly in the presence of water for releasing carbon dioxide
- Dissolved or dispersed in water before administration
- Contains sodium bicarbonate and either citric acid, tartaric acid, or sodium biphosphate
- Effervescence helps to coat salty or bitter taste medications
- Dispensed in tightly closed glass containers to protect from humidity
Preparation of Effervescent Granules
- Wet Method: Oldest method; ingredients powdered and passed through sieve; wet massing with granulating agent; passed through mesh screen; dried in hot air oven
- Hot Melt Extrusion Technique: Ingredients heated to 50–80°C until molten; cooled; passed through sieve No. 8 or 10; dried at not more than 60°C
- Dry Method (Fusion Method): Most important method for effervescent granules; powders heated using water of crystallisation as binding agent; passed through sieve; dried in hot air oven
- Non-Aqueous Method: Ethanol added dropwise until mould obtained; passed through sieve No. 10; dried at 55°C for 12 hours
5.12.2. Advantages of Granules
- Good flowability than powders
- Remove or control the dust
- Increase compressibility
- Physical and chemical stability is much more than powders (smaller surface area)
- Used in preparing solutions as they can be wetted easily
- Particle size uniformity leading to content uniformity
5.12.3. Disadvantages of Granules
- Difficult to dispense in case of large doses
- Difficult to dispense due to bitter and nauseous taste
- Relatively expensive
- Cannot be given to children due to risk of carbon dioxide toxicity
- Undergo degradation if not packaged properly
- Prolonged shelf life as compared to other dosage forms
Dpharmguru’s exam insights:
Granules are frequently tested. Remember: Granules have better flowability than powders. Effervescent granules contain sodium bicarbonate and acids. The fusion method uses water of crystallisation as binding agent. Granules are used as intermediates for tablets and capsules. These are classic exam questions!
COMPARISON: POWDERS VS GRANULES
| Feature | Powders | Granules |
|---|---|---|
| Flowability | Poor | Good |
| Dust Formation | High | Low |
| Compressibility | Low | High |
| Stability | Less (larger surface area) | More (smaller surface area) |
| Wettability | Difficult | Easy |
| Particle Size Uniformity | Variable | Uniform |
| Cost | Less expensive | More expensive |
FREQUENTLY ASKED QUESTIONS (FAQs)
1. What is the difference between powders and granules?
Powders are fine, dry particles with poor flowability and high dust formation. Granules are dried aggregates of powder particles with good flowability, low dust, and better compressibility.
2. What are effervescent powders?
Effervescent powders produce effervescence in the presence of water as they release carbon dioxide. They contain sodium bicarbonate and organic or inorganic acids such as citric acid or tartaric acid.
3. What are insufflations?
Insufflations are inhalational type of dusting powders intended to be applied into the nose, throat, ear, and vagina with the help of insufflators. They are extremely fine powders meant for introduction into body cavities.
4. What are the methods of preparing effervescent granules?
The methods include Wet Method, Hot Melt Extrusion Technique, Dry Method (Fusion Method), and Non-Aqueous Method. The fusion method uses water of crystallisation from citric acid as binding agent.
5. What are the advantages of granules over powders?
Granules have better flowability, less dust, higher compressibility, greater stability, easy wettability, and uniform particle size compared to powders.
6. Why are dusting powders sterilised?
Dusting powders are sterilised by dry heat method (160°C for 2 hours) because talc and kaolin usually get contaminated with pathogenic bacteria.
SUMMARY
Powders and granules are fundamental dosage forms in pharmaceutical manufacturing. This guide covered:
- Powders: Uniform dry mixtures; types include insufflations, dusting powders, and effervescent powders
- Powder Advantages: Stable, portable, less incompatibility, rapid dissolution
- Powder Disadvantages: Not suitable for bitter, hygroscopic, or deliquescent drugs; time-consuming
- Granules: Dried aggregates of powder particles; normal size range 4–12 sieves
- Effervescent Granules: Contain sodium bicarbonate and acids; prepared by wet, hot melt extrusion, dry, or non-aqueous methods
- Granule Advantages: Better flowability, less dust, higher compressibility, greater stability
As I always tell my students: “Powders and granules are the building blocks of solid dosage forms—mastering them is essential for successful tablet and capsule manufacturing.”
REFERENCES AND FURTHER READING
- Pharmacy Council of India (PCI). (2022). Pharmaceutics Syllabus. New Delhi: PCI.
- Aulton, M. E., & Taylor, K. M. G. (2018). Aulton’s Pharmaceutics: The Design and Manufacture of Medicines (5th ed.). Elsevier.
- Allen, L. V., & Ansel, H. C. (2014). Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems (10th ed.). Wolters Kluwer.
- Lachman, L., Lieberman, H. A., & Kanig, J. L. (2018). The Theory and Practice of Industrial Pharmacy (4th ed.). CBS Publishers.
- Subrahmanyam, C. V. S. (2019). A Textbook of Pharmaceutics. Vallabh Prakashan.
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for medical concerns. Pharmaceutical regulations and guidelines may vary by region—always refer to your local regulatory authorities for specific requirements.
written by:
Dr. N. Sujith Kumar
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