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BMJ Clin Evid. 2008; 2008: 1707.
Published online 2008 August 22.
PMCID: PMC2907996

Scabies

Professor Paul Johnstone, Regional Director of Public Health England (North)# and Professor Mark Strong, Clinical senior lecturer in public health, School of health and related research#

Abstract

Introduction

Scabies is a common public health problem, with an estimated prevalence of 300 million cases worldwide, the majority in resource-poor countries. In industrialised countries, it is most common in institutionalised communities.

Methods and outcomes

We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of topical treatments for scabies? What are the effects of systemic treatments for scabies? We searched: Medline, Embase, The Cochrane Library, and other important databases up to October 2007 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

Results

We found two systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

Conclusions

In this systematic review we present information relating to the effectiveness and safety of the following interventions: benzyl benzoate (topical), crotamiton (topical), ivermectin (oral), lindane (topical), malathion (topical), permethrin (topical), and sulphur compounds (topical).

Key Points

Scabies is an infestation of the skin by the mite Sarcoptes scabiei. In adults, the most common sites of infestation are the fingers and the wrists, although infection may manifest in older people as a diffuse truncal eruption.

  • It is a very common public health problem, with an estimated prevalence of 300 million cases worldwide, the majority in resource-poor countries.

Topical permethrin is highly effective at increasing clinical and parasitic cure of scabies within 28 days.

  • Topical lindane is also effective in treating scabies, although it has now been withdrawn from the UK market.
  • Both lindane and permethrin may be more likely to be related to rare severe adverse effects, such as death or convulsions, compared with other treatments, such as benzyl benzoate, crotamiton, or malathion.

Topical crotamiton successfully produces clinical or parasitic cure after 28 days, although it is less effective than permethrin.

We found insufficient evidence to judge the effectiveness of topical benzyl benzoate, topical malathion, or topical sulphur compounds for treating scabies.

Oral ivermectin seems effective at increasing clinical cure rates compared with placebo.

  • Observational data suggest that oral ivermectin may be effective when included in the treatment of hyperkeratotic crusted scabies, and in people with concomitant HIV.

About this condition

Definition

Scabies is an infestation of the skin by the mite Sarcoptes scabiei. Typical sites of infestation are skin folds and flexor surfaces. In adults, the most common sites are between the fingers and on the wrists, although infection may manifest in older people as a diffuse truncal eruption. In infants and children, the face, scalp, palms, and soles are also often affected. Infection with the scabies mite causes discomfort and intense itching, particularly at night, with irritating papular or vesicular eruptions. The discomfort and itching can be especially debilitating in immunocompromised people, such as those with HIV/AIDS.

Incidence/ Prevalence

Scabies is a common public health problem, with an estimated prevalence of 300 million cases worldwide, mostly affecting people in resource-poor countries, where prevalence can exceed 50%. In industrialised countries it is most common in institutionalised communities. Case studies suggest that epidemic cycles occur every 7–15 years, and that these partly reflect the population's immune status.

Aetiology/ Risk factors

Scabies is particularly common where there is social disruption, overcrowding with close body contact, and limited access to water. Young children, immobilised older people, people with HIV/AIDS, and other medically and immunologically compromised people are predisposed to infestation and have particularly high mite counts.

Prognosis

Scabies is not life-threatening, but the severe, persistent itch and secondary infections may be debilitating. Occasionally, crusted scabies develops. This form of the disease is resistant to routine treatment and can be a source of continued reinfestation and of spread to others.

Aims of intervention

To eliminate the scabies mites and ova from the skin; to cure pruritus (itching); to prevent reinfestation; to prevent spread to other people, while minimising adverse effects of interventions.

Outcomes

Cure rate: Clinical cure: the healing of original lesions, the absence of any new lesions, and the absence of any live mites in a clinically diagnosed case. Parasitic cure: the healing of original lesions, the absence of any new lesions, and the absence of any live mites in a parasitologically confirmed case. Clinical and parasitic cure measured at 28–30 days after treatment, which is the time it takes for lesions to heal and for eggs and mites to reach maturity, if treatment fails. Symptom improvement: Itch persistence and pruritus; adverse effects of treatment.

Methods

Clinical Evidence search and appraisal October 2007. The following databases were used to identify studies for this systematic review: Medline 1966 to October 2007, Embase 1980 to October 2007, and The Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Clinical Trials 2007, Issue 3. Additional searches were carried out using these websites: NHS Centre for Reviews and Dissemination (CRD) — for Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA), Turning Research into Practice (TRIP), and NICE. We also searched for retractions of studies included in the review. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the authors for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews and RCTs in any language, at least single-blinded, and containing more than 20 individuals of whom more than 80% were followed up. There was no minimum length of follow-up required to include studies. We excluded all studies described as "open", "open label", or not blinded unless blinding was impossible. In addition, we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the MHRA, which are added to the reviews as required. We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).

Table
GRADE Evaluation of interventions for Scabies.

Glossary

High-quality evidence
Further research is very unlikely to change our confidence in the estimate of effect.
Low-quality evidence
Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Moderate-quality evidence
Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Onchocerciasis
A tropical disease caused by the filarial worm Onchocerca volvulus. The disease affects the skin, causing disfiguration and itching, and is a major cause of blindness, particularly in West Africa. The worm is transmitted to humans in its larval stage through the bite of the black fly, genus Simulium.
Very low-quality evidence
Any estimate of effect is very uncertain.

Notes

Disclaimer

The information contained in this publication is intended for medical professionals. Categories presented in Clinical Evidence indicate a judgement about the strength of the evidence available to our contributors prior to publication and the relevant importance of benefit and harms. We rely on our contributors to confirm the accuracy of the information presented and to adhere to describe accepted practices. Readers should be aware that professionals in the field may have different opinions. Because of this and regular advances in medical research we strongly recommend that readers' independently verify specified treatments and drugs including manufacturers' guidance. Also, the categories do not indicate whether a particular treatment is generally appropriate or whether it is suitable for a particular individual. Ultimately it is the readers' responsibility to make their own professional judgements, so to appropriately advise and treat their patients. To the fullest extent permitted by law, BMJ Publishing Group Limited and its editors are not responsible for any losses, injury or damage caused to any person or property (including under contract, by negligence, products liability or otherwise) whether they be direct or indirect, special, incidental or consequential, resulting from the application of the information in this publication.

Contributor Information

Professor Paul Johnstone, Blenheim House, Leeds, UK.

Professor Mark Strong, University of Sheffield, Sheffield, UK.

References

1. Meinking TL, Taplin D. Infestations. In: Schachner LA, Hansen RC, eds. Pediatric dermatology. New York, NY: Churchill Livingston, 1995.
2. Stein DH. Scabies and pediculosis. Curr Opin Pediatr 1991;3:660–666.
3. Green M. Epidemiology of scabies. Epidemiol Rev 1989;11:126–150. [PubMed]
4. Meinking TL, Taplin D, Hermida JL, et al. The treatment of scabies with ivermectin. N Engl J Med 1995;333:26–30. [PubMed]
5. Strong M, Johnstone PW. Interventions for treating scabies. In: The Cochrane Library, Issue 2, 2013. Chichester, UK: John Wiley & Sons, Ltd. Search date 2010. [PubMed]
6. Meinking TL, Taplin D. Safety of permethrin vs lindane for the treatment of scabies. Arch Dermatol 1996;132:959–962. [PubMed]
7. WHO Collaborating Centre for International Drug Monitoring. Reported adverse reactions to ectoparasiticides, including scabicides, insecticides, and repellents. Uppsala, Sweden, 2002. The WHO Collaborating Centre receives summary clinical reports from National Centres in countries participating in a collaborative programme. The information is not homogenous at least with respect to origin or likelihood that the pharmaceutical product caused the adverse reaction. The information does not represent the opinion of the World Health Organization.
8. Brown S, Becher J, Brady W. Treatment of ectoparasitic infections: review of the English-language literature. Clin Infect Dis 1995;20(suppl 1):104–109. [PubMed]
9. Hall RC. Long-term psychological and neurological complications of lindane poisoning. Psychosomatics 1999;40:513–517. [PubMed]
10. Elgart ML. A risk-benefit assessment of agents used in the treatment of scabies. Drug Saf 1996;14:386–393. [PubMed]
11. Nordt SP, Chew G. Acute lindane poisoning in three children. J Emerg Med 2000;18:51–53. [PubMed]
12. Kaur GA, Nadeswary K. Field trials on the management of scabies in Jengka Triangle, Pahang. Med J Malaysia 1980;35:14–21. [PubMed]
13. Haustein UF, Hlawa B. Treatment of scabies with permethrin versus lindane and benzyl benzoate. Acta Derm Venereol 1989;69:348–351. [PubMed]
14. Burgess I, Robinson RJF, Robinson J, et al. Aqueous malathion 0.5% as a scabicide: clinical trial. BMJ 1986;292:1172. [PMC free article] [PubMed]
15. Hanna NF, Clay JC, Harris JRW. Sarcoptes scabiei infestation treated with malathion liquid. Br J Vener Dis 1978;54:354. [PMC free article] [PubMed]
16. Thianprasit M, Schuetzenberger R. Prioderm lotion in the treatment of scabies. Southeast Asian J Trop Med Public Health 1984;15:119–121. [PubMed]
17. Nnoruka EN, Agu CE. Successful treatment of scabies with oral ivermectin in Nigeria. Trop Doct 2001;31:15–18. [PubMed]
18. Pacque M, Munoz B, Greene BM. Safety of and compliance with community-based ivermectin therapy. Lancet 1990;335;1377–1380. [PubMed]
19. De Sole G, Remme J, Awadzi K, et al. Adverse reactions after large-scale treatment of onchocerciasis with ivermectin: combined results from eight community trials. Bull World Health Organ 1989;67:707–719. [PubMed]
20. WHO Collaborating Centre for International Drug Monitoring. Reported adverse reactions to ivermectin. Uppsala, Sweden, 2002. The WHO Collaborating Centre receives summary clinical reports from National Centres in countries participating in a collaborative programme. The information is not homogenous at least with respect to origin or likelihood that the pharmaceutical product caused the adverse reaction. The information does not represent the opinion of the World Health Organization.
21. Barkwell R, Shields S. Deaths associated with ivermectin treatment of scabies. Lancet 1997;349:1144–1145. [PubMed]
22. Diazgranados JA, Costa JL. Deaths after ivermectin treatment. Lancet 1997;349:1698. [PubMed]
23. Sullivan JR, Watt G, Barker B. Successful use of ivermectin in the treatment of endemic scabies in a nursing home. Australas J Dermatol 1997;38:137–140. [PubMed]
24. Aubin F, Humbert P. Ivermectin for crusted (Norwegian) scabies. N Engl J Med 1995;332:612. [PubMed]
25. Haas N, Henz BM, Ohlendorf D. Is single oral dose of ivermectin sufficient in crusted scabies? Int J Dermatol 2001;40:599–600. [PubMed]
2008; 2008: 1707.
Published online 2008 August 22.

Permethrin (topical)

Summary

Topical permethrin is highly effective at increasing clinical and parasitic cure of scabies within 28 days.

Permethrin may be more likely to be related to rare severe adverse effects, such as death or convulsions, compared with other treatments, such as benzyl benzoate, crotamiton, or malathion.

Benefits and harms

Topical permethrin versus placebo:

We found no systematic review or RCTs. For further information on safety of permethrin, see comment.

Topical permethrin versus topical crotamiton:

We found one systematic review (search date 2007, 2 RCTs, 194 people).

Cure rate

Topical permethrin compared with topical crotamiton Topical permethrin is more effective at decreasing the proportion of people with failed clinical cure at 28 days (high-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
194 people
2 RCTs in this analysis
Proportion of people with failed clinical cure 28 days
6/97 (6%) with topical permethrin
25/97 (26%) with topical crotamiton

RR 0.24
95% CI 0.10 to 0.55
P = 0.0007
Moderate effect sizepermethrin

Symptom improvement

Topical permethrin compared with topical crotamiton Topical permethrin seems more effective at decreasing the proportion of people reporting a persistence of itch (high-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Itch persistence

Systematic review
94 people
Data from 1 RCT
Itch persistence 28 days
5/47 (11%) with topical permethrin
19/47 (40%) with topical crotamiton

RR 0.26
95% CI 0.11 to 0.65
P = 0.004
Moderate effect sizepermethrin

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Adverse effects

Systematic review
94 people
Data from 1 RCT
Adverse effects/worsening of symptoms 28 days
with topical permethrin
with topical crotamiton

Topical permethrin versus topical lindane:

We found one systematic review (search date 2007, 5 RCTs, 753 people), which compared permethrin versus lindane.

Cure rate

Topical permethrin compared with topical lindane We don't know how topical permethrin and topical lindane compare at decreasing the proportion of people with failed clinical cure at 14–28 days (low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
753 people
5 RCTs in this analysis
Proportion of people with failed clinical cure rates 14 to 28 days
29/377 (8%) with topical permethrin
78/376 (21%) with topical lindane

RR 0.32
95% CI 0.13 to 0.75
P = 0.009
Results should be interpreted with caution; significant statistical heterogeneity among RCTs (P = 0.02)
Moderate effect sizepermethrin
Parasitological cure

Systematic review
484 people
3 RCTs in this analysis
Failed cure rates in parasitologically confirmed cases 14 to 28 days
17/238 (7%) with topical permethrin
42/246 (17%) with topical lindane

RR 0.31
95% CI 0.09 to 1.09
P = 0.07
Not significant

Symptom improvement

Topical permethrin compared with topical lindane Topical permethrin is more effective at decreasing the proportion of people reporting a persistence of itch (high-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Itch persistence

Systematic review
490 people
2 RCTs in this analysis
Itch persistence 28 days
41/243 (17%) with topical permethrin
68/247 (28%) with topical lindane

RR 0.62
95% CI 0.44 to 0.87
P = 0.006
Small effect sizepermethrin

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Adverse effects

Systematic review
683 people
3 RCTs in this analysis
Adverse effects
58/342 (17%) with topical permethrin
49/341 (14%) with topical lindane

Significance not assessed

Topical permethrin versus oral ivermectin:

We found one systematic review (search date 2007, 1 RCT, 95 people), comparing topical permethrin versus oral ivermectin.

Cure rate

Topical permethrin compared with oral ivermectin Topical permethrin is more effective at decreasing the proportion of people with treatment failure at 14 days (high-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
95 people
Data from 1 RCT
Failed clinical cure rates 14 days
1/45 (2%) with topical permethrin
12/40 (30%) with oral ivermectin

RR (ivermectin v permethrin) 13.5
95% CI 1.84 to 99.26
Large effect sizepermethrin

Symptom improvement

No data from the following reference on this outcome.

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Adverse effects

Systematic review
95 people
Data from 1 RCT
Aggravation of symptoms
0/45 (0%) with topical permethrin
3/43 (7%) with oral ivermectin

Significance not assessed

Further information on studies

None.

Comment

From 1990 to 1995, six adverse events were reported per 100,000 units of topical permethrin distributed in the USA (1 central nervous system adverse effect reported per 500,000 units of permethrin distributed). Resistance to permethrin seems rare.

Comparative adverse effects of treatments for scabies:

It is difficult to draw firm conclusions on the relative occurrence of severe adverse effects of different preparations reported to the WHO Collaborating Centre for International Drug Monitoring, because of incomplete information on incidence in relation to use. However, topical lindane and permethrin may be more likely to be related to rare severe adverse effects, such as death or convulsions, than topical benzyl benzoate, crotamiton, or malathion. Resistance to topical lindane has been reported in many countries. Safety results from trials and observational studies need to be summarised, particularly regarding additional risks in infants and pregnant women.

Substantive changes

Permethrin (topical) Updated systematic review added, one RCT added to review comparing topical permethrin versus topical lindane. Categorisation unchanged (Beneficial).

2008; 2008: 1707.
Published online 2008 August 22.

Lindane (topical)

Summary

Topical lindane is effective in treating scabies, although it has now been withdrawn from the UK market.

Lindane may be more likely to be related to rare severe adverse effects, such as death or convulsions, compared with other treatments, such as benzyl benzoate, crotamiton, or malathion.

Benefits and harms

Topical lindane versus placebo:

We found no systematic reviews or RCTs. For further information on safety of lindane, see comment.

Topical lindane versus topical crotamiton:

We found one systematic review (search date 2007, 1 RCT, 100 adults and children) comparing topical lindane versus topical crotamiton.

Cure rate

Topical lindane compared with topical crotamiton Topical lindane and topical crotamiton seem equally effective at reducing the proportion of people with failed clinical cure at 28 days (moderate-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
100 people
Data from 1 RCT
Failed clinical cure rates 28 days
13/50 (26%) with topical lindane
6/50 (12%) with topical crotamiton

RR (crotamiton v lindane) 0.46
95% CI 0.19 to 1.12
Not significant

Symptom improvement

No data from the following reference on this outcome.

Adverse effects

No data from the following reference on this outcome.

Topical lindane versus topical permethrin:

See option on topical permethrin.

Topical lindane versus oral ivermectin:

See option on oral ivermectin.

Topical lindane versus topical sulphur compounds:

We found one systematic review (search date 2007, 1 RCT, 100 children).

Cure rate

Topical lindane compared with topical sulphur compounds We don't know how topical lindane and topical sulphur ointment compare at decreasing the proportion of people with failed clinical cure at 28 days (very low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
100 children aged 6 months to 13 years
Data from 1 RCT
Failed clinical cure rates 28 days
3/32 (9%) with topical lindane
3/36 (8%) with topical sulphur ointment

RR 1.13
95% CI 0.24 to 5.18
Results should be interpreted with caution as a large proportion of children in both groups were lost to follow-up
Not significant

Symptom improvement

Topical lindane compared with topical sulphur compounds We don’t know how topical lindane and topical sulphur ointment compare at decreasing the proportion of people reporting a persistence of itch (very low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Itch persistence

Systematic review
100 children aged 6 months to 13 years
Data from 1 RCT
Itch persistence 28 days
2/32 (6%) with topical lindane
3/36 (8%) with topical sulphur ointment

RR 0.75
95% CI 0.13 to 4.21
Results should be interpreted with caution as a large proportion of children in both groups were lost to follow-up
Not significant

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Adverse effects

Systematic review
100 children aged 6 months to 13 years
Data from 1 RCT
Foul odour
3/50 (6%) with topical lindane
10/50 (20%) with topical sulphur ointment

P = 0.03
Effect size not calculatedlindane

Systematic review
100 children aged 6 months to 13 years
Data from 1 RCT
Skin burning
6/50 (12%) with topical lindane
2/50 (4%) with topical sulphur ointment

P = 0.2
Not significant

Systematic review
100 children aged 6 months to 13 years
Data from 1 RCT
Erythema
5/50 (10%) with topical lindane
2/50 (4%) with topical sulphur ointment

P = 0.28
Not significant

Further information on studies

None.

Comment

Lindane was withdrawn from the market in the UK in 1995. Three case reports and evidence reported to the WHO linking lindane with convulsions are suggestive but not conclusive.

Comparative adverse effects of treatments for scabies:

See comment on topical permethrin.

Substantive changes

Lindane (topical) Updated systematic review added, one RCT added to review comparing topical lindane versus oral ivermectin, another RCT added to review comparing topical lindane versus topical permethrin. Categorisation unchanged (Trade-off between benefits and harms).

2008; 2008: 1707.
Published online 2008 August 22.

Crotamiton (topical)

Summary

Topical crotamiton successfully produces clinical or parasitic cure after 28 days, although it is less effective than permethrin.

Benefits and harms

Topical crotamiton versus placebo:

We found no systematic review or RCTs.

Topical crotamiton versus permethrin:

See option on topical permethrin.

Topical crotamiton versus lindane:

See option on topical lindane.

Further information on studies

None.

Comment

Both topical crotamiton and topical permethrin have been categorised as "Beneficial" based on current evidence. However, the contributors would like to stress that permethrin is more effective than crotamiton (see option on topical permethrin).

Comparative adverse effects of treatments for scabies:

See comment on topical permethrin.

Substantive changes

Crotamiton (topical) Updated systematic review added. Categorisation unchanged (Beneficial).

2008; 2008: 1707.
Published online 2008 August 22.

Benzyl benzoate (topical)

Summary

We found insufficient evidence to judge the effectiveness of benzyl benzoate for treating scabies.

Benefits and harms

Topical benzyl benzoate versus placebo:

We found no systematic review or RCTs.

Topical benzyl benzoate versus topical sulphur ointment:

We found one systematic review (search date 2007, 1 RCT, 158 adults and children) comparing topical benzyl benzoate versus topical sulphur ointment.

Cure rate

Topical benzyl benzoate compared with topical sulphur ointment We don’t know how topical benzyl benzoate and topical sulphur ointment compare at reducing the proportion of people with failed cure at 15 days (low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Cure rate

Systematic review
158 adults and children, identified in a house-to-house survey of a semi-urban area of India
Data from 1 RCT
Failed cure 15 days
8/89 (9%) with topical benzyl benzoate
2/69 (3%) with topical sulphur ointment

RR 3.10
95% CI 0.68 to 14.14
Not significant

Symptom improvement

No data from the following reference on this outcome.

Adverse effects

No data from the following reference on this outcome.

Topical benzyl benzoate versus oral ivermectin:

See option on oral ivermectin.

Further information on studies

None.

Comment

Non-randomised trials suggest that benzyl benzoate has variable effectiveness (as low as 50%). The low cure rate may be related to the concentration of the preparation and resistance of the mite to benzyl benzoate.

Comparative adverse effects of treatments for scabies:

See comment on topical permethrin.

Substantive changes

Benzyl benzoate (topical) Updated systematic review added, two further RCTs added comparing topical benzyl benzoate versus oral ivermectin. Categorisation unchanged (Unknown effectiveness).

2008; 2008: 1707.
Published online 2008 August 22.

Malathion (topical)

Summary

We found insufficient evidence to judge the effectiveness of malathion for treating scabies.

Benefits and harms

Topical malathion:

We found one systematic review on treatments for scabies (search date 2007), which identified no RCTs on the effects of topical malathion.

Further information on studies

None.

Comment

Case series suggest that topical malathion is effective in curing infestation with scabies, with a cure rate of over 80% of people at 4 weeks. The safety results from trials and observational studies need to be systematically reviewed, particularly with regard to additional risks in infants and pregnant women.

Comparative adverse effects of treatments for scabies:

See comment on topical permethrin.

Substantive changes

Malathion (topical) Updated systematic review added; no new evidence identified. Categorisation unchanged (Unknown effectiveness).

2008; 2008: 1707.
Published online 2008 August 22.

Sulphur compounds (topical)

Summary

We found insufficient evidence to judge the effectiveness of topical sulphur compounds for treating scabies.

Benefits and harms

Topical sulphur compounds versus placebo:

We found one systematic review on treatments for scabies (search date 2007), which identified no RCTs.

Topical sulphur compounds versus topical benzyl benzoate:

See option on topical benzyl benzoate.

Topical sulphur compounds versus topical lindane:

See option on topical lindane.

Further information on studies

None.

Comment

A risk-benefit assessment found that use of topical sulphur has been associated with increased local irritation in about 25% of cases.

Comparative adverse effects of treatments for scabies:

See comment on topical permethrin.

Substantive changes

Sulphur compounds (topical) Updated systematic review added. Categorisation unchanged (Unknown effectiveness).

2008; 2008: 1707.
Published online 2008 August 22.

Ivermectin (oral)

Summary

Oral ivermectin seems effective at increasing clinical cure rates compared with placebo.

Observational data suggest that oral ivermectin may be effective when included in the treatment of hyperkeratotic crusted scabies, and in people with concomitant HIV.

Benefits and harms

Oral ivermectin versus placebo:

We found one systematic review (search date 2007, 1 RCT) comparing oral ivermectin versus placebo. For further information on safety of ivermectin in adults, children and older people, see comment.

Cure rate

Oral ivermectin compared with placebo Oral ivermectin seems more effective than placebo at increasing the proportion of people with clinical cure at 7 days (moderate-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
55 young adults and children aged over 5 years
Data from 1 RCT
Failed clinical cure 7 days
6/29 (21%) with oral ivermectin
22/26 (85%) with placebo

RR 0.24
95% CI 0.12 to 0.51
Outcomes were assessed 7 days after the intervention was administered, which may have allowed insufficient time to achieve cure in some people with failed clinical cure at 7 days
Moderate effect sizeivermectin

Symptom improvement

No data from the following reference on this outcome.

Adverse effects

No data from the following reference on this outcome.

Oral ivermectin versus topical benzyl benzoate:

We found one systematic review (search date 2007, 3 RCTs, 182 people).

Cure rate

Oral ivermectin compared with topical benzyl benzoate We don’t know how oral ivermectin and topical benzyl benzoate compare at increasing cure rates (very low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
182 people
3 RCTs in this analysis
Failed clinical cure 21 to 30 days
28/95 (29%) with oral ivermectin
44/87 (51%) with topical benzyl benzoate

RR 0.50
95% CI 0.20 to 1.25
P = 0.1
Significant statistical heterogeneity among studies (P = 0.02); heterogeneity may have been because of differences in drug regimen and length of follow-up
Not significant

Symptom improvement

Oral ivermectin compared with topical benzyl benzoate We don't know how oral ivermectin and topical benzyl benzoate compare at reducing symptoms (rash or itch) at 30 days (very low-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Rash and itch

RCT
58 adults and children
In review
Mean clinical rash score 30 days
1.1 with oral ivermectin
3.5 with topical benzyl benzoate

Significance not assessed

RCT
58 adults and children
In review
Pruritus response graded as excellent 30 days
27/29 (93%) with oral ivermectin
14/29 (48%) with topical benzyl benzoate

Significance not assessed

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Skin reactions

Systematic review
182 people
3 RCTs in this analysis
Skin reactions
4/95 (1%) with oral ivermectin
24/87 (28%) with topical benzyl benzoate

Significance not assessed

RCT
58 adults and children
In review
Pruritus and irritation
0/29 (0%) with oral ivermectin
7/29 (24%) with topical benzyl benzoate

Significance not assessed

Oral ivermectin versus topical lindane:

We found one systematic review (search date 2007, 2 RCTs).

Cure rate

Compared with topical lindane Oral ivermectin seems more effective at reducing the proportion of people with treatment failure (high-quality evidence).

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Clinical cure

Systematic review
193 people with clinically diagnosed cases of scabies
2 RCTs in this analysis
Treatment failure 2 to 4 weeks
17/88 (19%) with oral ivermectin
56/105 (53%) with topical lindane

RR 0.36
95% CI 0.23 to 0.58
P = 0.00002
Moderate effect sizeivermectin

Symptom improvement

No data from the following reference on this outcome.

Adverse effects

Ref (type)PopulationOutcome, InterventionsResults and statistical analysisEffect sizeFavours
Adverse effects

Systematic review
53 people
Data from 1 RCT
Headache
1/26 (4%) with oral ivermectin
6/27 (22%) with topical lindane

Significance not assessed

Systematic review
200 people
Data from 1 RCT
Headache
1/100 (1%) with oral ivermectin
0/100 (0%) with topical lindane

Oral ivermectin versus topical permethrin:

See option on topical permethrin.

Further information on studies

The RCT reported that subjective pruritus scores were measured on a visual analogue scale (VAS) of 0 = not present to 10 = extremely severe. However, pruritus results were reported on a 4-point scale of poor, fair, good, or excellent, with no details provided of how VAS scores of 0 to 10 were transferred on to this scale.

Comment

In adults:

Oral ivermectin has been used widely in adults with onchocerciasis, and two large cohort studies found that, even with repeated doses, serious adverse effects have been rare. Summary reports to the WHO Collaborating Centre for International Drug Monitoring from five countries indicate that it is associated with rare severe adverse effects, including three convulsions and eight deaths.

In children:

We found no good evidence about its safety in children.

In older people:

An increased risk of death has been reported among older people taking oral ivermectin for scabies in a long-term care facility. It is not clear whether this was caused by oral ivermectin, interactions with other scabicides (including lindane and permethrin), or other treatments such as psychoactive drugs. Other studies reported no such complications from its use in older people.

Clinical guide:

Case series suggest that oral ivermectin may be effective when included in the treatment of hyperkeratotic crusted scabies (also known as Norwegian scabies), and in people with concomitant HIV disease. Experience suggests that oral ivermectin is safe in younger adults being treated for onchocerciasis, but no such experience exists for children, and there have been reports of increased risk of death in older people.

Substantive changes

Ivermectin (oral) Updated systematic review added; two RCTs added to review comparing oral ivermectin versus topical benzyl benzoate, one RCT added to review comparing oral ivermectin versus topical lindane. Categorisation unchanged (Likely to be beneficial).


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