Thiomersal

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Thiomersal

General
Systematic name	Ethyl(2-mercaptobenzoato-(2-)-O,S) mercurate(1-) sodium
Trivial names	Elcide Mercurothiolate Merfamin Merthiolade Merthiolate Mertorgan Merzonin Merzonin sodium Sodium ethylmercuric thiosalicylate Sodium merthiolate Thimerosal Thimerosalate Thiomersalate Vitaseptol
Molecular formula	C₉H₉Hg Na O₂S
Molar mass	404.81 g/mol
Appearance	White or slightly yellow powder
CAS number	[54-64-8]
EC-No	[200-210-4]
Properties
Density and phase	500 kg/m³
Solubility in water	1000 g/l (20°C)
Melting point	232 - 233 °C (decomposition)
Boiling point	---
Basicity (pK_b)	---
Acidity (pK_a)	---
Thermodynamic data
Std enthalpy of formation Δ_fH°_gas	---
Standard molar entropy S°_gas	---
Hazards
EU classification	---
MSDS	External MSDS
R-phrases	R26/27/28R33R50/53
S-phrases	S13S28S36S45S60S61
NFPA 704	---
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Regulatory data	Flash point, RTECS number, etc.
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

For discussion on alleged health effects of thiomersal in vaccines, see Thiomersal controversy.

Thiomersal (INN) (C₉H₉HgNaO₂S), formerly and still commonly known in the United States as thimerosal, is an organomercury compound (approximately 49% mercury by weight) used as an antiseptic and antifungal agent.

It was developed and registered under the trade name Merthiolate in 1929 by the pharmaceutical company Eli Lilly and Company, and has been used as a preservative in vaccines, immune globulin preparations, skin test antigens, antivenoms, ophthalmic and nasal products, and tattoo inks.

The compound is being phased out from most childhood vaccinations. Packaging the vaccines in single-dose vials eliminates the need for bacteriostatics such as thiomersal.

1 Stability
2 Toxicology
3 History
- 3.1 Timeline
4 Thiomersal and Allergies
5 References
6 External links

[edit] Stability

Stable. May degrade in sunlight. Incompatible with strong acids, strong bases, strong oxidizing agents, iodine, heavy metal salts.

[edit] Toxicology

Thiomersal is harmful by inhalation and ingestion, lethal between 50 and 1000 times^{[citation needed]}^[1] the usual intake (hazard symbol T+).^[2] It is a neoplastigen and a teratogen. Thiomersal is also dangerous for the environment (hazard symbol N).

For more safety information on how to handle thiomersal, consult an MSDS.

Thiomersal causes susceptible bacteria to autolyze (break down their own cells with self-produced enzymes) via an unknown mechanism.^{[citation needed]} In the body, it is metabolized to ethylmercury (C₂H₅Hg⁺) and thiosalicylate.^[3]

[edit] History

Thiomersal was developed by Dr. Morris S. Kharasch, a chemist and Eli Lilly and Company fellow at the University of Maryland and then at the University of Chicago.^{[citation needed]}

A patent for the alkyl mercuric sulfur compound, which was felt to have possibilities as an antiseptic and antibacterial product, was filed in the 1920s.^{[citation needed]} Eli Lilly and Company registered the compound under the trade name Merthiolate in 1929. It was used to kill bacteria and prevent contamination in antiseptic ointments, creams, jellies, and sprays used by consumers and in hospitals. Thiomersal was used in e.g. nasal sprays, eye drops, contact lens solutions, immunoglobulins, and vaccines.

Thiomersal was first put in vaccines in 1931 by Eli Lilly Corporation and used as a preservative (bactericide) so multi-dose vials of vaccines could be used instead of single dose vials, which were more expensive.^[4]

Products that may contain thiomersal include blood plasma components such as Rho(D) Immune Globulin, pit viper, coral snake and black widow spider antivenom^[5] and vaccines in which it is not used as a preservative ^[6] may contain a trace of thiomersal from steps in manufacture.^[1].

[edit] Timeline

Early-1930s- first added to vaccines as a bactericide.^[4]
Mid-1980s- used as a preservative in virtually all whole-cell DPT vaccines, which were routinely administered four times each to children before eighteen months of age, starting at two months.
Late 1980s- Hib vaccines are recommended for administration to children at eighteen months. They contain thiomersal.
Early 1990s- In the USA three doses of Hepatititis B vaccine (at that time containing Thiomersal) are recommended for infants under six months of age, beginning on the day of birth; four doses of Hib are recommended within an eighteen month period, beginning at age two.
Late 1990s- three of the vaccines included in Vaccination schedules for children between six and eighteen months of age contain thiomersal.
1999- The American Academy of Pediatrics requests removal of thiomersal from all pediatric vaccines.
2001- The Institute of Medicine, citing insufficient evidence, is unable to prove or disprove any link between thiomersal and autism. However, they conclude that a causal connection between thiomersal and autism is "biologically plausible".^[1]
2002- The USA Centers for Disease Control (CDC) and the USA Food and Drug Administration (FDA) state that: although thiomersal was to be discontinued in some paediatric vaccines, they would not be recalling any unused stocks, as there is no proof that low doses of thiomersal is dangerous, and that the change was purely cautionary.
2004- The Institute of Medicine, based on new information from epidemiological studies undertaken since its 2001 report, rejects the hypothetical causative link between thiomersal and autism.^[1]
2006- Some vaccines provided by the World Health Organization for children in developing countries contain the same amounts of thiomersal as vaccines used previously for American children. Current vaccination schedules^{[citation needed]} give these in a shorter time period.^{[citation needed]}
2006- In the latest review by the WHO committee (at its meeting of 6-7 June 2006) the conclusion previously reached was reaffirmed that there is no evidence of toxicity in infants, children or adults exposed to thiomersal in vaccines.^[7]

[edit] Thiomersal and Allergies

Thiomersal is used commonly in patch testing^{[citation needed]} people who have dermatitis, conjunctivitis and other potentially allergic reaction. The substances implicated ethyl mercury, phenyl mercury, and other mercurious compounds. Allergies to mercury compounds are reported^{[citation needed]} to be quite common especially^{[citation needed]} among young people and women.