these antigens help the body to neu-
tralize or destroy the invading micro-
organisms. Antibodies may be formed
in response to vaccines, thereby giving
immunity. Antibodies are also known as
immunoglobulins.
Inappropriate or excessive formation
of antibodies may lead to illness, as in
an allergy. Antibodies against antigens
in organ transplants may result in rej-
ection of the transplanted organ. In
some disorders, antibodies are formed
against the body’s own tissues, result-
ing in an autoimmune disorder.
antibody, monoclonalAn artificially
produced antibodythat neutralizes only
one specific antigen(foreign protein).
Monoclonal antibodies are produced
in a laboratory by stimulating the growth
of a large number of antibody-producing
cells that are genetically identical. In
effect, this process enables antibodies
to be tailor-made so that they will react
with a particular antigen.
Monoclonal antibodies are used in
the study of human cells, hormones,
microorganisms, and in the develop-
ment of vaccines. They are also being
used in the diagnosis and treatment of
some forms of cancer.
anticancer drugsDrugs that are used
to treat many forms of cancer. They are
particularly useful in the treatment of
lymphomas, leukaemias, breast cancer,
cancer of the testis (see testis, cancer of),
and prostate cancerand are often used
together with surgery or radiotherapy.
Most anticancer drugs are cytotoxic
(kill or damage rapidly dividing cells),
but some act by slowing the growth of
hormone-sensitive tumours. Anticancer
drugs are often prescribed in combina-
tion to maximize their effects.
Treatment with cytotoxic drugs is often
given by injection in short courses
repeated at intervals. Some drugs cause
nausea and vomiting and may result in
hair loss and increased susceptibility to
infection. Others, such as tamoxifen,
which is used for breast cancer, are
given continuously by mouth for months
or years and cause few side effects.
anticholinergic drugs A group of
drugs that block the effects of acetyl-
choline, a chemical released from nerveendings in the parasympathetic auto-
nomic nervous system. Acetylcholine
stimulates muscle contraction, increases
secretions in the mouth and lungs, and
slows the heartbeat.
Anticholinergic drugs are used in the
treatment of irritable bowel syndrome,
urinary incontinence, Parkinson’s disease,
asthma, and bradycardia(abnormally
slow heartbeat). They are also used to
dilate the pupil before eye examination
or surgery. Anticholinergic drugs are
used as a premedicationbefore general
anaesthesiaand to treat motion sickness.
They may cause dry mouth, blurred
vision, urinary retention, and confusion.
anticoagulant drugsA group of drugs
used to treat and prevent abnormal
blood clotting, to treat thrombosis, and
to prevent and treat strokeand transient
ischaemic attack. Anticoagulant drugs
are also given to prevent abnormal
blood clotting after major surgery (esp-
ecially heart-valve replacement) or
during haemodialysis (see dialysis). The
most common anticoagulants are hep-
arin and the newer heparin-derived
drugs, such as tinzaparin, all of which
have to be given by injection, and warf-
arin, which is taken orally.
Excessive doses of anticoagulant drugs
increase the risk of unwanted bleeding,
and regular monitoring is needed.
anticonvulsant drugsA group of drugs
used to treat or prevent seizures. They
are used mainly in the treatment of epi-
lepsybut are also given to prevent
seizures following serious head injuryor
some types of brain surgery. They may
be needed to control seizures in children
with a high fever (see convulsions,febrile).
Anticonvulsants may produce various
side effects, including impaired memory,
reduced concentration, poor coordina-
tion, and fatigue. If the side effects are
severe, they can often be minimized by
use of an alternative anticonvulsant.
antidepressant drugsDrugs used in
the treatment of depression.Most of the
commonly used antidepressant drugs
belong to one of the following groups:
tricyclicdrugs, selective serotonin reup-
take inhibitors(SSRIs), and monoamine
oxidase inhibitors(MAOIs). These drugs
are usually successful at relieving theANTIBODY, MONOCLONAL ANTIDEPRESSANT DRUGSA