Granules - Pharmaceutics - I B. Pharma 1st Semester



      List the advantages of granules

      Explain the methods for the preparation of effervescent granules


• Prepared by agglomeration of small particles.

• Generally irregular in shape, as opposed to spherical.

• Often in 4 to 12 mesh size, but size can vary greatly depending on the application.

• May be dispensed in bulk as a dosage form for oral administration, e.g. as antacid, dietary supplement etc.

• Widely used as an intermediate for making compressed tablets.

• Powders may also be granulated prior to filling into capsules.

Why granules?

• Flow better than powders (granulation is a size enlargement process) and have better compatibility than powders (binders)

• Advantage in making tablets or filling capsules (feeding of high-speed equipment)

• Less surface area per unit weight than powders

• More stable to atmospheric moisture/oxygen

• Less likely to cake in the container than powders.

• Granulation of a powder allows addition of flavouring agents and coloring agents

• Easily handled

• Attractive product.

• “Wet” granulation provides for the addition of liquid phase suited to dispersion of low dose drugs in solution to ensure content uniformity.

• Permits handling of powders without loss of blend quality (i.e., drug is locked in granules...a form of ordered mixing)

• When used as an intermediate for tablets or capsules, this feature is particularly important as a way to achieve content  uniformity for low dose drugs. 

• “Wet” granulation may improve drug dissolution (e.g. from a tablet) by enhancing wettability through hydrophilization.

• The hydrophilic binder, which covers particle surfaces and is intimately dispersed throughout the matrix of the granules, attracts water and can enhance the ability of hydrophobic, poorly soluble drugs to be wetted by dissolution fluids.

Examples of Granules as a Dosage Forms

• Reconstituted antibiotics

• Bulk laxatives, e.g. Senokot Granules [granules contain standardized senna concentrate]

• Bulk analgesics, e.g., effervescent granules such as BromoSeltzer

Granules - Preparation

• A suitable granulating agent is added to moisten the powders so as to make a coherent mass.

• These coherent mass will be passed through sieve no. 10 or 16 to make granules.

• Granules will be dried in a hot air oven at a temp not exceeding 60⁰C. 

• The dried granules are passed through sieve no. 20 or 24 and stored in a dry well closed wide mouthed bottles.

Effervescent granules

Effervescent Granulated Salts “Effervescent Salts”

• Effervescent granules contain medicinal substance usually in combination with sodium bicarbonate, citric acid and tartaric acid

• Carbon dioxide forms when granules are placed in water

• Carbonation helps mask the unpleasant taste of drugs

• Granular form (as opposed to power form)

– Dissolves more slowly and provides a more controlled reaction

• Specially prepared solid dosage form of medicament

• Meant for oral intake

• Contain a medicament mixed with citric acid, tartaric acid and sodium bicarbonate.

• Saccharin or sucrose may be added as a sweetening agent.

Ingredients used

1. Sodium bicarbonate: It reacts with the acids when the preparation is added to water. The evolved carbondioxide produces effervescence.

2. Citric acid and tartaric acid: The quantity of these is slightly more than is necessary to neutralise the sodium bicarbonate because effervescent preparations are more palatable if slightly acidic.

• Tartaric acid is anhydrous but

• Citric acid has one molecule of water of crystallization

• Heating liberates this water

• The moist condition thus produced allows partial interaction between the acids and bicarbonates, during which more water is formed

• The water of crystallization of the citric acid and the water from the reactions makes the material coherent

Methods of preparation

• Hot method

• Wet method

Hot method

Step 1. Evaporating dish heated on water bath

Step 2. Powders taken in the hot dish

Step 3. Liberation of water of crystallization from citric acid

Step 4. Water produced from reactions of acids with bicarbonate

Step 5. Damp mass

Step 6. Passed through sieve and dried

Wet method

Step 1. Dry mixture of powders

Step 2. Moistened with non aqueous liquid (eg. Alcohol)

Step 3. Coherent mass

Step 4. Seived and dried


Before administration, the desired quantity is dissolved in water, the acid and bicarbonate react together producing effervescence.

• The carbonated water produced from the release of carbondioxide serves to mask the bitter and saline taste of


• Carbondioxide stimulates the flow of gastric juice and helps absorption of medicament.


• Granules – advantages over powders

• Effervescent granules – Combination of citric acid, tartaric acid and sodium bicarbonate

• Preparation of effervescent granules

– Dry gum method

– Wet gum method


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