[Chromosome studies in persons treated with anticonvulsant drugs]

Parental epilepsy, anticonvulsant drugs, and reproductive outcome: epidemiologic and experimental findings spanning three decades; 2: Human studies

Evidence accumulated over the past three decades has established AEDs as human teratogens. Important developments in the delineation of these compounds as human teratogens include: the demonstration of a consistent association between in utero exposure to AEDs and an increased occurrence of single major malformations, the description of AED-induced dysmorphogenic syndromes; demonstration of a dose-response relationship, both in terms of the number and dosage of AEDs; and evidence that pharmacogenetic differences in the metabolism of AEDs are strongly correlated with the occurrence of congenital malformations. Furthermore, the experimental animal findings, having accumulated in parallel to those of human studies, strongly support the teratogenic role of AEDs. Areas that require further amplification and clarification in future studies are the relative contribution of AEDs and other factors, such as genetic predisposition and maternal seizures, particularly with respect to the occurrence of minor anomalies, growth retardation, and developmental outcome; the relative teratogenicity of specific monotherapies and polytherapies; the predictive role of pharmacogenetic differences in the metabolism of AEDs in the occurrence of structural and functional abnormalities; and characterization of the precise nature of the pharmacogenetic defect underlying the aforementioned differences in AED metabolism. Attempts should also be made in future prospective studies to monitor metabolite levels of AEDs, particularly the oxidative metabolites, in order to further elucidate the relative contribution of individual differences in metabolism in the determination of adverse fetal outcome. Similarly, further efforts should be made to assess the clinical significance of decreased growth parameters in terms of mental and neurologic development, and to ascertain whether there is any risk for such abnormalities in children who do not display overt or persistent reductions in physical growth parameters. This is critically important in light of the animal studies that have shown functional abnormalities at doses that do not necessarily produce structural defects. Future investigations would be conducted through collaborative studies that would encompass sufficiently large numbers of women to provide adequate power to the statistical analyses of the data obtained. Care would have to be exercised to establish a uniform protocol for the collaborating centers. Regionally based investigations would be preferable to studies based at special centers, in order to assess the relative role of risk factors associated with abnormal pregnancy outcomes in the epileptic population at large.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytogenetic effects of phenytoin and/or carbamazepine on human peripheral leukocytes

The cytogenetic effects of phenytoin (PHT) and/or carbamazepine (CBZ) were studied to determine clastogenic potential. Comparative analysis of chromosome breakage and sister chromatid exchange (SCE) was performed between 18 patients with epilepsy receiving PHT and/or CBZ and 10 healthy nontreated controls. These studies failed to detect a significant increase in chromosome aberrations or SCEs in groups of treated individuals as compared with controls. No correlation was observed between the rate of either chromosome damage or SCEs and age, sex, drug blood level, or daily dose. The results indicate no detectable chromosome damaging effects of PHT alone, CBZ alone, or a combination of these two antiepileptic drugs (AEDs).

Lack of sister chromatid exchange induction in phenytoin-treated patients with epilepsy

Phenytoin (PHT) has been suspected of having a mutagenic effect with chronic administration, but the existing evidence is equivocal. Contradictory results have been obtained using different testing systems. Sister chromatid exchange (SCE), a sensitive indicator of genotoxic environmental influences, has been used in only a few limited studies of PHT users, with varying results. The present study was designed to evaluate the potential mutagenicity of PHT in a more objective and reliable way than has been done previously. Following careful screening procedures, 16 adult male patients with epilepsy receiving long-term PHT monotherapy and 16 healthy controls were selected for a study of SCE frequencies in peripheral lymphocytes. The patients and controls were matched for sex, age, and smoking habits. Strict exclusionary criteria were observed, including all factors known to affect or suspected of affecting the SCE frequencies. Statistical analyses did not reveal any significant differences between the SCE rates of PHT-treated patients and controls, indicating a lack of PHT mutagenicity as expressed by induction of SCE in adults.

Effect of anticonvulsants on human chromosomes. 2. In vitro studies

The effects of 3 anticonvulsant drugs (diphenylhydantoin, ethosuximide, and phenobarbital) on human peripheral lymphocytes in vitro were studied. The rate of chromosomal aberrations induced by the 3 anticonvulsants was significantly increased from the first concentration analyzed, similar to half the therapeutic serum concentration. These findings are compared with other previous reports.

Diphenylhydantoin and mitotic spindle abnormalities in cultured mouse and human cells

The present study demonstrates that the antiepileptic drug diphenylhydantoin (DPH) is capable of inducing aneuploidy but not structural aberrations in cultured mouse embryonic fibroblasts. A high concentration of 200 micrograms/ml was found to increase the percentage of hyperdiploidy from 4.8 (control) to 16.0. The treatment was found to increase mitotic indices as a consequence of a mitotic-arresting action of the drug. These effects are probably due to the effect of the drug on the structure of the mitotic apparatus. Abnormal cell divisions and mitotic disturbance were found to increase in a dose-dependent manner after DPH treatment. In a parallel study, human amnion cells were found to show similar response to DPH treatment.

Chromosome examination of patients under lithium therapy

The chromosomal aberrations of 13 patients who had received continuous lithium therapy for affective disorders were examined. Healthy college women were used as controls. There was a high frequency in gaps among the patients compared with the controls, but there was no significant difference between them. Although there was a significant relationship between the age of patients and the incidence of abnormal cells, there was no relationship between the duration of lithium therapy and the incidence of abnormal cells. These results suggest that lithium carbonate has neither the suppression effect of chromosomal repair mechanisms nor mutagenic activity. In order to discuss the teratogenicity of lithium salts on human beings, it seems necessary to conduct chromosome examinations of babies born to lithium-treated women.

Effect of primidone in somatic and germ cells of mice

Primidone, an anti-convulsant drug, was tested in mice for mutagenicity in somatic cells by the micronucleus test and in germ cells by the sperm-head abnormality assay. Mice were treated orally with the drug at doses of 4.37, 8.75 and 13.11 mg/mouse. The results indicate that the drug is capable of inducing mutations both in somatic and germ cells of mice.

Chromosomal studies of peripheral blood from epileptic patients treated with phenobarbital and/or diphenylhydantoin

Chromosome studies were carried out on the peripheral blood of 26 epilepsy patients treated with phenobarbital and/or diphenylhydantoin, on ten healthy controls and on eight untreated epileptic controls. There was a significant increase in the individual numbers of sister chromatid exchanges per metaphase for all the patients treated with drugs compared with the mean of the pooled values from all the controls. There was no significant increase in the number of chromosome aberrations in the treated patients compared with the controls. There were very few structural aberrations in either the treated patients or the controls.

Chromosomal investigations in epileptic children during long-term therapy with phenytoin or primidone

In epileptic children the long-term therapy with anticonvulsant drugs is absolutely necessary. However, anticonvulsant drugs have been suspected to be mutagenic and teratogenic. To investigate this problem metaphase chromosome observations were performed using short-time culture of peripheral blood lymphocytes from twenty children. Ten of the children had been treated with phenytoin and the other ten with primidone on monotherapy. The long-term administration of anticonvulsant drugs was monitored by measurement of the serum concentrations of phenytoin and primidone, by seizure anamnesis, and by repeated EEG investigations. Analyzing 100 mitoses from each proband, we found no increase of structural or numerical aberrations in our patients compared with six controls. In adults, however, anticonvulsant drugs have been found to cause structural aberrations and chromosomal damage. The absence of these lesions in children may reflect the higher efficiency of DNA-repair in local DNA-damage.

Chromosomal investigations in children with pyknolepsy on dipropylacetate monotherapy

We analyzed chromosome preparations obtained from leukocytes of ten children with pyknolepsy and treated with dipropylacetate (DPA) as monotherapy. Structural or numerical aberrations were not found more frequently in our patients than in five normal children (control group).

Chromosome studies of bone marrow cells and peripheral blood lymphocytes from diphenylhydantoin-treated patients

Chromosome studies were performed on both bone-marrow cells and peripheral blood lymphocytes from ten patients with epilepsy, treated with diphenylhydantoin alone. There was no evidence of chromosome damage. Furthermore, the bone-marrow smears from five of the patients were studied for the presence of micronuclei. There was no increase in the number of micronuclei compared with control persons. Conflicting results about the cytogenetic effect of diphenylhydantoin have appeared in the literature. It is emphasized that, in studies on the chromosome-damaging effect of chemical agents in man, bone marrow cells seem to be most indicative of the conditions in vivo.