A Powerpoint presentation on Ectoparasiticides suitable for reading by Undergraduate Medical and Nursing Students

1. Ectoparasiticides
Dr. D. K. Brahma
Associate Professor
Department of Pharmacology
NEIGRIHMS, Shillong

2. Introduction
•Drugs used to kill parasites that live on body
surface
• Lice – Pediculosis sp. – wingless insects
•Mites – Sarcoptes/Acarus scabiei –
Arachnids – minute arthropods infesting
human hair and skin

3. Scabies
• Highly contagious mite
•Burrows through the epidermis, laying eggs –
form papules – immenseitching
• Secondary infection – antibiotics
• Finger webs
• Forearm, trunks, genitals and lower legs
• Family members
• Cross infection andre-infection

4. Source: Google Images

5. Pediculosis
•The lice thrive on head - P. capitis
• Body – P. corporis
• Pubic region – P. pubis
•Cause itching, suck blood and produce typhus and
relapsing fever
•The eggs are called nits – attached to hair and
clothes by chitin like content

6. Source: Google Images

7. Available drugs
•Permethrin
• Lindane
• Benzyl benzoate
• Crotamiton
• Sulfur
• Dicophane (DDT)
• Ivermectin

8. Sulfur ointment
• Oldest scabicide – weak pediculocide, antiseptic, fungicide an
keratolytic
• MOA: Slowly reduced to H2S and SO2on skin and pentathionic acid
• pentathionic acid – dissolve the cuticle of mice and kill it
• Reactions are carried out by epidermal cells and arthropod
themselves
• Used as 10% ointment – After a warm scrubbing bath (to open up
burrows) – messaged over the entire body (below neck) – 3
consecutive nights – soap water bath on 4th day
• Disadvantages:
•Messy treatment
•Socially unacceptable – interfere with person`s vocation
•Repeated applicationneeded

9. Permethrin
• Broad spectrum
• Most efficacious and most convenient for both scabies and lice
• MOA: Neurological paralysis of insects – delayed
depolarization
• Toxicity lower in human than lindane
• Persists over skin for days but systemic absorption low
• 100% cure rate and resistance rare
• Effective in lindane non-responsivecases
• ADRs: Transient burning, itching, tingling, erythema and rash
• Preparations: For scabies – 5% cream, 1$ soap and 5% lotion
For head lice: 1% lotion and 5% cream
• First choice drug now for scabies and lice

10. Source: Google Images

11. Lindane
•Gamma benzene hexachloride
• broad spectrum – lice and mites
•MOA: Penetrates to insects through their chitinous cover and
affects nervous system
• Head lice – 67% to 92%cure rate and scabies – 84 t0 92%
• Lower efficacy than permethrin andresistance
• Combines with Benzyl benzoate –100%
• Preparations: 1% lotion and cream
•Pediculosis: apply over scalp, 12 – 24 hours, shower cap – repeat
after one week if needed, avoideyes
•For Scabies: Rubbed over body below neck and scrub bath after
12 -24 hours – repeat after one week if needed
•Disadvantages: Lipid soluble, gets absorbed, systemic toxicity –
CN stimulation, vertigo, convulsion (Children) and cardiac
arrhythmia

12. Lindane
•Widely distributed in the body – fats
•Metabolized and eliminated and half-life 24
hours
• Microsomal enzyme inducer
• Less favoured for treatment of scabies
• Whole body application – systemic toxicity
•Avoid in infants, young children and
pregnancy
Source: Google Images

13. Benzyl benzoate
• Oily liquid with faint aromatic smell
• The emulsion is applied all over the body and 2nd
coat on next day – except face and neck
• Wash off after 24 hours
• Convenient and does not interfere normal works
•70 – 100% cure rate in scabies – no systemic
toxicity
• Contraindicated in children - Neurological symptoms
• Preparatin – 25% lotion

14. Other drugs
Crotamiton
• Scabicidal, pediculocide and antipruritic
• Low cure rate
• Lesser systemictoxicity
• Preferred in children
•10% cream andlotion
Dicophane (DDT)
• Popular insecticide fpor mosquitoes, flies and pests
• Scabies and pediculosis 1 – 2% lotion or cresam
• Washed off after 24 hours
•Absorbed through skin and – enzyme induction, rashes, tremor
etc.
• Acts as neurotoxin forarthropods

15. Ivermectin
• Source: Streptomyces avermitilis
•Anthelmintic drug – also useful in scabies
and pediculosis
• SARS Cov 2 ???
•Only orally effective drug – 12 mg single
dose – 100% cure rate
• AIDS with scabies and head lice also
• Replaced DEC – in River blindness
• DOC in Strongyloidosis
• Bancroftian and brugian filaria
Source: Google Images

16. Ivermectin – contd.
MOA:
•Nematodes develop tonic paralysis
• Acts through special type of Cl- channel present
only in invertebrates
•No such channel in flukes and tapeworm –
ineffective
• Potentiation of GABAergic receptors
• p-glycoprotein related efflux from brain in human –
no action

17. Any question ?

18. Thank you