Menstruation is often irregular for the
first few years, and for several years
before the menopause.
mental ageA measurement of the intel-
lectual development of a person, with
regard to the normal age at which that
level of achievement is attained. For
example, a 13 year-old child with learning
difficultiesmay have a mental age of 5.
mental handicapImpaired intellectual
development, also known as general
learning difficultiesor disability.
Mental Health ActThe Mental Health
Act (1983) details the rights of patients
with mental illnessand the grounds for
detaining mentally ill people against
their will. It also outlines forms of legal
guardianship for such patients.
When a person is endangering his or
her own or other people’s health or
safety (for example, threatening harm
or suicide) because of a recognized
mental illness, he or she may be com-
pulsorily taken into hospital to be given
treatment. If a person breaks the law
because of a mental disorder, the courts
may remand him or her to hospital.
mental hospitalA hospital, formerly
known as an asylum, specializing in the
treatment of psychiatric illness.
Most admissions to mental hospitals
are for acute psychiatric illness. The
majority of admissions are voluntary,
but in some cases detention under the
Mental Health Actmay be necessary.
mental illnessA general term that des-
cribes any form of psychiatric disorder.
mental retardationSeeLearning diffi-
culties.
mentholAn alcohol prepared from mint
oils. Menthol is an ingredient of several
over-the-counter inhalation preparations
used to treat a blocked or stuffy nose.
meprobamateAn antianxiety drug used
in the treatment of anxietyand stress. It
also acts as a muscle relaxant.
meptazinolA weak opioid analgesic
drugused for the short-term relief of
moderate to severe pain, such as after
surgery and during childbirth. Possible
adverse effects include nausea, vomit-
ing, and dizziness.
mercaptopurineAn anticancer drug
used to treat certain types of leukaemia.
Adverse effects include nausea, mouth
ulcers, and appetite loss. Rarely, it may
cause liver damage, anaemia, and ab-
normal bleeding.
mercuryThe only metal that is liquid at
room temperature. Mercury is used in
thermometers, sphygmomanometers, and
fillings for teeth (see amalgam, dental).
mercury poisoningToxic effects of
mercury on the body. The most com-
mon cause of mercury poisoning is
breathing in vapour given off by liquid
mercury, usually as a result of industrial
exposure. Swallowing a small amount
of liquid mercury is unlikely to lead to
poisoning. Mercury compounds may
cause poisoning by absorption through
the intestines (causing nausea, vomit-
ing, diarrhoea, and abdominal pain) or
the skin (causing severe inflammation).
After entering the body, mercury accu-
mulates in organs, principally the brain
and kidneys. Mercury deposits in the
brain cause tiredness, incoordination,
excitability, tremors, and numbness in
the limbs. In severe cases, there may
be impaired vision and dementia. De-
posits of mercury in the kidneys may
lead to kidney failure.
Treatment may involve chelating agents,
which help the body to excrete the mer-
cury quickly; haemodialysis (see dialysis);
and induced vomiting or pumping out
the stomach, if mercury has been swal-
lowed within the previous few hours.
mesalazineA drug used to treat ulcera-
tive colitis. Adverse effects of mesalazine
include nausea, diarrhoea, abdominal
pain, and headache.
mescalineA hallucinogenic drugobtain-
ed from the Mexican peyote cactus.
mesenteric lymphadenitisAn acute
abdominal disorder, mainly affecting
children, in which lymph nodesin the
mesenterybecome inflamed. The main
symptoms of pain and tenderness in
the abdomen may mimic appendicitis.
There may also be mild fever. Mesen-
teric lymphadenitis usually clears up
rapidly, needing only analgesic drugsto
reduce pain and fever.
mesenteryA membrane that attaches
organs to the abdominal wall. The term
is used particularly to refer to the mem-
branous fold that encloses the small
intestine, attaching it to the back of theMENTAL AGE MESENTERY
M