Cinnabar and realgar in traditional chinese medicines:remedies or poisons?

Cinnabar(96% of HgS)and realgar(90% of As4S4)have been used in traditional Chinese medicines for thousands of years.Both mercury(Hg)and arsenic(As)are well-known toxic substances and the safety of cinnabar-and realgar-containing traditional Chinese medicines is of concern.It is presumed that any intentional use of known toxic metals in medicine is an unacceptable risk,but an opposing opinion holds that cinnabar and realgar have a long history of clear pharmacological utility with tolerable side effects.Are cinnabar-and/or realgar-containing Chinese medicines remedies or poisons? This chapter summarizes recent progress of toxicological and pharmacological studies on this issue and highlights that(1)the use of total Hg and As for risk evaluation of cinnabar and realgar is inappropriate,(2)the right dose and duration of cinnabar and realer administration differentiate a remedy from a poison,and(3)cinnabar and realgar are active ingredients in Chinese medicines.The well-designed studies are needed to support or to reject their existence in traditional remedies.