I
for distant vision, when its lens is thin
and flat. To focus on a nearer object, the
ciliary muscle of the eye contracts,
which reduces the pull on the outer
rim of the lens, allowing it to become
thicker and more convex.
With age, the lens loses its elasticity.
This
makes
accommodation increas-
ingly difficult and results in a form of
longsightedness called
presbyopia.
accouchement
The French word for the
delivery
of an
infant from the uterus (womb). (See
also
childbirth.)
accretion
A manner of growth involving the accu-
mulation of additional material of the
same type as that already present. The
term accretion is used in dentistry to
refer to the collection of foreign mat-
erial,
such
as
plaque
(see
plaque,
dental),
on the surface of a tooth or
in a dental cavity.
acebutolol
A
beta-blocker drug
used to treat
hyper-
tension
(high blood pressure),
angina
pectoris
(chest pain caused by impaired
blood supply to the heart muscle), and
certain types of
arrhythmia
(abnormal
heart rhythm) in which the heart beats
too rapidly.
ACE inhibitor drugs
COMMON DRUGS
• Captopril •Cilazapril •Enalapril •Fosinopril
• Lisinopril •Moexipril • Perindopril
• Quinapril •Ramipril •Trandolapril
A group of drugs that are used to treat
heart failure
(reduced pumping effici-
ency of the heart),
hypertension
(high
blood pressure), and kidney problems
associated with
diabetes mellitus.
ACE
(angiotensin-converting enzyme)
inhib-
itors are often prescribed with other
drugs such as
diuretic drugs
or
beta-
blocker drugs.
HOW THEY WORK
ACE inhibitors block the action of an
enzyme
that is responsible for converting
angiotensin
(a protein present in the
blood) from inactive angiotensin I to
angiotensin II. Angiotensin II encour-
ages
blood
vessels
to
constrict;
its
absence permits them to dilate, thus
reducing blood pressure. In diabetic
nephropathy, ACE inhibitors slow the
progress of the disorder and reduce the
loss of
albumin
in the urine.
ACHALASIA
SIDE EFFECTS
Possible side effects include nausea, loss
of taste, headache, dizziness, and a dry
cough. The first dose may dramatically
reduce blood pressure.
acellular
A term meaning “without cells” that is
generally
used to
describe
pertussis
(whooping cough)
vaccines
that contain
only
certain
parts,
rather
than
the
whole, of the pertussis bacteria cell.
acetabulum
A cuplike hollow in the pelvis into
which the head of the femur (thigh
bone) fits to form the
hip
joint.
acetaminophen
An
analgesic drug
that is more commonly
known as
paracetamol
.
acetazolamide
A drug that is used in the treatment of
glaucoma
(raised pressure in the eye-
ball) and, occasionally, to prevent or
treat
symptoms
of
mountain sickness
(headache, weakness, and other symp-
toms occurring at high altitudes).
Possible side effects of acetazolamide
include lethargy, nausea, diarrhoea, and
reduced libido.
acetic acid
The colourless, pungent, organic acid
that gives vinegar its sour taste. In med-
icine, acetic acid is an ingredient of
antiseptic gels that are used to treat cer-
tain vaginal infections.
acetone
A chemical produced naturally when
the body enters a state known as
ketosis
,
in which fats are broken down to pro-
duce energy. This can occur as the result
of metabolic changes caused by
diabetes
mellitus
or, sometimes, as the result of
extreme dieting.
Pharmaceutical preparations contain-
ing acetone are used as antiseptics and
solvents. Acetone is also used in cosmet-
ics such as nail varnish remover. (See
also
solvent abuse.)
acetylcholine
A type of
neurotransmitter
(a chemical
that transmits messages between nerve
cells
or between nerve and muscle
cells).
Acetylcholine
is
the
neuro-
transmitter found at all nerve-muscle
junctions and at many other sites in the
nervous system. The actions of acetyl-
choline are called cholinergic actions,
and these can be blocked by
anticho-
linergic drugs.
acetylcholinesterase inhibitors
COMMON DRUGS
• Donepezil •Rivastigmine
A group of drugs that are used in the
treatment of mild to moderate
dementia
caused by
Alzheimer’s disease,
in which
there is a deficiency
of the neuro-
transmitter
acetylcholine
in the brain.
HOW THEY WORK
Acetylcholinesterase inhibitors work by
blocking
the
action
of
acetylchol-
inesterase, the enzyme in the brain
responsible
for
the
breakdown
of
acetylcholine. This raises acetylcholine
levels, and, in up to half of all patients,
the drugs slow the rate of progression
of dementia. However, they have no
effect on dementia due to other causes,
such as stroke or head injury.
SIDE EFFECTS
Common side effects include nausea,
dizziness, and headache. Rarely, difficul-
ty in passing urine may occur.
acetylcysteine
A drug that is used in the treatment of
paracetamol
overdose
and also
as
a
mucolytic
drug to loosen sputum
in
chronic
bronchitis.
To be effective as an antidote to
paracetamol poisoning,
acetylcysteine
must be given by injection within a few
hours of the
overdose having been
taken. The drug works by reducing the
amount of toxic substances produced
during the breakdown of paracetamol,
thereby reducing the risk of liver dam-
age. When taken orally, acetylcysteine
makes the mucus in sputum less sticky
and therefore easier to cough up.
When acetylcysteine is taken in large
doses, vomiting, rash, or breathing dif-
ficulties may occur as rare side effects.
achalasia
A rare condition, of unknown cause, in
which the muscles at the lower end of
the
oesophagus
and
the
sphincter
(valve) between the oesophagus and the
stomach fail to relax to allow food into
the stomach after swallowing. As a
result, the lowest part of the oesophagus
is narrowed and becomes blocked with
food, while the part above widens.
SYMPTOMS AND SIGNS
Symptoms include difficulty and pain in
swallowing, and pain in the lower chest
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