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Risks to the offspring of women treated with hydantoin anticonvulsants, with emphasis on the fetal hydantoin syndrome.

The fetal hydantoin syndrome is a variable pattern of altered growth and performance which includes unusual facies, distal phalangeal hyoplasia, and other defects occurring in some infants exposed in utero to hydantoins. A prospective study of 35 infants exposed prenatally to this class of anticonvulsants showed that 11% had sufficient features to be classified as having the fetal hydantoin syndrome. An additional 31% displayed some features compatible with the prenatal effects of hydantoins. A case-control study of 104 infants whose mothers received hydantoins during pregnancy supports these conclusions. Reduction of intellectual ability in infants with the fetal hydantoin syndrome is the area of greatest concern. Women being treated with hydantoin anticonvulsants should be told of the nature and magnitude of risks to the developing fetus before considering a pregnancy.

Abnormalities, Drug-Induced

Biopharmaceutical studies on hydantoin derivatives. I. Physico-chemical properties of hydantoin derivatives and their intestinal absorption.

The physico-chemical properties of a series of hydantoin derivatives and their intestinal absorption from solution were studied. The introduction of the benzenesulfonyl group at the 1-position of the hydantoin ring greatly affects the physico-chemical properties: the acid dissociation constants were increased 1000-fold and the partition coefficients were increased 100- to 1000-fold in the chloroform/water system and 10- to 100-fold in the n-octanol/water system. The solubilities of 1-benzenesulfonylhydantoin derivatives increased with increasing pH of the solution at pH more than 5, but the solubilities of the 1- unsubstituted hydantoin derivatives were scarcely dependent on the pH of the solution in the pH 1 to 8 region. The intestinal absorption from solution was found to be caused by the passive transport according to the first-order kinetics. The rate constants of absorption of 1-benzenesulfonylhydantoin derivatives were rather large even under the condition where they were 99% ionized in the solution than that of the corresponding 1-unsubstituted hydantoin derivatives which exist mainly as the unionized from under the same condition. The intestinal absorption from a solution and the partitioning to chloroform produced linear free energy relationships to each other for the 1-benzenesulfonylhydatoin derivatives and for the 1-unsubstituted hydantoin derivatives independently. However when the partition coefficients in the n-octanol/water system were applied, the hydroxyl derivatives were found to deviate from linear relationships. On the basis of the results, a suggestion was made on the in vivo behavior and the bioavailability.

Animals

Biopharmaceutical studies on hydantoin derivatives. II. Pharmacokinetics and bioavailability of hydantoin derivatives in dogs.

Pharmacokinetics and bioavailability for the 1-benzenesulfonylhydantoin derivatives and 1-unsubstituted hydantoin derivatives were evaluated from the plasma concentrations after oral and intravenous administrations to dogs. Apparent volume of distribution of the 1-benzenesulfonylhydantoin derivatives was about 0.25 l/kg, while that of the 1-unsubstituted hydantoin derivatives was about 1.3 l/kg. The result suggests that introduction of the benzenesulfonyl group at 1-position of the hydantoin ring has marked effect on the distribution into the fluids and tissues of the body. Bioavailabilities of sodium 5,5-diphenylhydantoin and sodium 1-benzenesulfonyl-5,5-diphenylhydantoin exceeded those of their corresponding free forms. The results were well explicable in terms of the excellent dissolution behaviours of the salt forms. The bioavailabilities of 5-ethyl-5-phenylhydantoin and 1-benzenesulfonyl-5-ethyl-5-phenylhydantoin were almost perfect. The results suggest that the dissolution rate is a rate-determining step in the bioavailability of the derivatives having two phenyl groups at 5-position of the hydantoin ring, irrespective of the presence of the benzenesulfonyl group at 1-position.

Administration, Oral

Patch test reactivity to DMDM hydantoin. Relationship to formaldehyde allergy.

The relationship between contact allergy to formaldehyde and positive patch test reactions to DMDM hydantoin was investigated. 35 formaldehyde-allergic patients were patch tested with serial dilutions of formaldehyde (0.1%-0.3%-1.0% aq.) and DM hydantoin (the non-formaldehyde-containing parent compound of DMDM hydantoin). 21 were also patch tested with MDM hydantoin (1 molecule formaldehyde) in serial dilutions: 7 (33%) reacted to 1 or more concentrations. The other 14 were also tested with DMDM hydantoin (2 molecules formaldehyde) in serial dilutions: 8 (57%) reacted to 1 or more concentrations. Patients patch-test-positive to formaldehyde 0.1% and/or 0.3% tended to show more patch test reactivity to (D)MDM hydantoin than those who reacted only to 1%. Aqueous solutions of (D)MDM hydantoin in concentrations as used in cosmetic products therefore contain enough free formaldehyde to cause dermatitis in a patch test system in some formaldehyde-allergic patients: 12 such patients applied a cream containing 1% DMDM hydantoin to the flexor aspect of the lower arm twice daily for 1 week; 4 (33%) developed dermatitis. The use of a cream containing 0.25% DMDM hydantoin in these 4 patients still caused dermatitis in 1 and provoked itching in another. An increase in the use of DMDM hydantoin in cosmetic products will also inevitable increase the risk of cosmetic dermatitis in consumers allergic to formaldehyde.

Cosmetics

Fetal hydantoin syndrome: inhibition of placental folic acid transport as a potential mechanism for fetal growth retardation in the rat.

Maternal hydantoin ingestion during pregnancy results in a well defined clinical entity termed "fetal hydantoin syndrome". The clinical characteristics of this syndrome includes growth retardation, and congenital anomalies. Because folic acid is essential for protein synthesis and growth, and since hydantoin interferes with intestinal transport of folic acid, we postulated that part of the fetal hydantoin syndrome may be due to inhibition of placental folic acid by maternal hydantoin. Therefore, we studied in vivo placental folate transport in a well-established model for fetal hydantoin syndrome in the rat. Our results indicate that maternal hydantoin ingestion, significantly decreased fetal weight and placental and fetal uptake of folate compared to controls. To determine whether maternal hydantoin ingestion has a generalized or specific effect on placental function, we examined placental and fetal zinc transport in the same model. Our results indicate that zinc transport is not altered by hydantoin ingestion. We conclude that maternal hydantoin ingestion results in fetal growth retardation which may be due in part to inhibition of placental folate transport.

Animals

Bicyclic hydantoins with a bridgehead nitrogen. Comparison of anticonvulsant activities with binding to the neuronal voltage-dependent sodium channel.

The anticonvulsant activity of diphenylhydantoin (DPH or phenytoin) is consistent with its actions on the neuronal voltage-dependent sodium channel. To further elucidate the binding requirements for this site, we synthesized several hydantoin analogs and evaluated these in in vitro sodium channel-binding and/or in vivo whole animal anticonvulsant assays. 5-Pentyl-5-phenylhydantoin (8), the most potent binder to the sodium channel in this study, had the same affinity as DPH (IC50 = 40 microM), revealing that one phenyl ring is sufficient for good interactions. Since our previous studies with monophenyl-substituted bicyclic 2,4-oxazolidinediones suggested that N3-alkylation and the conformational constraint of a 5-alkyl substituent over one face of the oxazolidinedione ring improved activity, we synthesized two examples of analogous bicyclic hydantoins. However, the bicyclic hydantoins were much less potent binders to the neuronal voltage-dependent sodium channel than their monocyclic counterparts. The binding activity for the more potent bicyclic hydantoin, 1,8-diaza-9,10-dioxo-7-phenylbicyclo[5.2.1]decane (4) (IC50 = 427 microM), was comparable to that of the ring-opened, N3-methylated monocyclic hydantoin model, 5-butyl-3-methyl-5-phenylhydantoin (9) (IC50 = 285 microM), and these were 8-11 times less potent than the monocyclic model 8, which contains a free imide NH. Furthermore, 5-butyl-5-phenylhydantoin (7; IC50 = 103 microM) was less potent than 8, suggesting that increased log P may enhance binding. Thus, unlike 2,4-oxazolidinediones, N3-alkylation of hydantoins dramatically decreases sodium channel-binding activity. Bicyclic hydantoin 4 was nevertheless a good anti-MES anticonvulsant in mice (ED50 = 86 mg/kg), although this activity likely results from mechanisms other than interactions at the neuronal voltage-dependent sodium channel. Compound 4 was also relatively neurotoxic (TD50 = 124 mg/kg). These results suggest that the binding of hydantoins to the sodium channel may be enhanced by (a) a free imide NH group and (b) an increased log P. Furthermore, 2,4-oxazolidinediones and hydantoins must either orient differently in the same binding site or interact with different sites on the neuronal voltage-dependent sodium channel.

Alkylation

Effect of L-penicillamine hydantoin, an analogue of glutathione, on rat liver glutathione peroxidase, reductase and transferase reactions.

In soluble fractions prepared from rat liver homogenates, L-penicillamine hydantoin appeared to be, on the basis of SH consumption measurements, a substrate for glutathione peroxidase but not transferase reactions. When glutathione is incubated with rat liver soluble proteins in the presence of penicillamine hydantoin, formation of oxidized glutathione is inhibited. Calculations from Lineweaver-Burk plots point out that inhibition by L-penicillamine hydantoin of the peroxide-dependent oxidations of glutathione is mixed, since both apparent Km and Vmax values are modified. Preincubation of rat liver soluble proteins with L-penicillamine hydantoin led to a progressive inactivation of glutathione peroxidase. The kinetics of this inactivation process with respect to time and inactivator concentration were studied. Inclusion in the preincubation mixture of SH-containing molecules such as dithiothreitol, L-cysteine or glutathione protected the enzyme against inactivation. However, none of these molecules and neither hydantoin, Triton X-100, phenol, nor dialysis could reverse the enzyme from inactivated to activated form. Mitochondrial glutathione peroxidase was inhibited and inactivated by L-penicillamine hydantoin to the same extent as its cytosolic counterpart. Modifications by penicillamine hydantoin of various subcellular markers enzymes (lactate dehydrogenase, N-acetyl beta-glucosaminidase, arylsulfatase C, butyryl-CoA dehydrogenase, lauryl-CoA and glycolate oxidases) were of weak amplitude consisting of either inhibition, inactivation or stimulation.

Animals

Purification and characterization of the hydantoin racemase of Pseudomonas sp. strain NS671 expressed in Escherichia coli.

The hydantoin racemase gene of Pseudomonas sp. strain NS671 had been cloned and expressed in Escherichia coli. Hydantoin racemase was purified from the cell extract of the E. coli strain by phenyl-Sepharose, DEAE-Sephacel, and Sephadex G-200 chromatographies. The purified enzyme had an apparent molecular mass of 32 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. By gel filtration, a molecular mass of about 190 kDa was found, suggesting that the native enzyme is a hexamer. The optimal conditions for hydantoin racemase activity were pH 9.5 and a temperature of 45 degrees C. The enzyme activity was slightly stimulated by the addition of not only Mn2+ or Co2+ but also metal-chelating agents, indicating that the enzyme is not a metalloenzyme. On the other hand, Cu2+ and Zn2+ strongly inhibited the enzyme activity. Kinetic studies showed substrate inhibition, and the Vmax values for D- and L-5-(2-methylthioethyl)hydantoin were 35.2 and 79.0 mumol/min/mg of protein, respectively. The purified enzyme did not racemize 5-isopropylhydantoin, whereas the cells of E. coli expressing the enzyme are capable of racemizing it. After incubation of the purified enzyme with 5-isopropylhydantoin, the enzyme no longer showed 5-(2-methylthioethyl)hydantoin-racemizing activity. However, in the presence of 5-(2-methylthioethyl)hydantoin, the purified enzyme racemized 5-isopropylhydantoin completely, suggesting that 5-(2-methylthioethyl)hydantoin protects the enzyme from inactivation by 5-isopropylhydratoin. Thus, we examined the protective effect of various compounds and found that divalent-sulfur-containing compounds (R-S-R' and R-SH) have this protective effect.

Cloning, Molecular

Rotationally restricted mimics of rigid molecules: nonspirocyclic hydantoin aldose reductase inhibitors.

Sorbinil (1), a spirocyclic hydantoin, is a potent inhibitor of the enzyme aldose reductase. Simulation of the rigid spirocyclic ring orientation found in sorbinil was achieved with nonspirocyclic 5-[5'-chloro-2'-(alkylsulfonyl)-phenyl]hydantoins and 5-[5'-chloro-2'-[(N-alkylamino)sulfonyl]phenyl]hydantoins. The 2'-substituent (SO2R) was sufficiently large to hinder rotation of the hydantoin ring, forcing an orientation similar to that of a spirocyclic hydantoin. Calculated conformational preference, X-ray data, and inhibitory IC50 values for these nonspirocyclic 2'-substituted (SO2R) phenylhydantoins are in accord with what is expected for spirocyclic hydantoins and comparable to those of sorbinil.

Aldehyde Reductase

[Fetal hydantoin syndrome in siblings].

The two children of an epileptic woman who underwent therapy with hydantoin during both pregnancies showed the characteristic findings of the fetal hydantoin syndrome: growth retardation, microcephaly, mental retardation, and a distinct hysmorphic pattern. Both exhibited a ridged metopic suture, hypertelorism, a short nose with a broad base, hypoplasia of the distal phalanges and nails of the toes, and inguinal hernias. In addition the 18-month-old girl exhibited epicanthal folds, strabismus, ptosis, and a small ventricular septal defect; she had been exposed in utero to 300 mg mesantoin daily. Her 6 1/2-year-old brother was more severely retarded, lacking speech and presenting with infantile autism. During pregnancy the mother had taken 400 mg mesantoin daily. About half of the offspring of epileptic women treated with hydantoin during pregnancy are mentally retarded, and 11% exhibit in addition the pattern of dysmorphic findings known as the fetal hydantoin syndrome. Hydantoin should therefore be strictly avoided in epileptic women of child-bearing age unless safe contraceptive measures are taken. In the event of pregnancy, therapeutic abortion should be considered if hydantoin therapy must be maintained.

Abnormalities, Multiple

Hydantoin-induced teratogenesis: are arene oxide intermediates really responsible?

A large body of literature indicates that prenatal exposure to hydantoin anticonvulsant drugs can be teratogenic and therefore result in offspring with congenital malformations [6, 10-12, 18, 27, 30]. Literature discussing the actual etiologic agent responsible for the malformation and the types of anomalies typical of hydantoin-induced teratogenicity is contradictory [3, 10, 11, 35]. The majority of published cases of the fetal hydantoin syndrome have been associated with maternal ingestion of the most widely prescribed of all the hydantoin anticonvulsants, phenytoin (Dilantin; Parke, Davis) [11]. Occasional reports of mephenytoin (Mesantoin; Sandoz) teratogenicity have been noted [10-11, 27], but our review of the literature yielded only one case report of birth defects in a child exposed to ethotoin (Peganone; Abbott Laboratories in utero [38]. We wish herein to describe three siblings prenatally exposed to ethotoin, all of whom had clinical features compatible with in utero exposure to hydantoin anticonvulsants. Unlike phenytoin and mephenytoin, ethotoin is not metabolized through an arene oxide intermediate. The presence of these clinical findings suggests, therefore, that epoxide metabolites are not the causative agents in hydantoin-induced teratogenicity.

Abnormalities, Drug-Induced

Relationship of molecular structure to in vivo scintigraphic distribution patterns of carbon-11 labeled compounds. 3. (11C)Hydantoins.

The preparation and gamma-scintigraphic evaluation of the in vivo distribution patterns in dogs of a series of structurally related hydantoins labeled with the positron emitting, 20.4 min half-life radionuclide, carbon-11 are described. Carbon-11 labeled HCN was collected in water or aqueous Me2SO containing carrier KCN following cyclotron bombardment of 99% N2-1% H2 gas mixture with 22 MeV protons for 1 hr at 25-35 muA. Five 11C-labeled 5,5-dialkylhydantoins, three [11C]diarylhydantoins, five [11C]-5-alkyl-5-phenylhydantoins, and five [11C]spirohydantoins were prepared by heating generally under pressure, a mixture of 11C-labeled KCN, which was produced by isotopic exchange with carrier KCN, the corresponding aldehyde or ketone, and excess (NH4)2CO3 in aqueous ethanol or Me2SO solvent. The 11C-labeled hydantoins were dissolved in 1-1.5% aqueous NaOH for intravenous administration to dogs. Total synthesis time was 70-106 min and 1-59 mCi of final product was available for conducting serial in vivo imaging for up to 2 hr or more with the gamma-scintillation camera. Carbon-11 activity from all compounds showed initial blood-pool distribution with variable concentration of activity in the brain, lungs, liver, and kidney. All of the 11C-labeled diarylhydantoins, and most having one phenyl substituent, and one having a hexamethylene moiety showed initial accumulation of 11C activity in brain. Carbon-11 labeled 5,5-diphenylhydantoin (dilantin) showed the greastest qualitative accumulation of activity in the brain. Those 11C-labeled hydantoins having a carboxyl substituent showed prominent renal concentration and urinary excretion of activity. Most 11-c-labeled hydantoins showed a progressive homogenous whole body distribution of activity in all cellular tissues of the body. The relatively uniform distribution of activity in cellular tissues and slow excretion from the body support the thesis that the pharmacologic action of the hydantoins is related to physical effects on biomembranes rather than to specific chemical interactions with cell constituents.

Animals

Purinylhydantoins. Facile conversion of the naturally occurring N-(purin-6-ylcarbamoyl)-L-amino acids into 3-pruin-6-ylhydantoins and 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins.

The naturally occurring N-(purin-6-ylcarbamoyl)-L-threonine (PCT, 1b), N-(purin-6-ylcarbamoyl)glycine (PCG, 1a), and some of their analogs were converted into novel purine derivatives, the purinylhydantoins. The PCT and PCG underwent intramolecular cyclization in the presence of N,N-dicyclohexylcarbodiimide (CDD) to give the 3-purin-6-ylhydantoins (2a-c). The same hydantoins were also obtained when the PCT and PCG were allowed to react through the mixed anhydride formed from cyclohexyl isocyanate or ethyl chloroformate. 1,3-Dicyclohexyl-1-(N-(purin-6-ylcarbamoyl)aminoacyl)ureas 3a and 3c, by-products obtained from the DCC reaction, were rapidly converted in aqueous NaOH to another type of purinylhydantoins, the 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins 4a and 4b. Compound 4a when heated in base underwent hydrolysis of the hydantoin ring giving biuret N-(cyclohexylcarbamoyl)-N-(purin-6-ylcarbamoyl)glycine (5a) and N-(purin-6-ylcarbamoyl)glycine cyclohexylamide (6a). The characterization of these hydantoins was carried out by uv, nmr, and mass spectrometry. The 3-purin-6-ylhydantoins and 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins showed growth inhibitory activity in the cultured leukemic cells, while the parent amino acid compounds were inactive.

Amino Acids

[Malignant lymphoma following years of hydantoin treatment for epilepsy].

The cases are presented of 4 hydantreated epileptic patients developing malignant lymphomas (1 Hodgkin's lymphoma). The duration of the hydantoin therapy ranged from 7 to 23 years. There was no evidence of an allergic drug reaction, with the exception of slight blood eosinophilia. Prior to the lymphoma one patient exhibited leukopenia and a second thrombocytopenia. Hydantoins were discontinued in 3 cases but the lymphomas never disappeared spontaneously and only once did tumor progression came to a stillstand. Two patients were successfully treated with either chemo- or radiotherapy. Possible correlations between the documented immunosuppressive action of hydantoin derivatives and tumor induction are discussed. Malignant lymphomas may be sequelae of long-term hydantoin therapy and are not always preceded by the well-known reversible hydantoin lymphadenopathy.

Drug Hypersensitivity

Melanotic neuroectodermal tumor of infancy and fetal hydantoin syndrome.

Fetal hydantoin syndrome (FHS), a characteristic pattern of altered growth and development, has been well described in recent years in offsprings of epileptic mothers taking phenytoin or other hydantoin anticonvulsants during the gestational period. Recent reports of neuroblastoma in three patients with the FHS further raise the questions of the "oncogenic effect " of hydantoin compounds. A case of melanotic neuroectodermal tumor of infancy (MNTI) has been studied clinically and pathologically including light microscopy, histochemistry, and electron microscopy. This case strengthens the evidence for the teratogenic and oncogenic effects of hydantoin compounds and we believe that it represents the first reported case of FHS associated with MNTI. It would be most important from a clinical standpoint to carefully scrutinize individuals with the FHS for neoplasias. Furthermore, detailed gestational drug history in children with neuroblastoma and other neoplasias should be carefully searched for, with the hope of clarifying the definitive oncogenic effect of hydantoin compounds.

Abnormalities, Drug-Induced

Relation of in vivo drug metabolism to stereoselective fetal hydantoin toxicology in mouse: evaluation of mephenytoin and its metabolite, nirvanol.

Anticonvulsant therapy during pregnancy with the hydantoin phenytoin carries a risk of teratologic sequelae and developmental retardation known as the fetal hydantoin syndrome. The putative teratogen is a highly reactive arene oxide intermediate produced during phenytoin metabolism. By using two structurally similar hydantoins, mephenytoin and its in vivo demethylated metabolite nirvanol, we examined the possibility for a stereoselective dissociation of fetal hydantoin toxicity from maternal anticonvulsant activity. The d-isomers (S-enantiomers) of mephenytoin and nirvanol are p-hydroxylated via an arene oxide and hence were suspect teratogens. The l-isomers (R-enantiomers), being eliminated primarily via alternate pathways, were expected to be less toxic. Equimolar doses of the d- or l-isomers of mephenytoin or nirvanol were administered to pregnant Swiss ICR mice i.p. on gestational day 10. An 8-fold increase in fetal resorptions and a significant 11% decrease in fetal body weight was observed in the group treated with l-nirvanol, whereas no or minimal toxicity was observed in the other treatment groups. The blood clearance for d-nirvanol was double that for l-nirvanol, with correspondingly higher urinary concentrations of arene oxide-mediated metabolites. ANIH shift during metabolism supported the presence of an arene oxide intermediate. Contrary to our expectations, only l-nirvanol, the isomer producing less arene oxide, demonstrated fetal toxicity, thus raising some doubt concerning the arene oxide as the putative hydantoin teratogen. Further animal studies with the d-isomers of mephenytoin and nirvanol may lead to an anticonvulsant of choice during pregnancy.

Animals