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Variable patterns in anticonvulsant drug-induced malformations in mice: comparisons of phenytoin and phenobarbital
R H Finnell1, H E Shields, G F Chernoff
1Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, Washington State University, Pullman 99164-6520.
Abstract:
Anticonvulsant drugs are known to induce a varied pattern of malformation in both humans and in experimental rodent models. Often the clinical overlap between the pattern of defects induced by different anticonvulsant drugs is so striking that many clinicians question the role these compounds play relative to the existing maternal seizure disorder in the etiology of the observed malformations. In three inbred mouse strains exposed to phenytoin or phenobarbital in utero, the pattern of malformation differed markedly. From the types of anomalies observed, it is apparent that phenobarbital induced more malformations, while phenytoin produced a higher frequency of anomalies related to incomplete development. Thus, while there exists a certain degree of similarity between some of the minor features characteristic of each drug-induced syndrome, there are distinct differences in pregnancy outcome in experimental animals exposed to these drugs. Given the fact that phenobarbital induces more malformations that can be traced to exposure during early organogenesis, it may be wise to consider a therapeutic strategy in which phenytoin is utilized only during organogenesis, and is then replaced with phenobarbital for the remainder of the pregnancy.
Insights
Anticonvulsant drugs like phenytoin and phenobarbital cause distinct malformations in mice. Phenobarbital causes more malformations, while phenytoin leads to incomplete development, suggesting different therapeutic uses during pregnancy.
Area of Science:
- Teratology
- Developmental Toxicology
- Pharmacology
Background:
- Anticonvulsant medications can cause birth defects in humans and animal models.
- The overlap in malformations from different anticonvulsants raises questions about their specific roles versus maternal seizure disorders.
- Understanding drug-specific teratogenic effects is crucial for managing epilepsy during pregnancy.
Purpose of the Study:
- To investigate and compare the teratogenic patterns of phenytoin and phenobarbital in different inbred mouse strains.
- To determine if anticonvulsant-induced malformations exhibit distinct profiles.
- To inform potential therapeutic strategies for epilepsy management during pregnancy.
Main Methods:
- Exposure of three inbred mouse strains to phenytoin or phenobarbital during gestation.
- Detailed observation and classification of malformations in offspring.
- Comparative analysis of anomaly patterns between drug treatments and control groups.
Main Results:
- Phenytoin and phenobarbital exposure resulted in markedly different patterns of malformation in mice.
- Phenobarbital induced a higher overall number of malformations.
- Phenytoin was associated with a greater frequency of anomalies related to incomplete development.
Conclusions:
- Distinct differences exist in pregnancy outcomes following in utero exposure to phenytoin versus phenobarbital.
- Phenobarbital appears to induce more malformations attributable to early organogenesis disruption.
- A potential therapeutic approach involves using phenytoin during early organogenesis, followed by phenobarbital for the remainder of pregnancy.