Pharmaceutical creams are semisolid preparations containing one or more semisolid agents dissolved or dispersed in either a water-in-oil emulsion or an oil-in-water emulsion or in an-other type of water-washable base. So we can say that creams is a semi-solid dosage form containing one or more drug substances dissolved or dispersed in a suitable base.
Creams find primary application in topical skin products and used rectally and vaginally. Many patients and physicians prefer creams or ointments because they are much more easier to spread and remove.
t Advantages of creams:
1) They gives prolong contact in their site of application than any other pharmaceutical semi-solid dosage forms.
2) They are not stick in nature, so easily washable
3) Injured area can be dried quickly by creams than other semi-solid preparations.
4) They have three dimensional (3D) thicksotropic properties. Applying pressure cause breakdown of this 3D structure.
5) non-irritating when applied to the skin.
6) Not expensive.
t Disadvantages of creams:
1) They are less hydrophobic than other semi-solid preparation, so risk of contamination is high than the others.
2) Less viscous then other semi-solid preparation.
t Purposes of creams:
1) To dried the injured area as soon as possible
2) To prevent the irritation, inflammation and microbial growth of the skin.
3) To prevent infections in some sensitive organs.
4) To prolong the action in the injured site.
5) To prevent grittiness of the skin.
t Criteria of a good quality cream:
1) Their affectivity should be high.
2) They should give rapid onseto action
3) They should be biocompatible and bio-miscible
4) Free from grittiness.
5) They should be smooth
6) They should be readily washable
7) They should be non-irritant
8) They should be non-allergic
9) They should be non-toxic
10) They should be physically and chemically stable
[ Differences between creams and ointments:
Ointment | Creams |
1) Ointment base are highly hydrophobic so they are sticky in nature | 1) Creams are not so sticky |
2) Ointment are not readily washable as it is sticky in nature | 2) Creams are readily washable. |
3) Ointment do not show prolong contact in their site of action | 3) Creams show prolong contact in the site of action. |
4) Injured area dried slowly by ointment | 4) Injured area dried quickly by creams. |
0 Formulation of a cream:
1) Active ingredient: Drug or raw materials are used as active ingredient
2) Base: Base is used as carrier of the drug.
3) Preservative: Preservatives are used to protect the drug from microbial content.
4) Antioxidant: It is used to prevent oxidation of the drug that causes degradation.
5) Surfactant: Used to prevent surface tension of two immiscible phases.
6) Complexing agent: It enhances the stability and prolongs action.
7) Viscosity enhancer: Decrease the flow property of creams.
8) Humectants: Protect the drug from moisture.
' Antimicrobial agents: Among the microbial preservatives used to prevent microbial growth in topical preparations are-
a) Methylparaben
b) Propylparaben
c) Phenols
d) Benzoic acid
e) Sorbic acids and
f) Quaternary ammonium salts
' Emulsifier and bases:
Bases that are usually used in the cream preparations are water removable bases. Stearyl alcohol, white petrolatum is the usual oleaginous bases. It melts at 38 to 600c which indicates that it melts easily in the body temperature. Na-lauryl sulfate are usually used as emulsifying agents.
' Complexing agents:
EDTA is the mostly used complexing agents that produce complex with active drug to produce more stability and to prolong the duration of action.
' Antioxidants:
Na-benzoate, benzoic acid, ascorbic acid are the common antioxidants used in extended amounts in pharmaceutical industries.
