METABOLITE
METHYLPHENIDATE
metabolite
Any substance involved in a
metabolic reaction (a biochemical reac-
tion in the body). The term metabolite
is sometimes used to refer only to the
products of a metabolic reaction. (See
also
metabolism.)
metacarpal bone
One of 5 long, cylin-
drical bones within the hand. The bones
run from the wrist to the base of each
digit, with the heads of the bones form-
ing the knuckles.
metaplasia
A change in tissue resulting
from the transformation of one type of
cell into another. Usually harmless, but
occasionally precancerous, metaplasia
can affect the lining of various organs,
such as the bronchi (airways) and blad-
der. Metaplasia of the cervix, which
occurs in
cervical erosion
, can be detec-
ted by a
cervical smear test
.
metastasis
A secondary cancerous tu-
mour (one that has spread from a
primary
cancer
to another part of the
body). The term also applies to the pro-
cess by which such spread occurs.
Metastases can spread through the lym-
phatic system, in the bloodstream, or
across a body cavity.
metatarsal bone
One of 5 long, cylin-
drical bones within the foot. The bones
make up the central skeleton of the foot
and are held in an arch by the surround-
ing
ligaments.
metatarsalgia
Pain in the foot. Causes
include fracture of a
metatarsal bone
,
flat-
feet
, or
neuroma
of a nerve in the foot.
metatarsophalangeal joint
The joint
between each
metatarsal bone
and its
adjoining toe bone (see
phalanges
). The
metatarsophalangeal joint at the base
of the big toe is commonly affected by
gout
and by
hallux rigidus.
metformin
An oral hypoglycaemic drug
(see
hypoglycaemics
,
oral
) that lowers
blood glucose levels and is used to
treat type 2
diabetes mellitus.
Possible
adverse effects include loss of appetite, a
metallic taste in the mouth, nausea,
vomiting, and diarrhoea.
methadone
A synthetic opioid
analg-
esic drug
that resembles morphine.
Methadone is used under supervision
to relieve withdrawal symptoms in peo-
ple undergoing a heroin or morphine
detoxification programme. Side effects
may include nausea, vomiting, consti-
pation, dizziness, and dry mouth.
methane
A colourless, odourless, highly
inflammable gas that occurs naturally
in oil wells and coal mines. Methane is
also produced by the decomposition of
organic matter; it is one of the gases
present in intestinal gas (see
flatus
).
methanol
A poisonous type of
alcohol
that is used as a solvent or paint re-
mover and in some types of antifreeze.
Methanol poisoning usually occurs as a
result of drinking it as a substitute for
ordinary alcohol. Symptoms of poison-
ing include headache, dizziness, nausea,
vomiting, and unconsciousness. Dam-
age may also occur to the
retina
and the
optic nerve
, causing blurred vision. Re-
peated or large doses of methanol may
result in permanent blindness.
methicillin-resistant staphylococcus
aureus
See
MRSA.
methotrexate
An
anticancer drug
used
to treat
lymphoma
(cancer of the lymph
nodes) and some forms of
leukaemia
.
Methotrexate is also used to treat can-
cers of the uterus, breast, ovary, lung,
bladder, and testis, and severe
psoriasis
when other treatments are ineffective.
Methotrexate may cause nausea, vomit-
ing, diarrhoea, mouth ulcers,
anaemia
,
increased susceptibility to infection,
and abnormal bleeding.
methyl alcohol
An alternative name
for
methanol
.
methylcellulose
A bulk-forming
laxative
drug
used to treat
constipation
,
irritable
bowel syndrome
, and
diverticular disease
.
Methylcellulose increases the firmness
of faeces in chronic watery
diarrhoea
and regulates their consistency in peo-
ple who have a
colostomy
or
ileostomy
.
It is also given as eyedrops to relieve
dry eyes. As methylcellulose causes a
feeling of fullness, it is sometimes used
to help treat
obesity
.
methyldopa
An
antihypertensive drug
.
Adverse
effects
include
drowsiness,
depression, and nasal congestion.
methylenedioxymethamfetamine
See
Ecstasy.
methylphenidate
A
central
nervous
system
stimulant drug
used, under spe-
cialist supervision, to treat
attention
deficit hyperactivity disorder (ADHD)
in
367
previous page 365 BMA Illustrated Medical Dictionary read online next page 367 BMA Illustrated Medical Dictionary read online Home Toggle text on/off