When it comes to skin problems, chronic pruritus is one of the most common complaints—yet as many as half of these patients don’t even have a dermatological disorder. Instead, their pruritus arises from systemic disease, neurologic conditions, psychiatric disorders or as a reaction to medications.
Many of these patients will self-treat with OTC products and, when they don’t find relief, they’ll ask the pharmacist for recommendations. You’ll be better prepared to assess their condition and answer questions when you have a working knowledge of underlying causes, pathophysiology, and treatment recommendations for chronic pruritus in the absence of specific skin disease.
Causes of Chronic Pruritus Without Skin Disease
Patients with chronic pruritus that’s not caused by a dermatologic disorder may have itchy skin that appears perfectly healthy, but they’re more likely to have lesions caused by long-term scratching, such as lichenification—thick, leathery patches—and the hard, crusty lumps characteristic of prurigo nodularis. The intensity of their itch may be mild or so severe it’s disabling. When they finally see a physician, the first step is ruling out a skin disease, then the complex process of identifying one of the many causes of chronic pruritus begins:
Neurologic Chronic Pruritus: Neurologic pruritus may stem from hyperstimulation of the somatosensory system or damaged nerves. The characteristics of the itch—burning vs stinging, concurrent pain, local or generalized itch—depend on its origination. Potential underlying causes of neurologic pruritus include:1
Diabetes mellitus
HIV
Lupus
Rheumatoid arthritis
Vulvodynia
Post-herpetic neuralgia
Spinal nerve compression causes chronic itch along the affected dermatome, for example:
Brachioradial pruritus – primarily affects upper arms
Notalgia paresthetica – itching in upper to middle back
Systemic Chronic Pruritus: Pruritus is a common symptom associated with a number of diseases from the following categories:2
Cholestatic pruritus – cirrhosis, hepatobiliary diseases
Hematologic pruritus – iron deficiency
Endocrine pruritus – hyperthyroidism, hypothyroidism
Pruritus related to malignancy – Hodgkin’s lymphoma, polycythemia vera
Malabsorption syndromes – celiac disease, inflammatory bowel disease
Renal – uremic pruritus due to chronic kidney disease—affects more than one-third of patients receiving hemodialysis3
Remember that these lists aren’t comprehensive. There are other underlying health conditions and even additional causes, which further illustrates the challenge of diagnosing chronic pruritus. Some psychiatric disorders cause patients to experience intense pruritus. And pharmacists are quite familiar with the fact that pruritus can be an adverse effect of medications such as:
Angiotensin-converting enzyme inhibitors
Amiodarone
Estrogen
Simvastatin
Hydrochlorothiazide
Allopurinol
Opioids
Pathophysiology of Chronic Pruritus
The pathophysiology of chronic pruritus is as varied as the many pruritogens, peripheral and central receptors, nerve fibers and central pathways involved in itch. Histamine, proteases, serotonin, bradykinin, endothelin and neuropeptide substance P are just a few of the known pruritogens. While pathophysiology is well known for some underlying causes, it remains to be determined for others. However, two aspects are especially important to include in patient counseling:
Chronic itch-scratch cycle – The constant scratching due to chronic pruritus causes inflammation, which activates nerves and increases itch intensity. Additionally, cells involved in the inflammation response release pruritogenic substances. As a result, a persistent itch-scratch cycle develops.
Central sensitization – Either an acute pruritic event or long-term pruritus can trigger changes in the central nervous system that impair itch-inhibiting neurons. The resulting central sensitization leads to ongoing pruritus even after the underlying cause is treated.
Neuroimaging studies of the brain are beginning to show the functional and anatomic changes associated with chronic itch.4 As more research is published, experts hope to learn how chronic pruritus alters the central nervous system, ultimately opening the door to new therapies.
Treatment Recommendations for Chronic Pruritus
Chronic pruritus—defined as itch that lasts at least six weeks—demands a highly individualized approach. In addition to treating the underlying disease, the patient’s itch must be relieved as quickly as possible to prevent ongoing chronicity due to central sensitization and/or the itch-scratch cycle. Treatment options include:
Skin care – Patients benefit from hydrating emollients that protect the skin barrier. Products containing urea are recommended.
Topical treatments – A variety of active ingredients—anesthetics, antipruritics and cooling agents—are applied topically to relieve itch. Capsaicin, menthol, polidocanol, lidocaine and calcineurin inhibitors are options for chronic pruritus. Topical gabapentin cream and gamma linolenic acid help for neurogenic and uremic pruritus respectively.
Antidepressants – The tetracyclic antidepressant mirtazapine and tricyclic antidepressants relieve pruritus. SSRIs such as paroxetine or a combination of paroxetine and fluvoxamine are also effective antipruritics.
Anticonvulsants – Gabapentin and pregabalin are recommended for neuropathic pruritus, pruritus associated with chronic kidney disease, and they also show promise for treating chronic pruritus of unknown origin. The therapeutic effect may be improved when anticonvulsants are combined with antidepressants.
Behavioral therapy – Therapy that targets the itch-scratch cycle can help stop patients from unconscious, automatic scratching. These programs focus on educating the patient about skin anatomy and possible treatments, keeping a diary to record scratching behavior, discussing alternatives to scratching, and stress management.5
For pruritus therapy to be successful, comorbidities must also be assessed and treated. These patients commonly experience sleep deficiency, emotional distress and psychological disorders such as anxiety and depression.
Pharmacist Counseling Puts Patients on the Right Path
A study published in Dermatology in 2010 reported statistics that are hard to believe. In an observational study of more than 11,000 people in Germany, half of those with chronic pruritus never sought medical advice and 94 percent had not received professional treatment.6 Of course, there are any number of reasons why that could happen, but it’s feasible to believe that the lack of a rash or any other skin problems led them to believe they didn’t have anything serious to ask the doctor about. Beyond recommending topical products that will help relieve symptoms, pharmacists can put patients with chronic pruritus on the right path by encouraging them to seek medical attention.
Pharmaceutica North America provides prescription drug products such as lidocaine, OTC supplements containing capsaicin and menthol, and high-quality bulk active pharmaceutical ingredients. Contact us today to talk about how we can help you provide high-quality care for all your patients.
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