Usage
Thiomersal is primarily used as a preservative in some multi-dose vials of vaccines to prevent bacterial and fungal contamination. It is not used for treating any medical condition on its own. Its pharmacological classification is antiseptic and antifungal. Thiomersal’s mechanism of action involves inhibiting bacterial and fungal growth by binding to sulfhydryl groups in microbial proteins, disrupting their function.
Alternate Names
Thiomersal is also known as thimerosal (primarily in the US). Brand names vary depending on the specific product it is used in.
How It Works
Pharmacodynamics: Thiomersal exerts its antimicrobial effect by disrupting the function of essential microbial proteins, leading to their inactivation or death.
Pharmacokinetics: When administered via injection (as a component of a vaccine), thiomersal is metabolized to ethylmercury and thiosalicylate. Ethylmercury is further broken down into inorganic mercury. Ethylmercury is cleared from the body more quickly than methylmercury (found in some fish) and is less likely to accumulate. Elimination occurs primarily through the kidneys.
Mode of Action: Thiomersal binds to sulfhydryl groups (-SH) in proteins, particularly those involved in essential microbial functions. This binding disrupts the protein’s structure and activity, ultimately leading to the microbe’s inactivation.
Receptor Binding, Enzyme Inhibition, Neurotransmitter Modulation: The primary mode of action is through direct binding to sulfhydryl groups rather than specific receptor binding, enzyme inhibition, or neurotransmitter modulation.
Dosage
Thiomersal is not prescribed or dosed independently. It is present in trace amounts as a preservative in certain multi-dose vaccines.
Side Effects
Common Side Effects
Mild reactions at the injection site, such as redness and swelling, are the most common side effects.
Rare but Serious Side Effects
Allergic reactions, though rare, can occur.
Long-Term Effects
No long-term adverse effects associated with thiomersal in vaccines have been established.
Contraindications
Known hypersensitivity to thiomersal is a contraindication.
Drug Interactions
Limited specific drug interactions have been reported with thiomersal. However, concomitant administration of thiomersal-containing eye drops with oral tetracyclines may cause ocular irritation.
Pregnancy and Breastfeeding
Available evidence suggests that the small amount of thiomersal in vaccines does not pose a risk to pregnant women or breastfeeding infants.
Drug Profile Summary
- Mechanism of Action: Antiseptic/antifungal; binds to sulfhydryl groups in microbial proteins, disrupting function.
- Side Effects: Primarily local injection site reactions (redness, swelling). Rarely allergic reactions.
- Contraindications: Hypersensitivity to thiomersal.
- Drug Interactions: Potential for ocular irritation with concomitant tetracycline eye drops.
- Pregnancy & Breastfeeding: Generally considered safe.
- Dosage: Present as a preservative in some multi-dose vaccines; not independently dosed.
- Monitoring Parameters: Not typically required as used in vaccines.
Popular Combinations
Thiomersal is not used in drug combinations in a therapeutic sense. It is present as a preservative in some multi-dose vaccines that may contain multiple antigens.
Precautions
- General Precautions: Screen for hypersensitivity.
- Specific Populations: No specific precautions beyond hypersensitivity for pregnant women, breastfeeding mothers, children, or the elderly.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Thiomersal?
A: Thiomersal is not a medication that is independently prescribed or dosed. It is a preservative found in trace amounts in some vaccines.
Q2: Does thiomersal cause autism?
A: No. Extensive research has not shown a causal link between thiomersal in vaccines and autism.
Q3: Is thiomersal safe in pregnancy?
A: Current evidence suggests that the trace amounts of thiomersal in vaccines are not harmful during pregnancy.
Q4: Can breastfeeding mothers receive vaccines containing thiomersal?
A: Yes. The small amount of thiomersal present in vaccines does not appear to pose a risk to breastfeeding infants.
Q5: What are the common side effects of vaccines containing thiomersal?
A: The most common side effects are mild, local reactions at the injection site like redness or swelling.
Q6: What should I do if a patient has a history of allergy to thiomersal?
A: Vaccines containing thiomersal should be avoided in individuals with a documented history of thiomersal hypersensitivity.
Q7: Is thiomersal still used in childhood vaccines?
A: In many countries, including the US, thiomersal has been removed from or is present only in trace amounts in childhood vaccines, with the exception of some influenza vaccines.
Q8: Are there any long-term side effects associated with thiomersal exposure from vaccines?
A: No long-term adverse effects have been linked to the trace amounts of thiomersal found in vaccines.
Q9: What is the difference between ethylmercury (in thiomersal) and methylmercury (in some fish)?
A: Ethylmercury is metabolized and eliminated from the body much more quickly than methylmercury, making it less likely to accumulate and cause harm.
