Whenever I donate they ask questions about if I’ve ever taken tegason, soriatane, accutane or propecia, all of which either treat or cause baldness. They said it has something to do with birth defects in pregnant women, does anyone know the mechanism? Do the baldness drugs screw up testosterone production in the womb in women who take them?
I know why they won’t let people (fear of birth defects) but I’m wondering how big is the risk? My understanding is that the vitamin zinc will also block the 5-alpha reductase enzyme (the same enzyme blocked by propecia) but they don’t ask anything about taking vitamins or zinc.
Tagamet also blocks DHT from the hair follicle, but they dont’ ask about it.
I know I should talk to them about it and I’m going to today. I am just wondering if anyone has any idea why they treat baldness drugs so seriously when things like zinc are not treated so seriously.
If you’ve ever seen teh commercials for propecia they warn tha tpregnant women shouldn’t even touch propecia pills for fear it’ll pass through the skin. So why isn’t zinc a tetragenic or cimetidine?
Propecia is known to cause fetal defects, especially in male fetuses.
According to Drugs.com, it prevents conversion of testosterone to dihydrotestosterone.
Basically, a high-enough plasma concentration of Propecia can cause birth defects, and this is something no one wants to risk.
In fact, Propecia is one of several drugs on the list of questionable or disallowed medications. Here is a list of drugs and waiting times. They generally fall into two categories: drugs that cause birth defects and drugs that cause clotting or bleeding problems.
Robin
True. However what about zinc & B6? Zinc blocks the 5-AR enzyme as well. So does cimitidine but for some reason cimetidine isn’t a teratogenic
I’m confused as to why one 5-AR inhibitor is a major tetarogenic and another isn’t, or why they don’t ask about zinc usage.
Those are questions for a pharmacologist.
However, I was warned not to take supplements over and above what was in the prenatal vitamins my obstetrician prescribed, so there may be something to that, at least in very large (that is, more than what is required for health) doses.
Robin
Exerpted from Endotext.org
Bolding mine.
A competitive antagonist basically binds reversibly to an enzyme’s active site for a brief time, essentially wasting the enzyme’s time until it pops loose and the intended target molecule can bind there. Increasing the concentration of a competitive inhibitor can slow down an enzymatic process by orders of magnitude but cannot completely stop it. A non-competitive inhibitor, on the other hand, binds irreversibly to the enzyme and effectively kills it. A large enough dose of a non-competitive inhibitor can completely stop a reaction by destroying all the enzyme present. Thus the ‘killed’ enzymes remain ‘killed’ even after any unbound finasteride has been flushed from the system.
I would suspect (ie haven’t bothered to check) that zinc and cimetidine are competitive inhibitors of the enzyme in question. Therefore their effects decrease predictably as their half-lives pass. For a developing fetus, there can be a major difference in effect if enzyme activity is, say, decreased by 50% for 50% of the day as opposed to a permanent 50% decrease.
There could be other reasons as well specific to plasma donation. Perhaps the plasma is stored in a way that destroys cimetidine or other drugs, but not finasteride. Or it is titrated and thus excess Zn is bound up, etc. More specific info would be needed.
It is also to stop women becoming hairy after a transfusion?
The drugs do cause premature adulthood in childern. Medical sites have examples of problems that have occured. A father ussing the patch rough housed with his toddler and after a month he was found to be maturing sexually. He had start growing facial hair. The doctors caught on to what was going on before his bones stopped growing. As for specicific drugs on the list, I can’t tell you their specific worry. The baldness drugs affect maturation and change a persons body chemistry.