Why ointment base is used in case of ointment?
Hydrocarbon or Oleaginous Bases :
Hydrocarbon bases neither contain nor absorb water. These Bases are used for their emollient effect and are occlusive. They are non-water washable. These Bases are chemically inert and may be useful in preparing ointments containing water-insoluble or water-incompatible drugs.
There are three major types of ointment bases: oleaginous (greasy) bases, which are water repellent; water-absorbing bases, which are greasy but allow absorption of water, and water -miscible bases (vanishing creams or water -soluble bases).
Petrolatum (which may be stiffened with wax) is the most widely used greasy ointment base and is suitable for the incorporation of oleaginous materials. Ointment bases are usually Pharmacologically inert but may entrap water and serve to keep the skin from dying or to provide an emollient protective film.
There are 4 main ointment bases:
Hydrocarbon bases, e.g. hard paraffin, soft paraffin, microcrystalline wax and ceresine.
Absorption bases like as wool fat, beeswax.
Water soluble bases like as macrogols 200, 300, 400.
Emulsifying bases like as emulsifying wax.
Factors affecting the selection of an ideal ointment base are as follows,
- Absorption and penetration. Absorption: entry in the blood stream i.e systemic absorption.
- Effect on skin function.
- Miscibility with skin secretion.
- Compatibility with skin secretion.
- Free from irritant effect.
- Emollient properties.
- Ease of application and removal.
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