BIGUANIDES
Other types of beta-blocker, such as ox-
prenolol, propranolol, and timolol, may
be given to prevent
migraine
attacks by
acting on blood vessels in the head.
They are also used to reduce the physi-
cal symptoms of
anxiety
and to control
the symptoms of
thyrotoxicosis
(an over-
active thyroid gland). Beta-blockers such
as timolol are sometimes given in the
form of eye-drops to treat
glaucoma
;
they work by lowering the fluid pres-
sure within the eyeball. (See also the
illustrated box.)
POSSIBLE ADVERSE EFFECTS
Beta-blocker
drugs
may
reduce
an
individual’s capacity for strenuous exer-
cise. They may worsen the symptoms of
asthma, bronchitis,
or other forms of
lung disease. They may also reduce the
flow of blood to the limbs, causing cold
hands and feet. In addition, sleep dis-
turbance and depression can be side
effects of beta-blockers. Anyone taking
beta-blockers should not suddenly stop;
a severe recurrence of previous symp-
toms and a significant rise in blood
pressure may result.
betahistine
A drug that is used in the treatment of
the inner-ear disorder
Meniere’s disease.
Betahistine reduces the frequency and
severity of the characteristic attacks of
nausea and vertigo.
beta interferon
A type of
interferon
(a protein produced
naturally by body cells) sometimes used
in the treatment of
multiple sclerosis.
beta-lactam antibiotics
A group of
antibiotic drugs
that includes
the penicillins and the cephalosporins.
Beta-lactam antibiotics work by altering
chemical activity in bacteria, thereby
killing them.
beta-lactamase
An enzyme, also known as
lactamase,
that inactivates antibiotic drugs such as
penicillins. Bacteria that are able to pro-
duce this enzyme are therefore resistant
to treatment with these kinds of anti-
biotic drugs.
betamethasone
A
corticosteroid drug
that is used in the
treatment of inflammation. Betametha-
sone is applied to the skin as a cream
to treat contact
dermatitis
and
eczema.
The drug is also prescribed as nasal
spray to treat allergic
rhinitis
(hay fever)
and is taken by mouth to treat some
cases of
asthma
and
arthritis.
Adverse effects of betamethasone are
unlikely with short-term use. However,
prolonged topical use of the drug can
cause thinning of the skin and may
aggravate any infection that has devel-
oped. Taken orally over a prolonged
period or in high doses, betamethasone
can cause adverse effects typical of other
corticosteroid drugs.
betel nut
The seed of the tropical palm A
reca
c a t -
e c h u
,
which, when chewed, acts as a
stimulant and digestant. Betel nut is
commonly used throughout India and
Southeast Asia.
Betnovate
A brand name for the corticosteroid
drug
betamethasone,
which is used in
topical preparations.
bezafibrate
A
lipid-lowering drug
used to reduce
blood cholesterol levels.
bezoar
A ball of food and mucus, vegetable
fibre, hair, or other indigestible material
in the stomach. Trichobezoars, which
are composed of hair, may form in the
stomachs of children or emotionally
disturbed adults who nibble at, or pull
out and swallow, their hair.
Symptoms include loss of appetite,
constipation, nausea and vomiting, and
abdominal pain. If trichobezoars pass
into the intestines, they may cause a
blockage (see
intestine, obstruction of).
Bezoars can be removed by
endoscopy
(a
procedure in which a flexible viewing
tube is passed down the digestive tract)
or by conventional surgery.
bi-
A prefix meaning two or twice, as in
bilateral (two-sided).
bicarbonate of soda
See
sodium bicarbonate
.
biceps muscle
The name that is given to any muscle
that originates as two separate parts,
which then fuse. The term biceps mus-
cle is commonly used to refer to the
biceps brachii muscle of the upper arm,
which bends the arm at the elbow and
rotates the forearm. Another example of
a biceps muscle is the biceps femoris
muscle, located at the back of the thigh,
which bends the leg at the knee and
extends the thigh.
bicornuate uterus
The term that is used to describe an
abnormally shaped uterus (womb) that
divides into two halves in its upper
part. Bicornuate literally means “having
two horns”.
bicuspid
A term meaning to have two cusps
(curved, pointed structures). Bicuspid
describes certain
heart valves
and is used
as an alternative name for a premolar
tooth (see
teeth).
bifocal
A spectacle lens with two different focal
lengths. Glasses that have bifocal lenses
make corrections both for close and for
distant vision. (See also
myopia; hyper-
metropia
.)
biguanides
Oral hypoglycaemic drugs (see
hypo-
glycaemics, oral)
used in the treatment
of type 2 (non-insulin-dependent)
dia-
betes mellitus.
Metformin, which is the
only available type of biguanide drug,
reduces
the
production
of
glucose
B
97
previous page 96 BMA A Z Family Medical Encyclopedia   2004 read online next page 98 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off