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Pertinent practical points for dermatology drugs

Pertinent practical points for dermatology drugs

Compliance and instructions to patients for using dermatology drugs

Noncompliance with clinician’s instructions has been estimated at around 30% in some studies. In the treatment of dermatological disease where patients may be asked to apply sticky and unpleasant preparations, this rate of noncompliance may well be higher.

An understanding of their disease encourages patients to comply with the instructions from their medical attendant. Patient involvement in the decision making process can be helpful in building rapport when dealing with a chronic problem like psoriasis or atopic dermatitis.

Compliance can be affected by the cost of medication so a clear indication of the likely cost and quantities needed for adequate treatment should be given, especially if the patient is financially disadvantaged.

Following treatment or advice from a doctor, some patients forget what the doctor has said. Information slips or pamphlets can sometimes be a useful tool in a practice. Chronic disorders such as psoriasis, atopic dermatitis or vitiligo warrant information pamphlets or photocopies from texts to enable the patient to better understand the disease process. Reliance on word of mouth or nonpeer reviewed medical information from the World Wide Web can occasionally give patients inaccurate facts and unrealistic expectations.

Some patients find it hard to absorb all the information provided by their doctor in consultation and these pamphlets or hand-outs provide them with the opportunity to peruse the information in their own time.

Points on topical corticosteroid use

Topical corticosteroids should not be used on a patient where the diagnosis is uncertain. For example, patients may use topical corticosteroids for years on a groin rash where the diagnosis is tinea cruris, which is curable with correct treatment.

It is common for patients to express reluctance to use topical corticosteroids because of misconceptions about the risks of their use.

Another problem with the use of topical corticosteroid creams is that patients are often under-supplied with medication. The prescription of a 15g tube of cream to treat a widespread dermatosis is inadequate and the prescriber should provide for adequate quantities of a corticosteroid of appropriate strength [Note] for that dermatosis. Full body coverage requires 40g of a cream and slightly less if applying an ointment.

Some adverse effects of topical corticosteroids include: formation of striae (atrophy of the skin); telangiectasia (development of prominent blood vessels); promotion of infection; idiosyncratic reactions, eg allergic contact dermatitis, perioral dermatitis; purpura in the elderly.

Suggested potencies and preparations for long-term use of topical corticosteroids for chronic dermatoses are:

           face and flexures (hydrocortisone 1%)

           trunk (betamethasone valerate 0.02%, triamcinolone acetonide 0.02%)

           elbows/knees and palms/soles (betamethasone dipropionate 0.05%, mometasone 0.1%, methylprednisolone aceponate 0.1%).

Potent corticosteroids should be avoided on the face. The only corticosteroid that is safe to use is hydrocortisone. However, more potent corticosteroids may be used intermittently for up to 2 weeks, but the greater the potency the greater the risk of local adverse effects, particularly perioral dermatitis.

Points on phototherapy

Phototherapy involves treating patients with ultraviolet (UV) light of three types:

           broadband ultraviolet B (UVB), wavelength 290 to 320nm

           narrowband UVB, wavelength 311nm

           ultraviolet A (UVA), wavelength 320 to 380nm.

UVA phototherapy usually involves the use of psoralens as photosensitisers. This is known as PUVA (psoralen and UVA radiation) therapy. The psoralen used is usually methoxsalen.

Patients taking psoralens to photosensitise themselves take the drug 2 hours before phototherapy. They remain photosensitive to a decreasing extent for 24 hours, so whilst on these drugs they must protect themselves generally from natural UV light, including the wearing of suitable eye protection. A typical course of phototherapy, either PUVA or narrowband UVB, for plaque psoriasis (see Plaque psoriasis and Phototherapy) may involve three treatments a week for 6 to 8 weeks. Patients need to stand unaided in the phototherapy apparatus for periods of up to 10 minutes. Claustrophobia is a relative contraindication for phototherapy.

Points on difficult to use preparations

Dithranol, which is principally used in plaque psoriasis, stains skin and clothing and may cause irritation and frank chemical burns if used in high concentrations. It should not be used on the face and intertriginous areas. It should be kept away from the eyes and mucous membranes, and the hands should be washed after its use. Two different modes of application are used.

Low-strength, long-contact therapy - Low-strength dithranol (0.05% to 0.1%) ointment or paste is applied for a few hours at commencement of therapy. The strength is gradually increased as necessary to 1% or 2%. The duration of contact is increased to overnight periods or longer. This regimen is particularly suitable for hospital in-patient use.

High-strength, short-contact therapy - Dithranol in a cream or ointment base is applied for 10 to 30 minutes daily before being washed off. The strength is gradually increased from 0.5% up to 2%, or occasionally 5%. The short-contact period minimises the inconvenience to the patient and makes it suitable for home use. Nightwear and sheets can be permanently stained and if the preparation is used on blonde or grey hair it produces a pinkish light brown hue.

Fluorouracil cream is used to remove superficial solar keratoses. It is used on the face for a period of 2 weeks, and on the arms and legs for 3 weeks, although these times may vary. It causes severe chemical irritationwith erythema and crusting,but heroic patients who complete a course reap significant benefits. Some irritation is needed for the preparation to be effective. It may cause some photosensitivity. If added potency is required, tretinoin can be applied along with the fluorouracil, as the two act synergistically.

Tretinoin creams in concentrations ranging from 0.025 to 0.1% can be used for acne and sun damage. Acne sufferers can experience some erythema, dryness and irritation, which can be managed by decreasing the frequency of application or discontinuing the preparation.

Patients with sun-damaged skin react more vigorously to topical tretinoin, and its use should be titrated for the individual patient, starting with a daily application for 10 minutes before washing off. The duration of application can be increased until the preparation is eventually left on overnight.

The best results in the treatment of sun damage are not seen until the preparation has been used for 6 months but include improvement in texture, reduction of pigmentation, removal of superficial solar keratoses and effacement of small wrinkles. Tretinoin is applied once daily at night and a sunscreen is used on the same area of skin each morning.

Topical isotretinoin and adapalene are used in acne and may also cause drying, erythema, burning and photosensitivity, but generally these symptoms would be less than with tretinoin.

 Points on use of modified dressings

Where increased absorption of a topically applied preparation is required, occlusion with an impermeable film such as a waterproof dressing or plastic film wrap may be considered. This is especially used to increase absorption of topical corticosteroids. It may be used where skin surfaces are thick, such as on the palms and soles, or where the dermatosis is hypertrophic, as in nodular prurigo, hypertrophic lichen planus, or in a hypertrophic scar.

Occlusion potentiates the adverse effects of topical corticosteroids, such as atrophy and telangiectasia, see adverse effects of topical corticosteroids.

The main use of wet dressings is to allow greater penetration of topically applied corticosteroids by over-hydration of the epidermis. Several methods are used, but the one used for in-patients is complex and not suitable for home use. Wet dressings can be used 3 to 4 times a day and should be stopped once significant improvement occurs. The absorption of topical corticosteroid with wet dressings is equivalent to moderate doses of oral prednisolone.

Patients have their shower or bath before application of the topical medicaments. Creams are the preferred bases. Wet towels, wet gauze bandages or wet pyjamas can be used to supply the hydration. Warm water makes the procedure more pleasant. The patient should sit or lie on plastic sheeting and extra warm water can be applied to the dressing to keep it at a comfortable temperature. After 15 minutes or so the wet dressing is removed and the skin dried with a towel.

Wet dressings are useful in settling a severe or acute eruption but are generally only needed for a few days.

Systemic absorption of corticosteroid and folliculitis are the main complications of prolonged use of wet dressings.

Points on cryotherapy

Cryotherapy is very useful in the treatment of solar keratoses, viral warts, small seborrhoeic keratoses and small skin tags (acrochordons); however, it is frequently used inappropriately by the inexperienced practitioner. A firm diagnosis is needed prior to consideration of cryotherapy.

Liquid nitrogen is the preferred cryogen. The method of application of the nitrogen is somewhat immaterial as the damage to the tissue is determined by the depth of the resultant ice ball and the thaw time. Nitrogen is usually applied with a cotton-tipped applicator or sprayed on with a cryotherapy gun. After cryotherapy, patients may be alarmed at the blistering reaction. If they are forewarned they are less likely to be anxious. A suggested patient information slip for cryotherapy would read:

Points on allergy testing

In dermatology, allergy patch testing is more helpful than prick testing in diagnosis and treatment. Allergy patch testing measures cell-mediated immunity (a type IV response) whereas prick and RAST (radio-allergosorbent test) testing measure immediate hypersensitivity (a type I reaction). Diagnosis of an allergic contact skin eruption may be obvious, as in the dermatitis one sees around earring studs in a patient sensitive to nickel. However, frequently the allergen is obscure and allergy patch testing needs to be carried out to 30 or more allergens from an international standard set to determine the source of the likely allergen.

Patches containing the allergens are applied to the skin on adhesive tape and left in place for 48 hours. The first reading is made at 48 hours when the patches are removed, and generally a second reading is made at 72 or 96 hours to see if there are any late reactions. A similar procedure (photopatch testing) is carried out when a photoallergy is suspected, but includes irradiation of the allergy test site.

Prick testing is often carried out inappropriately in the search for aetiological factors in skin disease, and while it may clarify the cause of an acute urticaria or contact urticaria it is rarely helpful in atopic dermatitis or any of the other endogenous forms of dermatitis. Patients with atopic dermatitis have sensitive skin and may react to one or more allergens on prick testing, but this reaction is no proof that the allergen is involved in aetiology of the disorder. Careful history taking, including diet, will be more useful than prick testing in determining possible causes of dietary allergy in children with atopic dermatitis.

Points on skin scrapings

If a fungal disease is suspected, microscopy and culture of skin scrapings should be carried out. Microscopy and culture of nail clippings should be performed where the nail dystrophy is suspected of being fungal. Failure to seek laboratory confirmation can lead to inappropriate treatment and long delays in diagnosis of many fungal infections. It is also common for nonfungal dermatoses to be treated as fungal ones and vice versa. Laboratories differ in their technical skill and some are less liable than others to produce false negative results from scrapings.

Points on eye testing and antimalarials

Patients on long-term antimalarial agents (chloroquine, hydroxychloroquine) should have an ophthalmological examination at the start of therapy and at 6-monthly intervals during therapy. The suggested examination should include slit-lamp microscopy, and fundus and visual field studies. Visual changes may occur at any stage during therapy. It is believed that early changes are reversible and that the crucial determinant is daily dosage rather that total cumulative dose. The risk of eye damage decreases with duration of treatment.

Points on antibiotics and the contraceptive pill

There are conflicting reports on oral antibiotics affecting the efficacy of the oral contraceptive pill. The pill has a small failure rate normally, even without the addition of oral antibiotics, and the data available today are inconclusive. For more information see the section on antimicrobial drug interactions.

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