The suspected teratogenicity of Diphenylhydantoin (DPH) in man is important, especially to the 0.3 to 0.5% of pregnant women who are epileptic and, therefore, candidates for anticonvulsant drug therapy. To separate the teratogenic effect of epilepsy from DPH treatment, an animal model closely approximating the human condition was developed to meet the following criteria: (i) the test animal must have spontaneous seizures (ii) the seizures must be controlled or eliminated by DPH treatment (iii) the drug must be administered orally (iv) serum DPH levels must fall within the optimal human therapeutic range between 5 and 20 micrograms per ml serum (v) treatment must begin prior to mating and continue throughout gestation (vi) the offspring of treated animals must exhibit the spectrum of malformations observed in the offspring of epileptic women The first criterion was met by mutant quaking (qk) mice. The seizure activity of these animals was reduced (from 2.1 to .34 seizures per mouse day) by DPH treatment. To separate the effect of this gene from that of the DPH in the etiology of the malformations, heterozygous (+/qk) and homozygous non- quaking (+/+) mice were also studied. Monitoring of DPH levels with the SYVA Emit spectrophotometry assay technique indicated serum concentrations within the human therapeutic range at 40 and 60 mg/kg body weight dosages. The incidence of fetuses born with skeletal or soft-tissue abnormalities increased with increasing DPH dosages. This was observed in all three genotypes. The ability of the untreated quaking (qk/qk) dams to -produce normal offspring implicates the drug rather than the mutant gene as the cause of malformations. A preliminary application of this animal model produced what can be considered the mouse equivalent of the fetal hydantion syndrome. The similarities between the human and mouse syndromes include prenatal growth deficiency, neural, cardiac, orofacial, ocular and genitourinary anomalies. Further large-scale application of the model should provide insight into the role of DPH in the etiology of the malformations observed amongst the offspring of epileptic women on hydantoin anticonvulsant drug therapy. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

Cell-cycle progression in mammalian cells is coordinated by a series of control points. The D-type cyclins are a family of key cell cycle regulators that are controlled largely by mitogens and their association with and activation of cdk 4 and 6 at the G1 phase of the cell cycle. This study seeks to first analyze cyclins D1, D2, and D3 expression patterns in preimplantation mouse embryos using in vivo studies and then analyze the effects of Dilantin on the cyclin D1 expression pattern in cultured embryos. Antibody staining against cyclin D1, D2, and D3 via indirect immunofluorescence using a Zeiss Confocal Microscope and analysis of individual embryo staining intensities using Zeiss computer software were employed to evaluate expression patterns throughout the first three cell cycles. The data showed that all three D cyclins were present throughout the first three cell cycles. Cyclin D1 had peak average fluorescence intensity at the G2 phase of the second cell cycle with a decrease at the G1 in the third cell cycle. Cyclin D2 had a consistent increase of fluorescence intensity throughout all three cell cycles. Cyclin D3 had peak average fluorescence intensity at the G2 phase of the second cell cycle with an immediate decrease at the Gl phase in the third cell cycle. Cyclin D1 was localized to the nucleus in G1 phases of the cell cycle. In contrast, cyclin D2 was found in the nucleus during G2 phases of the cell cycle rather than in G1. Cyclin D3 was not localized to the nucleus in either cell cycle phase throughout the first three cell cycles. These unique nuclear staining patterns seen by D1, D2, and D3 may reflect a function in the cell cycle. Embryos cultured in the presence of l0gg/ml of Dilantin were found to be slowed in development indicated by the absence of transition from the one-cell to the two-cell stage when compared to the controls. Since the Dilantin cultured embryos never reached G1 of the second cell cycle the increase in fluorescence intensity seen was still considered to be a representation of the G2 phase of the first cell cycle. Cyclin Dl's fluorescence intensity was affected by Dilantin and accompanied with unstained nuclei during the G2 phase of the first cell cycle. The peak average fluorescence intensity occurred during the G1 phase of the second cell cycle for cyclin D1 stained CZB control, while the vehicle control, 0.001N NaOH, remained constant. Both CZB and 0.001N NaOH had similar expression patterns seen previously in the cyclin D1 in vivo data. The information gained from the in vivo and in vitro experiments will help to better understand what causes the problems associated with exposure to Dilantin, and also the effects Dilantin has on the cell cycle. / Department of Biology

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Agnes Van Langenhove. / Ph.D.

Part I. In order to determine the effect of dose size on the bioavailability of phenytoin (Dilantinᴿ), a single intravenous dose of 15 mg/kg, single oral doses of 400, 800, 1600 mg, and 1600 mg in divided doses (i.e. 400 mg every three hours) were administered to six healthy male subjects. Values of V(max) and K(m) obtained from the intravenous dose were used to determine the extent of absorption from the oral doses. Although no statistically significant difference in extent of phenytoin absorption was observed, the time to reach maximum phenytoin serum concentrations increased significantly from 8.4 hours for the 400 mg dose and 13.2 hours for the 800 mg dose to 31.5 hours for the 1600 mg dose. Peak serum concentrations of 3.9, 5.7, 10.7, and 15.3 mg/1 were observed after the 400, 800, 1600 and 1600 mg divided doses, respectively. It is suggested that the prolonged, but complete, absorption of large phenytoin doses is due to a slow dissolution and continued absorption from the colon. Owing to the prolonged absorption of phenytoin, it may be necessary to use a larger oral than intravenous loading dose to produce similar maximum phenytoin serum concentrations. Part II. The effects of age and obesity on the pharmacokinetics of thiopental were studied in 7 morbidly obese (aged 25 to 46 years) and 22 lean patients (aged 25 to 83 years), who were primarily undergoing abdominal surgery. In all 29 patients, serum thiopental concentrations were determined by gas-liquid chromatography using a nitrogen-selective detector. Based upon total (bound+free) thiopental concentrations, the average (±S.E.) volumes of distribution (Vᵦ and V(ss)) were significantly larger in the obese (7.94 ± 1.72 1/kg and 4.72 ± 1.03 1/kg, respectively) than in the age-matched lean patients (1.95 ± 0.22 1/kg and 1.40 ± 0.16 1/kg, respectively). Clearance based on total thiopental concentrations normalized to total body weight (TBW) was not significantly different between the obese (0.18 ± 0.03 1/hr/kg) and lean patients (0.21 ± 0.02 1/hr/kg). However, total body clearance not normalized to TBW was significantly larger in the obese (24.98 ± 5.62 1/hr) than in the lean patients (11.86 ± 1.29 1/hr). The half-life of thiopental was significantly larger in the obese (31.87 ± 4.53 hours) than in the lean patients (6.61 ± 0.52 hours) and was primarily a function of the larger apparent volume of distribution for thiopental. The unbound fraction of thiopental in serum (range, 17.8% to 27.6%) did not depend on the degree of obesity, but was found to be greater with advancing age. The apparent volumes of distribution, Vᵦ and V(ss), were also related to age. No significant relationship was found between total body clearance with increasing age. Thus, the half-life of thiopental was positively correlated with age, and as in the obese study, was found to be primarily influenced by the apparent volume of distribution.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves 177-194).

Class of 2015 Abstract / Objectives: To determine if a change in the amount of sodium bicarbonate (NaHCO3) in 5 different IV solutions will help prevent phenytoin from falling out of solution (i.e. precipitating). Our working hypothesis is that the stability of the phenytoin solution will change with different IV solutions and will increase with increasing the amount of sodium bicarbonate. Methods: A constant amount of phenytoin injection solution was mixed with a constant amount of one IV solution per beaker. Different amounts of alkalizing agents were then added to each phenytoin and IV mixture. Precipitation of the mixtures was observed every 30 minutes for 4 hours, then again in 24 hours. Results: When different IV solutions were added to the phenytoin and alkalizing agent mixture , the pH of the mixture dropped from 10 to 9 independent of the amount of alkalizing agent present in the mixture. All phenytoin mixtures precipitated within 60 minutes; 0.9% NaCl and phenytoin mixture being the one with the most delayed precipitation. Conclusions: Based on the result of this experiment, we rejected both of our specific aim hypotheses. Our hypothesis is rejected because the stability of the phenytoin solution will not change by using different IV solutions or by changing the amount of sodium bicarbonate.

The pharmacokinetics of phenytoin is complicated by the nonlinearity of the dose-concentration relationship which is a consequence of capacity-limited metabolism. Individualized therapy with phenytoin is therefore optimally required. As no data are available on the population pharmacokinetics of phenytoin in the Western Cape, this study was undertaken to address this issue. This study was conducted prospectively primarily to: (1) investigate the influence of various patient variables on the population pharmacokinetic parameters of phenytoin, (2) assess whether the parallel Michaelis-Menten and first-order elimination model provides a better fit to the data than the Michaelis-Menten model, (3) determine population pharmacokinetic parameter estimates of phenytoin representative of the patient population, and (4) validate and compare the clinical applicability of the parameter estimates and the models. The study population comprised 332 black and coloured, adult, male and female epileptic patients residing in the Western Cape, South Africa. All patients were on phenytoin monotherapy for the management of their epilepsy and no drugs known to interfere with phenytoin pharmacokinetics were taken concurrently. Clinical pharmacokinetic dosing services were initiated at 9 clinics from which patients were selected for this study. The service entailed a patient interview, a chart review, drug analysis and provision of either a written or verbal consultation report. The data were analyzed using NONMEM (nonlinear mixed-effects modelling), a computer programme designed for population pharmacokinetic analysis that allows pooling of data from many individuals. The Michaelis-Menten and the parallel Michaelis-Menten and first-order elimination models were fitted to 853 steady-state dose: serum concentration pairs.

We investigated whether chronic administration of guanidinoethane sulfonate, an inhibitor of taurine uptake, could modify the antiepileptic actions of phenobarbital and phenytoin on maximal electroshock seizures in mice. Treatment with 1% guanidinoethane sulfonate decreased the taurine concentration in the brain to 76% of the control value. Under these conditions, neither the severity of tonic convulsions of maximal electroshock seizures nor the threshold for tonic extension caused by electroshock was altered. However, treatment with guanidinoethane sulfonate lessened the antiepileptic actions of phenobarbital and phenytoin on electroshock seizures. The brain concentrations of phenobarbital and phenytoin were unaltered by administration of guanidinoethane sulfonate. The brain concentrations of guanidinoethane sulfonate and total guanidino compounds were unchanged by the injection of either phenobarbital or phenytoin. It is suggested that the observed loss of anticonvulsive potency of phenobarbital and phenytoin may have been related to the decrease in taurine concentration produced by guanidinoethane sulfonate.

No description available.

Thesis (doctoral)--Karolinska Institutet, Stockholm, 1986. / Extra t.p. with thesis statement inserted. Includes bibliographical references.