Page 34 - Practical DF2 Corrected (2)
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Pharm D Clinical Pharmacy program 2024-2025 Level 2, Semester 2 Pharmaceutical Dosage Forms II (PT 405)
Comment:
1. This cream is non-greasy and should soften the skin. On application over
the skin, water evaporates, and stearic acid precipitates on the skin in finest
crystals with a considerable increase in the smoothness of skin. Stearic
acid on precipitating acts as a base for applied powders.
2. The selection of alkali affects the properties of the cream. The most
common base are sodium hydroxide, potassium hydroxide, or
triethanolamine. HLB (Hydrphilic lipopilic balance) values of their
stearates are given below.
Emulsifier HLB Consistency of Note
produced cream
[1] Sodium 18 Hard
stearate
[2] Potassium 20 Lies between [1]
stearate and [3]
[3] 12 Soft Regarding to irritation, it’s
Triethanolamine the mildest base
stearate
o The desired cream is often achieved by using two alkalies together.
o In older formulations, ammonia or sodium carbonate are often
suggested, with the disadvantages of ammonia odor of the cream of the
former, and the instability of the cream of the latter. Moreover, sodium
carbonate cause bulky frothing due to CO2 release.
o Borax induces pearly luster to the cream. However, its incompatibility
with glycerol and sorbitol forbidden its use in vanishing cream.
Uses:
It used as a base for protective, sunscreen, non-foaming shaving and
nourishing creams.
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