Uremic Pruritus

• The pathophysiology of uremic pruritus is poorly understood
• Hypotheses implicating immunologic and opioidergic systems have been proposed
• May be result of systemic inflammation
• opioid hypothesis proposes that imbalances in the expression of mu and kappa opioid receptors cause pruritus

Risk Factors

• Inadequate dialysis
• Hyperparathyroidism
• Elevated calcium x phosphorus product
• Xerosis (dry skin caused by sweat gland atrophy)
• Elevated serum magnesium and aluminum concentrations

Management

Dialysis modification

• Increasing the dose of dialysis may improve pruritus 

Parathyroid, calcium, and phosphate 

• Limited data suggest that the treatment of hyperparathyroidism, hyperphosphatemia, and an elevated calcium x phosphate product reduces uremic pruritus

Emollients  

• Emollients are the preferred topical treatment of uremic pruritus, especially if xerosis (dry skin)

Resistant pruritus 

• We define resistant pruritus as continued symptoms despite adequate dialysis, optimization of metabolic parameters, and the use of topical emollients and analgesics for approximately four weeks.
• Such patients may be treated with an oral antihistamine and, if that is ineffective after a one- to two-week trial, gabapentin or pregabalin.

Oral antihistamines 

• The beneficial effects of antihistamines in pruritus are believed to be mediated via both their sedating properties and ability to stabilize mast cell
• suggest the use of either hydroxyzine (25 mg orally three to four times daily) or diphenhydramine (25 mg orally three to four times daily) for patients who do not respond to other measures
• suggest trying a less sedating agent, such as loratadine, during the day, with the continued use of the sedating antihistamines at night

Gabapentin

• If oral antihistamines provide no relief of symptoms after a one-week trial, gabapentin may be prescribed.
• The preferred initiating dose of gabapentin is 100 mg after each dialysis session. The dose may be gradually increased to 350 mg daily. Doses greater than 350 mg daily are not recommended in dialysis patients.

Pregabalin

• The preferred initiating dose of pregabalin is 25 mg daily. The dose may be gradually increased to 75 mg daily. Doses greater than 75 mg daily are not recommended in dialysis patients

Sertraline 

• selective serotonin reuptake inhibitor (SSRI), sertraline, may be an effective treatment of uremic pruritus

Refractory pruritus 

• Most patients with uremic pruritus will at least partially respond to emollients, topical analgesics and oral antihistamines or gabapentin.
• For patients who are refractory to these agents, ultraviolet B (UVB) phototherapy is a therapeutic option.

Others

• Many oral therapies have been reported in small series to be effective for uremic pruritus. These include opioid receptor agonists and antagonists, omega-6 fatty acids, charcoal, 5-hydroxytryptamine receptors, cromolyn sodium
• Oral use of activated charcoal has been shown to completely resolve or significantly reduce pruritus symptoms in patients on chronic dialysis (6g od, based on some trials)

References:

1. www.uptodate.com
2. http://www.researchgate.net/publication/15633420_Oral_Activated_Charcoal_in_Patients_with_Uremic_Pruritus
3. http://www.medscape.org/viewarticle/587670_2