AMFEBUTAMONE
A
blood tests
to measure hormone levels.
CT scanning
or
MRI
(techniques that
produce
three-dimensional
or
cross-
sectional images) of the skull may be
carried out to exclude the possibility of
a pituitary tumour and
ultrasound scan-
ning
of the abdomen and pelvis to
exclude a tumour of the adrenal glands
or ovaries. In some cases,
laparoscopy
(examination
of
the
inside
of
the
abdomen using a rigid or flexible view-
ing tube) may be required to inspect
the ovaries.
Treatment of amenorrhoea, if found
to be necessary, is of the underlying
cause. (See also
dietary amenorrhoea.)
amfebutamone
A drug used, along with self-help mea-
sures, as an aid to stopping smoking.
Side effects include a dry mouth and
gastrointestinal disturbances.
amfetamine
An alternative spelling for amphetamine
(see
amphetamine drugs
). (See also
con-
trolled drugs.)
amiloride
A potassium-sparing
diuretic drug,
amil-
oride is used in combination with loop
or thiazide diuretics in the treatment of
hypertension
(high blood pressure) and
the oedema (fluid retention) that results
from
heart failure
(reduced pumping
efficiency of the heart) or liver
cirrhosis.
amino acids
A group of chemical compounds that
form the basic structural units of all
pro-
teins.
Each amino acid molecule consists
of amino and carboxyl groups of atoms
that are 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 dif-
ferentiates 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
obtained from the diet. The other eight,
the essential amino acids, cannot be
made
by
the
body
and
must
be
obtained in the diet.
The 20 amino acids that make up pro-
teins also occur free within cells and in
body fluids. In addition, there are more
than 200 other amino acids that are not
found in proteins but play an important
role in chemical reactions within cells.
aminoglutethimide
An
anticancer drug
used to treat certain
types of breast cancer, prostate cancer,
and some endocrine gland tumours.
aminoglycoside drugs
Aminoglycosides, a type of
antibiotic drug,
are given by injection and, because their
use can damage the inner ear or kidneys,
are generally reserved for the treatment
of serious infections. Important exam-
ples of these drugs are
gentamicin
and
streptomycin,
which are also used topi-
cally for eye and ear infections.
aminophylline
A
bronchodilator drug
that is used to treat
chronic
bronchitis, asthma,
and, occa-
sionally,
heart failure
(reduced pumping
efficiency of the heart).
Aminophylline relieves breathing dif-
ficulty by widening the bronchi (the
main air passages to the lungs). It also
dilates (widens) blood vessels, thereby
improving blood flow from the heart,
and increases the production of urine.
Possible side effects of aminophylline
include
nausea,
vomiting,
headache,
dizziness, and palpitations.
amiodarone
An
antiarrhythmic drug
used in the treat-
ment of various types of
arrhythmia
(irregular heart rate or rhythm). Long-
term use of amiodarone may result in
inflammation of the liver, thyroid prob-
lems, and damage to the eyes and lungs.
For this reason, amiodarone is usually
given
only when
other
drugs have
failed to be effective.
amitriptyline
A tricyclic
antidepressant drug
with a
sedative effect. Amitriptyline is useful in
the treatment of
depression
accompa-
nied by
anxiety
or
insomnia.
Possible
adverse effects include blurred vision,
dizziness, and drowsiness.
amlodipine
A
calcium channel blocker
drug that is
used to prevent
angina
and to treat
hypertension
(high blood pressure). Pos-
sible side effects of amlodipine include
headaches and dizziness.
ammonia
A colourless, pungent gas that dissolves
in water to form ammonium hydrox-
ide, an alkaline solution (see
alkali).
Ammonia consists of one nitrogen atom
linked to three hydrogen atoms. Ammo-
nia is produced in the body and helps
to maintain the
acid-base balance.
In severe liver damage, the capacity of
the liver to convert ammonia to
urea
is
diminished. This leads to a high con-
centration of ammonia in the blood,
which is thought to be a major cause of
the impaired consciousness that occurs
in
liver failure.
amnesia
Loss of the ability to memorize infor-
mation and/or recall information stored
in
memory.
Amnesic conditions affect
mainly long-term memory (where infor-
mation is retained indefinitely) rather
than short-term memory (where it is
only retained for seconds or minutes).
Many people with amnesia have a
memory gap that extends back for some
time before the onset of the disorder.
This condition, known as retrograde
amnesia, is principally a deficit of recall.
In the majority of cases, the memory
gap gradually shrinks over time.
Some people with amnesia are unable
to store new information in the period
following the onset of the illness. The
resultant gap in memory, known as
anterograde amnesia, extends from the
moment of onset of the amnesia to the
time
when
the
long-term
memory
resumes (if at all). This memory gap is
usually permanent.
CAUSES
Amnesia is the result of damage to, or
disease of, regions in the brain that are
concerned with memory function. Pos-
sible causes of such damage are
head
injury;
degenerative disorders such as
Alzheimer’s disease
and other forms of
dementia;
infections such as
encephalitis;
thiamine deficiency in problem drink-
ers, which leads to
Wernicke-Korsakoff
syndrome; brain tumours; strokes;
and
sub-
arachnoid haemorrhage.
Amnesia can also
occur in some forms of psychiatric ill-
ness (in which there is no apparent
physical damage to the brain). Some
deterioration of memory is a common
feature of
aging
.
amniocentesis
A diagnostic procedure in which a small
amount of
amniotic fluid
is withdrawn,
using a syringe guided by
ultrasound
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