how to avoid mishaps with drugs that come in different salt forms (doxycycline, desvenlafaxine, etc)

We're getting questions about how to avoid mishaps with drugs that come in different salt forms (doxycycline, desvenlafaxine, etc).

Drug molecules are often combined with other compounds to form pharmaceutical "salts." Combining hydroxyzine with a pamoate compound gives you Vistaril...while combining hydroxyzine with a hydrochloride compound gives you Atarax.

This is important because a med's salt form can affect use, efficacy, absorption, and tolerability. For example, calcium citrate is better absorbed than calcium carbonate if stomach acid is low...and carbonyl iron (elemental iron) is absorbed more slowly than ferrous sulfate, ferrous fumarate, and ferrous gluconate.