Topical Drugs Used in the Treatment of Skin Disorders
TOPICAL ANTI-INFECTIVES
Localized skin infections may require the use of a topical anti-infective. The topical anti-infectives include antibiotic, antifungal, and antiviral drugs.
Actions and Uses
Topical Antibiotic Drugs Topical antibiotics exert a direct local effect on specific microorganisms and may be bactericidal(i.e., lethal to bacteria) or bacteriostatic(i.e., inhibit bacterial growth). Bacitracin inhibits cell wall synthesis. Bacitracin, gentamicin, and erythromycin are examples of topical antibiotics.
These drugs are used to
• Treat primary and secondary skin infections • Prevent infection in minor cuts, wounds, scrapes, and minor burns • Treat acne vulgaris
Topical Antifungal Drugs
Superficial mycotic infections occur on the surface of, or just below, the skin or nails. Superficial infections include tinea pedis(athlete’s foot), tinea cruris(jock itch), tinea corporis (ringworm), onychomycosis(nail fungus). Antifungal drugs exert a local effect by inhibiting growth of fungi. Examples of antifungal drugs include miconazole, ketoconazole, and ciclopirox.
Antifungal drugs are used for treating: • Tinea pedis, tinea cruris, tinea corporis • Cutaneous candidiasis • Other superficial fungal infections of the skin
Topical Antiviral Drugs
Acyclovir and penciclovir are topical forms of antiviral drugs used to treat oral HSV. These drugs are used to inhibit viral activity during: • Initial episodes of HSV (prodrome phase) • Directly on lesions to speed up recovery Docosanol is a cream sold over the counter (OTC) and speeds healing as well.
Adverse Reactions
Adverse reactions to topical anti-infectives are usually mild. Occasionally, the patient may experience a rash, itching, urticaria (hives), dermatitis, irritation, or redness, which may indicate a hypersensitivity(allergic) reaction to the drug. Prolonged use of topical antibiotic preparations may result in a superficial superinfection(an overgrowth of bacterial or fungal microorganisms not affected by the antibiotic being administered).
Contraindications, Precautions, and Interactions
These drugs are contraindicated in patients with known hypersensitivity to the drugs or any components of the drug. The topical antibiotics are pregnancy category C drugs and are used cautiously during pregnancy and lactation. Acyclovir and penciclovir are pregnancy category B drugs and are used cautiously during pregnancy and lactation. The pregnancy categories of the antifungals are unknown except for econazole, which is in pregnancy category C, and ciclopirox, which is in pregnancy category B; both are used with caution during pregnancy and lactation. There are no significant interactions for the topical anti-infectives.
TOPICAL ANTISEPTICS AND GERMICIDES
An antiseptic is a drug that stops, slows, or prevents the growth of microorganisms. A germicide is a drug that kills bacteria.
Actions
The exact mechanism of action of topical antiseptics and germicides is not well understood. These drugs affect a variety of microorganisms. Some of these drugs have a short duration of action, whereas others have a long duration of action. The action of these drugs may depend on the strength used and the time the drug is in contact with the skin or mucous membrane.
Chlorhexidine
Chlorhexidine affects a wide range of microorganisms, including gram-positive and gram-negative bacteria.
Hexachlorophene
Hexachlorophene (pHisoHex) is a bacteriostatic drug that acts against staphylococci and other gram-positive bacteria. Cumulative antibacterial action develops with repeated use.
Iodine
Iodine has anti-infective action against many bacteria, fungi, viruses, yeasts, and protozoa. Povidone–iodine (Betadine) is a combination of iodine and povidone that liberates free iodine.
Povidone–iodine is often preferred over iodine solution or tincture, because it is less irritating to the skin and treated areas may be bandaged or taped.
Uses
Topical antiseptics and germicides are used for the following:
• To reduce the number of bacteria on skin surfaces • As a surgical scrub and preoperative skin cleanser
For washing the hands before and after caring for patients • In the home to cleanse the skin • On minor cuts and abrasions to prevent infection .
Adverse Reactions
Topical antiseptics and germicides provoke few adverse reactions. Occasionally, an individual may be allergic to the drug, and a skin rash or itching may occur. If an allergic reaction is noted, use of the topical drug is discontinued.
Contraindications, Precautions, and Interactions
These drugs are contraindicated in patients with known hypersensitivity to the individual drug or any component of the preparation. There are no significant precautions or interactions when the drugs are used as directed.
TOPICAL CORTICOSTEROIDS
Topical corticosteroids vary in potency, depending on the concentration (percentage) of the drug, the vehicle (lotion, cream, aerosol spray) in which the drug is suspended, and the area (open or denuded skin, unbroken skin, thickness of the skin over the treated area) to which the drug is applied. Examples of topical corticosteroids include amcinonide, betamethasone, fluocinolone, hydrocortisone, and triamcinolone.
Actions and Uses
Topical corticosteroids exert localized anti-inflammatory activity. When applied to inflamed skin, they reduce itching, redness, and swelling.
These drugs are use in treating skin disorders such as: • Psoriasis • Dermatitis • Rashes • Eczema • Insect bites • First- and second-degree burns, including sunburn .
Adverse Reactions
Localized reactions may include burning, itching, irritation, redness, dryness of the skin, allergic contact dermatitis, and secondary infection. These reactions are more likely to occur if occlusive dressings are used. Systemic reactions may also occur with hypothalamic-pituitary-adrenal axis suppression, Cushing’s syndrome, hyperglycemia, and glycosuria.
Contraindications, Precautions, and Interactions
Topical corticosteroids are contraindicated in patients with known hypersensitivity to the drug or any component of the drug; as monotherapy for bacterial skin infections; for use on the face, groin, or axilla (only the high-potency corticosteroids); and for ophthalmic use (may cause steroid-inducedglaucoma or cataracts).
The topical corticosteroids are not used as sole therapy in widespread plaque psoriasis. The topical corticosteroids are pregnancy category C drugs and are used cautiously during pregnancy and lactation. There are no significant interactions when these drugs are administered as directed.
• TOPICAL ANTIPSORIATICS
Action and Uses
Topical antipsoriatic drugs are drugs used to treat psoriasis (a chronic skin disease manifested by bright red patches covered with silvery scales or plaques) by helping to remove the plaques associated with the disorder. Examples of antipsoriatics include anthralin and calcipotriene.
Adverse Reactions
These drugs may cause burning, itching, and skin irritation. Anthralin may cause skin irritation, as well as temporary discoloration of the hair and fingernails.
Contraindications, Precautions, and Interactions
Topical antipsoriatics are contraindicated in patients with known hypersensitivity to the drugs. Anthralin and calcipotriene, pregnancy category C drugs, are used cautiously during pregnancy and lactation.
TOPICAL ENZYMES
Actions and Uses
A topical enzyme is used to help remove necrotic (dead) tissue from: • Chronic dermal ulcers • Severely burned areas These enzymes aid in the removal of dead soft tissues by hastening the reduction of proteins into simpler substances. The process is called proteolysis or a proteolytic action. The components of certain types of wounds, namely necrotic tissues and purulent exudates (pus-containing fluid), prevent proper wound healing. Removal of this type of debris by application of a topical enzyme aids in healing. Examples of conditions that may respond to application of a topical enzyme include second- and third-degree burns, pressure ulcers, and ulcers caused by peripheral vascular disease. An example of a topical enzyme is collagenase.
Adverse Reactions
The application of collagenase may cause mild, transient pain and possibly numbness and dermatitis. There is a low incidence of adverse reactions to collagenase.
Contraindications, Precautions, and Interactions
Topical enzyme preparations are contraindicated in patients with known hypersensitivity to the drugs, in wounds in contact with major body cavities or where nerves are exposed, and in fungating neoplastic ulcers. These drugs are pregnancy category B drugs and are used cautiously during pregnancy and lactation. Enzymatic activity may be impaired by certain detergents and heavy metal ions, such as mercury and silver, which are used in some antiseptics. The optimal pH for collagenase is 6 to 8. Higher or lower pH conditions decrease the enzyme’s activity.
• KERATOLYTICS
Actions and Uses
A keratolytic is a drug that removes excess growth of the epidermis (top layer of skin) in disorders such as warts. These drugs are used to remove: • Warts • Calluses • Corns • Seborrheic keratoses (benign, variously colored skin growths arising from oil glands of the skin) Examples of keratolytics include salicylic acid and masoprocol. Some strengths of salicylic acid are available as nonprescription products for the removal of warts on the hands and feet.
Adverse Reactions
These drugs are usually well tolerated. Occasionally a transient burning sensation, rash, dry skin, scaling, or flulike syndrome may occur.
Contraindications, Precautions, and Interactions
Keratolytics are contraindicated in patients with known hypersensitivity to the drugs and for use on moles, birthmarks, or warts with hair growing from them, on genital or facial warts, on warts on mucous membranes, or on infected skin. Prolonged use of the keratolytics in infants and in patients with diabetes or impaired circulation is contraindicated. Salicylic acid may cause salicylate toxicity with prolonged use. These drugs are pregnancy category C drugs and are used cautiously during pregnancy and lactation.
• TOPICAL LOCAL ANESTHETICS
A topical anesthetic may be applied to the skin or mucous membranes.
Actions and Uses
Topical anesthetics temporarily inhibit the conduction of impulses from sensory nerve fibers. These drugs may be used to relieve itching and pain due to skin conditions, such as minor burns, fungal infections, insect bites, rashes, sunburn, and plant poisoning (e.g., poison ivy). Some are applied to mucous membranes as local anesthetics.
ِ Examples of local anesthetics include benzocaine, dibucaine, and lidocaine.
Adverse Reactions
Occasionally, local irritation, dermatitis, rash, burning, stinging, and tenderness may be noted.
Contraindications, Precautions, and Interactions
These drugs are contraindicated in those with a known hypersensitivity to any component of the preparation. Topical anesthetics are used cautiously in patients receiving class I antiarrhythmic drugs such as tocainide and mexiletine, because the toxic effects are additive and potentially synergistic.
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