Mercury-containing vaccine preservative

The viability of all examined cell lines was suppressed entirely in the presence of 4.6 μg/ml (12.5 μM) of Thimerosal. The MTD for HepG2, C2C12, PBMC, and Vero cells was 2, 1.6, 1, and 0.29 μg/ml (5.5, 4.3, 2.7 and 0.8 μM), respectively. The IC50 of Thimerosal exposure for HepG2, C2C12, PBMC, and Vero cells was 2.62, 3.17, 1.27, and 0.86 μg/ml (7.1, 8.5, 3.5 and 2.4 μM), respectively. As for antimicrobial effectiveness, the growth capability of Candida albicans and Staphylococcus aureus was suppressed entirely in the presence of 6.25 µg/ml (17 μM) Thimerosal. The complete growth inhibition of Pseudomonas aeruginosa in culture media was achieved in 100 µg/ml (250 µM) Thimerosal concentration. This value was 12.5 µg/ml (30 μM) for Aspergillus brasiliensis.[3]

In the periaqueductal gray (PAG), the injection of Thimerosal (THIM) results in a dose-dependent increase in the density of μ-opioid receptors (MORs). MOR density in the lateral periaqueductal gray (LPAG) and dorsomedial periaqueductal gray (DMPAG) areas is statistically significantly increased by treatment with increasing doses of Thimerosal. In the caudate putamen (CPU), Thimerosal likewise increases MOR density at a dosage of 3,000 μg Hg/kg. On the other hand, MOR density in the dentate gyrus (DG) is decreased when Thimerosal is administered at both higher doses [1]. Measuring 10 to 14 weeks after the injections, glutamate and aspartate levels rise but glycine and alanine levels fall due to the long-lasting effects of immerosal treatment (4 injections, im, 240 μg Hg/kg on postnatal days 7, 9, 11, and 15). Glutamate and aspartate concentrations at microdialysis time are unaffected by four injections of Thimerosal at a dose of 12.5 μg Hg/kg. When Thimerosal is applied to the perfusion fluid of the prefrontal cortex (PFC), glutamate overflow increases quickly. The Thimerosal impact on glutamate and aspartate is inhibited by coadministration of the neurosteroid dehydroepiandrosterone sulfate (DHEAS; 80 mg/kg; ip); the steroid does not affect these amino acids on its own. Thimerosal's acute effect on glutamate is likewise inhibited by co-application of dehydroepiandrosterone sulfate (DHEAS) in perfusion fluid[2].

The safety of Thimerosal exposure on cells was analyzed through an MTT cell toxicity assay. The viability of four cell types, including HepG2, C2C12, Vero Cells, and Peripheral blood mononuclear cells (PBMCs), was examined in the presence of different Thimerosal concentrations and the maximum tolerable dose (MTD) and the half maximal inhibitory concentration (IC50) values for each cell line were determined. The antimicrobial effectiveness of Thimerosal was evaluated on four control strains, including Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus brasiliensis, to obtain the minimum inhibitory concentration (MIC) of Thimerosal. The MIC test was performed in culture media and under optimal growth conditions of microorganisms in the presence of different Thimerosal concentrations.[3]

Thimerosal, a mercury-containing vaccine preservative, is a suspected factor in the etiology of neurodevelopmental disorders. We previously showed that its administration to infant rats causes behavioral, neurochemical and neuropathological abnormalities similar to those present in autism. Here we examined, using microdialysis, the effect of thimerosal on extracellular levels of neuroactive amino acids in the rat prefrontal cortex (PFC). Thimerosal administration (4 injections, i.m., 240 μg Hg/kg on postnatal days 7, 9, 11, 15) induced lasting changes in amino acid overflow: an increase of glutamate and aspartate accompanied by a decrease of glycine and alanine; measured 10-14 weeks after the injections. Four injections of thimerosal at a dose of 12.5 μg Hg/kg did not alter glutamate and aspartate concentrations at microdialysis time (but based on thimerosal pharmacokinetics, could have been effective soon after its injection). Application of thimerosal to the PFC in perfusion fluid evoked a rapid increase of glutamate overflow. Coadministration of the neurosteroid, dehydroepiandrosterone sulfate (DHEAS; 80 mg/kg; i.p.) prevented the thimerosal effect on glutamate and aspartate; the steroid alone had no influence on these amino acids. Coapplication of DHEAS with thimerosal in perfusion fluid also blocked the acute action of thimerosal on glutamate. In contrast, DHEAS alone reduced overflow of glycine and alanine, somewhat potentiating the thimerosal effect on these amino acids. Since excessive accumulation of extracellular glutamate is linked with excitotoxicity, our data imply that neonatal exposure to thimerosal-containing vaccines might induce excitotoxic brain injuries, leading to neurodevelopmental disorders. DHEAS may partially protect against mercurials-induced neurotoxicity.[2]

Absorption, Distribution and Excretion
Less than 0.01% of an ingested dose is absorbed from the GI tract (rat study).
Gastrointestinal tract.
266 L in one study
The high concentrations of mercury identified in stool samples suggest that ethylmercury may be eliminated through the gastrointestinal tract.
Mercury concentrations were measured in the aqueous humor and excised corneal buttons of nine patients undergoing keratoplasty. A contact lens stored for several weeks in a solution containing thimerosal was applied to one eye for 4 hours. After 4 hours the lens was removed and mercury concentrations were determined in aqueous humor, corneal buttons, and the contact lens itself. Markedly elevated levels of mercury were determined in both aqueous humor and corneal buttons of subjects as compared to controls; however, there was little residual mercury on the contact lens after 4 hours.The mercury content in the corneal buttons of subjects ranged from 0.6 to 14 ng per tissue. The mercury content in samples of aqueous humor from subjects ranged from 20 to 46 ng/mL.
Ten of 13 infants exposed to topical applications of a thimerosal tincture 0.1% for the treatment of exomphalos died. The total number of applications ranged from 9 to 48. Mercury concentrations were determined in various tissues from 6 of the infants. Mean tissue concentrations in fresh samples of liver, kidney, spleen, and heart ranged from 5152 to 11,330 ppb, suggesting percutaneous absorption from repeated topical applications.
Urine mercury levels were studied in 26 patients with hypogammaglobulinemia who received intramuscular weekly IgG replacement therapy preserved with 0.01% thimerosal. The dosage of IgG ranged from 25 mg/kg to 50 mg/kg, containing 0.6-1.2 mg of mercury per dose. The total estimated dose of mercury administered ranged from 4 to 734 mg over a period of 6 months to 17 years. Elevated urine mercury levels were determined in 19 patients; however, no patients had clinical evidence of chronic mercury toxicity.
Forty full-term infants aged 6 months and younger were given vaccines that contained thiomersal (diptheria-tetanus-acellular pertussis vaccine, hepatitis B vaccine, and in some children Haemophilus influenzae type b vaccine). 21 control infants received thiomersal-free vaccines. We obtained samples of blood, urine, and stools 3-28 days after vaccination. Total mercury (organic and inorganic) in the samples was measured by cold vapour atomic absorption. Mean mercury doses in infants exposed to thiomersal were 45.6 microg (range 37.5-62.5) for 2-month-olds and 111.3 microg (range 87.5-175.0) for 6-month-olds. Blood mercury in thiomersal-exposed 2-month-olds ranged from less than 3.75 to 20.55 nmol/L (parts per billion); in 6-month-olds all values were lower than 7.50 nmol/L. Only one of 15 blood samples from controls contained quantifiable mercury. Concentrations of mercury were low in urine after vaccination but were high in stools of thiomersal-exposed 2-month-olds (mean 82 ng/g dry weight) and in 6-month-olds (mean 58 ng/g dry weight). Estimated blood half-life of ethylmercury was 7 days (95% CI 4-10 days). Administration of vaccines containing thiomersal does not seem to raise blood concentrations of mercury above safe values in infants. Ethylmercury seems to be eliminated from blood rapidly via the stools after parenteral administration of thiomersal in vaccines.

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Metabolism / Metabolites
Ethylmercury (etHg) is derived from the metabolism of thimerosal (o-carboxyphenyl-thio-ethyl-sodium salt), which is the most widely used form of organic mercury.
Organic mercury is absorbed mainly by the gastrointestinal tract, then distributed throughout the body via the bloodstream. Organic mercury complexes with free cysteine and the cysteine and sulfhydryl groups on proteins such as haemoglobin. These complexes are able to mimic methionine and thus be transported throughout the body, including through the blood-brain barrier and placenta. Organic mercury is metabolized into inorganic mercury, which is eventually excreted in the urine and faeces. (T11)

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Biological Half-Life
A study was done to study the pharmacokinetics of Thimerosal in mice. Estimated half-lives (in days) were 8.8 for blood, 10.7 for brain, 7.8 for heart, 7.7 for liver and 45.2 for kidney. The the long half-life of ethylmercury (~50 days on average in humans) results in accumulation that may be harmful to the developing fetal brain, as it is more susceptible to organomercurial compounds than the adult brain.

Protein Binding
95 to 99% (depending on animal species and experimental conditions) of the mercury in plasma is bound to albumin (along with other plasma proteins). As significant proportion of albumin is filtered at the glomerulus.

[1]. Olczak M, et al. Neonatal administration of thimerosal causes persistent changes in mu opioid receptors in the ratbrain. Neurochem Res. 2010 Nov;35(11):1840-7.
[2]. Duszczyk-Budhathoki M, et al. Administration of thimerosal to infant rats increases overflow of glutamate and aspartate in the prefrontal cortex: protective role of dehydroepiandrosterone sulfate. Neurochem Res. 2012 Feb;37(2):436-47.
[3]. J Trace Elem Med Biol. 2023 May:77:127129. doi: 10.1016/j.jtemb.2023.127129. Epub 2023 Jan 4.

Mercury((o-carboxyphenyl)thio)ethyl, sodium salt is a light cream-colored crystalline powder with a slight odor: pH (1% aqueous solution) 6.7. Slight odor. (NTP, 1992)
Thimerosal is an alkylmercury compound (approximately 49% mercury by weight) used as an antiseptic and antifungal agent. It has a role as a disinfectant, an antifungal drug, an antiseptic drug and a drug allergen. It contains an ethylmercurithiosalicylate.
Thiomersal (INN), commonly known in the U.S. as thimerosal, is an organomercury compound. This compound is a well-established and widely used antiseptic and antifungal agent. Developed in 1927, thimerosal has been and is still being used as a preservative in some cosmetics, topical pharmaceuticals, and biological drug products, which includes vaccines. There has been significant concern regarding its safety and toxicity in the last several decades. Although thimerosal is banned in several countries, it continues to be included as a preservative in some vaccines in the United States and many vaccines in the developing world.
Thimerosal is a Standardized Chemical Allergen. The physiologic effect of thimerosal is by means of Increased Histamine Release, and Cell-mediated Immunity.
Thimerosal is an organomercurial compound and derivative of thiosalicyclic acid with antibacterial and antifungal properties. Although the mechanism of action has not been fully elucidated, thimerosal inhibits sulfhydryl-containing active site of various enzymes and binds to sulfhydryl compounds, such as glutathione, cysteine, and SH groups of proteins. In addition, thimerosal activates the InsP3 calcium channel on endoplasmic reticular membrane, thereby triggering the release of calcium from intracellular stores resulting in a calcium-induced calcium-influx of extracellular calcium. Consequently, thimerosal may induce or inhibit cellular functions dependent on calcium signaling.
Thiomersal is an organomercuric compound. It is used mainly as an antiseptic and antifungal agent. Thiomersal was developed and registered under the trade name Merthiolate in 1928 by the pharmaceutical corporation Eli Lilly and Company and has been used as a preservative in vaccines, immunoglobulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Mercury is a heavy, silvery d-block metal and one of six elements that are liquid at or near room temperature and pressure. It is a naturally occuring substance, and combines with other elements such as chlorine, sulfur, or oxygen to form inorganic mercury compounds (salts). Mercury also combines with carbon to make organic mercury compounds. (L1, L267)
An ethylmercury-sulfidobenzoate that has been used as a preservative in VACCINES; ANTIVENINS; and OINTMENTS. It was formerly used as a topical antiseptic. It degrades to ethylmercury and thiosalicylate.

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Drug Indication
Used as preservative in some cosmetics, topical pharmaceuticals, and biological drug products, which includes vaccines.

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Mechanism of Action
Although its mechanism of action is not fully understood, thimerosal inhibits sulfhydryl-containing active site of various enzymes and binds to sulfhydryl compounds, including glutathione, cysteine, and sulfhydryl groups of proteins. In addition, thimerosal activates the InsP3 calcium channel on the endoplasmic reticular membrane, thereby triggering the release of intracellular calcium resulting in a calcium-induced calcium-influx of extracellular calcium. Therefore, thimerosal may induce or inhibit various cellular functions that are dependent on the signaling of calcium. Ethylmercury is metabolized to inorganic mercury more rapidly than methylmercury. This difference in metabolism may account for kidney pathology that can result from toxic quantities. Also, whereas the increase in oxidative stress and induction of apoptosis observed in vitro with large doses (405 μg/L to 101 mg/L) of thimerosal may explain its damaging neurological effects. The effects of low-dose ethylmercury are not completely understood to date. It is known, however, that the shorter half-life of ethylmercury (the metabolite of thimerosal) allows for very limited opportunities of ethylmercury derived from thimerosal in vaccines. Ethylmercury is a lipophilic cation that is capable of crossing the blood-brain barrier. The octanol/water partition coefficients of methyl and ethylmercury are 1.4 to 1.8, at intracellular pH and [Cl−], therefore, both organomercury compounds will primarily exist as intracellular lipophilic cations. It has been demonstrated that lipophilic cations accumulate inside mitochondria, in a Nernstian fashion, driven by the steady state membrane potential. As the typical mitochondrial membrane potential of astrocytes and neurons is between 140–170 mV, one would expect the concentration of these organomercury compounds within mitochondria to be approximately 1000 times greater than the cytosolic concentration.

C11H15HGNAO2S

404.81

405.992

C, 26.70; H, 2.24; Hg, 49.55; Na, 5.68; O, 7.90; S, 7.92

54-64-8

16684434

Cream colored, crystalline powder

298.6ºC at 760mmHg

234-237 °C (dec.)(lit.)

250 °C

1.577

0

3

3

14

180

0

C1=CC=C(C(=C1)C(=O)[O-])[S-].[CH2]C.[Hg+].[Na+]

RTKIYNMVFMVABJ-UHFFFAOYSA-L

InChI=1S/C7H6O2S.C2H5.Hg.Na/c8-7(9)5-3-1-2-4-6(5)10;1-2;;/h1-4,10H,(H,8,9);1H2,2H3;;/q;;2*+1/p-2

sodium;(2-carboxylatophenyl)sulfanyl-ethylmercury

HSDB7151; HSDB-7151; HSDB 7151

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : 100 mg/mL (229.95 mM )

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)