Skin Disorders - Pharmacology

The skin is the site of several common disorders that include acne vulgaris, psoriasis, eczema dermatitis, contact dermatitis, drug-induced dermatitis, and burns. Some disorders result from viral infections such as herpes simplex and herpes zoster. Some result from fungal infections such as tineapedis (athlete’s foot) and tineacapitis (ringworm).

Lesions may also appear on the skin as macules (flat with varying colors), papules (raised, palpable, and less than 1 cm in diameter), vesicles (raised, filled with fluid, and less than 1 cm in diameter), or plaques (hard, rough raised, and flat on top).

Nearly all the disorders can be treated using mild or aggressive drug therapy in the form of topical creams, ointments, pastes, lotions, and solutions some of which are available over the counter.

ACNE VULGARIS

Acne vulgaris, commonly called acne, is inflammation of the pilosebaceous glands. These are the glands which produce oil for the hair. Acne is more likely to occur in adolescent males and is associated with testosterone level and the ingestion of “greasy” foods food containing trans-fatty acids (TFA). TFA are synthetic alterations of naturally fatty acids and are present in processed foods, candies, and potato chips.

Medication for systemic therapy.

TABLE : Medication for systemic therapy.

Inflammation of the pilosebaceous glands form papules, nodules, and cysts on the face, neck, shoulders, and back as a result of keratin plugs at the base of the pilosebaceous oil glands near the hair follicles.

The increase in androgen production that occurs during adolescence increases the production of sebum, an oily skin lubricant. Sebum combines with keratin to form a keratin plug. An individual has little control over acne except to eat a nutritionally healthy diet and practice good hygiene. Acne is significantly influenced by age, heredity, stress, hormonal changes, and onset of puberty. All of these are beyond the patient’s control.

Acne is treated by gently applying a cleansing agent several times a day to the skin. Vigorous scrubbing should be avoided. In addition, the patient can administer topical anti-acne medication such as keratolytics. These include benzoyl peroxide, resorcinol, and salicylic acid that dissolves keratin, the outer layer of the epidermis.

The patient should undergo systemic treatment if he or she has a severe case of acne vulgaris that results in scarring, has persistent hyperpigmentation, or when topical treatment fails (see Table Medication for systemic therapy).

PSORIASIS

Psoriasis is a chronic skin disorder characterized by erythematous papules and plaques covered with silvery scales appearing on the scalp, elbows, palms of the hands, knees, and soles of the feet. This is caused by an accelerated growth of epidermal cells—more than five times its normal rate. Less than 3% of the population of the United States is affected by psoriasis. More caucasians are affected than African-Americans and onset occurs between 10 and 30 years old.

Patients who have psoriasis are treated with antipsoriatic medications that loosen erythematous papules and plaques. However, patients usually experience periods of exacerbation and remission.

Psoriasis scales are loosened with keratolytics (salicylic acid, sulfur). Topical glucocorticoids are used for mild psoriasis. Other topical preparations that are effective for psoriasis include anthralin (Anthra-Derm, Lasan) and coal tar (Estar, PsoriGel).

Applications of 1% anthralin may cause erythema to occur and can stain clothing, skin, and hair. Coal tar products are available in shampoos, lotions, and creams. However, they have an unpleasant odor and can cause burning and stinging. Systemic toxicity does not occur with anthralin and coal tar.

Calcipotriene (Dovonex), a synthetic vitamin D3 derivative, is used to suppress cell proliferation, but it may cause local irritation, hypercalciuria, and hypercalcemia (increased calcium levels in urine).

Methotrexate, an anti-cancer drug, slows cellular growth and is prescribed to decrease the acceleration of epidermal cell growth in severe psoriasis. Etretinate (Tegison) is used for severe pustular psoriasis when other medications have failed. Etretinate has an anti-inflammatory effect and inhibits keratinization and proliferation of the epithelial cells.

Ultraviolet A (UVA) may also be used to suppress mitotic (cell division) activity. Photochemotherapy, a combination of ultraviolet radiation with a psoralen derivative, methoxsalen (photosensitive drug), is used to decrease proliferation of epidermal cells. This is called psoralen and ultraviolet A (PUVA) and permits lower doses of drug and ultraviolet A to be used.

WARTS

A wart is a benign lesion characterized as a hard, horny nodule that may appear anywhere on the body, but particularly on the hands and feet. Warts are removed by freezing, electrodesiccation, or surgical excision.

Salicyclic acid, podophyllum resin, and cantharidin are three medications commonly used to remove warts. Salicylic acid promotes desquamation. However, salicylic acid is also absorbed through the skin and can result in salicylism (toxicity).

Podophyllum resin is used to remove venereal warts, but is not as effective against the common wart. Podophyllum also can be absorbed through the skin resulting in toxic symptoms such as peripheral neuropathy, blood dyscrasias, and kidney impairment. Podophyllum can cause teratogenic effects and should not be used during pregnancy.

Cantharidin (Cantharone, Verr-Canth) is used to remove the common wart, but can be harmful to the normal skin. Cantharidin is applied topically, allowed to dry, and covered with a nonporous tape for 24 hours. This treatment is repeated in a week or two.

DERMATITIS

Dermatitis is a skin eruption that is caused by medications (drug-induced dermatitis) or by a chemical agent coming in touch with the skin (contact dermatitis).

Drug-induced dermatitis is characterized by skin lesions that can be a rash, urticaria, papules, vesicles or life-threatening skin eruptions such as erythema multiforme (red blisters over a large portion of the body) or Stevens-Johnson syndrome (large blisters in the oral and anogenital mucosa, pharynx, eyes, and viscera). As a result of having a hypersensitive reaction to a drug, the patient may form sensitizing lymphocytes.

If the patient received multiple drug therapy, the last drug administered to the patient may have caused hypersensitivity and skin eruptions. Drug-induced dermatitis may take a few minutes, several hours, or a day for urticaria (hives) to appear. Certain drugs such as penicillin are known to cause hypersensitivity.

Other drug-induced dermatitis includes discoid lupus erythematosus (DLE) and exfoliative dermatitis. Hydralazine hydrochloride (Apresoline), isoniazid (INH), phenothiazines, anticonvulsants, and antidysrhythmics such as procainamide (Pronestyl) may cause lupus-like symptoms. If lupus-like symptoms occur, the drug should be discontinued.

Certain antibacterials and anticonvulsants may cause exfoliative dermatitis, resulting in erythema of the skin, itching, scaling, and loss of body hair.

Contact dermatitis, also called exogenous dermatitis, is caused by chemical or plant irritation and is characterized by a skin rash with itching, swelling, blistering, oozing, or scaling at the affected skin sites. The chemical contact may include cosmetics, cleansing products (soaps and detergents), perfume, clothing, dyes, and topical drugs. Plant contacts include poison ivy, poison oak, and poison sumac.

Non pharmacological treatment of contact dermatitis includes avoiding direct contact with the causative irritant. The patient should use protective gloves and clothing if the chemical agent is associated with his or her employment.

At the first sign of contact dermatitis, clean the skin area immediately. Patch testing may be needed to determine the causative factor. Apply wet dressings containing Burow’s solution (aluminum acetate), lotions such as calamine that contain zinc oxide, calcium hydroxide solution, and glycerin. Calamine lotion may contain the antihistamine diphenhydramine and is used primarily for plant irritations. If itching persists, antipruritics (topical or systemic diphenhydramine [Benadryl]) may be used. Topical antipruritics should not be applied to open wounds or near the eyes or genital area.

Other medications used as antipruritics are:

  • Systemic drugs such as cyproheptadine hydrochloride (Periactin) and trimeprazine tartrate (Temaril).
  • Antipruritic baths of oatmeal such as Alpha-Keri.
  • Solutions of potassium permanganate, aluminum subacetate, or normal saline.
  • Glucocorticoid ointments, creams, or gels.

Topical glucocorticoids can aid in alleviating dermatitis (see Table (Topical glucocorticoids) ). These include dexamethasone (Decadron) cream, hydrocortisone ointment or cream, methylprednisolone acetate (Medrol) ointment, triamcinolone acetonide (Aristocort), and flurandrenolide (Cordran).

Topical glucocorticoids are systemically absorbed into the circulation depending on whether it is a cream or lotion, drug concentration, drug composition, and skin area to which the glucocorticoid is applied.

Absorption is greater at the face, scalp, eyelids, neck, axilla, and genitalia with prolonged use of the topical drug and if the drug is continuously covered with a dressing. Prolonged use of topical glucocorticoids can cause thinning of the skin with atrophy of the epidermis and dermis, and purpura from small-vessel eruptions.

ALOPECIA (MALE PATTERN BALDNESS)

Alopecia occurs when the hair shaft is lost and the hair follicle cannot regenerate. This results in permanent hair loss. Alopecia is associated with a familial history and the aging process. Some patients experience alopecia earlier than others.

Some medications can cause temporary alopecia. These include anticancer (antineoplastic) agents, gold salts, sulfonamides, anticonvulsants, aminoglycosides, and non steroidealantiflammatory drugs (NSAIDs) such as indomethacin.

Topical glucocorticoids

TABLE : Topical glucocorticoids.

Severe febrile illnesses, pregnancy, myxedema (condition resulting from hypothyroidism), and cancer therapies are conditions contributing to temporary hair loss.

A 2% minoxidil (Rogaine) solution has been approved by the FDA for treating alopecia. Minoxidil causes vasodilation. This increases cutaneous blood flow and stimulates hair-follicle growth. However, alopecia returns within 3 to 4 months after the patient stops using minoxidil. Systemic absorption of minoxidil is minimal and adverse reactions seldom occur.

BURNS

A burn causes lesions that break down skin exposing the body to infection. There are three causes of burns: heat (thermal), electricity (electrical), and chemicals. All cause the same kind of skin lesion.

Burns are classified by degree, which is based on the tissue depth of the burn. There are three burn classifications: first-degree, second-degree, and third degree. Burns are assessed by the percentage of body area that has been burned. This is commonly referred to as the Rule of Nines (see Table (Rule of nines) ). For example, if a patient’s left leg is burned, then 18% of the patient’s body is burned.

First-degree (superficial) burns

First-degree burns affect only the epidermis (outer layer) of skin. The burn site is red, painful, dry, and with no blisters such as seen in a mild sunburn.

First-degree (superficial) burns

Rarely TABLE (Rule of nines). Rule of nines.

is there any long-term tissue damage and it usually results in an increase or decrease in the skin color.

Treatment involves placing a cold, wet compress on the burned area in order to constrict blood vessels and reduce swelling and pain. Less tissue damage occurs if the burned area is cooled quickly. Remove clothing immediately and flush the burned area with water if a chemical agent caused the burn.

Don’t apply greasy ointments, butter, or a dressing to the burned area. This inhibits heat loss and increases tissue damage. Bacitracin with polymyxin B (Polysporin) and similar over-the-counter antibiotics should be used.

Second-degree (partial thickness) burns

Second-degree burns expose the epidermis and part of the dermis layer of skin. The burn site appears red, blistered, and may be swollen and painful.

These burns can be quite painful and can become infected easily. They should be cleaned with a non-abrasive solution, treated with antibiotic ointment such as silver sulfadiazine (Silvadine), protected with a non-stick dressing, and the patient should be given an analgesic based on the amount of area burned and the pain experienced.

Third-degree (full thickness) burns

Third-degree burns destroy the epidermis and dermis and may also damage underlying nerve, bones, muscles, and tendons. The burn site appears white or charred and the patient has no sensation in the area since the nerve endings are destroyed.

Third-degree burns can be very painful because they are generally mixed (that is, second- and third-degree). Analgesics are used to manage the pain (see Narcotic Agonists). Burn patients are susceptible to infection. With the skin gone, the patient is exposed to infection.

Third-degree burns are treated by first removing the charred skin (eschar) which is called debridement. This is a painful procedure. The patient is then given multiple antibiotics to prevent infections. The patient is also at risk for fluid and electrolyte imbalances (see Fluid and Electrolyte Therapy) and at high risk for stress ulcers (see Gastrointestinal System). Burn patients must be assessed for possible smoke inhalation. If it exists, the patient is treated with respiratory medications (see Respiratory Diseases).

Burned areas must be cleansed with sterile saline solutions and an antiseptic such as povidone-iodine (Betadine). Broad-spectrum topical antibiotics are then applied to burn areas. These include antibacterials such as mafenideacetate (Sulfamylon), silver sulfadiazine (Silvadene), silver nitrate 0.5% solution, and nitrofurazone (Furacin).

Third-degree burns are best managed in a designated burn center by a burn specialist or surgeon.

ABRASIONS AND LACERATIONS

The most common skin injuries are abrasions and lacerations that are the result of accidents such as “road rash.” This is caused by the body scraping along the roadway such as in a motorcycle accident. Patients who receive an abrasion or laceration are exposed to the same risk as a burn patient.

The site of the abrasion and laceration must be cleansed very carefully and treated with topical and sometimes systemic antibiotics and analgesics. Incomplete cleansing can result in tattoo-type scars.

Lacerations, commonly referred to as cuts, are interruptions in the integrity of the skin and should be monitored for signs of infection after they are cleaned and treated with antibiotics. Infection will cause the wound to appear red, swollen, and have purulent drainage (pus) and persistent pain.

Most minor cuts and abrasions are treated by cleaning the area with hydrogen peroxide or betadine and the applying a topical antibiotic such as Neosporin.

Some lacerations need to be sutured to close the open areas of the skin or topical skin adhesives are used to bring the edges together. Before suturing, the area must be flushed with copious amounts of normal saline. Sutures remain in place for about 7-10 days before they dissolve or are removed.

Puncture wounds do not cause a large area of visible injury to the skin but can carry a risk of damage to underlying tissues and infection. Puncture wounds should be cleansed carefully and monitored for signs of infection. The need for a tetanus toxoid booster immunization should be assessed.


All rights reserved © 2018 Wisdom IT Services India Pvt. Ltd DMCA.com Protection Status

Pharmacology Topics