Potentiating effect of rifampicin on methimazole induced hepatotoxicity in mice
Zunera Hakim1, Akbar Waheed1, Salman Bakhtiar2
1Department of Pharmacology and Therapeutics, Islamic International Medical College, Rawalpindi, Pakistan.
Abstract:
Methimazole (MMI) is a widely used drug for hyperthyroidism. However, its clinical use is associated with hepatotoxicity. Though the precise mechanism of hepatic damage is still far from clear, role of metabolic activation and reactive metabolites have been implicated. The present study was designed to investigate the role of enzyme induction in bioactivation based hepatotoxicity of methimazole in mice. Thirty male mice were randomly divided into five groups. Hepatotoxicity was induced by single intraperitoneal injection of methimazole (1000mg/kg). Pretreatment with rifampicin which is a potent enzyme inducer was carried out for 6 days prior to administration of methimazole. The extent of hepatic damage was determined by measuring serum alanine aminotransferase (ALT) and alkaline phosphatase (ALP) along with histopathological grading of liver samples. The elevated levels of biochemical markers by methimazole were potentiated by pretreatment with rifampicin. This potentiation of hepatic injury was also observed in liver histopathological examination. These findings suggest induction of microsomal enzymes as a potentiating factor of methimazole induced hepatotoxicity.
Insights
Methimazole (MMI), used for hyperthyroidism, can cause liver damage. Enzyme induction by rifampicin worsened MMI-induced hepatotoxicity in mice, suggesting metabolic activation plays a key role.
Area of Science:
- Pharmacology
- Hepatology
- Toxicology
Background:
- Methimazole (MMI) is a primary treatment for hyperthyroidism.
- MMI use is linked to drug-induced liver injury (hepatotoxicity).
- The exact mechanisms underlying MMI hepatotoxicity, potentially involving reactive metabolites, remain unclear.
Purpose of the Study:
- To investigate the role of enzyme induction in methimazole-induced hepatotoxicity.
- To determine if enzyme induction exacerbates methimazole's toxic effects on the liver.
Main Methods:
- Thirty male mice were allocated into five experimental groups.
- Hepatotoxicity was induced via a single intraperitoneal injection of methimazole (1000mg/kg).
- Mice were pretreated with rifampicin, a known enzyme inducer, for six days prior to methimazole administration.
Main Results:
- Methimazole administration elevated serum alanine aminotransferase (ALT) and alkaline phosphatase (ALP) levels.
- Pretreatment with rifampicin significantly potentiated these elevated biochemical markers.
- Histopathological examination of liver samples corroborated the enhanced hepatic injury observed biochemically.
Conclusions:
- Enzyme induction by rifampicin potentiates methimazole-induced hepatotoxicity in mice.
- These findings support the hypothesis that metabolic activation contributes to methimazole's liver toxicity.
- Targeting enzyme induction pathways may offer a strategy to mitigate MMI-related liver damage.
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