AMILORIDE
AMNIOCENTESIS
A
In high doses, amfetamines can cause
tremor, sweating, anxiety, and sleeping
problems. Delusions, hallucinations, high
blood pressure, and seizures may also
occur. Prolonged use may produce
tol-
erance
and
drug dependence.
Amfetamines are often abused for
their stimulant effect.
amiloride
A potassium-sparing
diuretic
drug.
Combined with loop or thiazide
diuretics, amiloride is used to treat
hypertension
and fluid retention due to
heart failure
or
cirrhosis
of the liver,
amino acids
A group of chemical com-
pounds that form the basic structural
units of all
proteins.
Each amino acid
molecule consists of amino and carboxyl
groups of atoms linked to a variable
chain or ring of carbon atoms.
Individual amino acid molecules are
linked together by chemical
bonds
called
peptide
bonds to form short
chains of molecules called
polypeptides
.
Hundreds of polypeptides are, in turn,
linked together, also by peptide bonds,
to form a protein molecule. What differ-
entiates one protein from another is the
sequence of the amino acids.
There are 20 different amino acids that
make up all the proteins in the body. Of
these, 12 can be made by the body; they
are known as nonessential amino acids
because they do not need to be ob-
tained from the diet. The other 8, known
as the essential amino acids, cannot be
made by the body and must therefore
be obtained from the diet.
aminoglutéthimide
An
anticancer drug
used to treat certain types of breast
cancer, prostate cancer, and some en-
docrine gland tumours.
aminoglycoside drugs
A type of
anti-
biotic drug.
Aminoglycoside drugs are
given by injection and are generally
reserved for the treatment of serious
infections because their use can dam-
age the inner ear or kidneys. Important
examples are
gentamicin
and
strepto-
mycin,
which are also used topically for
eye and ear infections.
aminophylline
A bronchodilator drug
used to treat chronic
bronchitis
,
asthma
,
and, occasionally,
heart failure.
Nausea,
vomiting, headache, dizziness, and pal-
pitations are possible side effects.
amiodarone
An
antiarrhythmic drug
used
in the treatment of various types of
arrhythmia
(irregular heartbeat). Long-
term use of amiodarone may result in
inflammation of the liver, thyroid prob-
lems, and eye and lung damage.
amitriptyline
A tricyclic
antidepressant
drug
with a sedative effect. It is useful
in the treatment of
depression
accom-
panied by
anxiety
or
insomnia.
Possible
adverse effects include blurred vision,
dizziness, and drowsiness.
amlodipine
A
calcium channel blocker
drug used to prevent
angina
and to treat
hypertension
. Possible side effects are
headaches and dizziness.
ammonia
A colourless, pungent gas that
dissolves in water to form ammonium
hydroxide, an alkaline solution (see
alk-
ali
). Ammonia is produced in the body
and helps to maintain the
acid-base bal-
ance.
In severe liver damage, the ability
of the liver to convert ammonia to
urea
is reduced. This leads to a high level of
ammonia in the blood, which is thought
to be a cause of the impaired con-
sciousness that occurs in
liver failure.
amnesia
Loss of ability to memorize
information and/or to recall information
stored in
m em ory
. Possible causes of
amnesia are
head injury;
degenerative
disorders such as
Alzheimer's disease
and other forms of
dementia
; infections
such as
encephalitis
; thiamine defici-
ency in alcoholics, leading to
W ernicke-
Korsakoff syndrome;
brain
tumours;
strokes
; and
subarachnoid haem orrhage
.
Amnesia can also occur in some forms
of psychiatric illness.
In retrograde amnesia, the loss of
memory extends back for some time
before the onset of the disorder. In
anterograde amnesia, there is an inabil-
ity to store new information in the
period following the onset of illness.
amniocentesis
A diagnostic procedure
in which a small amount of
amniotic
fluid
is withdrawn, using a syringe and
guided by ultrasound scanning, from
the
amniotic sac
that surrounds the
fetus
in the
uterus
. This fluid contains
fetal cells that can be subjected to
chromosom e analysis
to identify chromo-
somal defects such as
Do'wn's syndrome
or genetic analysis to look for
genetic
26
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