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The information – pruritus in the elderly



 

The patient’s unmet needs (PUNs)

A 78-year-old man attends complaining of very itchy skin for a couple of months. He has no dermatological history, is fit and well and takes no medication. Examination reveals no obvious skin pathology other than widespread reddened areas which the patient attributes to scratching. He’s agitated and explains that it is getting him down – he’s keen for you to prescribe something to ease the symptom.

 

The doctor’s unmet needs (DENs)

It can be difficult to determine whether skin lesions are the cause or the result of itching. Which primary skin disorders should we suspect?

When assessing a patient with widespread pruritus, the first aim is to determine if it is due to an underlying skin disorder or a generalised pruritus without skin lesions. Common pruritic primary skin disorders in the elderly are listed in the box below. Xerosis (dry skin) is the most common cause.

Generalised pruritus without skin lesions is a diagnosis of exclusion. It presents with widespread excoriations and erythema on a background of normal skin, without any features of primary skin disorders.

Where there is no specific skin disease, how likely is a systemic cause? What investigations should we perform?

When a diagnosis of generalised pruritus without skin lesions is established, the next aim is to look for an underlying systemic cause, which is present in 13–50% of patients.1 The itch threshold can be lowered by systemic diseases and can be further exacerbated by xerosis in the elderly. Common underlying systemic causes are listed in the table (see PDF, right).

Drugs – commonly aspirin, opioids, ACE inhibitors and statins – may also be a systemic cause of pruritus in the elderly.

If, after a thorough history and examination, the underlying systemic cause is not obvious, request:

  • FBC
  • Blood film
  • U&Es
  • LFT
  • TFT
  • Ferritin
  • Fasting blood glucose
  • ESR or CRP

Depending on the history and examination, other investigations such as chest radiography and urinalysis may be requested.

If no primary skin disorders or systemic causes are found, consider idiopathic itch. Although xerosis is probably the most common factor, many elderly patients do mot have xerotic skin. Other factors like age-related changes in nerve fibres, central disinhibition of itch, decreased skin surface lipids, and reduced sweat and sebum production may be associated.

If no systemic or skin disease is apparent, what topical treatments should be offered? Do any specific emollients have particular advantages?

It is essential to recognise that cognitive and physical impairments in older people could affect compliance with topical treatments. The help of family members and carers may be required.

Before using topical treatments, offer general tips to ensure optimal skin hydration and prevent the itch-scratch cycle:

  • Maintain a humidified environment.
  • Wear light and loose clothing.
  • Don’t dwell too long in baths and showers, and use cool or lukewarm water. Apply emollients immediately afterwards.
  • Use soap substitutes and avoid alkaline or alcohol-containing cleansers.
  • Keep fingernails short.

Emollients are the mainstay of treatment, especially in patients with xerosis, and should be applied at least twice daily. They improve the skin barrier function, preventing water loss and entry of irritants. Ointments are more effective than creams or lotions but are less well tolerated. Emollients containing urea improve skin hydration but may cause irritation. Preparations like menthol in aqueous cream distract from the itch with cold sensation. Emollients containing lauromacrogols are reputed to relieve pruritus via their mild anaesthetic effect, but no studies of this are available.

Topical crotamiton is helpful for localised pruritus and may be trialled for widespread pruritus if emollients are unsatisfactory. Other treatments like doxepin and capsaicin creams, and topical antihistamines and anaesthetics are also helpful for localised pruritus but are not recommended for generalised pruritus because of side effects and impracticality in widespread use. Only use topical corticosteroids and calcineurin inhibitors if an inflammatory dermatosis is present.

Elderly patients with pruritus are commonly stressed or depressed. Is pruritis often a manifestation of underlying anxiety or depression, or are psychological symptoms usually secondary to the pruritis? Is a trial of an antidepressant worthwhile?

Chronic pruritus can affect patients’ quality of life comparably to chronic pain. Low self-esteem, distress and sleep impairment in particular, result in fatigue that influences work and family relationships. This can lead to anxiety and depression which is present in 32% of patients with generalised pruritus. On the other hand, pruritus is a presenting symptom of depression in 4% of patients.3 So anxiety and depression are most likely to be secondary to pruritus.

Tricyclic antidepressants (doxepin) and SSRIs (paroxetine) are reported to be effective in psychogenic pruritus. Mirtazepine has a sedative effect so is useful for nocturnal itch. Resolution of depression-associated pruritus has been seen when depression is treated with antidepressants. Whether this is because of improvement of the depression or the anti-pruritic effect of antidepressants is unknown. So a trial of antidepressants is worthwhile in anxious or depressed patients with pruritus. Start at low doses and taper up cautiously to avoid side effects.

Antihistamines are often prescribed in patients with pruritis. Is there any evidence behind their use? Is it best to prescribe a sedating antihistamine if one is used at all?

Histamine is one of several neurotrans- mitters that stimulate pruritus by binding with histamine 4 receptors and to a lesser degree with histamine 1 receptors (H1R). H1R antagonists are the only antihistamines currently available to treat pruritus. Sedating H1R antagonists, such as hydroxyzine and chlorphenamine, tend to be more effective than non-sedating H1R antagonists, such as cetirizine and loratadine. Histamine 2 receptor antagonists are ineffective.

Antihistamines are effective for pruritus in histamine-mediated diseases like urticaria, but are of limited efficacy in standard doses for pruritus of other causes, where high doses (four times the licensed dose) or a combination of different antihistamines are required.4 But high-dose antihistamines – particularly when taken over the counter – should be used with caution in the elderly due to their sedative and anticholinergic side effects, and interactions with other drugs.

If an antihistamine is used, sedating H1R antagonists are recommended for nocturnal pruritus and non-sedating H1R antagonists for daytime use. Sedating H1R antagonists in lower doses divided throughout the day are an alternative option.

 

Dr Paul Yesudian is a consultant dermatologist and Dr Kun Sen Chen is an ST4 dermatology specialty trainee at Betsi Cadwaladr University Health Board, North Wales