Treating Itch in Psoriasis

Aerlyn Dawn; Gil Yosipovitch

Disclosures

Dermatology Nursing. 2006;18(3):227-233. 

In This Article

Available Treatments

Historically, sedating antihistamines such as hydroxyzine and doxepin have been used to treat psoriatic itch. They may have some role in treating nocturnal itch; however, their antipruritic efficacy is limited. Nonsedating antihistamines are not part of the recommended treatment armamentarium.

Several types of remedies — both over-the-counter and prescription — may help control itch in patients with psoriasis. These include tar products, topical corticosteroids, topical salicylates, agents that alter skin sensation, phototherapy, vitamin D analogs, topical immunomodulators, methotrexate, oral mirtazapine, and biologics.

Some common treatments for psoriasis including topical retinoids may dry the skin and actually exacerbate itch (Dando & Wellington, 2005). Although topical retinoids, such as tazarotene, are effective for psoriasis, they do not have demonstrated antipruritic activity. Moisturizers and emollients can be beneficial adjunctive therapies to alleviate itch and are also usually inexpensive. These products moisturize, lubricate, and soothe dry and flaky skin (Van Onselen, 1998). Dry skin tends to worsen itch. Moisturizers and emollients produce an occlusive film that limits evaporation of water from the skin and increases the hydration of the stratum corneum, making it softer and more pliable. Epidermal cells are tightly packed and act as a barrier that maintains water within the skin. Often, chronic pruritus results from breakdown of the barrier function of the skin. Low pH moisturizers are particularly helpful in restoring the skin barrier function by maintaining the acidic pH of the skin's surface and reducing the irritative effects of pruritus. Application of a moisturizer throughout the day, particularly immediately after bathing, helps lock moisture in the skin. To be effective, these products must be applied liberally — often up to 3 times daily. However, moisturizers alone may not fully alleviate pruritus and additional medications are often needed.

Coal tar treatments have been used for psoriasis for over 100 years and are especially beneficial for severe pruritus. These products are usually well-tolerated and moderately priced. The precise mechanism of action of tar is not fully understood. Tar consists of a mixture of organic compounds, including phenols, heterocyclic oxygens, hydrocarbons, sulfurs, and nitrogens, which makes it difficult to determine which compound produces the therapeutic effects in psoriasis. Coal tar appears to have anti-proliferative and anti-inflammatory effects on the skin and decreases epidermal cell mitosis and scale development as well as the amount of sebum produced by sebaceous glands (Arnold, 1997; Bardolph & Ashton, 1998). Products available over-the-counter include lotions, creams, oils, gels, bath solutions, and shampoos. Such over-the-counter tar shampoos can help reduce scalp pruritus. Prescription compounds of tar in creams and ointments are also available, such as crude coal tar (2% or 3%) in triamcinolone (0.1%) cream. A preparation of 10% tar in a fatty-acid based lotion can also be effective.

Disadvantages of tar products include potential skin irritation, messiness, strong odor, and staining of skin or clothing. Coal tar products should be applied to a limited area to avoid skin irritation, which can cause an acneiform eruption, folliculitis, or rarely, contact dermatitis (Arnold, 1997). In erythrodermic or pustular psoriasis, irritation induced by tar products may lead to Koebner's phenomenon (Arnold, 1997). In animal studies, tar products have been associated with carcinogenic and teratogenic effects; however, there are little data demonstrating that medicated tar preparations cause such effects in humans.

Despite the development of newer agents, topical corticosteroids remain the mainstay of psoriasis treatment in the United States and are commonly used for itch in many skin diseases (McClelland, 1997). Corticosteroids have anti-inflammatory, anti-proliferative, and immunosuppressive properties but their mechanism of action in psoriasis is not fully understood. Unlike tar products, topical corticosteroids are generally non-irritating and well-accepted by patients. These products come in different strengths and formulations and are available as creams, ointments, lotions, gels, and, most recently, foams. Ointments are best for lesions that are dry, hyperkeratotic, and scaly but are generally inappropriate for hairy areas because of their greasy texture. Lotions and gels are often used for scalp psoriasis. For several topical corticosteroids, formulations are designed specifically for use on the scalp, including clobetasol, fluocinolone, fluocinonide, and triamcinolone spray, among others. The formulation can significantly affect the potency, side effects, and the effectiveness of the treatment.

Higher-potency corticosteroids are more effective but also have higher rates of adverse effects. Adverse effects include skin atrophy, which may lead to skin fragility, easy bruising, stretch marks, increased fine hair growth, hypopigmentation, allergic contact dermatitis, and systemic absorption leading to adrenal suppression. Skin atrophy may occur within 1 to 2 weeks after initial application. For these reasons, mid-potency and high-potency topical corticosteroids should not be used on the face or other sensitive areas, such as the groin. Low-potency corticosteroids can sometimes be used in such areas if monitored closely by a clinician. In addition, topical steroids should not be used continuously for long periods of time. Abruptly stopping steroid treatment can cause worsening of psoriasis.

High-potency topical corticosteroids, such as clobetasol (0.05%) and betamethasone (0.12%), are now available as low-residue foams. Foams become a liquid on contact with skin and are well-tolerated by patients. Recent studies found that patients with psoriasis prefer foam to other formulations, were able to apply it more quickly, and used it more consistently (Bergstrom, Arambula, & Kimball, 2003; Housman, Mellen, Rapp, Fleischer, Jr., & Feldman, 2002; Lebwohl et al., 2002; Stein, 2005; Stein, Sherr, Solodkina, Gottlieb, & Chaudhari, 2001). An additional advantage of foam is that, unlike other formulations, it can be used both on the body and on the scalp. Betamethasone foam has superior efficacy for scalp psoriasis and is preferred by patients over betamethasone lotion (Franz et al., 1999).

Occlusive therapy using topical corticosteroids can be more effective that corticosteroids alone (David & Lowe, 1989). Such occlusive therapy can be used either on the body or the scalp ("turban therapy"). For example, erythrodermic psoriasis is one of the most pruritic dermatoses clinicians encounter but responds well to occlusion. An emollient may be applied on top of the corticosteroid to moisturize psoriatic lesions and enhance the effectiveness of occlusion. For erythrodermic psoriasis, we recommend occlusion with mid-potency corticosteroids in combination with moisturizers or emollients.

In addition, turban therapy using topical corticosteroids can be very effective for scalp pruritus in psoriasis. Using this technique, a topical corticosteroid is applied to the scalp, and the scalp is covered with an airtight plastic wrap (such as saran wrap) like a turban. This type of occlusion increases the effectiveness of the topical steroid and the amount of medication absorbed into the scalp. However, occlusion should be employed carefully because it can also intensify adverse effects from corticosteroids including skin atrophy and systemic absorption.

Recent clinical trials have shown that applying a topical salicylic acid solution to the skin relieves itch. Topical salicylic acid is the most common keratolytic agent. It is thought that the keratolytic effects of salicylic acid result from decreasing corneocyte cohesion in the psoriatic horny layer. Salicylic acid may also increase hydration and soften the stratum corneum by decreasing its pH. A 3% salicylic acid solution is very effective for itch. In a previous study, we demonstrated that topical salicylates significantly reduced pruritus in many patients who had not responded to topical corticosteroids (Yosipovitch et al., 2001). In addition, topical salicylic acid appears to enhance the absorption and efficacy of other topical medications (Lebwohl, 1999). Products containing 6% salicylic acid are particularly effective when combined with topical corticosteroids. Topical salicylic acid is available in many different formulations over-the-counter including cream, gel, lotion, ointment, pads, plaster, shampoo, soap, and solution. Salicylate shampoos are particularly helpful for scalp itching. However, salicylic acid may sometimes cause temporary shedding of telogen hair. Hair loss is not permanent, however, and usually returns to normal after discontinuing treatment. In addition, strong salicylic acid preparations can cause local irritation if left in contact with the skin too long. Oral salicylates do not relieve itch in psoriasis or other dermatologic diseases.

Although the FDA rarely approves combination therapies in the United States, multiple topical products are available in Europe and Asia that contain both salicylates and mid-potency corticosteroids. The combination of salicylic acid and corticosteroids is considered a first-line treatment for thick, scaly psoriatic plaques (Lebwohl, 1999). Such combination products are effective in reducing itch for many patients with psoriasis and are more convenient for patients since only one product needs to be applied. However, enhanced penetration of topical corticosteroids when combined with salicylic acid has raised concerns about potential increases in side effects including skin atrophy and hypothalamic-pituitary-adrenal axis suppression (Endzweig-Gribetz, Brady, Lynde, Sibbald, & Lebwohl, 2002).

Agents such as 1% menthol can relieve itch in some patients by activating nerve fibers that transmit a cool sensation, thereby reducing the perception of itch. Many over-the-counter medicated shampoos contain menthol and these can be used alone or combined with other medications to reduce scalp pruritus. Pramoxine is a topical anesthetic that reduces itch, especially when applied to facial areas, by blocking the transmission of nerve impulses. Both menthol and pramoxine are available in a wide variety of formulations including creams, lotions, and gels.

Capsaicin is derived from hot chili peppers and was first shown to reduce itching in psoriasis nearly 20 years ago (Bernstein, Parish, Rapaport, Rosenbaum, & Roenigk, Jr., 1986). Several studies have confirmed the effectiveness of capsaicin for itch in patients with psoriasis (Ellis et al., 1993). The exact mechanism is not fully understood; however, prolonged application of capsaicin to the skin depletes stores of substance P, an undecapeptide neurotransmitter involved in the pathophysiology of psoriasis and pruritus (Bernstein, 1991). Several different formulations of 0.025% capsaicin are available over-the-counter; however, higher strength 0.075% capsaicin is more effective. Capsaicin often causes a transient burning sensation at application sites, but this usually resolves after using the medication for a few days.

Phototherapy has been used to treat various dermatologic conditions for over 100 years and is a key treatment for moderate-to-severe psoriasis. Both ultraviolet A (UVA) and ultraviolet B (UVB) have been used in the treatment of dermatologic problems. Narrow-band UVB phototherapy is effective in treating general pruritus (Samson, Gielczyk, Scherschun, & Lim, 2003) and, specifically, psoriatic itch (Gupta, Long, & Tillman, 1999). However, treatment with UVB may actually aggravate itch during the first 2 to 3 weeks of therapy. It is important to use moisturizers or emollients throughout phototherapy treatment.

Vitamin D Analogs. Vitamin D3 analogs are safe and effective treatments for psoriasis. The pathophysiology of psoriasis is characterized by impaired differentiation and increased proliferation of epidermal keratinocytes. Vitamin D3 analogs increase keratinocyte differentiation and inhibit proliferation and have similar efficacy to potent topical corticosteroids in psoriasis (Fogh & Kragballe, 2004). Calcipotriene is the most commonly used vitamin D3 analog for psoriasis. However, such vitamin D analogs are not effective alone for treatment of itch and often cause irritant contact dermatitis (Bruner, Feldman, Vent rapragada, & Fleischer, Jr., 2003). Nevertheless, combinations of topical corticosteroids and vitamin D analogs can relieve itch in some patients. Using calcipotriene in combination with topical corticosteroids increases efficacy, reduces irritation, improves patient tolerance, and minimizes potential steroid side effects (Lamba & Lebwohl, 2001).

Calcipotriene is available as an ointment, cream, and scalp solution. Combining calcipotriene and topical corticosteroids can be particularly helpful for scalp pruritus. One author recommends a multi-phase regimen, in which patients apply clobetasol solution or gel in the morning and calcipotriene solution in the evening daily for 2 weeks followed by tapering of the corticosteroid with subsequent maintenance on calcipotriene solution alone to prevent recurrence (Koo, 2002). Such a combination of calcipotriene and topical corticosteroids is significantly safer than using corticosteroids alone (Lebwohl et al., 1996).

New topical immunomodulators, such as tacrolimus and pimecrolimus, are used primarily for atopic dermatitis; however, these medications may have promise for relieving itch in some cases of psoriasis. Tacrolimus is similar to cyclosporine but has much more potent immunosuppressive activity. Tacrolimus interferes with the production of cytokines involved in chemotaxis of neutrophils toward psoriatic lesions. Higher-strength topical corticosteroids should be avoided in sensitive areas such as the face and groin, whereas tacrolimus and pimecrolimus are safe and effective in these areas (Kroft et al., 2005; Lebwohl et al., 2004). Tacrolimus and pimecrolimus do not penetrate through the skin adequately to be effective for psoriasis in most other areas of the body; however, a recent study found that combining tacrolimus (0.1%) ointment with salicylic acid (6%) gel was effective in reducing itch as well as redness and scale (Carroll, Clarke, Camacho, Balkrishnan, & Feldman, 2005). However, no other studies have yet examined the effectiveness of topical immunomodulators for itch in psoriasis.

Oral methotrexate is a well-established and highly effective systemic treatment for severe psoriasis, which has been used widely for over 30 years. Although methotrexate does not have direct antipruritic effects, its anti-proliferative properties may indirectly relieve itch in some patients. Methotrexate is associated with abnormal liver function tests, nausea, and gastric complaints. In rare cases, adverse effects include myelosuppression and hepatotoxicity, which is related to a high cumulative dose of methotrexate. Low-dose methotrexate therapy is generally well-tolerated. Patients should be selected carefully and monitored regularly for adverse effects and drug interactions. To minimize systemic exposure and toxicity associated with oral methotrexate, a topical methotrexate gel formulation has been developed; however, it is not yet commercially available. Sutton, Swinehart, Cato, and Kaplan (2001) found that use of methotrexate gel resulted in modest reductions in pruritus.

The oral antidepressant mirtazapine relieves itch in some patients (Davis, Frandsen, Walsh, Andresen, & Taylor, 2003; Hundley & Yosipovitch, 2004). We have successfully alleviated nighttime itching in many patients using a low dose of 15 milligrams at night (Hundley & Yosipovitch, 2004). This mirtazapine regimen is effective even in cases of severe pruritus associated with erythrodermic psoriasis. Mirtazapine has a sedative effect due to its H1-antihistamine properties, but it also acts as an antagonist at noradrenergenic α2-receptors and 5HT2 and 5HT3 serotonin receptors. Therefore, it enhances the release of norepinephrine and selectively increases serotonin transmission. It is not clear which mechanism of action is responsible for mirtazapine's anti pruritic properties; the α2-adrenergic antagonism may act to centrally reduce itch. Other common antidepressants like fluoxetine, citalopram, sertraline, and paroxetine do not appear to be effective for itch.

The new class of biologic therapies for psoriasis, including etanercept, efalizumab, and alefacept, have received significant attention in the dermatology community for their effectiveness in treating patients with moderate and severe psoriasis. These medications work by suppressing the immune system. In rare cases, they may be associated with serious infections or cancers. Recent studies (Gordon et al., 2003; Menter, Kosinski, Bresnahan, Papp, & Ware, Jr., 2004; Menter et al., 2005) demonstrated that efalizumab is effective in reducing itch in psoriasis. In a 12-week study, patients with psoriasis treated with efalizumab exhibited significantly greater mean percentage improvement in itch than placebo-treated patients as measured by itch intensity on a visual analog scale (38% vs. -0.2%, p<0.001) (Gordon et al., 2003). Menter et al. (2005) demonstrated that extending treatment from 12 to 24 weeks was associated with maintenance of the mean percentage improvement in patient-reported itch (42%). However, thus far, these are the only studies that have examined the effectiveness of any of the biologics for pruritus. Further clinical trials will be needed to determine if the other biologics also reduce itch.

No single therapy will be effective for all psoriasis patients with itch. Treatment must be tailored to each individual patient's response. In addition, psoriasis can become resistant to medications after repeated use and it is often necessary to rotate or combine different treatments. For many patients, the best treatment strategy for itch may involve combining two or more therapies. Most treatments that relieve psoriatic itch also treat psoriasis in general; however, the primary goal is to alleviate itch before clearance of visible lesions is achieved with topical and systemic therapies. It is important that such antipruritic therapies are part of each clinician's treatment armamentarium. Psoriasis patients often desire a role in selecting treatment as well (Van de Kerkhof et al., 2000) and therapies should be chosen in partnership with patients. We are optimistic that increasing understanding of itch will continue to lead to new and better therapies for patients with psoriasis.

The print version of this article was originally certified for CE credit. For accreditation details, please contact the publisher, Anthony J. Jannetti, East Holly Avenue Box 56, Pitman, New Jersey 08071-0056

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