nickelA metallic element that is pre-
sent in the body in minute amounts.
Nickel is thought to activate certain
enzymes(substances that promote bio-
chemical reactions), and it may also
play a part in stabilizing chromosomal
material in the nuclei of cells.
Exposure to nickel may cause dermati-
tis(inflammation of the skin). Lung
cancerhas been reported in workers in
nickel refineries.
niclosamideAn anthelmintic drugused
to treat tapeworm infestation. Niclosa-
mide causes the tapeworm to loosen its
grip on the inner wall of the intestine.
The worm is then passed out of the
body in the faeces.
Adverse effects include abdominal
pain, lightheadedness, and itching.
nicorandilA potassium channel opener
drug used in the prevention and long-
term treatment of angina. Side effects,
which include flushing, nausea, vomit-
ing, and dizziness, are mainly due to
nicorandil’s vasodilation effects and
usually wear off with continued treat-
ment. Rarely, mouth ulcers and muscle
pain can occur.
nicotinamideSee vitamin B complex.
nicotineA drug in tobacco which acts
as a stimulant and is responsible for
dependence on tobacco. After inhala-
tion, the nicotine in tobacco smoke
passes rapidly into the bloodstream.
The drug acts on the nervous system
until broken down by the liver and
excreted in the urine.
Nicotine acts primarily on the auto-
nomic nervous system, which controls
involuntary body activities such as the
heart rate. In habitual smokers, the
drug increases the heart rate and nar-
rows the blood vessels, the combined
effect of which is to raise blood pres-
sure. Nicotine also stimulates the
central nervous system, thereby reduc-
ing fatigue, increasing alertness, and
improving concentration.
Stopping smoking often causes with-
drawal symptoms such as headaches
and difficulty in concentrating. Nicotine
replacement therapy, such as the use of
nicotine skin patches and chewing gum,
can be effective in aiding withdrawal from
nicotine. (See also smoking.)
nicotine replacement therapy Prep-
arations containing nicotinethat are
used in place of cigarettes as an aid to
stopping smoking. Nicotine products
are available in the form of sublingual
tablets, chewing gum, skin patches,
nasal spray, or inhaler. Side effects may
include nausea, headache, palpitations,
cold or flu-like symptoms, hiccups, and
vivid dreaming. Nicotine replacement
therapy should be used as part of a
complete package of measures, includ-
ing the determination to succeed.
nicotinic acidA form of niacin (see
vitamin B complex). Apart from its use
as a vitamin supplement, nicotinic acid
is also prescribed as a lipid-lowering drug
and as a vasodilator drug. High doses
are used to treat certain types of hyper-
lipidaemia. Nicotinic acid derivatives are
used to improve circulation in disorders
such as peripheral vascular disease.
Adverse effects are more common with
high doses, and include flushing, dizzi-
ness, nausea, palpitations, and itching.
nifedipineA calcium channel blocker
drug used mainly to prevent and treat
angina pectoris. Nifedipine is also often
used to treat hypertension(high blood
pressure) and disorders affecting the
circulation, such as Raynaud’s disease.
Possible adverse effects include oedema
(accumulation of fluid in tissues), flush-
ing, headache, and dizziness.
night blindnessThe inability to see
well in dim light. Many people with
night blindness have no discernible eye
disease. The condition may be an inher-
ited functional defect of the retina, an
early sign of retinitis pigmentosa, or a
result of vitamin A deficiency.
nightmareAn unpleasant, vivid dream,
sometimes accompanied by a sense of
suffocation. Nightmares occur during
REM (rapid eye movement) sleepin the
middle and later parts of the night, and
they are often clearly remembered if the
dreamer awakens completely.
Nightmares are especially common in
children aged between 8 and 10, and
are particularly likely to occur when the
child is unwell or anxious. In adults,
nightmares may be a side effect of cer-
tain drugs, including beta-blocker drugs
and benzodiazepine drugs. RepeatedNICKEL NIGHTMARE
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