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Syrups: Monophasic liquid dosage form

SYRUPS : 

Monophasic Liquid Dosage Form


Syrups are sweet and viscous or nearly saturated aqueous solutions of sugar or sugar substitute.

  • Syrups containing therapeutic agent(s) are known as medicated syrups.
  • Syrups containing flavouring agents but not medicinal substance/ therapeutic agent are known as flavoured vehicles.

Role/advantages of syrups:

1. Palatable: nauseous, bitter tasting, saline drugs can be administered with ease.
2. Pediatric patients: Medicated syrups are the most frequently administered dosage forms in pediatrics. 
3. Little or no alcohol: Syrups are preferred for children due to less or no alcohol in syrups unlike elixirs.

Commonly Used sweeteners in syrup formulations:

1. Sugars: Sucrose, Dextrose
2. Non-sugars: Sorbitol, Glycerin, propylene glycol.

Why concentration of sucrose in sugar based syrup is important?

Reasons are:
  • the dilute solution of sucrose may cause microbial growth in formulation
  • while the saturated sucrose solution may lead to crystallization. 
  • the syrup which consists of 65% by weight or more sugar retard/prohibits the microbial growth.

Syrup IP : 66.7% w/w solution of sucrose
Syrup USP: 85% w/v or 64.74% w/w solution of sucrose in purified water.

Methods of preparation of syrup:

  1. Agitation: Sugar is added in sufficient quantity of water and stirred. At the point of saturation, rate of dissolution decreases. (Tedious and slow method).
  2. Simple solution (agitation with heat): The sugar and water mixture is heated with agitation until sugar dissolves. After cooling down total quantity of syrup is adjusted by addition of water. (Heat sensitive/ thermolabile substances cannot be formulated).
  3. Extraction: Initially tincture is prepared and then syrup is added in specified quantities/volume.
  4. Percolation: Sugar is placed in a suitable percolator and purified water is allowed to pass through it. The neck of the percolator is packed with cotton. Rate of addition of water determines the rate of dissolution of sugar. Example: Syrup USP

Examples of Syrups: 

  • Citric acid syrup
Citric acid + Lemon tincture + water + syrup (Use: as a flavoured vehicle).
  • Chlorpheniramine maleate syrup
Chlorpheniramine maleate + syrup.

Storage conditions:

Syrups are stored at temperature not exceeding 25°C.
These should be stored in the dry and cool environment. Bottle cap should be properly placed. 
When syrup is dilute, preservatives like methyl paraben, glycerin, sodium benzoate, benzoic acid are added to inhibit the microbial growth.





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