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Topic: Verapamil, another twist. (Read 296 times) |
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kody
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The following is extracted from Dr. Greg's link on this site:
"In the arteries of the brain, the muscles that cause the arteries to constrict use calcium to help regulate how hard they squeeze. By blocking the flow of calcium, the muscles don't react as quickly.
Cluster headaches seem to involve dilatation of the arteries in the brain. Whether that causes the pain, or is just a step in the process, we don't know. However, many of the medications that relieve cluster headache pain cause constriction of the vessels...so they definitely play a part. By blocking the calcium channels, the medication, in theory, decreases the irritability, or responsiveness, of these vessels".
The contradiction, as I see it, is that if CH is due to dilation of arteries in brain, then what you REALLY WANT is to facilitate the smooth muscle to contract. According to the above, this means YOU NEED calcium to trigger smooth muscle contraction. By calcium blocking these channels aren't you preventing contraction and therby prolonging the CH ? In other words, don't we want to increase arterial muscle irritability or responsiveness and thereby actually NEED calcium. It seems that Verapamil works some other way or i'm misreading Dr. Greg above.
To the CH Community: Please respond if you have another take on this
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Ueli
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Re: Verapamil, another twist.
« Reply #1 on: May 5th, 2002, 10:34pm » |
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As I understand it: A (wrong) triggering signal from the hypothalamus lets the vessels expand and the resulting pressure on the trigeminal nerve causes the pain.
Through some positive feedback the raise time of the attack is very fast, as you certainly know. 
There is an article on Medscape http://www.medscape.com/viewarticle/416383_7 that explains this in more detail (You need a pass word for Medscape, but everybody can sign up for free.)
The role of Verapamil: The receptors of the smooth muscles need Ca++ ions to receive a signal. By blocking the Ca channels, the Ca++ concentration in the receptors is reduced and the muscles respond only sluggish to a signal.
When the smooth muscles around the blood vessels are 'paralyzed' the above mentioned feedback loop is damped a lot, hence the attack is much reduced or even suppressed completely.
The Ca blocking makes the expansion of the vessels sluggish, the contraction still works: either through a massive dose of serotonin agonists (Imitrex) or the autonomous contraction to reduce the flow of very oxygen rich blood (due to O2 inhalation) in order to keep the supply to the brain constant.
There are a lot of smooth muscles around the intestines too, to move the contents forwards (or is it here backwards?  ). Making them work slowly results in the well known side effect of Verapamil: constipation.
PFNAD,
Ueli
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Ted
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I love YaBB 1G - SP1!
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Re: Verapamil, another twist.
« Reply #2 on: May 5th, 2002, 11:25pm » |
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That's a very legitimate question, Kody. Nice to see them still around.  To de-expand on the explanation of Verapamil, studies have shown that the pain starts, sometimes, before the blood vessels (or for you, Dannyboy, the veins, arteries, those little tunnels that carry blood in one direction or other) start to dilate. I think it's a step in the process but not necessarily the cause. As a matter of fact, if it was the central part of the pain we'd all get relief of some sort to Verapamil, wouldn't we (Or, by your well thought out question, anti-verapamil)?
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| « Last Edit: May 6th, 2002, 12:22am by Ted » |
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