Ointment

• Ointment is a semi-solid, greasy preparation for external application, typically containing less than 20% water and more than 50% hydrocarbons or waxes.
• They form an occlusive layer on the skin, enhancing drug absorption and providing a protective barrier against moisture loss.
• Different types of ointments exist, categorized by their base, which influences their occlusiveness, greasiness, and ability to absorb water.
• Ointments are commonly used for dry skin conditions, protective barriers, and the delivery of potent topical medications.
• A key distinction between ointments and creams lies in their water and oil content, affecting their texture, occlusiveness, and primary applications.

What is Ointment?

An Ointment is a semi-solid preparation intended for external application to the skin or mucous membranes. Characterized by their oleaginous (greasy) base, ointments typically contain a high proportion of oil or fat and a low percentage of water, often less than 20%. This composition gives them a thick, viscous consistency and makes them highly occlusive, meaning they form a protective layer on the skin surface that helps prevent moisture evaporation. This occlusive property is crucial for both hydrating dry skin and enhancing the penetration of active pharmaceutical ingredients.

The primary function of an ointment is to deliver medication topically, provide a protective barrier, or moisturize and soften the skin. Their greasy nature allows them to adhere well to the skin, providing prolonged contact for the active ingredients to exert their therapeutic effects. This makes them particularly effective for chronic dry skin conditions or areas requiring sustained drug release.

Types of Ointments, Their Applications, and Mechanism of Action

The classification of ointments often depends on the nature of their base, which dictates their physical properties and how they interact with the skin. Understanding the various types of ointments and their uses is essential for appropriate application. The primary mechanism of action for most ointments involves forming an occlusive layer on the skin, which hydrates the stratum corneum (outermost layer of skin) and facilitates the absorption of active ingredients.

Here are common types of ointment bases:

• Oleaginous (Hydrocarbon) Bases: These are water-repellent, anhydrous, and highly occlusive. Examples include petrolatum (Vaseline) and paraffin. They are excellent emollients and protective barriers, making them suitable for very dry skin or as a vehicle for lipid-soluble drugs. Their high occlusiveness helps to reduce transepidermal water loss.
• Absorption Bases: These bases are anhydrous but can absorb significant amounts of water to form water-in-oil emulsions. Lanolin and hydrophilic petrolatum are examples. They are less occlusive than oleaginous bases but still provide good emollient properties and are useful for incorporating aqueous solutions of active ingredients.
• Water-in-Oil Emulsion Bases: These are already hydrated and contain water dispersed in an oil phase (e.g., cold cream). They are less greasy and somewhat less occlusive than pure oleaginous bases, offering a balance between moisturization and spreadability.
• Water-Soluble Bases: Composed primarily of water-soluble polymers like polyethylene glycols (PEGs), these bases contain no oleaginous components. They are anhydrous but can absorb water, are non-greasy, and are easily washable. They are less occlusive and are often used when a non-greasy preparation is desired, or for drugs that are water-soluble.

Regarding how do ointments work, their primary mechanism involves creating a semi-permeable barrier on the skin’s surface. This barrier reduces the evaporation of water from the skin, leading to increased hydration of the stratum corneum. This enhanced hydration can improve the skin’s permeability, allowing active pharmaceutical ingredients to penetrate more effectively into the deeper layers of the epidermis or dermis. The prolonged contact time due to their viscous nature also contributes to sustained drug delivery, making them effective for conditions requiring continuous therapeutic action. Common applications for what is ointment used for include treating eczema, psoriasis, severe dry skin, minor burns, and delivering topical corticosteroids, antibiotics, or antifungals.

Ointment vs. Cream: Key Differences

While both ointments and creams are semi-solid topical preparations, they possess distinct characteristics that influence their application and therapeutic efficacy. Understanding the ointment vs cream difference is crucial for selecting the appropriate formulation for a specific skin condition.

The fundamental distinction lies in their composition, particularly their oil and water content, which dictates their texture, feel, and occlusive properties. Ointments are predominantly oil-based, while creams are typically emulsions of oil and water, often with a higher water content than ointments.