Posted by Cam W. on March 3, 2001, at 11:19:11
In reply to Re: Cam?, posted by willow on March 3, 2001, at 8:25:57
Willow - I am guessing here, but the probable reason that domperidone is not sold in the States is because it has not been approved for sale by the FDA, while at the same time the patent protection on it has probably run out. The FDA requires American clinical trials to be done (clinical trials from other countries are not enough) to prove that domperidone is as good as or better than drugs already available in the U.S. Domperidone is probably as good as most drugs in it's class, but a company would have to spend a hundred million or so dollars to have it approved and they would not be able to recoup this money. Because the patent protection has run out, as soon as the company received FDA approval to sell it, any other company could also sell it, too (without having to shell out for testing). This, and the fact that there are several other drugs in it's class (gastrointestinal [GI] motility modifier), there is no financial incentive to have domperidone approved for use in the U.S. Also, since it isn't better than other drugs in it's class, it would not capture a significant market share.
In a nutshell, Company A doesn't want to shell out a whole bunch of money on a drug that will not gain a large share of the market, and even if it did, Company B could produce and sell it because domperidone is not protected by a patent (which has expired). No profit = no incentive to have it approved for sale
These are probably reasons why Imovane™ (zopiclone) and Manerix™ (moclobemide) are not sold in the States, either. You are not going to be able to profitably market a drug that is not much better than other drugs in it's class, especially if the time left on it's patent protection is short.
Now, on to why both your doctor and pharmacist were both telling the truth:
This may be true in the sense that Effexor can cause constipation or diarrhea, thus affecting domperidone's actions on the intestines. Effexor is exerting this effect through peripheral (esp GI) serotonin-3 receptors, while domperidone is affecting peripheral (esp GI) dopamine receptors. So both drugs are acting on the intestines in different ways, affecting the action of each other (thus, your doc is right).
That being said, this is more or less a moot point, because after 2 to 4 weeks of Effexor therapy the serotonin-3 receptors in the GI tract are down-regulated and no longer affect the domperidone.
The domperidone does not cross the blood brain barrier, so it does not affect the brain's dopamine receptors. Therefore it does not affect Effexor's antidepressant activity to any appreciable extent. Except maybe a little bit, via an indirect action on the vagus nerve, but only enough to give you a slight headache (thus your pharmacist is right, too).
I hope this clears things up a bit. Simple, huh (but not as simple as just looking it up - I actually had to think it through, therefore I could be wrong)?
In any case, there is no problem taking these two drugs together- Cam
poster:Cam W.
thread:54959
URL: http://www.dr-bob.org/babble/20010302/msgs/55447.html