in which the patient is gradually expo-
sed to the cause of the fear.
desensitization, allergySee hyposen-
sitization.
desferrioxamineA drug used to rid
the body tissues of excess ironthat
accumulates as a result of repeated
blood transfusions in anaemias, such
as aplastic anaemiaand thalassaemia.It
is also used to treat iron poisoning and
may also be used to treat excess alu-
miniumin people on dialysis. The drug
is administered by intravenous injec-
tion or subcutaneous infusion and may
be given with vitamin Cto boost excre-
tion of the iron. Side effects may
include gastrointestinal disturbances,
dizziness, and skin reactions.
designer drugsA group of illegally
produced chemicals that mimic the
effects of specific drugs of abuse. They
can cause drug dependenceand drug
poisoning. Made in illicit laboratories,
they are cheap to produce and undercut
the street prices of drugs.
There are 3 major groups: drugs derived
from opioid analgesic drugs such as fen-
tanyl; drugs similar to amfetamines,
such as ecstasy; and variants of phency-
clidine (PCP), a hallucinogenic drug.
These highly potent drugsare not tested
for adverse effects or for the strength of
the tablets or capsules, making their use
hazardous. For example, some deriva-
tives of fentanyl are 20–2,000times more
powerful than morphine. Amfetamine
derivatives can cause brain damage at
doses only slightly higher than those
required for a stimulant effect. Many
designer drugs contain impurities that
can cause permanent damage.
desmoid tumourA growth, usually in
the abdominal wall. The tumour is hard,
with a well-defined edge. The tumours
occur most frequently in women who
have had children. They may also arise
at the sites of old surgical incisions.
Surgical removal is the usual treatment.
desmopressinA synthetic form of ADH
(antidiuretic hormone) that is used to
treat diabetes insipidusand bed-wetting
(seeenuresis).
desogestrel A progestogen drugused
with ethinylestradiolas an ingredient of
some combined oral contraceptives.Desogestrel is reported to have a slightly
higher risk of venous thromboembolism
than older drugs. Side effects of deso-
gestrel include weight changes and
fluid retention. There may also be nau-
sea, vomiting, headache, depression,
and breast tenderness.
detergent poisoningThe toxic effects
that occur as a result of swallowing the
cleaning agents in shampoos, laundry
powders, and cleaning liquids.
developmentThe process of growth and
change by which an individual matures
physically, mentally, emotionally, and
socially. Development takes place in
major phases: during the first 2 months
of pregnancy (see embryo); to a lesser
extent, during the rest of pregnancy
(see fetus); during the first 5 years of life
(see child development); and during
pubertyand adolescence.
developmental delay A term used if a
baby or young child has not achieved
new abilities within the normal time
range. Normally, new abilities and new
patterns of behaviour appear at given
ages, and existing patterns of behaviour
change and sometimes disappear (see
child development).
Delays vary in severity and may affect
the development of hand–eye coord-
ination, walking, listening, language,
speech, or social interaction. Delay may
first be noticed by parents or detected
during a routine developmental check.
There are many causes of develop-
mental delay. A child who is late in
most aspects of development usually
has a generalized problem. This may be
due to severe visual or hearing impair-
ment, limited intellectual abilities (see
learning difficulties), or damage to the
brain before, during, or after birth.
Specific areas of delay may occur in
movement and walking. Often there is
no serious cause. However, specific
causes may include muscular dystrophy
and spina bifida. Delay in developing
manipulative skills is often due to lack
of adequate stimulation.
A lack of response to sound may be
due to deafness. Autismis a rare cause
of unresponsiveness to the human
voice although hearing is normal. A
hearing problem may cause delayedDESENSITIZATION, ALLERGY DEVELOPMENTAL DELAYD