Mercury is a chemical element with the symbol Hg and the atomic number 80. It has long been used as a medicine. As early as the sixteenth century it was used to treat syphilis and in the 1800's it was used for among other things, constipation, depression and for toothaches. As recently as the 1930's it has been used to disinfect doctors instruments.

Today mercury is considered generally hazardous. It's use in thermometers is being phased out and is already illegal in some countries. Since 2003, it has been banned by Washington and Maine for use in blood pressure devices. This is all part of a gradual phaseout of Mercury in the medical sector. As of 2005 it is still found in many over the counter medications such as antiseptics, laxatives, diaper rash ointments, eye drops and nasal sprays. The FDA is reviewing the safety of all substances containing mercury. It's future in non-prescription medicines seems likely to end soon.