Downloadable PDF - Hedrin

Product Information Hedrin 4% Lotion
Presentation: cutaneous solution containing 4% dimeticone w/w.
Indications: for the eradication of headlice infestations Dosage and
administration: Adults and children over 6 months: Apply su cient lotion
to cover dry hair from the base to the tip to ensure that no part of the scalp
is left uncovered. Work into the hair spreading the liquid evenly from roots
to tips. Allow hair to dry naturally. Hedrin should be left on hair for a
minimum of 8 hours or overnight. Wash out with normal shampoo, rinsing
thoroughly with water. Repeat the treatment after seven days.
Contraindications: Hypersensitivity to any of the ingredients. Precautions
and Warnings: Discontinue at the appearance of a skin rash or any
other signs of local or general hypersensitivity. For external use only. If
accidentally introduced into the eyes, with water. Side E ects: Minor
adverse events include an itchy or scalp and dripping/irritation around
the eyes. Product Licence Holder: Thornton & Ross Ltd, HD7 5QH
Product Licence No: PL00240/0137 Date of preparation: May 2008
References:
1. Burkhart CG, Burkhart CN. Asphyxiation of lice with topical agents not a reality…yet, J Am
Acad Dermatol. 2006: 54: 721-2
2. Webb JE. Spiracle structure as a guide to the phylogenetic relationships of the Anoplura
(biting and sucking lice), with notes on the a nities of the mammalian hosts. Proc.
Zool Soc.1946 116: 49-119
3. Van Reeth, Wilson, Cosmetics & Toiletries Magazine, July 1994
4. Burgess IF, Brown CM, Lee PN, Treatment of head louse infestation with
4% dimeticone lotion: randomised controlled equivalence trial BMJ
2005; 330:1423 (18 June)
5. Burgess IF, Lee PN, Matlock G, Randomised, controlled, assessor
blind trial comparing 4% dimeticone lotion with 0.5% malathion
liquid for head louse infestation, PLoS ONE. 2007; 2(11):e1127
6. Burgess IF, Water - is it the “Achilles heel” of sucking lice? 3rd
International Congress On Phthiraptera, Buenos Aires,
Argentina, 16 - 20 October, 2006
Acknowledgements:
With thanks to
Mr Trevor Fairhead and Mr Jon Rickard
Sector of Biological and Soft Systems
Department of Physics
University of Cambridge
Cavendish Laboratory
Cambridge
United Kingdom
Licence Holder & Manufacturer:
Thornton & Ross Ltd.
Linthwaite, HD7 5QH, UK
Distributor:
Nice-Pak Products Pty Ltd.
2-4 Sullivan Street, Moorabbin 3189 Victoria Australia
Nice-Pak Products (NZ) Pty Ltd.
PO Box 2296, Auckland 1 New Zealand
For further information and ordering
07 3345 5598
Ian Burgess - Director, Medical Entomology Centre
“ Hedrin ® 4%
Dimeticone lotion is
a patented new
generation of head
louse treatment based
on silicone oils.
Its has been
proven
both in vitro and in
clinical trials” 4,5
®
®
The mode of action of Hedrin 4%
Dimeticone Lotion in killing head lice
This paper describes
how Hedrin ® ’s multiacting
optimised
formulation actually
kills the lice.
www.hedrin.com.au

Background and purpose
A new generation
of products based
on silicone oils has
been developed
human head lice
market.
Many of these
relatively new
products have not
Untreated head louse
been through the
rigours of a regulatory process and have not had
This has led to a number of simplistic and
inaccurate claims being made.
The purpose of this paper is to use evidence-based
data to describe how Hedrin ® 4% dimeticone
lotion kills head lice.
Death by asphyxiation? ...UNLIKELY!
A simplistic view is that physical blockage of spiracles and
tracheae eventually kill lice by oxygen starvation.
The theory of lice asphyxiation was reviewed by Burkhart 1
who discussed the practical issues and the implausibility of it
as a realistic mechanism of louse death, based on the
anatomy of louse spiracles and the defence systems in place
to protect the louse.
Lice can survive oxygen deprivation for many hours and
silicone oils are permeable to gases including oxygen, making
asphyxiation a highly unlikely cause of death in the head
louse.
This is the experimental paper of its kind to prove that
Hedrin ® 4% dimeticone lotion penetrates louse spiracles
beyond the
atrium and
into the
tracheae.
Thoracic
spiracle
Experimental method
Hedrin ® 4% dimeticone lotion is normally applied to the hair
and left overnight. To have a physical e ect on lice the lotion
must penetrate and/or block the spiracles.
Live adult head lice were collected from healthy volunteers.
They were treated by coating in Hedrin ® 4% dimeticone lotion
and left overnight at room temperature.
Treated and untreated lice were then viewed by scanning
electron microscopy and the chemical elements found in the
spiracles were determined by cutting the surrounding tissues
away using a focused ion beam and X-ray microanalysis to
the chemical element silicon, which is present in
dimeticone but not in lice.
Silicone plug inside spiracle
Shown below is a typical X-ray spectrum indicating the presence of silicon on the
surface of a treated louse (as seen at spectrum points 1- 3 above)
Experimental results
X-ray analysis showed silicon present over the whole surface
of treated lice but absent on untreated lice - it formed a plug
or a thin coating on the inside of the spiracles of treated lice.
Ion beam cutting in the scanning electron microscope created
a cross section of an abdominal spiracle. X-ray spectral analysis
of the sectioned area highlighted the distribution of silicon
from the dimeticone.
Colour-enhanced cross section of abdominal
spiracle showing distribution of silicon
The re (left) shows
the anatomical
structure of a spiracle,
as drawn by Webb 2 ,
superimposed on the
cross section of the
spiracle. The white
dots indicate the
distribution of silicon
in the spiracle atrium
and into the outer
section of trachea.
Disruption of water management in lice by
Hedrin® 4% dimeticone, causing death
Human head lice have a unique strategy of water
management. They do not produce urine, but eliminate excess
water by respiratory transpiration via the trachea and
spiracles. 6 Blockage of the spiracles was shown to prevent or
reduce water excretion, often leading to death by gut rupture.
When head lice were immersed in Hedrin ® 4% dimeticone
lotion, locomotion ceased within 30 seconds with no further
movements of appendages, although slight gut movements
could be seen in some lice.
When lice were treated using
Hedrin ® 4% dimeticone
lotion after taking a blood
meal they initially lost weight
at a similar rate to untreated
lice but, from about 30
minutes after treatment, the
rate of water excretion was
reduced, so that after 4 hours
the treated group had lost
only 15% of the weight of
the blood meal compared
with 45% in the untreated
group. This indicates a
blockage of the louse
transpiration process.
Fed louse treated with Hedrin ® 4%
dimeticone lotion with large blood
gut
Treated louse after several hours,
demonstrating gut rupture as evidenced
by the visible of blood into the
thoracic cavity
Some insects experienced gut rupture several hours after
treatment believed to be due to a reverse osmotic e ect. 6
It should be noted that gut rupture has only been observed in
fed lice with a blood gut. This is highly visible and an
extreme mechanism of death. However unfed lice also die as
a result of immobility, which is in e ect death from starvation.
Hedrin® 4% dimeticone – the optimal choice
for water management disruption
The water vapour barrier e cacy of silicones is a complex
relationship between the structure, molecular weight, and
thickness of the silicone oil m 3 - the higher the molecular
weight, the better its barrier properties.
Hedrin ® 4% dimeticone lotion contains
the very high molecular weight
dimeticone (100 000 CSt), providing
the best barrier function.
Hedrin ® 4% dimeticone lotion is an
optimised blend of silicones to
meet all parameters required of
a commercial product.
Conclusions
The experiments support the published work4,5 that
demonstrated the clinical performance of Hedrin ® 4%
dimeticone lotion.
Results indicate that blockage of the spiracles and
trachea by Hedrin ® 4% dimeticone lotion induces head
lice to enter a similar immobility state to that
caused by immersion in water.
The crucial observation is that lice
treated with Hedrin ® 4% dimeticone
lotion always enter a moribund
state and we have never observed
them to recover.
The exact mechanism of death has been debated and
simplistically attributed to asphyxiation, but observations
in this paper Burkhart’s view 1 that this is unlikely
to be the case.
We conclude that, although asphyxiation cannot be
ruled out as one mechanism by which Hedrin ® 4%
dimeticone lotion could kill head lice, the major cause is
undoubtedly the prolonged immobility associated
with osmotic disruption and gut rupture or starvation.