Ointment with lipids

By contrast, Vaseline and similar highly viscous, lipid bases from the outset form an impenetrable layer, virtually unaffected by external factors or effects emanating from the skin itself. Interactions with the skin lipids are only likely at the boundary between ointment and skin. 

Formulation additives used in topical drug or pesticide formulations can alter the stratum comeum barrier. Surfactants are least likely to be absorbed, but they can alter the lipid pathway by fluidization and delipidization of lipids, and proteins within the keratinocytes can become denatured. This is mostly likely associated with formulations containing anionic surfactants than non-ionic surfactants. Similar effects can be observed with solvents. Solvents can partition into the intercellular lipids, thereby changing membrane lipophilicity and barrier properties in the following order ether/acetone > DMSO > ethanol > water. Higher alcohols and oils do not damage the skin, but they can act as a depot for lipophilic drugs on the skin surface. The presence of water in several of these formulations can hydrate the skin. Skin occlusion with fabric or transdermal patches, creams, and ointments can increase epidermal hydration, which can increase permeability. 

Nonmedicated ointments are indicated for moderate to severe dry eye, especially with lagophthalmos, persistent inferior corneal stippling, or severe epithelial compromise. Esters of latty acids with long-chain alcohols, such as petrolatum, mineral oil, lanolin, and lanolin alcohols, serve as lubricants and create a lipid layer, retarding evaporation. Although these preparations (Table 14-2) melt at the temperature of the ocular tissue and disperse with the tear fluid, they appear to be retained longer than other ophthalmic vehicles. Because of their molecular... 

Watei in-oil creams, e.g. oily cream, zinc cream, behave like oils in that they do not mix with serous discharges, but their chief advantage over ointments (below) is that the water content makes them easier to spread and they give a better cosmetic effect. They act as lubricants and emollients, and can be used on hairy parts. Water-in-oU creams can be used as vehicles for lipid-soluble substances. A dry skin is mainly short of water, and oily substances are needed to provide a barrier that reduces evaporation of water, i.e. the presence of oils contributes to epidermal hydration. 

Increased absorption with occlusive dressing Used for lipid-soluble drugs with low dose and low MW Type of cream or ointment base affects drug release and absorption... 

Transdermal Slow absorption, rate may vary. Increased absorption with occlusive dressing. Transdermal delivery system (patch) is easy to use. Used for lipid-soluble drugs with low dose and low MW. Some irritation by patch or drug. Permeability of skin variable with condition, anatomic site, age, and gender. Type of cream or ointment base affects drug release and absorption. 

Important Treatment Modalities. Common ways of dealing with dermatological problems are topical treatments (such as ointments and creams) and oral treatments (drugs taken by mouth). Any bodily injury, irritation, or trauma that eliminates water, lipids, or protein from the epidermis compromises its function. Restoration of the normal epidermal barrier can often be accomplished using mild soaps and emollient creams or lotions. The often-cited dermatologic adage is If it is dry, wet it if it is wet, dry it. Consequently, wet compresses are a frequendy used remedy. A multitude of other topical treatments are available, from antibiotic, antiviral, or steroid ointments applied to treat infectious diseases or eczema to vitamin D derivative creams for psoriasis and retinoid creams for acne. Drugs can also be taken orally to treat a variety of conditions such as acne and autoimmune disorders. 

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