NADOLOL
NALOXONE
N
nadolol
A
beta-blocker
drug used in the
treatment of
hypertension
(high blood
pressure),
angina pectoris
(chest pain
due to impaired blood supply to heart
muscle), certain types of
arrhythmia
(irregularity of the heartbeat), and to
control symptoms of
hyperthyroidism
(overactivity of the thyroid gland). Pos-
sible adverse effects are typical of other
beta-blocker drugs.
n a e v u s
A type of skin blemish of which
there are 2 main groups: pigmented
naevi are caused by abnormality or
overactivity of melanocytes (skin cells
that produce the pigment
melanin);
vas-
cular naevi are caused by an abnormal
collection of blood vessels.
The most common types of pigmented
naevi are
frecMes, lentigos,
and
café au
lait spots-,
flat brown areas that may occur
where the skin is exposed to the sun.
Another common type is a mole, some-
times called a melanocytic naevus. In
rare cases, moles become cancerous
(see
melanoma
,
malignant).
Juvenile mel-
anomas (see
melanoma
,
juvenile)
are
red-brown naevi that occur in childhood.
Blue naevi are common in young girls.
Most black and Asian infants are born
with blue-black spots on their lower
backs (see
Mongolian blue spot
).
Port-wine stains and strawberry marks
(see
haemangioma
and
spider naevi
) are
examples of vascular naevi.
Most naevi are harmless. However, if a
naevus suddenly appears, grows, bleeds,
or changes colour, medical advice should
be sought immediately to exclude the
possibility of
skin cancer
.
nail
A hard, curved plate on the fingers
and toes composed of
keratin
(a tough
protein). Nails grow from an area called
the nail bed. At the base of each nail a
half-moon shape, the lunula, is crossed
by a flap of skin called the cuticle. The
surrounding skin is known as the nail
fold. A fingernail takes about
6
months
to grow from base to tip; toenails take
twice as long.
The nails are susceptible to damage
through injury, or by bacterial or fungal
infections, especially
tinea
and
candidi-
asis
. Sometimes they become abnormally
thick and curved: a condition known as
onychogryphosis
.
Nail abnormalities may
be a sign of skin disease, such as
alopecia
areata,
psoriasis
, and
lichen
planus
, or of more generalized disease,
for example iron-deficiency
anaemia
.
Un-
usual nail colour may indicate disease.
Treatment of nail disorders can be
difficult. Creams and lotions seldom
penetrate sufficiently; oral medication
may take months to be effective.
NAIL
Nail plate
Nail
plate
Cuticle
Nail
_
fold
. Cuticle
EXTERNAL
APPEARANCE
Bone
Skin
Nail bed
STRUCTURE OF NAIL
Lunula
matrix
n ail-bitin g A common habit in children
during their early years at school. Most
children grow out of it, although nail-
biting sometimes continues as a nervous
habit in adolescents and adults.
Various preparations with an unpleas-
ant taste can be painted on the nails as
a preventive measure.
nalidixic acid
An antibiotic drug used
to treat and/or to prevent
urinary tract
infection
. Possible adverse effects include
nausea, vomiting, increased sensitivity
to sunlight, blurred vision, drowsiness,
and dizziness.
naloxone
A drug that blocks the action
of
opioid drugs
.
Naloxone reverses the
breathing difficulty caused by high doses
of opioid drugs given during surgery.
The drug is also given to newborn babies
who are affected by opioid drugs used to
relieve the mother's pain during labour.
388
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