Ointments and Pastes

What are ointments?

Semisolids preparations for external uses for the skin/mucous membranes

Less than 20% water/volatiles

More than 50% hydrocarbons, waxes, polyols

The API is either dissolved, suspended, or emulsified in the base

What are oleaginous bases?

Emollient

Occlusive

Not water washable (w/o)

Hydrophobic 

Greasy

Examples of oleaginous bases

Petrolatum

Petroleum

Paraffin wax

Liquid Paraffin

Plastibase

Why are oleaginous bases useful for drugs sensitive to water?

They are anhydrous so they product water sensitive drugs

How much water can be incorporated into oleaginous bases?

Very little, making them perfect for water sensitive drugs

What is an occlusive base?

A base that covers skin with an impermeable film

Increases skin hydration, emollient

Remains on skins for long periods without drying out

Low patient acceptability

What are absorption bases?

Hydrophilic anhydrous materials

OR

Bases that are w/o and have the ability to absorb more water

Emollient and occlusive

Greasy

Some can accommodate significant amounts of water

What’s the difference between anhydrous and w/o absorption bases?

Anhydrous bases can absorb large amounts of water to form w/o emulsions

while

w/o are just bases that have the ability to absorb more water

Examples of Anhydrous absorption bases

Hydrophilic petrolatum, Aquaphor, Lanolin/wool fat

Examples of w/o emulsion absorption bases

Hydrous Lanolin, Eucerin, Cold Cream

Examples of a water-soluble ointment base

Polyethylene Glycol Ointment

Polybase

What are pastes?

Stiff ointments with a high concentration of solid particles, 20-505 in a fatty vehicle

OR

Thick preparations with a single aqueous phase and have a high polymer content

Does not soften/flow after application

Remains very adherent to the location they are applied at

Examples of pastes

Zinc Oxide Paste USP, Zinc Oxide and Salicylic Acid Paste USP, Carboxymethylcellulose sodium paste USP

Only oily ingredients (petrolatum, wax, oil)

Oleaginous

Oily + emulsifier (no water)

Absorption (anhydrous)

Oily + water + emulsifier

Absorption (w/o emulsion)

Water listed first + surfactant/emulsifier

Water-removable (o/w)

Only PEGs, no oils

Water-soluble