DERM 04 and 05: Head Lice Flashcards
Describe the pathophysiology of head lice.
- no causal relationship with hygiene status or nutritional status
- not a vector for disease
Describe the method of transmission of head lice.
- spread mainly through direct head-to-head/hair-to-hair contact (30 seconds)
- pets are not vectors for human head lice
What are the signs and symptoms of head lice?
- pruritis occurs as allergic reaction to lice saliva injected during feeding – onset 4-6 weeks in those with first infestation due to sensitization
- excoriations – neck, scalp, near ears
- secondary bacterial infections can occur with cervical lymphadenopathy
- some may be asymptomatic
How is head lice diagnosed?
at least 1 live louse
- viable nits alone not reliable predictor of infestation
How are nits detected?
visual inspection
How are live louse detected?
wet or dry combing – systemically combing wet or dry hair with fine-toothed nit comb better detects active louse infestation than visual inspection of hair and scalp alone
What is the difference between wet and dry combing methods?
- wet-combing: with lubricant such as hair condition
- dry-combing: without lubricant
- wet combing and dry combing have not been compared directly in clinical studies
What are the goals of therapy for head lice?
- eradicate causative organisms and eggs
- control symptoms (pruritis)
- prevent complications (secondary bacterial infection)
- prevent transmission to others
Who should be treated for head lice?
- only contacts with live lice or nits within 1 cm of scalp should be treated
- pets should not be treated
What are the non-pharmacological treatments for head lice?
identify and examine potential human contacts
clean
- sterilize combs and brushes – soak in disinfectant solution or immerse in boiling water
- machine wash clothing, linens, towels, hats, stuffed animals, pillow cases, headbands, etc. in hot water or store in sealed bag for 2 weeks
- dry clean articles that can’t be washed or seal in plastic bag for 2 weeks or overnight in freezer
remove nits
- mechanically after pharmacologic treatment – with comb, vinegar-soak first may help
- wet combing can be used on its own, but efficacy questionable
- no efficacy evidence for electric combs
What are the 3 main types of pharmacological treatment for head lice?
- suffocation
- dehydration
- paralysis of respiration
What is suffocation?
lice, nymphs, and nits breathe through channels on their bodies – occlusion is a physical mode of action (decreases risk of resistance)
What drug treats head lice via suffocation?
dimethicone 50% (NYDA)
- spray carefully over dry hair, massage until hair completely wet, leave for 30 mins, comb, let solution dry on hair then wash, (repeat after 8-10 days)
- adverse effects: may cause local irritation, caution around open flames
- not recommended for infants or children < 2 years old
- resistance to product is unlikely as it has a physical mode of action
- no data on safety during pregnany and breastfeeding
What is dehydration?
dissolves exoskeleton to dehydrate the organism
What drug treats head lice via dehydration?
isopropyl myristate 50%/cyclomethicone (Resultz)
- apply to dry hair and scalp, leave for 10 min, rinse with warm water (repeat in 7 days)
- adverse effects: may cause local irritation, immediately flush eyes with water upon contact, caution around open flames
- not recommended for infants or children < 2 years old
- resistance to product is unlikely as it has a physical mode of action
- no data on safety during pregnany and breastfeeding
What is paralysis of respiration?
affects lice sodium channels – disrupt neurons to paralyze louse such that they cannot feed
What drug treats head lice via paralysis of respiration?
permethrin 1% (Nix Cream Rinse, Kwellada-P)
AND
pyrethrins 0.33%/piperonyl butoxide 3% (R&C Shampoo, generics)
- first-line treatment in Canada
- contraindicated in patients with ragweed or chrysanthemum allergy, or other pyrethrin products
- resistance may result in treatment failure
- do not use on eyelashes or eyebrows
- recommended during pregnancy and breastfeeding.
- acceptable to use for children ≥ 2 months old
Permethrin 1% (Nix Cream Rinse, Kwellada-P)
- head: wash hair with conditioner-free shampoo, rinse with water and towel dry, apply permethrin to saturate hair and scalp, leave for 10 min then rinse (repeat after 7 days if live lice observed)
- pubic: saturate hair, leave for 10 min then rinse (repeat after 7 days if live lice observed)
- adverse effects: may temporarily exacerbate pruritus/erythema/scalp edema of lice infestation, burning/stinging/tingling/numb or scalp discomfort usually mild and transient
Pyrethrins 0.33%/Piperonyl Butoxide 3% (R&C Shampoo, generics)
- apply to thoroughly saturate dry hair and massage scalp/skin, leave for 10 min, add little water, work shampoo into hair and skin to lather then rinse (repeat in 7 days)
- adverse effects: few effects, potential eye irritation, caution around open flames
What should be considered when determining if treatment failure is a true failure?
- confirmation of diagnosis
- reinfestation
- treatment application technique
- pharmacologic treatment mode of action
- post-treatment side effects
What should be done after treatment failure?
consider switching to different pharmacological class
What should be done after two treatment failure?
refer to physician, public health nurse
- no studies to support higher dose
- no approval for oral SMX/TMP + permethrin 1% combination – concern for bacterial resistance
- no approval for oral ivermectin in children <15 kg – Special Access Programme
- no approval for topical ivermectin
- topical crotamiton 10%
