Granules
Objective
– List
the advantages of granules
– Explain
the methods for the preparation of effervescent granules
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
Use
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
drugs.
• Carbondioxide stimulates
the flow of gastric juice and helps absorption of medicament.
Summary
• 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