thimerosal

Action and Spectrum

Actions and Spectrum  

Actions: 

• Preservative:  thimerosal is primarily used in multi-dose vials of vaccines and certain other medical products. It prevents bacterial and fungal growth in these vials, extending their shelf life and ensuring their safety and efficacy during use. 
• Antiseptic: thimerosal has antiseptic properties and uses it as a preservative. It can be used as a topical antiseptic. 

Spectrum: 

• Vaccines: thimerosal has historically been used as a preservative in multi-dose vials of some vaccines. The purpose of its use in vaccines is to prevent contamination and maintain the sterility of the vaccine during repeated withdrawals from the vial. 
• Ophthalmic Solutions: thimerosal is used in some ophthalmic solutions, and eye drops as a preservative to prevent microbial contamination. 

Drug Interaction

Adverse Reaction

None reported 

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

Contraindications: 

• Hypersensitivity 

Cautions: 

• Pregnancy 
• Infants & young children 
• Renal impairment 

Pregnancy / Lactation

Pregnancy consideration:  

No data is available. 

Breastfeeding warnings:  

No data is available. 

Pregnancy category: 

Category A: well-controlled and satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: No data is available for the drug under this category. 

Pharmacology

Pharmacology:  

• Preservative Action: thimerosal is used as a preservative in vaccines and some other medical products. 
• Antimicrobial Action: thimerosal exerts its antimicrobial effect by releasing ethyl mercury ions. This action helps inactivate and kill microorganisms, thus preventing contamination and maintaining the integrity of vaccines and medical products. 
• Stability and Efficacy: thimerosal contributes to vaccines’ long-term stability and efficacy by preventing microbial growth and maintaining product quality over time. 
• Metabolism and Elimination: Ethylmercury, the form of thimerosal mercury, differs from the more toxic methylmercury found in certain fish and seafood. Ethylmercury is metabolized and eliminated from the body more rapidly than methylmercury, primarily excreted through the urine. 
• Reduced Use: Many countries have reduced or eliminated thimerosal from most childhood vaccines due to concerns about potential mercury exposure, especially in infants and young children. thimerosal is now used in a limited number of vaccines, primarily in some adult vaccines or multi-dose vials. 
• Safety: The safety of thimerosal-containing vaccines has been extensively studied, and they are safe and effective in preventing serious diseases. The benefits of vaccination generally outweigh any theoretical risks associated with thimerosal exposure. 
• Top of Form 

Pharmacodynamics: 

• thimerosal exerts its antimicrobial effect by releasing ethylmercury ions. 
• Ethylmercury interferes with the metabolic processes of microorganisms, leading to their inactivation and death. 
• This antimicrobial action helps prevent bacterial and fungal growth, thus extending the shelf life of vaccines and medical products. 

Pharmacokinetics: 

Absorption 

• thimerosal can be absorbed into the body through various routes of exposure, such as injection (in the case of vaccines) or topical application. 
• When administered as a preservative in vaccines, thimerosal is usually injected into the muscle (intramuscular) or just beneath the skin (subcutaneous). 
• When used in topical medical products, thimerosal can be absorbed through the skin. 

Distribution 

• After absorption, thimerosal is distributed throughout the body, but it tends to accumulate levels in the blood and tissues compared to methylmercury. 
• Ethylmercury, the form of mercury in thimerosal, has a shorter half-life in the blood than methylmercury, leading to lower overall exposure. 

Metabolism 

• Ethylmercury in thimerosal undergoes a metabolic transformation in the body, converting it into other chemical species. 
• Ethylmercury is primarily metabolized in the body through various enzymatic reactions, ultimately forming inorganic mercury. 

Elimination and excretion 

• The majority thimerosal and its metabolites are excreted through urine and feces. 
• The excretion of ethylmercury is relatively rapid compared to methylmercury, resulting in a shorter biological half-life and lower overall body burden. 

Adminstartion

Administration: 

• Vaccines containing thimerosal are typically administered through intramuscular (IM) or subcutaneous (SC) injection, depending on the specific vaccine. 
• thimerosal is not used in most single-dose vials of vaccines, as the risk of contamination is lower with single-dose preparations. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: thimerosal 

Pronounced as: thym-ro-sal 

Why do we use thimerosal? 

• thimerosal exerts antimicrobial effects through the release of ethylmercury ions. 
• Ethylmercury interferes with the metabolic processes of microorganisms, leading to their inactivation and death. 
• This antimicrobial action helps prevent bacterial and fungal growth, further contributing to the preservation of the product.