A second species of chlamydiae, CHLAMY-
DIA PSITTACI, mainly affects birds but can
occasionally spread to people who have
contact with pigeons, parrots, parakeets,
or poultry, causing a type of pneumonia
called psittacosis.
Treatment for chlamydial infections is
with antibiotic drugs.
chloasmaA condition, also called melas-
ma, in which blotches of pale brown
pigmentation appear on the forehead,
cheeks, and nose. The pigmentation is
aggravated by sunlight. Chloasmasome-
times develops during pregnancy. More
rarely, it is associated with the meno-
pause or use of oral contraceptives. The
condition usually fades but may recur.
chlorambucilAn anticancer drugused
to treat some types of cancer, for exam-
ple Hodgkin’s disease.
chloramphenicolAn antibiotic com-
monly used in the form of drops to treat
superficial eye infections. It is also used
to treat life-threatening infections when
the causative organism is unknown.
Rarely, tablets or injections are associ-
ated with aplastic anaemia.
chlorate poisoningThe toxic effects
of chemicals present in some defoliant
weedkillers. Ingesting chlorates can cause
kidney and liver damage, corrosion of
the intestine, and methaemoglobinae-
mia (a chemical change in haemoglobin
in the blood). Small doses of chlorates
can prove fatal. Symptoms of poisoning
include ulceration in the mouth, abdo-
minal pain, and diarrhoea.
chlordiazepoxideA benzodiazepine drug
mainly used to treat anxiety.
chlorhexidineA type of disinfectant
mainly used to cleanse the skin before
surgery or before taking a blood sample.
chlorineA poisonous, yellowish-green
gas with powerful bleaching and disin-
fecting properties. Inhaling even small
amounts is highly irritating to the
lungs; large amounts are rapidly fatal.
chloroformA colourless liquid produc-
ing a vapour that was formerly used as a
general anaesthetic (see anaesthesia,
general). Chloroform is associated with
liver damage and heart problems, and
safer drugs are now used instead.
chloroquineA drug used mainly in the
prevention and treatment of malaria. It is
also used as an antirheumaticto treat
rheumatoid arthritisand lupus erythema-
tosus. Side effects are nausea, headache,
diarrhoea, rashes, and abdominal pain.
Long-term use may damage the retina.
chlorphenamineAn antihistamine drug
used to treat allergies such as allergic
rhinitis(hay fever), allergic conjunctivitis,
urticaria, and angioedema. It is also
found in some cold remedies.
chlorpheniramineAn alternative name
for chlorphenamine.
chlorpromazineA widely prescribed
antipsychoticdrug used to relieve symp-
toms of major psychotic illnesses such
as schizophreniaand mania. The drug
reduces delusional and hallucinatory
experiences and may have an effect on
irritability and overactivity. It is also
used as an antiemetic. Chlorpromazine
may cause photosensitivity of the skin
and, in some cases, parkinsonism, slow
reactions, and blurred vision.
chlorpropamideA drug that is used to
treat diabetes mellitus (see hypogly-
caemics, oral).
choanal atresiaA congenitaldefect of
the nosein which 1 or both of the nasal
cavities are not fully developed.
chokingPartial or complete inability to
breathe due to an obstruction of the
airways. Choking is often due to food or
drink entering the tracheaand bronchi
instead of passing from the pharynx into
the oesophagus. Coughing normally dis-
lodges the food or drink. An obstruction
that partially blocks the airway and cannot
be dislodged by coughing is more seri-
ous. If the airway is completely blocked,
total suffocation will result if theblock-
age is not removed. If an obstruction
cannot be cleared by first aid techniques,
such as the Heimlich manoeuvre or
removed manually, an emergency tra-
cheostomymay be performed to restore
the airway before removal of the
obstruction with instruments.
cholangiocarcinomaA cancerous
growth in one of the bile ducts, which
causes jaundice and weight loss.
cholangiographyA procedure that uses
a contrast mediumto make bile ducts
visible on X-rays. Cholangiography is used
to look for biliary stones or to diagnose
narrowing or tumours of the bile ducts.CHLOASMA CHOLANGIOGRAPHY
C