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-
eranceand drug dependence.
Amfetamines are often abused for
their stimulant effect.
amilorideA potassium-sparing diuretic
drug. Combined with loop or thiazide
diuretics, amiloride is used to treat
hypertensionand fluid retention due to
heart failureor cirrhosisof the liver.
amino acidsA 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.
aminoglutethimideAn anticancer drug
used to treat certain types of breast
cancer, prostate cancer, and some en-
docrine gland tumours.
aminoglycoside drugsA 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 gentamicinand strepto-
mycin, which are also used topically for
eye and ear infections.
aminophyllineA bronchodilator drug
used to treat chronic bronchitis, asthma,
and, occasionally, heart failure. Nausea,
vomiting, headache, dizziness, and pal-
pitations are possible side effects.amiodaroneAn antiarrhythmic drugused
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.
amitriptylineA tricyclic antidepressant
drugwith a sedative effect. It is useful
in the treatment of depressionaccom-
panied by anxietyor insomnia. Possible
adverse effects include blurred vision,
dizziness, and drowsiness.
amlodipineA calcium channel blocker
drug used to prevent angina and to treat
hypertension. Possible side effects are
headaches and dizziness.
ammoniaA 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.
amnesiaLoss of ability to memorize
information and/or to recall information
stored in memory. 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 Wernicke–
Korsakoff syndrome; brain tumours;
strokes; and subarachnoid haemorrhage.
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.
amniocentesisA diagnostic procedure
in which a small amount of amniotic
fluidis withdrawn, using a syringe and
guided by ultrasound scanning, from
the amniotic sacthat surrounds the
fetusin the uterus. This fluid contains
fetal cells that can be subjected to
chromosome analysisto identify chromo-
somal defectssuch as Down’s syndrome
or genetic analysis to look for geneticAMILORIDE AMNIOCENTESISA