The thiol (-SH) functional group is found in a number of drug compounds and confers a
unique combination of useful properties. Thiol-containing drugs can reduce radicals and other toxic
electrophiles, restore cellular thiol pools, and form stable complexes with heavy metals such as lead,
arsenic, and copper. Thus, thiols can treat a variety of conditions by serving as radical scavengers,
GSH prodrugs, or metal chelators. Many of the compounds discussed here have been in use for decades,
yet continued exploration of their properties has yielded new understanding in recent years,
which can be used to optimize their clinical application and provide insights into the development of
new treatments. The purpose of this narrative review is to highlight the biochemistry of currently used
thiol drugs within the context of developments reported in the last five years. More specifically, this
review focuses on thiol drugs that represent the standard of care for their associated conditions, including
N-acetylcysteine, 2,3-meso-dimercaptosuccinic acid, British anti-Lewisite, D-penicillamine,
amifostine, and others. Reports of novel dosing regimens, delivery strategies, and clinical applications
for these compounds were examined with an eye toward emerging approaches to address a wide range
of medical conditions in the future.