PREVALENCE
PROCAINAMIDE
P
treatment with
antibiotic drugs
and, in
some cases, possibly
plastic surgery.
Good nursing care, including changing
the patient's position regularly, skin
care, protection of vulnerable areas,
and use of cushions and special mat-
tresses, should prevent pressure sores
from developing in most cases.
prevalence The total number of cases
of a disease at any one time in a
defined population. Prevalence is often
expressed as the number of cases per
100,000
people.
preventive dentistry An aspect of den-
tistry concerned with the prevention of
tooth decay and gum disease. It consists
of the encouragement of good
oral
hygiene, fluoride
treatment, and
scaling.
preventive medicine The branch of
medicine that deals with the prevention
of disease by public health measures,
such as the provision of pure water sup-
plies; by health education; by specific
preventive measures, such as
immu-
nization
against infectious diseases; and
by screening programmes to detect dis-
eases before they cause symptoms.
priapism Persistent, painful
erection
of
the
penis
without sexual arousal. Pri-
apism occurs when blood does not
drain from the spongy tissue of the
penis, thus keeping the penis erect. This
may be caused by clotting in the blood
vessels due to a blood disorder or as a
result of treatment for impotence. Urgent
treatment is needed in order to avoid
permanent damage. The treatment may
involve withdrawal of blood from the
penis with a needle.
prickly heat An irritating skin rash that
is associated with profuse sweating.
The medical name is miliaria rubra.
Multiple tiny, red, itchy spots cover the
affected areas of skin and are accompa-
nied by prickling sensations. The irri-
tation tends to affect areas where sweat
collects, such as the armpits. The cause
is not fully known, but unevaporated
sweat is an important factor. Sweat
ducts become blocked with debris and
leak sweat into the skin. Frequent cool
showers and sponging of the affected
areas relieve the itching.
primaquine A drug used to treat vivax
and ovale
malaria
. It is often given after
prophylactic treatment with
chloroquine
has failed to prevent infection.
Adverse effects include nausea, vomit-
ing, and abdominal pain. In people with
G6PD deficiency,
primaquine may cause
haemolytic
anaemia
.
primary A term applied to a disease
that has originated within the organ or
tissue affected, and is not derived from
any other cause or source. The term pri-
mary is also applied to the
1
st of
several diseases to affect a tissue or
organ in turn. Primary is also used to
mean “of unknown cause”.
primary care Health care provided by
a general practitioner or other health-
care professional who is the
1
st contact
for a patient seeking medical treatment.
primary teeth The 1st teeth (also known
as milk teeth), which usually start to
appear at age
6
months and are replaced
by the
permanent teeth
from about age
6
years. There are 20 primary teeth, 10
in each jaw. (See also
teeth
;
eruption of
teeth; teething.)
primidone An
anticonvulsant drug
used
to treat
epilepsy
and, occasionally,
tremor
.
It is usually prescribed with another
anticonvulsant. Adverse effects include
drowsiness, clumsiness, and dizziness.
Prinzmetal's angina See
variant angina.
prion A tiny, protein-based infectious
particle. Prions transmit diseases, includ-
ing
Creutzfeldt-Jakob disease
in humans
and
bovine spongiform encephalopathy
(BSE)
in cattle. Prions do not contain
nucleic acids and are difficult to des-
troy. As yet, no treatment is available
for prion diseases.
PRK The abbreviation for
photorefractive
keratectomy
.
probenecid A drug used in the long-
term treatment of
gout
. Probenecid also
slows the excretion of some
antibiotic
drugs
and so is occasionally prescribed
with these drugs to boost their levels
and thus their effects. It may cause nau-
sea
and
vomiting.
Other
possible
effects include flushing and dizziness.
probiotic bacteria Species of microor-
ganisms that inhabit the digestive tract,
guarding it against harmful bacteria,
yeasts, and viruses.
procainamide An
antiarrhythmic drug
that is used to treat certain types of
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