Syrups are sweet viscous concentrated aqueous solutions
of sucrose in purified water. Simple
syrup I.P contains 66.7%w/w sucrose in purified water (100 ml) Simple syrup USP contains 85%w/v sucrose in
purified water (100 m.)
Medicated Syrup:
Contains a therapeutic or medicinal agent e.g. Cough syrup.
Flavored Syrup: Contains flavoring agent but no medicinal substances e.g. Cherry syrup.
Advantages of Syrup
1. Syrup retards oxidation because it is partly
hydrolyzed into its reducing sugar such as laevulose and dextrose.
2. It prevents the decomposition of vegetable
substances. The syrup has a high concentration of sugar having high osmotic
pressure which prevents the growth of bacteria, fungi, and microbes. It acts as
a self-preservative.
3. They are palatable due to the sweetness of sugar.
It is a valuable vehicle for the administration of nauseous and bitter
substances.
4. Syrups are good demulcents and soothing agents and
hence they are of specialvalue in cough syrup.
5. Syrups have good patient compliance.
The concentration of sucrose in sugar-based syrup is
very important. A dilute solution may lead to the growth of micro-organisms
whereas a saturated solution may lead to the crystallization of the same part
of sucrose. Both syrup concentrations as per IP and USP give stable syrup.
Syrup containing various concentrations of sucrose needs an antimicrobial
preservative.
Method of Preparation
The choice of a particular method depends on the
physical and chemical characteristics of the substance being used.
1. Hot Process
This method is used when active constituents are neither volatile nor heat labile.
• Weighed sucrose is taken in a beaker.
• Purified water is
added.
• Heated on a water bath
(less than 70°C) till a solution is obtained.
• Product is
filtered.
• Volume is made upto
q.s.
Excessive heat may lead to the inversion of sucrose.
2. Percolation
• Sucrose is placed in
percolator.
• Water is passed through
sucrose slowly.
• The neck of a percolator
is packed with cotton.
• Rate of percolation
regulates the rate of dissolution.
• After complete
dissolution final volume is made up to q.s.
3. Agitation Without Heat
Procedure for heat labile constituents
• Sucrose and other ingredients are weighed properly.
• Dissolved in purified
water.
• Kept in a bottle of
about twice the volume of syrup followed by continuous agitation.
• Prepared syrup volume is
made up to q.s.
4. Addition of Medicating or Flavouring
Liquid to Syrup
This method is used when fluid extracts, tinctures, or other liquids are to be added to syrup.
• Alcohol is added to dissolve the resinous or oily substances.
• Alcohol acts as a
preservative also.
Formulation of Syrup
1. Vehicle:
Syrups are prepared by using purified water.
2. Adjuncts:
The following adjuncts are generally added to improve the formulation of
syrup.
• Chemical Stabilizer:
Glycerin, sorbitol, and propylene glycol is added in small quantity to syrup to
prevent crystallization.
• Colouring agent:
Many syrups are attractively colored with coal tar dyes such as amaranth,
compound tartarazine, and Green S.
• Flavouring agents:
(i) Tinctures: Lemon and ginger tincture
(ii) Fruit juice: Cherry, Raspberry
(iii) Essence: Vanilla, orange
Preservatives: Syrups
are self-preservatives, Generally, Benzoic acid, Sodium benzoate, Methylparaben,
etc.
Storage: Stored in well
dried, completely filled, and well-stopped bottle in a cool dark place. Store
at a temperature not exceeding 25°C.