scabies
SCABIES
Scabies is a contagious disease caused by the mite Sarcoptes scabiei var hominis.
The affected individual usually complains of having a highly pruritic rash that occurs at night.
It occurs more often in children <15 years of age, sexually active young adults, the immunocompromised and in persons living in crowded living conditions (eg nursing homes, military barracks).
Transmission is typically by direct skin contact with an infected person and in adults, sexual transmission is common.

Pharmacotherapy

Keratolytics (Topical)

  • The removal of crust and scales with keratolytics is necessary for scabicide penetration of crusted scabies

Ivermectin (Oral)

  • Effective treatment option for scabies patients unresponsive to 1st-line/2nd-line treatment
  • Combination therapy with topical scabicides is considered to be the best option for crusted scabies
  • May have a role in the treatment of refractory infestations and immunocompromised patients, or when administration of head-to-toe topical therapy would be difficult
    • May also be used in scabies epidemics in institutions
  • Interrupts gamma-aminobutyric acid (GABA)-induced neurotransmission of many parasites
  • Efficacy is comparable with topical Permethrin and more superior than Lindane

Scabicides (Topical)

Benzyl Benzoate

  • Effective in the management of Permethrin-resistant crusted scabies
  • Different treatment regimens have been used but no comparative data have been published
  • May be used alone or in combination with Sulfiram
  • Maybe used with Ivermectin for patients with relapses after single treatment of Ivermectin

Crotamiton

  • May be useful for the treatment of nodule scabies in children but may require up to 5 days of treatment
  • May be used for symptomatic relief from pruritus but there is conflicting evidence of its efficacy
  • Appears to be less effective as a scabicide than Permethrin and Lindane

Ivermectin

  • 1% lotion was reported to be as effective as 5% Permethrin cream

Lindane (Gamma Benzene Hexachloride)

  • Used only as an alternative therapy in patients intolerant of other therapies or when other therapies fail due to risk of neurotoxicity
  • When used properly, it is an effective scabicide
    • 1% formulation is usually effective after a single 6-hour treatment
  • Lindane-resistant scabies has been noted in North, Central and South America and in Asia
  • Not recommended in patients with crusted scabies due to risk of toxicity

Malathion

  • Overnight application of 5% aqueous preparation is an effective treatment option
  • Alternative for patients where treatment with Permethrin is not appropriate

Permethrin

  • Recommended 1st-line treatment for children and adults including pregnant and lactating women
  • Has been shown to be as effective as Lindane and more effective than Crotamiton
  • Impairs function of voltage-gated sodium channels in insects which leads to disruption of neurotransmission
  • Has low toxicity

Sulfur

  • The oldest known treatment for scabies
  • Safe and effective, but requires application on 3 consecutive days
  • Treatment option for infants and pregnant women with scabies
  • Reproduction studies have not been conducted

Sulfiram

  • May also be used to treat human scabies
    • Soap-containing monosulfiram have been used in the past as a prophylaxis for scabies

Other therapies

  • Nodular scabies may be treated with corticosteroids after completed scabicide therapy
  • Oral antihistamines may be given to help alleviate pruritus
  • Medium- or high-potency topical steroids may also be given to help control pruritus after scabicide therapy
  • Secondary infections should be treated with appropriate antibiotics
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