in a similar way to nitrates, and widens
both arteries and veins. Possible side
effects include flushing, nausea, vomit-
ing, and dizziness.
potassium citrateA substance used to
relieve discomfort in mild urinary tract
infectionsby making the urine less acid.
potassium permanganateA drug that
has an antisepticand astringenteffect;
and is useful in the treatment of derma-
titis. It can occasionally cause irritation
and can stain skin and clothing.
potencyThe ability of a man to perform
sexual intercourse; or the ability of a
drug to cause desired effects.
Pott’s fractureA combined fracture and
dislocation of the ankle caused by exces-
sive or violent twisting. Thefibulabreaks
just above the ankle; in addition, the
tibiabreaks or the ligamentstear, result-
ing in dislocation.
poulticeA warm pack consisting of a
soft, moist substance (such as kaolin)
spread between layers of soft fabric.
poxAny of various infectious diseases
characterized by blistery skin eruptions
(for example chickenpox). Pox is some-
times used as a slang word for syphilis.
pravastatinAlipid-lowering drug.
praziquantelAn anthelmintic drugused
to treat tapeworm infestation. Adverse
effects may include dizziness, drowsi-
ness, and abdominal pain.
prazosinA vasodilator drugused to treat
hypertension, heart failure, and Raynaud’s
disease. Prazosin is also used to treat uri-
nary symptoms resulting from an enlarged
prostate gland (see prostate, enlarged).
Side effects include dizziness and faint-
ing, nausea, headache, and dry mouth.
precancerousA term applied to any
condition in which there is a tendency for
cancer to develop. There are 3 types of
such conditions. In the 1st, there are no
tumours present but the condition car-
ries an increased risk of cancer. In the
2nd, there are noncancerous tumours
that tend to become cancerous or are
associated with the development of can-
cerous tumours elsewhere. The 3rd type
comprises disorders which have irregu-
lar features from the beginning but do
not always become fully cancerous.
precocious pubertyThe development of
secondarysexual characteristics beforeage 8 in girls and 9 in boys. It is uncom-
mon and may be caused by various
disorders that can result in production
of sex hormonesat an abnormally early
age. Possible underlying causes include
a brain tumouror other brain abnormali-
ties; abnormality of the adrenal glands
(for example, congenital adrenal hyper-
plasia); ovarian cysts,and tumours,or a
tumour in the testes. In some cases, no
underlying cause can be identified.
The hormones may cause a premature
growth spurt followed by early fusion of
the bones. As a result, affected children
may initially be tall but, if untreated,final
height is often greatly reduced.
The child’s pattern of pubertal devel-
opment is assessed by a doctor. Blood
tests are performed to measure hor-
mone levels. Ultrasound scanningof the
ovaries and testes, and CT scanning of
the adrenal glands or brain, may also be
carried out, depending on the underly-
ing cause suspected.
Treatment is of the underlying cause,
and hormone drugs may be given to
delay puberty and increase final height.
predisposing factorsFactors that lead
to increased susceptibility to a disease.
prednisoloneA corticosteroid drug.
prednisoneA corticosteroid drug.
pre-eclampsiaA serious condition in
which hypertension, oedema, and protein-
uriadevelop in the last (3rd) trimester
of pregnancy. If severe, symptoms may
include headache, nausea and vomiting,
abdominal pain, and visual disturban-
ces. The condition, which is sometimes
called pre-eclamptictoxaemia or PET, is
more common in 1st pregnancies and if
diabetes mellitus, hypertension, or kid-
ney disease is present. Untreated
pre-eclampsia may lead to eclampsia.
For some cases of pre-eclampsia, treat-
ment is bed-rest and antihypertensive
drugs. In late pregnancy, or if severe,
induction of labouror caesarean section
may be necessary.
pregnancyThe period from conception
to birth. Pregnancy begins with the fer-
tilization of an ovum (egg) and its
implantation. The egg develops into the
placentaand the embryo, which grows
to form the fetus. Most eggs implant
into the uterus. Very occasionally, anPOTASSIUM CITRATE PREGNANCYP