From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Newsgroups: sci.chem
Subject: Re: Why the Hydrochloride Salt?
Date: Sun, 21 Jun 1998 18:21:14 GMT

akilli@aol.com (Akilli) wrote:

>Greetings,
>         Just a casual look at the generic names of  medications shows  many
>which terminate in "hydrochloride". Is there some reason (solubility?) which
>determines the choice of a hydrochloride salt?

Pharmaceuticals are often available as either the "free" form, or
as a salt. The hydrochloride forms are usually both more water
soluble and stable in formulations than the free form, and
traditionally, recrystallising salts was a common method of
purifying chemicals. One requirement is that chemicals should be
anemable to, and able to withstand, the conditions during
formulation, and many of the "free" forms of chemicals are not
solids and may also react with other components.

For those pharmaceuticals taken orally, the hydrochloride forms
also can't cause significant increases in concentration of
a minor ionic species when encountering the hydrochloric acid
in our stomach, and thus it's easier to exclude such effects
during approval testing if *HCl forms are used.

Although *HCl is common, there still are a lot of other forms
used, depending on the desired properties, eg codeine phosphate.

        Bruce Hamilton