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Thinktank
11-21-2005, 07:40 PM
HI, seems every medicine I see anymore has HCI on the packaging.
Why is this such a popular "ingredient" ?

Q.E.D.
11-21-2005, 07:44 PM
That's HCL--the hydrochloride radical. It's appended to various fat-soluble drugs to make them water soluble, so that your body can absorb them more readily. Occasionally, you'll see the hydrobromide radical, HBr, instead of HCl. It serves the same purpose.

Rysdad
11-21-2005, 08:06 PM
So, HCl (small "L") is not the same as HCL? Makes sense I guess. HCl (small "L") would be hydrochloric acid. The same acid found in your stomach.

It doesn't seem like having HCl as an ingredient would make for a long shelf life for a number of products.

Huh. Whattya know.

Caiata
11-21-2005, 08:07 PM
As I understand it, it's actually hydrogen chloride (not a radical, but the actual ionic compound) added to the drug to, as Q.E.D. says, make it water-soluble.

Many drugs have a nitrogen in them, which has a lone pair of electrons hanging around on it. A H+ ion can be appended to this lone pair:

Drugmolecule-N: + HCl --> Drugmolecule-NH+ + Cl-

Because the drug molecule now carries a positive charge, the chloride ion is attracted to it, forming a new ionic compound known as "drugname HCl". The drug is now water-soluble, which is a good thing for those drugs that need to enter your blood stream, as your blood is, of course, aqueous in nature. The HCl bit might be removed by your body later to allow the drug to pass from the blood stream into your tissues, because in order to do so the drug must be able to dissolve in the fatty membranes of your cells so it can cross them.

HBr is sometimes used (but not that frequently, I am not sure why) and some drugs are also reacted with H3PO4; this is most popular with codeine, which appears as "codeine phosphate" in many pharmaceutical preparations.

Q.E.D.
11-21-2005, 08:12 PM
So, HCl (small "L") is not the same as HCL?
No, it's HCl, as in HC-small-"L". I only used the capital letter to emphasize it, since the lowercase "L" looks like an uppercase "i". Stoopid Latin alphabet!

Caiata
11-21-2005, 08:12 PM
Hi Rysdad, didn't see your post on preview.

My guess is Q.E.D. was capitalising and bolding the "L" to make it distinct from the letter "I", as the lower-case "l" looks too much like an I and is in fact one source of the OP's confusion. Chlorine is never formally abbreviated with "CL".

HCl is an ionic compound which is gaseous in nature. It is called "hydrogen chloride". Only when it is dissolved in water is it "hydrochloric acid". The drugs are reacted with hydrochloric acid in order to append the HCl bit onto the molecule and make it water-soluble. This typically results in the drug HCl molecule precipitating out of solution, or becoming a solid. The solid is filtered away and, now that the HCl is no longer in an aqueous environment, it no longer acts as an acid. Shelf life is not affected.

WonJohnSoup
11-21-2005, 08:50 PM
Hi Rysdad, didn't see your post on preview.

My guess is Q.E.D. was capitalising and bolding the "L" to make it distinct from the letter "I", as the lower-case "l" looks too much like an I and is in fact one source of the OP's confusion. Chlorine is never formally abbreviated with "CL".

HCl is an ionic compound which is gaseous in nature. It is called "hydrogen chloride". Only when it is dissolved in water is it "hydrochloric acid". The drugs are reacted with hydrochloric acid in order to append the HCl bit onto the molecule and make it water-soluble. This typically results in the drug HCl molecule precipitating out of solution, or becoming a solid. The solid is filtered away and, now that the HCl is no longer in an aqueous environment, it no longer acts as an acid. Shelf life is not affected.

Small nitpick. I don't think HCl is technically an ionic compound. It's just very very polar, right? Or is there some deeper level of chemistry I haven't reach yet?

Shalmanese
11-21-2005, 09:10 PM
Damn, I thought this would be about Human Computer Interaction, which I actually know something about.

JustAnotherGeek
11-21-2005, 09:10 PM
It's just very very polar, right? Or is there some deeper level of chemistry I haven't reach yet?
It depends and probably. (Sorry, I don't know what chem you're in.)

If you are referring to the difference of the Pauling electronegativities being less than 1.7, yes it is "polar covalent." There is, however more to the story than just the P.E.'s, including, for instance, who's in the neighborhood. Organic Chemistry deals with this subject.

But remember, even if HCl is by itself, "ionic" or "polar covalent" are really just terms we use to describe its behavior. For all practical purposes, when HCl finds H2O, it behaves "ionically."


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On another note. I think, Caiata needs to win a prize! Caiata's qualifications?
Not just two simulposts in one thread...
Not just two simulposts within five minutes of each other...
Not just that one simulpost was basically saying the same thing as the concurrent simulpost...
But that one simulpost was explaining a SDSAB's post, who simulposted explaining the earlier post!

My head hurts! :eek:

Caiata
11-21-2005, 09:33 PM
I'm all up for prizes :D

(I said some new stuff, right? Right? :( )