Pharmacologic control of pruritus

Pharmacological interventions for pruritus in adult palliative care patients

BACKGROUND

This is an update of the original Cochrane review published in 2013 (Issue 6). Pruritus occurs in patients with disparate underlying diseases and is caused by different pathologic mechanisms. In palliative care patients, pruritus is not the most prevalent but is one of the most puzzling symptoms. It can cause considerable discomfort and affects patients' quality of life.

OBJECTIVES

To assess the effects of different pharmacological treatments for preventing or treating pruritus in adult palliative care patients.

SEARCH METHODS

For this update, we searched CENTRAL (the Cochrane Library), and MEDLINE (OVID) up to 9 June 2016 and Embase (OVID) up to 7 June 2016. In addition, we searched trial registries and checked the reference lists of all relevant studies, key textbooks, reviews and websites, and we contacted investigators and specialists in pruritus and palliative care regarding unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) assessing the effects of different pharmacological treatments, compared with a placebo, no treatment, or an alternative treatment, for preventing or treating pruritus in palliative care patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the identified titles and abstracts, performed data extraction and assessed the risk of bias and methodological quality. We summarised the results descriptively and quantitatively (meta-analyses) according to the different pharmacological interventions and the diseases associated with pruritus. We assessed the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation) and created 10 'Summary of findings' tables.

MAIN RESULTS

In total, we included 50 studies and 1916 participants in the review. We added 10 studies with 627 participants for this update. Altogether, we included 39 different treatments for pruritus in four different patient groups.The overall risk of bias profile was heterogeneous and ranged from high to low risk. However, 48 studies (96%) had a high risk of bias due to low sample size (i.e. fewer than 50 participants per treatment arm). Using GRADE criteria, we downgraded our judgement on the quality of evidence to moderate in seven and to low in three comparisons for our primary outcome (pruritus), mainly due to imprecision and risk of bias.In palliative care participants with pruritus of different nature, the treatment with the drug paroxetine, a selective serotonin reuptake inhibitor, reduced pruritus by 0.78 points (numerical analogue scale from 0 to 10; 95% confidence interval (CI) -1.19 to -0.37; one RCT, N = 48, quality of evidence: moderate) compared to placebo.For participants suffering from uraemic pruritus (UP), gabapentin was more effective than placebo (visual analogue scale (VAS): 0 to 10), mean difference (MD) -5.91, 95% CI -6.87 to -4.96; two RCTs, N = 118, quality of evidence: moderate). The κ-opioid receptor agonist nalfurafine showed amelioration of UP (VAS 0 to 10, MD -0.95, 95% CI -1.32 to -0.58; three RCTs, N = 422, quality of evidence: moderate) and only few adverse events. Moreover, cromolyn sodium relieved UP participants from pruritus by 2.94 points on the VAS (0 to 10) (95% CI -4.04 to -1.83; two RCTs, N = 100, quality of evidence: moderate) compared to placebo.In participants with cholestatic pruritus (CP), data favoured rifampin (VAS: 0 to 100, MD -24.64, 95% CI -31.08 to -18.21; two RCTs, N = 42, quality of evidence: low) and flumecinol (RR > 1 favours treatment group; RR 1.89, 95% CI 1.05 to 3.39; two RCTs, N = 69, quality of evidence: low) and showed a low incidence of adverse events in comparison with placebo. The opioid antagonist naltrexone reduced pruritus for participants with CP (VAS: 0 to 10, MD -2.26, 95% CI -3.19 to -1.33; two RCTs, N = 52, quality of evidence: moderate) compared to placebo. However, effects in participants with UP were inconclusive (percentage difference -12.30%, 95% CI -25.82% to 1.22%, one RCT, N = 32). Furthermore, large doses of opioid antagonists (e.g. naltrexone) could be inappropriate in palliative care patients because of the risk of reducing analgesia.For participants with HIV-associated pruritus, it is uncertain whether drug treatment with hydroxyzine hydrochloride, pentoxifylline, triamcinolone or indomethacin reduces pruritus because the evidence was of very low quality (e.g. small sample size, lack of blinding).

AUTHORS' CONCLUSIONS

Different interventions tended to be effective for CP and UP. However, therapies for patients with malignancies are still lacking. Due to the small sample sizes in most meta-analyses and the heterogeneous methodological quality of the included trials, the results should be interpreted cautiously in terms of generalisability.

Pruritus

Pruritus is a common problem that can result from many conditions. Some, such as fungal or parasitic infection, may be fairly obvious. However, others, such as iron deficiency and psychogenic disorder, are more difficult to diagnose. Evaluation must include a thorough inspection of the skin, history taking for drug intake and chemical exposure, and appropriate laboratory testing. The location on the body and characteristics of the itching may point to a cause. In some cases, attention to exacerbating factors (eg, dry skin, coarse fabrics against the skin, dry environmental conditions) and application of topical preparations may be sufficient. Antihistamines are the foundation of oral treatment, and with the advent of second-generation agents, they can be taken with fewer concerns about their sedative effects. Specific conditions of which pruritus is one feature may require specific treatment. For example, in patients undergoing dialysis, activated charcoal, UV light treatment, or heparin therapy may be useful.

Pharmacological interventions for pruritus in adult palliative care patients

BACKGROUND

Pruritus is not the most prevalent but one of the most puzzling symptoms in palliative care patients. It can cause considerable discomfort and has a major impact on patients' quality of life. In the field of palliative care, pruritus is a symptom occurring in patients with disparate underlying diseases and based on different pathologic mechanisms but ending in the same phenomenon. The pathogenesis of pruritus is complex and not fully elucidated. Thus, it is still very difficult to treat pruritus effectively. Evidence-based treatment approaches are needed.

OBJECTIVES

The objective was to evaluate the efficacy of different pharmacological treatments for preventing or treating pruritus in adult palliative care patients.

SEARCH METHODS

A systematic literature search up to January 2012 was performed and it was updated in August 2012. The following databases were searched: The Cochrane Library (CENTRAL, DARE, CDSR) (2012, issue 8 of 12); MEDLINE (1950 to August 2012); EMBASE (1980 to August 2012) and three other databases. In addition, we searched trials registries and checked the reference lists of all relevant studies, key textbooks, reviews, and websites, and contacted investigators and specialists in pruritus and palliative care regarding unpublished data.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of different pharmacological treatments on preventing or treating pruritus in palliative care patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed identified titles and abstracts. Three independent review authors performed assessment of all potentially relevant studies, data extraction, assessment of risk of bias and methodological quality. Results were summarised descriptively according to the different pharmacological interventions and the type of underlying pruritus. Where possible, results were presented in meta-analyses.

MAIN RESULTS

In total, 38 reports comprising 40 studies and 1286 participants were included in the review. Altogether, 30 different treatments for pruritus in four different patient groups were included.The findings of this review indicated that the treatment of pruritus for palliative care patients is challenging and requires an individualistic approach. Results showed that effective therapeutic choices have to be guided by the pathophysiology of the pruritus. Various forms of pruritus occur, especially in the field of palliative care, and sometimes the origin of the pruritus is difficult to determine. Therefore, identifying the underlying cause of pruritus is of prime importance in order to develop tailored treatment plans, even if in palliative care the treatment is focused towards the symptom and not necessarily the underlying disease.Results show that in palliative care patients with pruritus of different natures, treatment with the drug paroxetine, a selective serotonin reuptake inhibitor, may be beneficial. For patients suffering from pruritus associated with HIV infection, indomethacin was described as the most effective drug, although the evidence was weak. For patients suffering from chronic kidney disease-associated pruritus, gabapentin may be an option. An alternative treatment for this patient group seems to be the κ-opioid receptor agonist nalfurafine, which has shown significant amelioration of pruritus and acceptable adverse effects. As they have exhibited a low incidence of adverse effects, rifampicin and flumecinol may be recommended for patients with cholestatic pruritus. The opioid antagonist naltrexone has been shown to offer a therapeutic alternative for patients suffering from uraemic or cholestatic pruritus. However, these drugs are often inappropriate in the palliative population because of the risk of reducing analgesia when giving high doses of naltrexone.

AUTHORS' CONCLUSIONS

The findings of this review indicate that the number of systemic and topical drugs used for the different subforms of pruritus is increasing. Different interventions have been shown to be effective in the treatment of pruritus of different origins. Nevertheless, an optimal therapy for pruritus is constrained due to the limited understanding of crucial itch mediators and receptors in the various subforms of itch. Ideal antipruritic therapies are still lacking, especially for palliative care patients.This systematic review also indicates that there is insufficient evidence to give any concrete recommendations regarding treatment of pruritus in palliative care patients. Due to the very small sample sizes and poor methodological quality of the majority of studies that were included, the results of this review need to be interpreted with caution. Furthermore, the generalizability is questionable. Additional studies, and particularly carefully designed treatment trials, are needed to provide valid evidence for adequate treatment of pruritus in palliative care patients.

Treatment of pruritus associated with systemic disorders in the elderly: a review of the role of new therapies

Generalised pruritus is common in the elderly. Idiopathic 'senile pruritus' is a diagnosis of exclusion, and an underlying systemic disorder should be sought. Thyroid disease, haematological malignancy, iron deficiency, cholestasis or renal impairment may be responsible for pruritus. Rarely pruritus may occur after cerebral infarction or as a paraneoplastic phenomenon. The mechanisms of pruritus are poorly understood. In systemic disorders, correction of the underlying disorder alleviates itch. However, when this cannot be achieved, a symptomatic approach is required. Response to treatment varies enormously and an empirical approach is often required. Topical applications are available to soothe the skin and bandaging techniques may improve their efficacy. A number of more targeted treatments are available for renal and cholestatic pruritus. Novel therapies such as thalidomide, opioid antagonists, ondansetron and phototherapy with ultraviolet (UV)-B radiation are now being used. Treatment of pruritus needs to be individualised, and the elderly present a particular challenge. Adequate delivery of simple emollients may be impossible because of physical impairment The elderly are more vulnerable to the adverse effects of treatments, comorbidities may alter the pharmacokinetics of drug metabolism and polypharmacy increases the likelihood of adverse drug interactions. Cognitive impairment can lead to poor compliance with treatment. The patient's general health, the severity of symptoms and the adverse effects of treatment all need to be considered. Most treatments are of benefit only to some patients; others derive only marginal improvement. Many of the newer treatments are unlicensed for pruritus and should preferably be administered under specialist supervision. We review the literature concerning the treatment of itch associated with systemic diseases, with particular emphasis on issues relevant to the elderly. Pruritus is a difficult symptom to treat. However, it is hoped that research into the mechanisms underlying the pruritus of systemic disease will allow a better understanding so that we should be able to look forward to more specific and effective therapies in the future.

Danazol relieves refractory pruritus associated with myeloproliferative disorders and other diseases

Severe pruritus is frequently associated with myeloproliferative and other systemic illnesses, and often fails to respond to conventional measures. We used danazol (Danocrine), a synthetic attenuated androgen, in the treatment of severe pruritus refractory to conventional therapy. Eight patients had myeloproliferative disorders (MPD), seven had autoimmune disorders, and seven had skin diseases. Danazol at 400-800 mg/day was administered, and previous medications were tapered off. When itching was controlled with danazol alone, the dosage was reduced or discontinued, and resumed if itching recurred. Clinical responses were graded, and side effects were monitored. Overall, in 12 of 22 patients refractory to other measures, itching was controlled with danazol alone. In 10 patients itching returned when danazol was discontinued or dosage was continued for up to 5 years in responders. No serious side effects were observed. Our experience indicates that danazol is a good alternative for patients with severe pruritus associated with myeloproliferative and other systemic disorders.

Pruritus in the elderly: management by senior dermatologists

BACKGROUND

Pruritus in older patients is common, yet remains a challenge for clinicians. By virtue of their years of experience and older age, senior dermatologists may have developed opinions and approaches that are insightful.

METHODS

A random sample of board-certified dermatologists older than 64 years of age was surveyed by a written anonymous questionnaire to assess their opinions, diagnostic approaches, and treatments of pruritus and xerosis in the older adult.

RESULTS

The 63 respondents whose surveys were analyzed believe the most common cause of generalized pruritus in the elderly is xerosis. Of those respondents who believe laboratory evaluation is necessary for generalized pruritus in this population, a complete blood cell count and a multichemistry panel were the most frequently ordered tests. Treatment regimens and products recommended were highly variable and included topical emollients, corticosteroids, and others. The most common systemic agent employed was hydroxyzine hydrochloride, followed by corticosteroids, doxepin, diphenhydramine, and terfenadine. Various topical, physical, and miscellaneous treatments were recommended.

CONCLUSION

This study provides a glimpse into the diagnostic and therapeutic approaches of senior dermatologists.

Pruritus: a practical approach

Pruritus is usually caused by a primary disorder of the skin, but can also be caused by a systemic disease (Table 1). Some dermatologic conditions that cause pruritus can be inconspicuous or nonspecific (Table 2), while others are usually apparent on physical examination (Table 3). Classification of pruritus as localized (Fig. 1) vs. generalized (Fig. 3) can be helpful in arriving at a correct diagnosis. The history and physical examination are the most important diagnostic tools, though laboratory testing for systemic disease may be necessary. In refractory cases, one should consider occult systemic disease (such as malignancy), psychiatric disease (especially depression), and HIV infection. Subsequent referral to a dermatologist may be indicted. When treatment of the underlying cause of pruritus is not possible, antihistamines and topical agents (menthol, phenol, and/or pramoxine) can be helpful.

Skin problems in advanced and terminal cancer patients

Disturbances caused by skin problems may compromise the quality of life of cancer patients. The main complications affecting the skin comprise the dermatologic toxicity of anticancer therapy, bedsores, malignant ulcers, sores due to nonmetastatic cancer, pruritus, and infections. Most of the information available about these entities has been acquired in the cancer patient without advanced disease. The little currently known about the epidemiology and physiopathology of such lesions in the advanced phase of cancer is presented, and approaches to management are suggested.

Pathophysiology of pruritus

In spite of the research that has been performed, pruritus remains a poorly understood sensation. It is important to remember that the majority of information presented here is derived from observations of human subjects. One can only speculate as to how much of this information can be extrapolated to pruritus in animals. Pruritus is closely intertwined with pain and touch. Pain and pruritus sensations are carried on A delta and C fibers, ascend on the lateral spinothalamic tract, and terminate in various brain centers, including the thalamus and the cortex. The gate control theory of pain and pruritus describes the substantia gelatinosa cells as "swinging gates" to modify peripheral input and result in stimulation of higher centers. Central factors reduce or amplify the perception of these cutaneous sensations. Histamine is the classic mediator of pruritus, although it is still unknown whether a final common mediator of pruritus exists. Numerous other mediators include proteases, peptides, substance P, opiate peptides, prostaglandins, and leukotrienes. These may have pruritic properties directly, or may act as histamine liberators to cause pruritus.

Effect of acupuncture on experimentally induced itch

The effect of acupuncture on experimentally induced itch was studied in 10 healthy volunteers. Itching was induced by intradermal injections of histamine on the upper arm. 'Placebo-acupuncture', acupuncture and electro-acupuncture at 2 Hz or 80 Hz were applied over the injection site, proximal to the injection site (in the same dermatome) or extrasegmentally (ipsilateral to the injected arm) for a period of 5 min following induction of itch. In addition, the effect of a 5 min period and a 20 min period of stimulation of the skin area prior to the induction of itch were studied. The same periods of stimulation were also applied to extrasegmental points prior to the induction of itch on the arm. Acupuncture and 2 Hz and 80 Hz electro-acupuncture significantly reduced subjective itch intensity when applied intrasegmentally. No significant effects were obtained when stimulation was applied extrasegmentally. The results suggest that acupuncture or electro-acupuncture could be tried in clinical conditions associated with pruritus.

Pharmacology and significance of nonsteroidal anti-inflammatory drugs in the treatment of skin diseases

Intensive studies of the molecular pathways involved in common inflammatory skin disorders, coupled with detailed pharmacologic evaluation of the responses of skin to the end products of these pathways, have resulted in a much clearer understanding of the mode of action of nonsteroidal anti-inflammatory drugs. In particular the development of lipoxygenase inhibitors is prompting intense interest in their possible role as anti-inflammatory agents in psoriasis and other dermatoses. Because of the potency of these and other classes of new anti-inflammatory drugs, careful monitoring of their pharmacokinetics in individual patients, especially those at risk for adverse reactions, will prove necessary, especially in the early stages of treatment. Meanwhile, currently available nonsteroidal anti-inflammatory drugs have a limited but significant place in the treatment of certain dermatoses. Current experience of the high incidence of adverse reactions to existing nonsteroidal anti-inflammatory drugs suggests that this will be no less a problem with new agents under development. The skin is frequently involved in adverse reactions to this class of drug, and past experience suggests that cutaneous reactions are among the earliest unwanted side effects reported in a new drug of this type. The dermatologist, therefore, has an important responsibility to observe, document, and report such "early warning signs" to the appropriate licensing authority and the manufacturer.

The influence of mechanical vibratory stimulation and transcutaneous electrical nerve stimulation on experimental pruritus induced by histamine

The effect of conditioning mechanical vibratory stimulation and transcutaneous electrical nerve stimulation (TENS) on experimentally induced pruritus was studied on 12 healthy subjects. Pruritus was provoked by intradermal injection of histamine on the upper arm. Vibration at 10, 100 and 200 Hz and TENS at 2 and 100 Hz were applied (i) over or (ii) proximal (in the same dermatome) to the pruritic area for a period of 5 min following itch elicitation. In addition the influence of a 5 min pre-stimulatory regimen of the injection area was investigated (iii). The results obtained were compared with unconditioned values and with those obtained following a placebo conditioning procedure (i, ii). It was found that vibratory as well as electrical stimulation, for all frequencies used, reduced subjective itch intensity. Vibration at 100 Hz was the most effective mode of stimulation especially when applied directly to the pruritic area. Conditioning with 100 Hz vibration was also the most effective mode for reducing the duration of the itch response as well as the total experience of pruritus (estimated as a total itch index). Induction time to partial and maximal itch alleviation was shortest for 100 Hz vibration. The results indicate that treatment of pruritic conditions with conditioning stimulation, especially vibration, may be of therapeutic interest.