Theories for the cause of PMS include
hormonal changes and vitamin or min-
eraldeficiencies, but none have been
confirmed. The most common emotional
symptoms are irritability, tension, depres-
sion, and fatigue. Physical symptoms
include breast tenderness, fluid reten-
tion, headache, backache, and lower
abdominal pain.
No single treatment has proved com-
pletely successful. Treatments to relieve
specific symptoms include diuretic drugs,
dietary changes, and relaxation tech-
niques. Pyridoxine (vitamin B 6 ) or even-
ing primrose oil may help some women.
Oral contraceptivescan relieve symptoms
by suppressing the normal menstrual
cycle. Progesterone supplements are
widely used but not always effective.
premenstrual tensionSee premen-
strual syndrome.
premolarOne of 8 permanent grinding
teeth, 2 in the upper and 2 in the lower
jaw on each side of the mouth, located
between the canines and molars. (See
also permanent teeth; eruption of teeth.)
prenatalThe period of pregnancy
before childbirth.
prepuceSee foreskin.
presbyacusisThe progressive loss of
hearing that occurs with age. Presbyacu-
sis is a form of sensorineural deafness,
which makes sounds less clear and tones
less audible. People with the condition
often find it difficult to understand
speech and cannot hear well when there
is background noise. Presbyacusis may
be exacerbated by exposure to high
noiselevels, diminished blood supply
to the inner ear due to atherosclerosis,
and damage to the inner ear from drugs
such as aminoglycoside drugs. Hearing-
aidshelp most people.
presbyopiaThe progressive loss of the
power of adjusting the eye (see accom-
modation) for near vision. The focusing
power of the eyes weakens with age.
Presbyopia is usually noticed around
age 45 when the eyes cannot accommo-
date to read small print at a normal
distance. Reading glasseswith convex
lenses are used to correct presbyopia.
prescribed diseasesA group of in-
dustrial diseases that give sufferers
legal entitlement to financial benefit. A
claimant has to have worked in an occu-
pation recognized to increase the risk of
developing a particular disease. Exam-
ples include conditions due to physical
agents (such as occupational deafness),
biological agents (for example, anthrax),
or chemical agents (such as lead poison-
ing); pneumoconiosis; and byssinosis.
(See also notifiable diseases; occupa-
tional disease and injury.)
prescriptionAn instruction written by
a doctor that directs a pharmacist to
dispense a particular drug in a specific
dose. A prescription details how often
the drug must be taken, how much is to
be dispensed, and other relevant facts.
prescription-only medicineDrugs and
medicines that are not available over the
counter and can only be obtained by
prescription. Prescription-only medicines
are those whose safe use is difficult to
ensure without medical supervision.
preservativeA substance that inhibits
growth of bacteria, yeasts, and moulds
and so protects foods from putrefying
and fermenting. Examples include sul-
phur dioxide, benzoic acid, salt, sugar,
and nitrites. (See also food additives.)
pressure pointsPlaces on the body
where arteries lie near the surface and
pressure can be applied by hand to
limit severe arterial bleeding (in which
bright red blood is pumped out in regu-
lar spurts with the heartbeat). Major
pressure points of the body include the
brachial pressure point in the middle
part of the upper arm and the carotid
pressure point at the side of the neck,
below the jaw.
pressure soresUlcers that develop on
the skin of patients who are unconscious
or immobile. They are also known as
decubitus ulcers or bedsores. Common
sites include the shoulders, elbows,
lower back, hips, buttocks, ankles, and
heels. Pressure sores may develop fol-
lowing stroke or spinal injuries that
result in a loss of sensation. Inconti-
nence, if it results in constantly wet skin,
may also be a contributory factor. Pres-
sure sores start as red, painful areas that
become purple before the skin breaks
down. At this stage, the sores often
become infected and are very slow to
heal. Deep, chronic ulcersmay requirePREMENSTRUAL TENSION PRESSURE SORES
P