Psoriasis – Management and complications

Vitamin D analogues

Calcipotriol (Dovonex), tacalcitol (Curatoderm) and calcitriol (Silkis) are topical synthetic vitamin D analogues for use in mild and moderate chronic plaque psoriasis. They inhibit cell proliferation and stimulate keratinocyte differentiation, correcting some of the epidermal cell proliferation changes in psoriasis. Patient acceptability is good as the preparations do not smell or stain, are easy to apply and do not have the risk of skin atrophy seen with topical steroids. Skin irritation may be a problem. Efficacy is commensurate with dithranol or topical steroids.

Hypercalcaemia is possible if the maximum dose is exceeded. Calcipotriol cream can be used up to 100 g/week (40% of the body surface on a twice-daily basis), and tacalcitol ointment up to 35 g/week (20% of body surface as a once-daily dose). Tacalcitol is tolerated on the scalp and face, where calcipotriol tends to irritate. Calcipotriol is available as a scalp preparation. Vitamin D analogues are often used in alternation with a topical steroid, and in combination with ultraviolet B or psoralen plus ultraviolet A (PUVA) therapy.

Topical corticosteroids

Topical steroids have the advantage of being clean, non-irritant and easy to use. However, against this must be balanced the risk of side-effects (p. 23) and of precipitating an unstable form of psoriasis, especially on their withdrawal. Topical steroids are the treatment of choice for face, genitalia and flexures, and are useful for stubborn plaques on hands, feet and scalp. Potent steroids should not be applied to the face, although they may be used judiciously on palms and soles. Elsewhere, moderately potent steroids normally suffice. Their use must be monitored carefully. Creams are often preferred to ointments. Lotions and gels are available for the scalp.

Coal tar preparations

Coal tar distillates have been used for decades to treat psoriasis. They are safe and seem to act by inhibiting DNA synthesis. The main disadvantages of tar are that it smells and is messy. Despite this, it can be useful for inpatient care, e.g. combined with ultraviolet B – the Goeckermann regimen. Refined tar (1–10%) is available in a cream or lotion base for outpatient use (e.g. Carbo-Dome, Exorex, Psoriderm). These preparations are suitable for chronic plaque psoriasis or guttate psoriasis once the acute phase is past.

Dithranol (anthralin)

Dithranol has an antimitotic effect and is irritant to normal skin. It cannot be used on the face or genitalia, and it stains skin, hair, linen, clothes and bathtubs a purple-brown colour. For inpatient use, the usual base is Lassar’s paste (zinc and salicylic acid paste BP). It is applied to the plaques of psoriasis initially in the 0.1% strength, increasing up to 2% if necessary. The surrounding skin is protected with a bland preparation such as white soft paraffin, and the treated area is covered with tube gauze. The combination of this with a daily tar bath and ultraviolet B is called the Ingram regimen. Psoriasis clears within 3 weeks in most patients on this treatment.

The ‘short contact regimen’, in which dithranol is applied for 30 min each day, is suitable for outpatients with stable plaque psoriasis. The dithranol is best washed off in a shower. Dithrocream is a suitable preparation and comes in concentrations from 0.1% to 2%.

Retinoids

A topical retinoid, tazarotene (0.05% and 0.1%; Zorac gel), is effective for chronic plaque psoriasis. It may irritate and is often used alternating with a topical steroid.

Keratolytics and scalp preparations

Hyperkeratotic psoriasis of the palms and soles can be treated with 5% salicylic acid ointment. Scalp psoriasis (Fig. 1) responds to 3% salicylic acid in a cream base (sometimes with 3% precipitated sulphur) applied daily or every 2 or 3 days, and is used in combination with a tar-containing shampoo (e.g. Alphosyl 2 in 1, Capasal, Polytar, T/Gel). Coconut oil compound (e.g. Cocois, with tar, salicylic acid and sulphur) also helps scaly scalps.

Fig. 1 Scaly plaques of psoriasis in the scalp, with localized hair loss.

Methotrexate

The folate antagonist methotrexate is well established as an effective treatment for severe psoriasis and may have anti-inflammatory as well as immune modulatory effects. It is given once a week orally as a single dose (usually 7.5–15 mg), although it can be given subcutaneously or intramuscularly. Normal liver, kidney and bone marrow function must be established before starting methotrexate, and these functions must be monitored during treatment. Liver disease, alcoholism and acute infection are contraindications to methotrexate, and drug interaction (e.g. with aspirin, non-steroidal anti-inflammatory drugs or co-trimoxazole) must be avoided. Improvement is seen within 2–4 weeks. Minor side-effects (e.g. nausea) are common, but liver fibrosis or cirrhosis is a risk long term. Liver damage can be monitored using the serum procollagen III aminopropeptide. Most authorities now regard the morbidity and cost of routine liver biopsy to be unjustified. Methotrexate is also a teratogen.

Retinoids

The vitamin A derivative acitretin (Neotigason) is particularly effective in treating pustular psoriasis and in thinning hyperkeratotic plaques. Acitretin may be used with topical therapies or with UVB or PUVA (‘Re-PUVA’), when it allows a more rapid clearance at a lower total dose of UV. Most patients develop minor side-effects, such as dry mucous membranes, itching and peeling skin. More serious complications include hyperostosis, abnormal liver function, hyperlipidaemia and teratogenicity. The last virtually precludes the use of acitretin in women of child-bearing age. Although acitretin has a half-life of 50 days, in some patients it is metabolized to etretinate, a retinoid that takes 2 years to be excreted.

Ciclosporin

Ciclosporin, an immunosuppressant widely used to prevent rejection of organ transplants, is effective in severe psoriasis. It acts by inhibiting T lymphocyte activation and interleukin-2 production. Dose-dependent reversible nephrotoxicity is a side-effect. Blood pressure and kidney function are monitored during treatment. There may be a risk of skin cancer or lymphoma, and concomitant UV treatment is avoided.