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P A R T 4
Drugs acting on the central and peripheral nervous systems
Migraines are generally classified as common or
classic. Common migraines, which occur without an
aura, cause severe, unilateral, pulsating pain that is
frequently accompanied by nausea, vomiting and sensi-
tivity to light and sound. Such migraine headaches are
often aggravated by physical activity. Classic migraines
are usually preceded by an aura—a sensation involving
sensory or motor disturbances—that usually occurs
about half an hour before the pain begins. The pain and
adverse effects are the same as those of the common
migraine.
It is believed that the underlying cause of migraine
headaches is arterial dilation. Headaches accompanied
by an aura are associated with hypoperfusion of the
brain during the aura stage, followed by reflex arterial
dilation and hyperperfusion. The underlying cause
and continued state of arterial dilation are not clearly
understood, but they may be related to the release of
bradykinins or serotonin, or as a response to other
hormones and chemicals.
ANTIMIGRAINE AGENTS
For many years, the one standard treatment for migraine
headaches was acute analgesia, often involving an
opioid, together with control of lighting and sound and
the use of ergot derivatives. In the late 1990s, a new class
of drugs, the triptans, was found to be extremely effec-
tive in treating migraine headaches without the adverse
effects associated with ergot derivative use. Because
these agents are associated with many systemic adverse
effects, their usefulness is limited in some people (see
Box 26.5). Table 26.2 includes additional information
about each class of antimigraine agents.
E
rgot derivatives
The
ergot derivatives
cause constriction of cranial blood
vessels and decrease the pulsation of cranial arteries.
As a result, they reduce the hyperperfusion of the basilar
artery vascular bed.
Available ergot derivatives include ergotamine
(
Cafergot
) (no longer available in Australia).
Therapeutic actions and indications
The ergot derivatives block alpha-adrenergic and sero-
tonin receptor sites in the brain to cause a constriction
of cranial vessels, a decrease in cranial artery pulsa-
tion and a decrease in the hyperperfusion of the basilar
Headache distribution
Headaches are distributed in the general population in a
definite gender-related pattern. For example:
• Migraine headaches are three times more likely to
occur in women than men.
• Cluster headaches are more likely to occur in men than
in women.
• Tension headaches are more likely to occur in women
than in men.
There is some speculation that the female
predisposition to migraine headaches may be related
to the vascular sensitivity to hormones. Some women
can directly plot migraine occurrence to periods of
fluctuations in their menstrual cycle.The introduction
of the triptan class of antimigraine drugs has been
beneficial for many of these women.
Gender considerations
BOX 26.4
BOX 26.5
Drug therapy across the lifespan
Antimigraine agents
CHILDREN
None of the drugs used to treat migraines are
recommended for use in children.The ergot derivatives
can have many adverse effects in children, and there is not
enough clinical experience with triptans to recommend
them for use in children.
ADULTS
Adults requesting treatment for migraine headaches
should be carefully evaluated before one of the
antimigraine drugs is used to ensure that the headache
being treated is of the type that can benefit from these
drugs.
PREGNANCY AND BREASTFEEDING
The ergots and the triptans are contraindicated during
pregnancy because of the potential for adverse effects in
the mother and fetus. Women of childbearing age should
be advised to use contraception while they are taking
these drugs. Women who are breastfeeding should be
encouraged to find another method of feeding the baby
because of the potential for adverse drug effects on the
baby.
OLDER ADULTS
Older adults are more likely to have chronic diseases such
as cardiovascular disease or renal or hepatic impairment
that would be exacerbated by the antimigraine drugs.They
should be used with extreme caution in older adults.The
older adult should be encouraged to take the least amount
of the drug possible and should be monitored closely
for any sign of chest pain, MI or acute vascular changes.
Safety measures are extremely important with the older
adult. If the person is in an institutional setting, side rails,
assistance with moving and careful monitoring should be
used.
