In the manufacture of ointments, bases serve as the primary medium in which active ingredients are dispersed. The choice of base impacts the drug's release, absorption, and overall therapeutic effect. Below is a classification of ointment bases, along with examples and their advantages:

1. Hydrocarbon (Oleaginous) Bases

  • Examples:
    • Petrolatum (Vaseline)
    • White petrolatum
    • Paraffin
  • Advantages:
    • Occlusive: These bases prevent water loss from the skin, making them ideal for dry or scaly skin conditions.
    • Inert and stable: They do not react with active ingredients.
    • Long-lasting: They adhere well to the skin and provide prolonged action.
    • Water-insoluble: They are not washed off easily by water, offering protection.

2. Absorption Bases

  • Examples:
    • Hydrophilic petrolatum
    • Anhydrous lanolin
    • Aquaphor
  • Advantages:
    • Hydrophilic properties: They can absorb water, forming w/o (water-in-oil) emulsions, which are useful for incorporating aqueous solutions of drugs.
    • Emollient and protective: They provide moisturizing effects and help retain moisture.

3. Water-Removable (Emulsion) Bases

  • Examples:
    • Hydrophilic ointment
    • Vanishing cream (oil-in-water emulsions)
  • Advantages:
    • Easily washable: These bases can be easily removed with water, leaving no greasy residue on the skin.
    • Good cosmetic appeal: Their non-greasy nature makes them more acceptable for patients.
    • Allows incorporation of water: They can hold both hydrophilic and lipophilic ingredients, making them versatile.

4. Water-Soluble Bases

  • Examples:
    • Polyethylene glycol (PEG) ointment
    • Glycerin
  • Advantages:
    • Non-greasy: They do not leave an oily residue, making them ideal for patients who prefer a non-greasy formulation.
    • Soluble in water: Easily washed off and ideal for conditions where water exposure or moisture is frequent.
    • Good for incorporation of hydrophilic drugs: Suitable for drugs that are water-soluble.

5. Oleaginous Emulsion Bases

  • Examples:
    • Cold cream
    • Hydrous lanolin
  • Advantages:
    • Moisturizing: These bases provide excellent hydration to the skin by trapping moisture.
    • Sustained drug release: They offer a longer release profile of the active drug, making them useful for prolonged therapeutic effects.

Each type of base has specific advantages based on the nature of the active ingredients and the desired therapeutic action. The selection of the appropriate base is crucial for optimizing drug efficacy and patient acceptability.