Ointment Bases
There are five (5) classes or types of ointment bases which are differentiated
on the basis of their physical composition. These are:
- oleaginous bases
- absorption bases
- water in oil emulsion bases
- oil in water emulsion bases
- water soluble or water miscible bases
Each ointment base type has different physical characteristics
and therapeutic uses based upon the nature of its components.
The following table summarizes the composition, properties, and
common uses of each of the five types. For more information consult
Remington's.
SUMMARY CHART: PROPERTIES OF OINTMENT BASES
|
| Oleaginous Ointment Bases
|
Absorption Ointment Bases
|
Water/Oil Emulsion Ointment Bases
|
Oil/Water Emulsion Ointment Bases
|
Water-miscible Ointment Bases>
|
| Composition |
oleaginous compounds |
oleaginous base + w/o surfactant |
oleaginous base + water (< 45% w/w) + w/o surfactant
(HLB <8) |
oleaginous base + water (> 45% w/w) + o/w surfactant
(HLB >9) |
Polyethylene Glycols (PEGs) |
| Water Content |
anhydrous |
anhydrous |
hydrous |
hydrous |
anhydrous, hydrous |
| Affinity for Water |
hydrophobic |
hydrophilic |
hydrophilic |
hydrophilic |
hydrophilic |
| Spreadability |
difficult |
difficult |
moderate to easy |
easy |
moderate to easy |
| Washability |
nonwashable |
nonwashable |
non- or poorly washable |
washable |
washable |
| Stability |
oils poor; hydrocarbons better |
oils poor; hydrocarbons better |
unstable, especially alkali soaps and natural colloids |
unstable, especially alkali soaps and natural colloids;
nonionics better |
stable |
| Drug Incorporation Potential |
solids or oils (oil solubles only) |
solids, oils, and aqueous solutions (small amounts) |
solids, oils, and aqueous solutions (small amounts) |
solid and aqueous solutions (small amounts) |
solid and aqueous solutions |
| Drug Release Potential* |
poor |
poor, but > oleaginous |
fair to good |
fair to good |
good |
| Occlusiveness |
yes |
yes |
sometimes |
no |
no |
| Uses |
protectants, emollients (+/-), vehicles for hydrolyzable
drugs |
protectants, emollients (+/-), vehicles for aqueous solutions,
solids, and non-hydrolyzable drugs |
emollients, cleansing creams, vehicles for solid, liquid,
or non-hydrolyzable drugs |
emollients, vehicles for solid, liquid, or non-hydrolyzable
drugs |
drug vehicles |
| Examples |
White Petrolatum, White Ointment |
Hydrophilic Petrolatum, Anhydrous Lanolin, Aquabase™,
Aquaphor®, Polysorb® |
Cold Cream type, Hydrous Lanolin, Rose Water Ointment,
Hydrocream™, Eucerin®, Nivea® |
Hydrophilic Ointment, Dermabase™, Velvachol®,
Unibase® |
PEG Ointment, Polybase™ |
*Varies depending upon specific content of the ointment base
and the relative polarity of the drug(s) incorporated. This table refers more
generally to the release of a typical nonelectrolyte (primarily lipophilic)
drug.