Topical Skin Medications

Topical Skin Medications

Virtually all skin medications are either topical or systemic. Topical medications are applied directly to the affected area of the skin. Systemic medications are taken by mouth or injected and are distributed throughout the body. Rarely, when a high concentration of a medication is needed at the affected area, a doctor may inject a medication just under the skin; this is called an intradermal injection.

Some skin medications require a prescription; others can be purchased without one. Although generally considered safer than prescription drugs, over-the-counter drugs must be used with caution. Applying the wrong medication may worsen a skin condition or may mask symptoms, making the diagnosis difficult for a doctor.

Topical Preparations
The active ingredients (medications) in a topical preparation are mixed with (suspended in) a vehicle (an inert carrier for the medications). Thus, the formulation and consistency vary among topical preparations. The vehicle determines the consistency of the product and whether the active ingredients remain on the surface or penetrate the skin-whether the preparation is thick and greasy or light and watery. Depending on the vehicle used, the preparation will be an ointment, cream, lotion, solution, powder, or gel.

Ointments, which contain a lot of thick oil and very little water. feel greasy and are difficult to wash off. Ointments are most appropriate when the skin needs lubrication or moisture.

Although messier to use than water-based cream preparations, ointments are usually better at delivering active ingredients into the skin.

Creams, the most commonly used preparations, are emulsions of oil in water. They're easy to apply and appear to vanish when rubbed into the skin.

Lotions are similar to creams but contain more water. They're actually suspensions of finely dispersed powdered material in a base of water or oil and water. Lotions are easy to apply and are particularly useful for cooling or drying the skin.

Solutions are liquids in which a drug is dissolved. Solutions tend to dry rather than moisturize the skin. The most commonly used liquids are alcohol, propylene glycol, polyethylene glycol, and plain water.

Powders are dried forms of substances that are used to protect areas where skin rubs against skin-for instance, between the toes or buttocks. in the armpits or groin, or under the breasts. Powders dry skin that's macerated (softened and damaged by moisture) and reduce friction by absorbing moisture. Powders may be incorporated into protective creams, lotions, and ointments.

Gels are water-based substances thickened without oil or fat. The skin doesn't absorb gels as well as it absorbs preparations containing oil or fat.

Types of Topical Medications
Topical medications can be divided into seven often overlapping categories: cleansing agents, protective agents, anti-infective agents, moisturizing agents, drying agents, symptom-relieving agents, and anti-inflammatory agents.

Cleansing Agents
The principal cleansing agents are soaps, detergents, and solvents, Soap is the most popular cleanser, but synthetic detergents are used as well, Certain soaps dry the skin; others have a creamy base that doesn’t dry it. Some liquid soaps moisturize the skin; others dry it.

Because baby shampoos are excellent cleansing agents and are usually gentle to the skin, they’re good for cleansing wounds, cuts, and abrasions. Also, people with psoriasis, eczema, and other scaling diseases can use baby shampoos to wash away dead skin. Oozing (weeping) lesions, however, should generally be cleaned only with water because even gentle soaps and detergents can irritate the area.

Many chemicals are added to cleansing agents. For example, antidandruff shampoos and lotions may contain zinc dipyrithone, elenium sulfide, or tar extracts to help treat flaking skin. Cleansing compounds may also contain small amounts of acetic acid, aluminum acetatem, and magnesium sulfate (as if Epsom salts).

Protective Agents
Many different kinds of preparations help protect the skin. Oils and ointments supply an oil-based barrier that can help protect scraped or irritated skin and retain moisture. Powders may protect skin that rubs against skin or clothing. Synthetic hydrocolloid dressings protect bedsores (Pressure ulcers) and other areas of raw skin. Sunscreens filter out harmful ultraviolet light.

Anti-infective Agents
Viruses, bacteria, and fungi can all infect the skin. By far, the best way to prevent such infections is by carefully washing the skin with soap and water. Other agents can disinfect more, strongly or treat established infections. Most disinfecting agents are used only by nurses and doctors to sterilize their skin and their patients' skin before surgery. However, certain medications are commonly used to treat fungal and bacterial infections. For instance, antibiotics are applied to the skin for acne and superficial skin infections. Clotrimazole and miconazole are commonly applied to the skin to treat fungal infections. Both are available without a prescription. Other anti-fungal agents such as ketoconazole creams are available by prescription only. Medications such as ganuna benzene hexachloride (lindane) help treat infections such as scabies.

Moisturizing Agents
Moisturizers don't actually add moisture to the skin: they help the skin hold its natural moisture. Most moisturizers are creams or lotions containing oil. Putting a thin film of oil on the skin helps prevent water in the skin from evaporating. The best time to apply these agents is when the skin is already moistened-immediately after a bath or shower, for instance. Some stronger moisturizers contain compounds such as urea.

Drying Agents
Excessive moisture in the skin can cause maceration-a problem that usually occurs where skin rubs skin, trapping moisture, especially on hot, humid days. The areas most commonly affected are between the toes or buttocks, in the armpits or groin, and under the breasts. These moist areas also provide fertile breeding grounds for infections, especially with fungi and bacteria.

Talcum powder is the most commonly used drying agent. Talc absorbs moisture from the skin surface. Most of the many talc preparations vary only in their scents and packaging. Cornstarch, another good drying agent, has the disadvantage of encouraging the growth of fungi. For this reason, talc is generally better.

Solutions containing aluminum salts are useful when the skin is damaged from excessive wetness. These solutions are often used in hospitals and nursing homes.

Symptom-Relieving Agents
Skin disease is often accompanied by itching. Sometimes one medication is applied to relieve the itching, while another is used to treat the disease. Itching and mild pain can sometimes be controlled with soothing agents such as chamomile. eucalyptus, camphor, menthol, zinc oxide, talc. glycerin, and calamine. Antihistamines such as diphenhydramine are sometimes included in topical preparations to relieve the itching associated with allergic reactions. Although antihistamines block certain types of allergic reactions. they probably relieve itching by their sedative effects.

However, antihistamines can sensitize a person and cause an allergic reaction. To control certain forms of itching, a person should use oral antihistamines rather than topical antihistamines.

Anti-inflammatory Agents
Topical or oral corticosteroids (cortisone-like drugs) can help reduce inflammation (swelling, itching, and redness). Corticosteroids are most effective for rashes caused by allergic or inflammatory reactions to poison ivy, metals, cloth, or other substances. Because they lower resistance to bacterial and fungal infections, they usually shouldn't be used on infected areas or wounds. However. corticosteroids are sometimes mixed with antifungal agents to help reduce itching caused by a fungus. Combinations of corticosteroids and antibiotics are seldom used because they're generally no more effective than the corticosteroids alone. Also. antibiotics (especially neomycin) increase the risk of an allergic reaction that can complicate the problem.

Topical corticosteroids are sold as lotions, creams, and ointments. Creams are most effective if rubbed in gently until they vanish. In general, the ointments are the most potent. The type and concentration of corticosteroid in the preparation determines the overall strength. Hydrocortisone is available in concentrations of up to 1 percent without a prescription; concentrations of 0.5 percent or less offer little benefit. Stronger corticosteroid preparations require a prescription. Doctors usually prescribe potent corticosteroids first, then less potent corticosteroids as the skin heals. Generally, topical corticosteroids are applied two to three times a day in small amounts. Where the skin is already thin, such as on the face. they should be used sparingly and never for more than a few days.

When a stronger dose is needed, a doctor may inject a corticosteroid just under the skin. Another way to deliver a strong dose is to apply a nonporous occlusive dressing over a topical corticosteroid to increase the drug's absorption and effectiveness. For example, a polyethylene film (household plastic wrap) may be applied over cream or ointment preparations and left on overnight. With this method, creams and ointments are less irritating than lotions. Occlusive dressings increase the risk of adverse reactions to the corticosteroids, so they're generally reserved for conditions such as psoriasis and severe eczema.

Itching (pruritus) is a Sensation That Instinctiuely Demands Scratching.
Persistent scratching may cause redness and deep cuts in the skin. In fact, scratching can so irritate the skin that it leads to more itching, creating a vicious circle. Prolonged scratching and rubbing can thicken and scar the skin.

Causes
Itching may be caused by a skin condition or a systemic disease (a disease that affects the body generally). Skin conditions that cause severe itching include infestations with parasites (scabies, pediculosis), insect bites, hives, atopic dermatitis and allergic and contact dermatitis. Often, contact with wool clothing or irritants such as solvents or cosmetics causes itching. Dry skin, especially in the elderly, causes severe, widespread itching.

Systemic diseases that can cause itching include liver disease (especially jaundice), kidney failure, lymphomas, leukemias, and other blood disorders. Sometimes people with thyroid disease, diabetes, or cancer develop itching. Itching is common during the later months of pregnancy.

Usually, it doesn't indicate any abnormality, but it can result from mild liver problems. Many drugs can cause itching, including barbiturates and aspirin as well as any drug to which a particular person has an allergy.

Treatment
Doctors treat itching by determining the cause and trying to eliminate it. Especially while the skin is inflamed, a doctor may encourage a patient to use a non-prescription, gentle, moisturizing cream or lotion without scents or colors. Additives that provide color or scent may irritate the skin and may even cause itching. Soothing compounds such as menthol, camphor, chamomile, eucalyptus, and calamine also can help. Corticosteroid creams, which help decrease inflammation and control itching, should be used only when itching is limited to a small area.

Taking antihistamines such as hydroxyzine and diphenhydramine by mouth may help, but they usually cause sleepiness. Generally, antihistamines shouldn't be applied to the skin because they can cause allergic reactions.

Submitted By
Professor Larsen Md

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