Finding cause of chronic pruritus helps to narrow down treatment strategies

QuickRead: Pruritus particularly when chronic and of an unknown etiology can be extremely difficult to treat. Individualizing treatment protocols in each patient using standard and emerging therapies can help manage symptoms.

Miami Beach, Fla. - An accurate assessment of the potential cause of chronic pruritus, coupled by a careful selection of current standard treatments as well as new and emerging therapies, can be instrumental in helping to quell the symptoms of this sometimes severely debilitating condition.

Identifying the cause of pruritus is essential and, according to Sarina Elmariah, M.D., Ph.D., it is crucial that the clinician distinguish between pruritus that reflects inflammation in the skin and that which reflects inflammation or damage within the nervous system, as conclusions from this critical assessment will help direct appropriate therapy.

“As the pathophysiology of pruritus in most cutaneous or systemic disorders remains unclear, anti-pruritic therapy is often directed against a variety of targets including the epidermal barrier, immune system or the nervous system,” says Dr. Elmariah, of the department of dermatology, Massachusetts General Hospital, Harvard Medical School, Boston. Dr. Elmariah spoke at the annual meeting of the American Academy of Dermatology.

“While topical therapies are the cornerstone of anti-pruritic treatment, combining such therapies with systemic anti-itch agents may prove beneficial for more challenging cases involving generalized pruritus or pruritus due to systemic disease,” she says.

Establishing treatment strategies

After taking a thorough history to elicit timing, duration, location, severity and potential triggers for a patient’s itch, Dr. Elmariah will assess the integrity of the skin for signs of inflammation, dryness and barrier disruption, helping to further establish the etiology of the pruritus and potential treatment strategies.

Particularly in elderly patients although not exclusively, one of the most common causes of chronic pruritus is xerosis Dr. Elmariah says, followed by other chronic inflammatory skin diseases such as atopic dermatitis, psoriasis, seborrheic dermatitis, lichen planus and urticaria.

While xerosis can be best treated by avoiding bathing in hot water, not using harsh soaps, and moisturizing with heavy creams or ointments, Dr. Elmariah says inflammatory skin diseases can be treated with several approaches including emollients, topical corticosteroids, phototherapy, oral antihistamines, as well as systemic immunosuppressive agents for more extreme cases.

Though idiopathic pruritus is relatively uncommon, it is one of the most difficult types of pruritus to treat because the therapeutic target remains unknown, she says. In many cases, however, underlying systemic diseases are identified as causing pruritus, whether due to renal or hepatic disease, endocrine abnormalities or underlying hematologic malignancies.

In those cases that remain “idiopathic,” Dr. Elmariah says she will often proceed with phototherapy or oral neuromodulatory agents, such as anticonvulsants, selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs) and other antidepressants, or drugs that alter opioid signaling to help with potential neuropathic components and/or when underlying systemic disease is contributing to the patient’s itch.

“Pouring on topical steroids or giving antihistamines doesn’t help when the patient’s itch isn’t due to inflammation or excess histamine in the skin,” she says. “Finding the ‘right’ therapy may take time and will often require patience on the part of the patient and physician.”

Drug reactions

A cutaneous reaction to medications is another common cause that is often overlooked in patients with chronic pruritus, Dr. Elmariah says. This possibility must always be considered in the clinical evaluation and diagnostic follow-up of the patient.

“It is important not to overlook potential drug reactions as the cause of ‘idiopathic itch.’ Many medications can cause pruritus even after years of being taken, particularly in elderly patients where poly-pharmacy is an issue. To adequately assess if a drug is the culprit, I find that patients must discontinue the drug for at least three to six months,” Dr. Elmariah says.

The gold standard of topical therapy for chronic pruritus is corticosteroids in cream or ointment bases. In those cases where pruritus is due to primary inflammatory skin disease and where topical regimens prove inadequate, Dr. Elmariah says antihistamines or immunosuppressive drugs such as mycophenolate mofetil, azathioprine and cyclosporine could be used, the latter of which may often be the most effective in gaining control of inflammation and associated pruritus.

For idiopathic or noninflammatory pruritic skin recalcitrant to topical therapy, Dr. Elmariah says she may try phototherapy as well as a host of oral neuromodulatory agents - including her first choice, gabapentin, due to its high tolerability and good efficacy, followed by SSRIs, SNRIs, mu-opioid antagonists or kappa-opioid agonists. Finding the most effective drug in a given patient can be very challenging and therapy needs to be individualized, as there is no magic bullet across the cases, she says.

“There are many medications already available that can help to effectively treat pruritus of any cause. As our understanding about the mechanisms of itch sensation and cutaneous inflammation grows, our therapeutic armamentarium is also expanding and here, new and innovative therapies to target itch pathways are just on the horizon,” Dr. Elmariah says.

Disclosures: Dr. Elmariah reports no relevant financial interests.