ArticlePDF Available

Possible cancer hazard associated with 5-methoxypsoralen in suntan preparation

Authors:
BRITISH
MEDICAL
JOURNAL
21
JUNE
1980
1537
transferred
and
not
transferred
?
This
would
be
of
great
value
to
many
medical
and
geriatric
services
who
do
not
have
the
facilities
of
a
stroke
unit
and
who
regularly
indulge
in
transferring
stroke
patients,
albeit
at
times
it
seems
in
a
wholly
random
fashion.
COLIN
POWELL
University
Department
of
Medicine
(Geriatric
Medicine),
Royal
Liverpool
Hospital,
Liverpool
L7
8XP
***We
sent
this
letter
to
Dr
W
M
Garraway
and
his
colleagues,
whose
reply
is
printed
below.-ED,
BMJ.
SIR,-The
limitations
inherent
in
conducting
controlled
trials
of
methods
of
providing
health
services,
which
we
refer
to
in
our
paper,
mean
that
we
have
no
information
on
the
criteria
which
were
used
to
transfer
a
selected
group
of
patients
from
medical
units
during
the
acute
phase
of
rehabilitation.
But
we
have
been
able
to
examine
the
results
of
standard
clinical
tests
which
were
designed
to
predict
outcome
following
acute
stroke,
and
which
will
form
the
subject
of
a
future
publication.
No
difference
was
found
in
the
pattern
of
neurological
impairment
present
in
the
transferred
group
compared
with
those
patients
remaining
in
medical
units
through-
out.
Therefore
it
may
not
be
surprising
that
there
was
no
difference
in
outcome
between
the
two
groups.
Transferring
stroke
patients
from
medical
units
for
further
rehabilitation
appears
to
be
a
common
practice
in
Britain,
and
on
the
basis
of
our
results
these
transfers
should
be
arranged
earlier
rather
than
later
if
the
full
benefits
of
intensive
therapy
are
to
be
realised.
But,
as
Dr
Powell
correctly
infers,
conclusive
evidence
to
support
this
statement
can
come
only
from
further
randomised
con-
trolled
trials.
W
M
GARRAWAY
A
J
AKHTAR
R
J
PRESCOTT
L
HOCKEY
University
Department
of
Community
Medicine,
Usher
Institute,
Edinburgh
EH9
lDW
Preventing
infection
in
laboratories
SIR,-As
we
were
not
consulted
on
the
draft-
ing
of
the
original
report
perhaps
you
will
permit
us
to
make
several
observations
on
the
article
by
Sir
James
Howie
and
Mr
C
H
Collins
(19
April,
p
1071)
entitled
"The
Howie
Code
for
preventing
infection
in
clinical
laboratories:
comments
on
some
general
criticisms
and
specific
complaints."
It
is
important
to
realise
that
the
code
relates
to
clinical
laboratories,
a
point
which
is
often
not
appreciated
by
authorities
re-
sponsible
for
ensuring
safety
standards
in
non-clinical
laboratories.
While
this
does
not
imply
that
the
code
is
irrelevant
to
non-
clinical
laboratories,
it
does
mean
that
its
interpretation
in
these
non-clinical
situations
needs
careful
consideration
and
possible
modification
to
meet
local
requirements.
In
particular,
we
have
in
mind
the
use
of
Salmonella
typhi
in
the
Rideal
Walker
test
for
disinfectants.
While
we
would
not
disagree
with
the
general
comments
regarding
the
dangers
of
Salmonella
typhi
as
isolated
in
a
clinical
situation
we
do
believe
that
the
Salmonella
strain
NCTC
786
as
used
in
the
Rideal
Walker
test
presents
a
different
picture.
The
strain
is
a
virulence-negative
variant
and
while
this
is
not
positive
proof
of
the
non-
virulence
of
the
organism
it
does
differentiate
it
from
the
normal
virulent
strains.
The
strain
has
been
in
use
in
members'
laboratories
from
as
early
as
1904
with
well
over
450
000
Rideal-
Walker
tests
conducted
during
this
time,
involving
more
than
200
laboratory
personnel.
There
is
no
recorded
case
of
infection
resulting
from
the
use
of
this
strain
during
this
period.
These
facts
speak
for
themselves
and
need
to
be
taken
into
account
in
reacting
to
the
use
of
Salmonella
typhi
NCTC
786
in
the
Rideal-
Walker
test.
All
too
often
the
applicability
of
Salmonella
typhi
NCTC
786
to
the
testing
of
modern
disinfectants
clouds
the
issue
of
the
safety
aspect.
Manufacturers
of
disinfectants
sell
products
on
an
international
basis
and
the
Rideal-Walker
test
forms
an
integral
part
of
this
operation.
Naturally,
the
imposition
of
excessive
restrictions
will
place
UK
companies
in
an
unfavourable
competitive
position.
In
seeking
to
clarify
the
situation
with
regard
to
Salmonella
typhi
NCTC
786
we
support
those
who
oppose
the
unnecessary
use
of
the
Rideal-Walker
technique
using
Sal-
monella
typhi-for
instance,
for
teaching
pur-
poses
or
evaluating
disinfectants
for
hospital
use,
where
because
of
the
readily
availability
of
Salmonella
cultures
alternatives
to
strain
NCTC
786
may
be
inadvertently
used.
While
we
agree
with
the
Howie
Code's
recommendation
that
the
use
of
exhaust
protective
cabinets
(class
1)
is
necessary
for
most
category
B
pathogens,
which
cause
air-
borne
infections,
we
do
not
agree
that
it
is
appropriate
for
organisms
causing
infection
by
the
alimentary
route
such
as
Salmonella
typhi.
To
cover
this
case
the
association
had
drawn
up
its
own
code
of
practice
for
the
handling
of
Salmonella
typhi
NCTC
786
in
members'
laboratories.
R
A
COWEN
Chairman,
Disinfectant
Testing
Committee,
British
Association
for
Chemical
Specialities,
London
SE1
7TU
Why
has
Swann
failed?
SIR,-In
your
leading
article
(17
May,
p
1195)
you
state
that
legislation
enacted
as
a
con-
sequence
of
the
Swann
Report
has
failed
to
prevent
the
emergence
of
multiple
drug
resistance
in
Salmonella
typhimurium
in
bovines
in
Britain
despite
the
fact
that
it
was
precisely
intended
to
do
so.
The
legislation
was
not
designed
to
do
this.
Its
purpose
was
to
stop
the
feeding
of
pigs
and
table
chickens
continuously
on
diets
containing
antibiotics
that
are
commonly
used
in
human
and
veterinary
medicine,
because
the
practice
had
given
rise
to
enormous
populations
of
antibiotic-resistant
bacteria
in
these
animals.
The
feeding
of
such
diets
to
bovines
in
Britain
had
never
been
permitted.
The
Swann
legislation,
in
essence,
has
now
been
adopted
by
many
other
countries
and
I
think
Britain
can
take
some
pleasure
in
having
initiated
it.
H
WILLIAMS
SMITH
Houghton
Poultry
Research
Station,
Huntingdon,
Cambs
PE17
2DA
SIR,-In
the
excellent
leading
article
"Why
has
Swann
failed"
(17
May,
p
1195)
I
was
surprised
that
attention
was
not
directed
also
to
the
current
agricultural
practice
of
spread-
ing
raw
fluid
slurry
on
the
fields.
This
practice
could
be
a
possible
source
for
dissemination
of
these
organisms.
If
the
fluid
comes
from
stock
some
of
which
is
infected
with
or
is
a
carrier
of
salmonella
it
may
reasonably
be
supposed
that
when
the
field
so
treated
is
next
grazed
the
grazing
stock
are
at
risk
of
infection.
It
must
also
place
anybody
who
may
have
contact
either
with
the
fluid
or
with
the
surface
of
the
field
at
some
risk
of
infection.
This
is
less
likely
to
occur
if
all
the
manure
is
allowed
to
rot
down
fully
to
compost
in
a
dung
heap,
for
the
simple
reason
that
the
heat
of
a
well-made
heap
will
inhibit
if
not
destroy
bacteria.
The
broad-
casting
of
fluid
slurry
in
this
way
is
also
socially
unacceptable
to
those
unfortunate
enough
to
live
to
leeward
of
the
fields
so
treated.
The
epidemiology,
both
animal
and
human,
described
in
your
article
suggests
that
this
practice
requires
careful
scientific
study.
A
IAN
L
MAITLAND
St
Andrews,
Fife
Possible
cancer
hazard
associated
with
5-methoxypsoralen
in
suntan
preparation
SIR,-With
regard
to
the
current
discussion
(3
November,
p
1144;
1
March,
p
648;
29
March,
p
940)
on
the
safety
of
cosmetics
containing
5-methoxypsoralen
(bergapten)
I
would
like
to
add
a
number
of
points.
(1)
Although
the
current
controversy
concerns
the
suntanning
aids
containing
bergamot
oil,
they
are
not
the
only
cosmetics
involved.
Of
a
total
of
108
perfumes
investi-
gated,
57
40
contained
bergapten
in
con-
centrations
ranging
from
0
00004
to
0
0108%.1
Perfumes
are
therefore
likely
to
produce
phototoxicity
unless
the
psoralens
are
removed
or
the
content
of
5-methoxypsoralen
reduced
to
0.001%.2
Subjects
known
to
be
sensitive
to
small
concentrations
of 5-methoxypsoralen
and
patients
suffering
from
poikiloderma
of
civatte
should
therefore
be
warned
about
all
these
preparations.'
(2)
The
suntanning
aids
of
current
concern
contain
up
to
0
003',
(30
ppm)
(Chefaro
Proprietaries
Ltd,
personal
communication).
The
amount
of
5-methoxypsoralen
necessary
for
the
achievement
of
an
enhanced
tan
has,
however,
been
reported
to
exceed
1%.3
(3)
Not
only
is
there
a
possible
risk
of
human
carcinogenicity
associated
with
the
use
of
methoxypsoralens
in
combination
with
ultra-
violet
A
light,
but
also
there
may
be
as
yet
unknown
effects
on
the
microbial
ecology
of
human
skin.
Methoxypsoralens
are
known
to
induce
mutations
in
various
bacteria
and
fungi.4
Any
genetic
changes
in
skin
organisms
may
be
clinically
important
with
regard,
for
example,
to
acquisition
and
transfer
of
antibiotic
resistance.5
(4)
Many
substances
are
photosensitisers.
They
include
several
fluorescent
dyes
(ery-
throsin
B),
some
metabolites
(for
example,
bilirubin
and
porphyrins,
and
drugs
like
phenothiazines,
tetracyclines,
sulphonamides,
thiazides,
nalidixic
acid,
frusemide,
quinine,
and
anthracene).6
The
topical
application
therefore
of
preparations
containing
another
phototoxic
compound,
5-methoxypsoralen,
could
lead
to
an
increased
photosensitivity
in
individuals
already
sensitised
to
solar
radiation.
(5)
All
tanning
aids
contain
sunscreens,
which
are
substances
designed
to
prevent
1538
BRITISH
MEDICAL
JOURNAL
21
JUNE
1980
erythema
by
absorbing
ultraviolet
B
rays.
The
efficacy
of
some
of
these
compounds,
however,
is
being
questioned.3
Some
sun-
screens
may
themselves
be
phototoxic7-for
example,
amyl
dimethylaminobenzoate
(Padi-
mate
A,
Escalol
506).
Some
can
prevent
erythema,
but
not
premalignant changes
in
the
epidermis8
-for
example,
mexenone
(2-
hydroxy-4-methoxy-4-methylbenzophenone).
Furthermore,
a
5
°'
ethanolic
solution
of
para-
aminobenzoic
acid
(PABA),
though
an
effective
sunscreen,
cannot
protect
against
drug-
induced
phototoxic
reactions.
9
Broad-spectrum
sunscreens
combining
a
PABA
ester
with
a
benzophenone
ester
appear
currently
to
provide
the
most
protection
from
ultraviolet
light.
9
The
Council
of
Europe
is
currently
con-
sidering
sunscreens
and
one
hopes
that
in
the
future
proper
standardisation
and
toxicological
tests
will
be
required
for
all
sunscreens
and
tanning
aids,
studies
which
would
dispel
much
concern
regarding
their
safety.
INGRID
HOOK
Department
of
Pharmacognosy,
School
of
Pharmacy,
Trinity
College,
Dublin
4
'Zaynoun
ST.
J
Soc
Cosmet
Chem
1978;29:247-63.
aMarzulli
FN,
Maibach
HI.
J
Soc
Cosmet
Chem
1970;
21:695-715.
3
Greiter
F,
Doskoczil
S,
Bilek
P.
In:
Breuer
MM,
ed.
Cosmetic
science,
vol
I.
London:
Academic
Press,
1978.
'
Scott
BR,
Pathak
MA,
Mohn
GR.
Alutat
Res
1976;
39:29-74.
5Weissmann
A,
Noble
WC.
Br
J'
Dermatol
1980;102:
185-93.
eMoore
DE.
7
Pharmaceut
Sci
1977;66:1282-4.
7Emmett
EA.
Photochem
Photobiol
1979;30:429-36.
8
Pearse
AD,
Wolska
H,
Marks
R.
Br3'
Dermatol
1979.
101,
suppl
17:22.
9
Akin
FJ,
Rose
AP,
Chamness
TW,
Marlowe
E.
Toxicol
Appl
Pharmacol
1979;49:219-24.
Distalgesic
poisoning-cause
for
concern?
SIR,-Dr
Robert
Wall
and
others
are
right
to
draw
attention
to
the
dangers
of
dextro-
propoxyphene
(17
May,
p
1213).
Some
years
ago
I
became
aware
that
patients
for
whom
Distalgesic
had
been
prescribed
frequently
requested
further
supplies
in
circumstances
which,
in
my
opinion,
did
not
warrant
this
level
of
analgesia.
It
was
also
noticeable
that
the
difficulty
of
weaning
patients
off
this
preparation
increased
in
proportion
to
the
duration
of
medication.
I
now
rarely
prescribe
Distalgesic
or
similar
drugs,
and
never
for
more
than
a
short
period.
In
my
view
any
preparation
containing
dextropropoxyphene
should
be
controlled
under
the
Misuse
of
Drugs
Act,
and
the
dangers
of
dependence
should
be
publicised
widely.
H
W
K
ACHESON
University
Department
of
General
Practice,
Manchester
M13
OFW
SIR,-Any
Glasgow
graduate
of
my
vintage
will
have
clear
memories
of
the
depressing
remark
by
our
brilliant
professor
of
"materia
medica,"
the
late
Professor
Ralph
Stockman,
when
at
the
end
of
nearly
an
hour's
discourse
on
some
drug
he
would
sum
it
all
up
with
a
deprecating
"But
it
is
of
no
use
whatever."
Younger
generations
can
hardly
realise
how
few
were
the
really
effective
drugs
that
were
at
our
disposal
in
these
presulphonamide
days
of
the
early
1930s.
The
corollary
that
the
highly
effective
drugs
of
today
result
in
many
unexpected
and
dangerous
side
effects
appears
to
occasion
surprise
and
sometimes
what
seems
undue
alarm.
The
correct
action
is
surely
to
accept
their
benefits
while
retaining
an
alert
outlook
for
any
unwanted
reaction.
With
regard
to
the
specific
warnings
on
the
dangers
resulting
from
Distalgesic,
although
I
do
not rank
as a
"controlled
experiment"
yet
I
can
speak
from
personal
experience,
having
suffered
from
severe
disability
from
back
pain
and
sciatica,
which
started
a
year
ago
and
which
eventually
put
me
on
my
back
for
some
weeks.
A
slipped
disc
and
any
more
sinister
cause
having
been
excluded,
it
may
be
guessed
that
almost
all
the
available
range
of
analgesics
was
tried
(hiatus
hernia
and
a
tendency
to
peptic
ulceration
being
a
problem).
I
can
assure
Drs
R
J
Young
and
A
A
H
Lawson
(12
April,
p
1045)
that
Distalgesic,
in
associa-
tion
with
the
peripherally acting
aspirin
in
the
form
of
Nu-seals,
was
quite
the
most
effective,
avoiding
the
disastrously
constipating
effect
of
codeine.
Certainly
the
pain
was
such
that
I
at
one
time
required
a
daily
total
of
390
mg
of
dextropropoxyphene,
3
9
g
paracetamol,
and
3
9
aspirin,
in
addition
to
various
physical
forms
of
treatment
in
combination
with
the
anti-inflammatory
indomethacin.
Despite
this
large
dosage,
there
were
no
ill
effects
and
I
had
no
difficulty
in
gradually
reducing
it
as
the
condition
improved,
until
now
I
am
down
to
single
capsules
a
day
with
no
withdrawal
symptoms
or
apparent
develop-
ment
of
dependence.
Is
it
not
true,
with
perhaps
the
exception
of
the
hard
drugs
(although
after
a
month
of
codeine
I
stopped
it
with
alacrity),
that
much
of
addiction
depends
as
much
on
a
patient's
personality
as
on
the
particular
drug?
The
patient
of
Dr
Robert
Wall
and
others
(17
May,
p
1213)
seems
to
be
a
case
in
point.
Let
us
not
throw
out
the
baby
with
the
bath
water
but
retain
Distalgesic
for
what
it
can
do,
without
forgetting
the
caution
in
the
use
of
any
drug
that
Stockman
would
have
approved.
W
0
G
TAYLOR
Ayr
Investigating
constipation
SIR,-Your
leading
article
(8
March,
p
669)
"Investigating
constipation,"
which
described
the
pathological
and
iatrogenic
causes
of
the
condition,
contained
some
questionable
state-
ments-for
example:
"From
infancy
the
British
are
brought
up
to
regard
a
daily
bowel
action
almost
as
a
religious
necessity
and
to
believe
in
autointoxication
from
the
cesspool
of
the
unemptied
colon;
so
it
is
little
wonder
that
their
doctors
see
vast
numbers
of
patients
obsessed
with
the
frequency,
consistency,
diameter,
and
appearance
of
their
stools."
This,
surely,
is
an
exaggeration
and
carries
with
it
the
unfortunate
implication
that
regular
bowel
habits
are
of
little
importance.
This
illustrates
once
again
that
physiological
yardsticks,
in
numerical
terms,
for
human
bowel
function
are
badly
needed.'
Recently,
a
number
of
investigators2-6
have
compared
the
effects
of
high-
and
low-fibre
diets
on
bowel
function.
Their
data
suggest
that
in
healthy
subjects
good
fibre-containing
diets
produce
at
least
one
motion
daily,
stool
wet
weight
of
150-200
g/day,
and
a
transit
time
of
approximately
48
hours.
Multicentre
studies
are
now
necessary
to
confirm
these
findings;
and
close
co-ordination
is
essential
to
secure
uniformity
of
methodology,
which
should
include
an
objective
method
of
measuring
consistency.7
Reference
values
established
in
this
way
would
have
wide
applications
in
pharmacological
research,
clinical
practice,
and
health
care
and
would
also
provide
the
basis
for
a
scientific
definition
of
constipation.
In
the
mean
time
Painter7
has
provided
a
useful
working
definition,
which
states:
"Any
patient
who
strains
to
defecate
and
does
not
pass
at
least
one
soft
stool
daily
without
effort
is
constipated."
With
the
present
enthusiasm
for
the
"bulk"
principle
it
has
become
somewhat
fashionable
to
denigrate
chemical
laxatives
as
unnecessary
evils-as
is
evident
in
your
leading
article.
That
there
has
been
gross
abuse
of
laxatives
in
the
past
and
is
some
continued
misuse
today
is
unquestioned.
However,
there
is
ample
evidence
to
show
that
a
chemical
laxative,
carefully
selected
and
used,
has
a
valuable
place
in
many
cases
of
disordered
gut
motility.8
Painter7
illustrates
the
comple-
mentary
actions
of
a
chemical
laxative
and
dietary
fibre
when
he
states:
"Idiopathic
slow
transit
constipation,
megacolon
and
mega-
rectum
are
a
persistent
problem.
Besides
dietary
fibre
they
require
standardised
senna
tablets
(Senokot).
Usually
2-4
tablets
daily
are
sufficient,
but
the
dosage
must
be
found
by
trial
and
error.
It
may
be
possible
to
reduce
the
initial
dose
when
the
high-fibre
diet
has
taken
effect."
EDMUND
W
GODDING
Totland,
Isle
of
Wight
P039
OEB
lGodding
EW.
Lancet
1976;ii:1294-5.
s
Harvey
RF,
Pomare
EW,
Heaton
KW.
Lancet
1973;i:
1278-80.
'Eastwood
MA,
Kirkpatrick
JR,
Mitchell
WD,
Bone
A,
Hamilton
T.
Br
MedJ
1973;iv:392-5.
4Payler
DK,
Pomare
EW,
Heaton
KW,
Harvey
RF.
Gut
1975;16:209-13.
5Curnmings
JH,
Jenkins
DJA,
Wiggins
HS.
Gut
1976;
17:210-18.
'Cummings
JH,
Southgate
DAT,
Branch
W,
Houston
H,
Jekins
DJA,
James
WPT.
Lancet
1978;i:5-9.
7
Painter
NS.
Practitioner
1980;224:387-91.
8
Avery
Jones
F,
Godding
EW,
eds.
Managemenr
of
constipation.
Oxford:
Blackwell,
1972.
Diagnosis
of
infectious
mononucleosis
SIR,-Your
leading
article
(10
May,
p
1153)
dealt
with
a
common
problem-the
accurate
diagnosis
of
infectious
mononucleosis-in
which
there
is
much
misunderstanding.
Pfeiffer's1
"glandular
fever"
was
a
different
disease
from
that
of
Sprunt
and
Evans.2
In
the
former
the
disease
occurred
in
infants,
was
very
contagious
and
of
short
duration,
and
atypical
lymphocytes
were
not
described.
The
infectious
mononucleosis
of
Sprunt
and
Evans
occurred
in
adolescents,
was
not
very
conta-
gious
and
lasted
longer,
and
atypical
lympho-
cytes
were
present.
The
diagnosis
of
infectious
mononucleosis
formerly
depended
on
finding
clinical,
haema-
tological,
and
serological
evidence
of
the
disease.
Recently,
the
presence
of
specific
IgM
anti-Epstein-Barr
virus
antibody
has
been
accepted
as
diagnostic
of
the
disease.
This
test
is
of
particular
value
in
children
and
in
the
elderly,
where
the
Paul-Bunnell-Davidsohn
test
may
be
negative
and
the
illness
atypical.
However,
many
laboratories
use
only
commer-
cial
screening
kits
(for
example,
Monospot),
which
are
associated
with
a
number
of
false-
positive
results.
We
have
studied
the
serology
of
100
patients
with
clinical
and
haematological
evidence
of
infectious
mononucleosis.3
All
patients
had
atypical
lymphocytes
constituting
over
20%
of
the
total
leucocyte
count.
Positive
Article
The skin of the female hairless albino mouse (Skh 1) was used to study the enhancement of solar simulated radiation (SSR) tumorigenesis by 5-methoxypsoralen (5-MOP) in model perfumes that contain bergamot oil. This work was done in association with yeast mutagenicity studies and human skin phototoxicity studies. Analyses of time-to-onset of tumour observation with 5-MOP at 0, 5, 15 and 50 ppm show a highly significant 5-MOP dose effect and the data indicate that 5-MOP has phototumorigenic potential even at 5 ppm. The addition of 0.5% UVB and 0.5% UVA sunscreens significantly reduces the tumorigenicity associated with the vehicle (i.e. 5-MOP at 0 ppm) and 5-MOP at all concentrations. Pairwise comparisons of 5-MOP (at 5 or 15 ppm) plus sunscreens with vehicle plus sunscreens show that the sunscreens afford total protection at the lower 5-MOP concentrations. Additional studies show that a 5-6 h delay between 5-MOP application and SSR exposure defers the time-to-onset of tumours as does intermittent 5-MOP and SSR treatment. A comparison of 5-MOP at 50 ppm in bergamot oil with 5-MOP at 50 ppm prepared from pure 5-MOP crystals shows identical results, indicating that the active phototumorigenic agent in bergamot oil is 5-MOP and not other related compounds, which may be present at greater concentrations. Analyses of tumour histology at death show, in general, similar patterns of malignancy for all groups. Thus although it is possible to delay tumorigenesis by various strategies, the tumours that eventually develop are just as likely to be malignant, if not more so, when compared with non-delayed groups.
Article
Full-text available
Sunscreen preparations containing 5-methoxypsoralen at 25 micrograms/ml and 50 micrograms/ml, and the appropriate vehicle only, sunscreen only, and 5-methoxypsoralen only controls, were assessed for tumorigenic potential in hairless albino mice exposed to solar simulated radiation for a period of 44-46 weeks. Some animals were observed for a 15 week post-irradiation period. A wide range of statistical analyses has shown that, during the course of irradiation, the inclusion of sunscreens eliminates the enhancement of phototumorigenesis and malignancy that is normally observed with 5-methoxypsoralen. There was, however, some indication of increased risk at the end of the postirradiation follow-up period. Possible reasons for the protective effect of the sunscreens and the relevance of these data to the assessment of human risk are discussed.
Article
Phototoxicity was induced in animal models by photoreactive drugs in order to test sunscreen efficacy. In combination with uv-A irradiation, 8-methoxypsoralen and to a lesser extent chlorpromazine and demeclocycline elicited cutaneous erythema, edema, and ulcerative lesions in mice and guinea pigs. A commercial preparation of 5% para-amino-benzoic acid (PABA) in alcohol with proven effectiveness in preventing normal sunburn failed to protect against phototoxic drug reactions. An experimental, broad-spectrum sunscreen, PL-254—containing esters of PABA and benzophenone-blocked virtually all phototoxic response to all three drugs. Absorbance spectra of the PABA product and of PL-254 in solution and on the skin of hairless mice confirmed that PABA absorbs uv energy primarily in the uv-B range while PL-254 absorbed both uv-A and uv-B radiant energy. The uv absorbance spectra of both products on skin differed significantly from their spectra in solution.
Managemenr of constipation
  • F, Avery Jones