receptor antagonist can reduce
central sensitization due to increased
NMDA, which is a central nervous
system neuro-transmitter. So ketamine
is a general anesthetic, which we've mentioned,
but in small doses it's an effective analgesic.
It's also currently become
a drug of abuse and
it has become a street drug and the name on the street
is Special K. Ketamine is also occasionally used
for labour analgesia and analgesia prior
to surgery, but only in very small doses.
When used as an anesthetic, it,
or an analgesic in higher doses,
it can produce the recovery phenomena
that I mentioned in a previous lecture.
Other side-effects include nausea and vomiting,
increased heart rate and blood pressure and,
occasionally, agitation and hallucinations.
Carrying on, more drugs.
Alpha2-agonists. The classic of these
is Clonidine. These
are receptor drugs that work on the Alpha2 receptor,
which is a central nervous system receptor.
They can be given either orally or they can be given
along with spinal anesthesia in a dilute concentration.
They produce sedation and can produce severe
postural hypotension. So, in other words,
when you stand up, your blood pressure drops and that
can lead to fainting or even loss of consciousness
and seizures. So, that's not a good thing. They produce
a very dry mouth and patients complain about that.
The newer drug, Dexmedetomidine is very
heavily marketed for ICU sedation.
I'm personally doubtful that it's any better than
Clonidine, it certainly cost more. For migraine
headache there have been great problems
finding substances that are useful.
And one of the agents of drugs that has been found
to be useful in some people with migraine, are
the 5HT1-agonists, 5-hydroxytryptamine 1
the classic drug in this group is Sumatriptan,
but there's a series of drugs. They are
used for treatment of migraine headaches.
They can be self-administered by syringe,
pre-loaded syringe. They can be, you can take tablets
or you can actually use a nasal spray, which is quite quick
because it's rapidly absorbed by the nasal
mucosa and you're right
near the brain when you administer it,
so it can actually be quite effective. They cause
Vasoconstriction, tightening of blood vessels, and reduction
of inflammation of the cranial artery. So, the arteries
that come on the outer surface of the skull
primarily, some of them perforate the skull,
and these are the arteries that become
dilated and throbbing in migraine headache.
This vasoconstriction can increase the risk
of vascular bed, in vascular
bed such as a cardiac bed, where if you get vasoconstriction,
you can get cardiac ischemia, myocardial
infarction, and it can also increase the possibility
of stroke, if it causes intracranial
vessels also to constrict.