Prescription Question - What is HCl For?

[DrTacoElf]

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[Gut Shot]

From the Wikipedia article on hydrochloride:

Converting otherwise insoluble amines into their hydrochlorides is a common way to make them water and acid-soluble. This is particularly desirable for substances used in medications. Many pharmaceutical substances used are prepared as hydrochlorides so that they may be quickly absorbed in the gastrointestinal tract. The typical breadth of time needed for a hydrochloride to be absorbed thusly is 15-30 minutes.

 

[DrTacoElf]

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[dilated]

There are a bunch of reasons. One is water solubility. A big one is that most amines are liquids and by converting to the HCl salt you get the friendly solid form. There are actually many pills that use things besides HCl as the acid (acetate for example) for reasons like stability, crystalline structure, other stuff. It's actually a fairly complex area of medicinal chem.

 

[Critical Mass]

I just think about it the way that Tris-HCl buffer is prepared. The chemical itself is neutral, but it becomes protonated and thus charged at the lower pH. In solution, it's charged. When the chemical comes out of solution, it brings nearest anion with it. Chloride is a good anion because it's harmless. Fluoride is actually beneficial, but I wouldn't want to be messing around with HF any more than I had to if I were running a drug company.

 

[SeventhSon]

sildenafil citrate

 

[Critical Mass]

sildenafil citrate

I take it strictly for the nutritional value of the citrate. I enjoy the side effects even if nobody else does.