2. Learning Objectives
• Uses
• Factors Influencing Absorption
• Raw Materials For Semisolids
• Type Of Vehicle
• Factors Which Influence The
Choice Of Semisolid Vehicles
• Classes Of Semisolid – Usp
• Ophthalmic Ointment
• Preparation Of Ointment
• Semisolids
• Manufacture Of Emulsified
Semisolid
7. MOISTURE AND TEMPERATURE
- The moisture balance on the stratum corneum
(horny layer of the epidermis) of the skin has been
due to the presence of a combination of compounds
known as “natural moisturizing factor”.
8. MOISTURE AND TEMPERATURE
- The fat in the skin provides a protective film to
prevent this factor from being removed from the skin
during excessive contact with water as a bathing
9. PATHOLOGIC INJURY TO THE SKIN
- Skin penetration has been enhanced by abrasions or
stripping the skin of its barrier layer
- Skin penetration of the drug substances can be the
use of suitable vehicles
10. HYDROCARBONS
Petrolatum and mineral oil are perhaps the widely used substance in
semisolids next to water
Petrolatum – a complex mixture of semisolids containing
hydrocarbon alipathic, cyclic, saturated, unsaturated branch and
unbranched substance in varying proportions
Mineral oil – obtained from petroleum acid. Lower viscosity is more
preferred since it is less tacky.
11. HYDROCARON WAXES
Employed to increase the viscosity of mineral oil to prevent
separation from ointment.
Paraffin and ceresin wax
12. OLEAGINOUS SUBSTANCES
Vegetable oil such as peanut, almond oil, almond oil, sesame
oil and olive oil and glycerides of mixtures of unsaturated
fatty acids
13. FATTY ACIDS AND ALCOHOLS
Stearic acids – used in water removable creams as an emulsifier to
develop a certain consistency in the cream
Stearyl alcohol and cetyl alcohol (palmityl alcohol) – used in
creams as auxiliary emulsifiers and emollients; in sufficient stearyl
alcohol produces a firm cream which maybe softened by cetyl
alcohol.
14. EMULSIFIERS
- The water soluble soaps (triethanolamine stearate soap) were
among the first emulsifiers used for semisolid oil in water
emulsions. The viscosity of the cream or emollient prevents
coalescence of the emulsified phases and helps to stabilize the
emulsion. The interfacial film formed around the dispersed phase
globules is generally solid making emulsified preparation more
rigid.
15. POLYOLS
Glycerin, propylene glycol, sorbitol 70% and the
lower molecular weight polyethylene glycols are used
as humectants (prevent drying up) and prevent
formation of crust on the top of the cream
16. INSOLUBLE POWDERS
Insoluble powders must be uniformly dispersed
throughout the vehicle to assure homogeneity of the
product. The solid must be impalpable to touch. Particles
less than 74 microns in size equivalent to the mesh
openings in a number 200 mesh sieve of the US standard
sieve series are considered impalpable to most people
17. - The vehicle used for semisolid pharmaceutical
preparation differs from that used for cosmetics because
with a cosmetic, penetration to the skin is not desired.
- A well formulated pharmaceutical semisolid should be
both effective therapeutically and cosmetically appealing
but in major effort must be in medicinal direction
18. - Nature of the skin lesion
- Solubility and stability of the drug
20. HYDROCARBON BASE
Petrolatum and white ointment (petrolatum with 5% beeswax) are
typical lipophilic vehicles
Petrolatum is the most commonly used in ointment vehicles
because of its consistency, bland and neutral characteristics and its
ability to spread easily on the skin
These vehicle is difficult to wash off and are used as occlusive
dressings which produces sensation of warmth because of the
normal evaporation of perspiration is inhibited
21. ABSORPTION BASES
Hydrophilic mixtures formed by the addition of substances
miscible with hydrocarbons and possessing polar groupings
such as SO4, sulfonate, carboxyl, hydroxyl or an ether
linage.
E.g. lanolin, cholesterol, sterols, sorbitan monostearate,
sorbitan monooleate
22. ABSORPTION BASES
- Mineral oil is added to these bases to reduce tackiness of the
base
- Cold cream type w/o emulsion belongs to this type of the
base. This is a borax-beeswax combination with mineral oil or
vegetable oil as the continuous phase. A protective oil film
remains on the skin and slow evaporation of water gives the
skin a cooling effect.
23. WATER REMOVABLE BASE
- They are oil in water emulsions
- Upon application and rubbing into the skin, there is
little or no visible evidence of its presence
- The vanishing cream - o/w emulsion but with
absorption base which is w/o emulsion
24. WATER SOLUBLE BASE
- Prepared from mixtures of high and low molecular weight polyethylene glycols
- Characteristics:
• Low molecular weight are liquids; moderately higher molecular are unctuous,
high molecular weight are solids
• No water is required for their preparation
• Combination of high and low molecular weight polyethylene glycols yield
products having ointment like consistency which softens or melts when applied
to the skin
• Have polar group
• Also known as greaseless ointment base
25. - Semisolid ophthalmic vehicles frequently contain soft
petrolatum, a brand adsorption base or water soluble base
- Material used should avoid the eye discomfort and irritation
- Should be sterile when used in injure eye
26. Fusion method (anhydrous ointments) – dissolving the
active ingredients in the melted fats and waxes or in the
vehicle and then mixed with the base.
• Melted mass must be mixed while cooling to ensure
homogenous distribution of the ingredients
28. CHARACTERISTICS OF PRESERVATIVES
• Some preservatives becomes inactive in the presence
of other ingredients
- 5% tween 80 in activates 80% of the total methyl
paraben – higher conc. of preservatives is required
• Boric acid may be used in ophthalmic preparation
29. ANTIOXIDANTS
-Added whenever oxidative deterioration is anticipated.
-Choice of antioxidants depends on:
Toxicity
Irritating potency
Compatibility
Odor
Discoloration
Solubility
Stability
30. Aeration should be prevented for stability and
consistency in density. This can be done by introducing
one phase below the surface of the other liquid or
phase and mixing carefully
In filling into tubes, the hopper should be filled with the
product to prevent incorporation of air
31. RHEOLOGICAL CHANGES
Rheology – study of deformation and flow property of liquid and
semisolid; when subjected to stress (homogenization) tend to deform
in shape and flow
Rheological changes in semisolid increases the consistency due to
increase of the number of emulsified droplets but may decrease
viscosity due to electrolyte effect
Consistency is also affected by the number of times the preparation
is passed through a homogenizer
32. 3 factors to be controlled during manufacturing:
Time of mixing
Temperature
Mechanical works including rate of agitation
Equipment should be automatically controlled as to
regulation on temperature by jacket around tank. Regulation
of mixing time and rate of agitation
33. STEPS IN MANUFACTURING
Preparation of oil and aqueous phase
Mixing of phases
Cooling of semisolid emulsions
Homogenization
Storage while awaiting test
Transfer of material for packaging
Editor's Notes
A semisolid thing is something that is not really a solid or a liquid. Mayonnaise is an example. Mayonnaise does not hold its shape like a solid but does not flow like a liquid. Normally semisolids are covalent things. Covalent substances get softer and softer until they melt.
