Common types of topical formulations
- cream
- ointment
- paste
- lotion
- gel
- factors to consider when choosing a topical preparation
Common types of topical formulations:
1. Cream
- emulsion of water and oil
- classified as oil in water (o/w) or water in oil (w/o) emulsions
- o/w creams (e.g. vanishing creams) spread easily and do not leave the skin greasy and sticky
- w/o creams (e.g. cold cream) are more greasy and more emollient
- creams contain emulsifiers and preservatives which may cause contact allergy
2. Ointment
- semi-solid preparations of hydrocarbons (petrolatum, mineral oil, paraffins, synthetic hydrocarbons)
- strong emollient effect makes it useful in dry skin conditions
- occlusive effect enhances penetration of active drug and improves efficacy (especially in thickened, lichenified skin)
- provides a protective film on the skin (e.g., useful in housewifes hands, irritant dermatitis)
- greasy, sticky, retains sweat (therefore, not suitable in wet weepy dermatitis, hairy areas, skin prone to folliculitis, or hot weather conditions)
- contains no water and does not require a preservative
3. Paste
- mixture of powder and ointment (e.g., zinc oxide 20% paste)
- addition of powder improves porosity (breathability). For example, when treating diaper rash, a protective ointment base which also allows breathability of the skin is desired.
- addition of powder to change an ointment into a paste also increases the consistency of the preparation so that it is more difficult to rub off. This property is useful when one does not want an irritating preparation to get onto the normal skin (e.g., anthralin paste for treating psoriasis).
4. Lotion
- a loosely used term that nowadays includes any liquid preparation in which inert or active medications are suspended or dissolved
- an o/w emulsion with a high water content to give the preparation a liquid consistency can be considered a lotion
- most lotions are aqueous or hydroalcoholic systems; small amounts of alcohol are added to aid solubilization of the active ingredient(s) and to hasten evaporation of the solvent from the skin surface
- most acne lotions are hydroalcoholic which evaporate fast; they are non-sticky and drying
- emulsion type lotions are usually not drying, depending on the water content (higher water and/or less oil is more drying)
- lotions are easy to apply to large areas
- lotions are suitable for hairy areas, skin prone to folliculitis/acne, intertriginous areas
5. Gel
- transparent preparations containing cellulose ethers or carbromer in water or a water-alcohol mixture
- gels liquify on contact with the skin, dry and leave a thin film of active medication
- gels tend to be drying
- they are useful in hairy areas
- they are cosmetically acceptable
Factors to consider when choosing a topical preparation:
- Always consider the effect of the vehicle. An occlusive vehicle enhances penetration of the active ingredient and improves efficacy. The vehicle itself may have a cooling, drying, emollient, or protective action. It can also cause side effects by being excessively drying or occlusive.
Match the type of preparation with the type of lesions. For example, avoid greasy ointments for acute weepy dermatitis.
Match the type of preparation with the site (e.g., gel or lotion for hairy areas).
Consider irritation or sensitization potential. Generally, ointments and w/o creams are less irritating, while gels are irritating. Ointments do not contain preservatives or emulsifiers if allergy to these agents is a concern.
