Chronic Administration Of Phenytoin Research Articles

Phenytoin–levetiracetam adjunctive treatment-induced neurotoxicity and deregulation of cholinergic neurotransmission with evidence of neurocognitive impairment in male Wistar rats

ABSTRACT Introduction The effects of chronic administration of phenytoin (PHT), levetiracetam (LEV), and PHT + LEV adjunctive treatments were examined on the cognitive functions of male rats. Methods Twenty-eight male Wistar rats (150–180 g) were randomized into 4 groups (N = 7). Groups I–IV received daily intraperitoneal administration of normal saline (0.2 ml), therapeutic doses of PHT (50 mg/kg), LEV (50 mg/kg) or sub-therapeutic dose of PHT (25 mg/kg) and LEV (25 mg/kg) combination, respectively, for 28 days. Thereafter, the animals were subjected to behavioral assessment and evaluation of the activities of acetylcholinesterase, lipid peroxidation, and lastly the morphological evaluation of the brain. Data were analyzed using descriptive and inferential statistics. The results were presented as mean ± SEM in graphs or tables, while the level of significance was taken at p < 0.05. Results Working & spatial memory, exploratory activities, and motor-coordination indices were significantly (p = 0.0099) impaired with a reduction in the frontal lobe and hippocampal weight following PHT and PHT + LEV adjunctive treatments. The frontal lobe and hippocampal activities of acetylcholinesterase increased significantly (p = 0.0437) following PHT and PHT + LEV adjunctive treatment. The concentrations of malondialdehyde increased significantly (p = 0.0473) in PHT, LEV, and PHT + LEV compared with the control. There was disorganization in the histoarchitectural profile with chromatolysis, hyalinization, and neural vacuolation in the pre-frontal cortex, hippocampus, and cerebellar tissue, especially in the PHT + LEV treated rats. Conclusion Impairment of cognitive functions following PHT and PHT + LEV adjunctive treatments may be attributable to the deregulation of cholinergic transmission and neurotoxicity.

Improving effect of mild foot electrical stimulation on pentylenetetrazole-induced impairment of learning and memory

Epilepsy is a common neurological disorder that affects learning and memory. Recently it has been shown that mild foot electrical stimulation (MFES) can increase learning and memory in normal rats. Pentylenetetrazole (PTZ) kindling is a model of human epilepsy. As with human epilepsy, PTZ kindling impairs learning and memory in rats. The purpose of this study was to investigate the effect MFES on kindling-induced learning and memory deficits in rats. Forty-nine male Wistar rats weighting 200 to 250 g were divided into the following seven groups: PTZ only, phenytoin only, MFES only, PTZ plus phenytoin, PTZ plus MFES, phenytoin plus MFES, and saline (control), with the treatments administered for 26 days. Forty-eight hours after the last injection, the animals performed the Morris water maze (MWM) task, and spatial learning and memory were measured. The results indicated that although chronic administration of phenytoin inhibited the development of PTZ kindling, it did not exert a protective effect against kindling-induced spatial learning and memory impairment in rats. On the other hand, pretreatment of PTZ-kindled animals with MFES significantly improved spatial working and reference memory. The results point to potential novel beneficial effects of MFES on learning and memory impairment induced by PTZ kindling in rats.

Chronic administration of phenytoin and pleomorphic adenoma: A case report and review of literature

Adverse drug effects that are uncommon or appear only on chronic administration of a drug may not be detected in clinical trials. This explains the need of strict post-marketing vigilance on drug use. Phenytoin administration has been shown in the literature to be associated with development of neoplasia (benign/malignant). In our knowledge current work represents the first case of pleomorphic-adenoma of sub-mandibular salivary gland developed following chronic phenytoin use. A 40 year old male having a history of head trauma twenty years back, had been on tablet phenytoin 100 mg thrice daily since then. One year back he noticed a small swelling in left sub-mandibular region and gradually increasing in size. FNAC and CECT revealed the diagnosis of pleomorphic-adenoma of sub-mandibular salivary gland. Other causes were ruled out. Surgical excision was performed successfully and continuing follow-up with no recurrence at the end of 6 months. Histo-pathogical examination of the tissue did not show any malignant changes.

The effect of chronic phenytoin administration on single prolonged stress induced extinction retention deficits and glucocorticoid upregulation in the rat medial prefrontal cortex.

Post-traumatic stress disorder (PTSD) is a chronic, debilitating disorder. Only two pharmacological agents are approved for PTSD treatment, and they often do not address the full range of symptoms nor are they equally effective in all cases. Animal models of PTSD are critical for understanding the neurobiology involved and for identification of novel therapeutic targets. Using the rodent PTSD model, single prolonged stress (SPS), we have implicated aberrant excitatory neural transmission and glucocorticoid receptor (GR) upregulation in the medial prefrontal cortex (mPFC) and hippocampus (HPC) in fear memory abnormalities associated with PTSD. The objective of this study is to examine the potential protective effect of antiepileptic phenytoin (PHE) administration on SPS-induced extinction retention deficits and GR expression. Forty-eight SPS-treated male Sprague Dawley rats or controls were administered PHE (40, 20 mg/kg, vehicle) for 7 days following SPS stressors; then, fear conditioning, extinction, and extinction retention were tested. Fear conditioning and extinction were unaffected by SPS or PHE, but SPS impaired extinction retention, and both doses of PHE rescued this impairment. Similarly, SPS increased GR expression in the mPFC and dorsal HPC, and PHE prevented SPS-induced GR upregulation in the mPFC. These data demonstrate that PHE administration can prevent the development of extinction retention deficits and upregulation of GR. PHE exerts inhibitory effects on voltage-gated sodium channels and decreases excitatory neural transmission via glutamate antagonism. If glutamate hyperactivity in the days following SPS contributes to SPS-induced deficits, then these data may suggest that the glutamatergic system constitutes a target for secondary prevention.

Gingival Enlargement in Epileptic Patients on Phenytoin Therapy-An Evidence Based Approach

Epilepsy is a common neurological disorder with recurrent seizures due to a chronic underlying process. Despite tremendous advances in the field of understanding the etio-pathogenesis of epilepsy, phenytoin still remains the drug of choice in its management. Chronic administration of phenytoin has been associated to have a number of adverse effects. Gingival enlargement is one such most often reported adverse drug sequela of long term phenytoin usage with exclusion of local factors contributing towards gingival enlargement. Hence, the study was planned to investigate the association of phenytoin and gingival enlargement seen in epileptic patients being treated with phenytoin. For this, 25 patients between the ages of 18-50 years clinically diagnosed with epilepsy prior to the start of phenytoin therapy were included based on selection criteria and written informed consents were obtained. Assessment of gingival status was done using the index originally described by Angelopoulos and Goaz and later modified by Miller and Damm [Go Index]. The results of the study confirmed a significant association between long term usage of phenytoin and the onset and severity of gingival enlargement in epileptic patients being treated with phenytoin. This is a baseline study; the results of the study suggest a higher incidence of gingival enlargement in phenytoin treated epileptic patients with local factors having a little role, if any, towards phenytoin induced gingival enlargement.

Bisphosphonates in phenytoin-induced bone disorder

Chronic administration of phenytoin (PHT) has been associated with bone loss. Bisphosphonates [alendronate (ALD), ibandronate (IBD) and risedronate (RSD)] are potential candidates to prevent PHT-induced bone disorders, and the present study evaluated their effect on the antiepileptic efficacy of PHT. The PHT-induced depletion in folic acid (FA), vitamin B6 and vitamin B12 results in hyperhomocysteinemia. The elevated circulating homocysteine (hcy) could be a risk indicator for micronutrient-deficiency-related osteoporosis via generation of free radicals. Thus, an attempt was also made to unravel the PHT's and bisphosphonates' effect on hcy. Male mice received PHT (35 mg/kg, p.o.) for 90 days to induce bone loss. ALD, RSD and IBD were administered orally at doses 0.65 mg/kg, 0.33 mg/kg, and 0.17 mg/kg respectively, for prevention and 1.3 mg/kg, 0.65 mg/kg, and 0.33 mg/kg respectively, for treatment of PHT-induced bone loss. The bone loss was confirmed by bone mineral density (BMD) analysis and bone turnover markers. Serum levels of hcy and FA were estimated along with hydrogen peroxide levels and total antioxidant capacity in order to assess the antioxidant profile of bisphosphonates. The induction of bone loss by PHT was marked by lowered BMD and altered bone turnovers. ALD and RSD administration to PHT treated groups significantly reverted the bony adverse effects. No such effects were observed with IBD. In the bisphosphonates treated groups, hcy levels were statistically at par with the control group. PHT at 35 mg/kg, p.o. could compromise bone mass and thus, could be a model of bone demineralization in mice. The ALD, IBD and RSD have no pharmacodynamic interaction when administered along with PHT at the experimental level. Thus, their usage in the management of PHT-induced bone disease could be worthwhile if clinically approved.

Curcumin is protective against phenytoin-induced cognitive impairment and oxidative stress in rats

The present study investigates the effect of chronic curcumin administration on phenytoin-induced cognitive impairment and oxidative stress in rats. Male Wistar rats were administered drugs/vehicle for 21 days. Learning and memory was evaluated using the passive avoidance paradigm and the elevated plus maze. On day 21, serum phenytoin concentrations and whole brain malondialdehyde (MDA) and glutathione (GSH) levels were estimated. Phenytoin (75 mg/kg, i.p.) produced significant deficits in learning/memory as indicated by the significant increase in retention transfer latency in elevated plus maze test and a significant decrease in retention latency in the passive avoidance paradigm. Chronic administration of phenytoin also produced significant elevations in brain MDA and reduction of brain GSH levels. Curcumin (100, 200 and 300 mg/kg, orally), when administered with phenytoin, significantly prevented phenytoin-induced cognitive impairment and oxidative stress in a dose-dependent manner. There were no significant differences in the serum levels of phenytoin in any of the treatment groups. This study demonstrates that curcumin is effective in preventing phenytoin-induced cognitive impairment and oxidative stress in rats without altering the serum phenytoin levels. This suggests the potential of adjuvant curcumin therapy in ameliorating cognitive impairment caused by chronic phenytoin therapy.

The Effect of Phenytoin on Rocuronium-Induced Neuromuscular Block in the Rat Phrenic Nerve-Hemidiaphragm Preparation

Anticonvulsant therapy alters the action of nondepolarizing muscle relaxants. We determined the effects of acute and chronic administration of phenytoin on rocuronium-induced neuromuscular block using the rat phrenic nerve-hemidiaphragm preparation. Rats were divided into 3 groups: a saline control group (n = 10), an acute phenytoin-treated group (n = 30), and a chronic phenytoin-pretreated group (n = 30). Phrenic nerve-hemidiaphragm was dissected, mounted in a bath containing oxygenated Krebs solution, and the nerve was stimulated at supramaximal intensity. Single twitch responses were recorded by physiogram. In the acute phenytoin-treated group, acute effects of phenytoin were determined based on the phenytoin concentration of 1, 10, or 100 microg/mL in the bath. The chronic effects of phenytoin were determined using phrenic nerve-diaphragms from rats pretreated with phenytoin (50 mg/kg/d) for 1, 7, or 28 days. In rats with phenytoin 100 microg/mL in the bath, all concentrations of rocuronium produced twitch depression significantly different from those of other groups (P < 0.05), and the concentration-response curve shifted to the left. In rats with phenytoin 10 microg/mL in the bath, the effective concentrations for 50%, 90%, and 95% twitch depression values were significantly different from those of the control group (P < 0.05). In chronically (28 days) phenytoin-pretreated rats, the concentration-response curve significantly shifted to the right (P < 0.05). These findings show that acute administration of phenytoin augmented the neuromuscular blocking effects of rocuronium, whereas chronic phenytoin treatment causes resistance to the neuromuscular blocking effects of rocuronium in target organs.

Studying long-term effect of phenytoin either alone or combined with ascorbic acid on the anesthetic effect of urethane in rats.

Phenytoin is an anticonvulsant drug known to interact with many other drugs. Previous data suggest that chronic administration of phenytoin delays urethane-induced loss of righting reflex (LRR) and this phenomenon being potentiated by concomitant administration of ascorbic acid (ASC). Therefore, we examined how phenytoin at two different doses combined or not with ASC (fixed dose) interact with both the latency to, and the duration for urethane-induced LRR in experimental rats. The results showed that lower dose of phenytoin (60 mg/kg rat b.i.d.) has significantly shortened the duration of LRR while higher dose of the drug (120 mg/kg b.i.d.) has delayed the latency to LRR (cut-off period of 15 min). Furthermore, addition of ASC to any of the two doses of phenytoin gave results similar to that observed for latency to and duration of LRR when phenytoin was given alone at the higher dose (120 mg/kg b.i.d.). Our data suggest a resistant effect of chronic administration of phenytoin on latency to and/or duration of loss righting reflex induced by urethane in experimental animals. A dose-response relationship of phenytoin in this regard is expected and needs further investigations. The resistant effect of phenytoin on righting reflex has been augmented when ASC was chronically given in combination. This result supports a possible interaction between the two drugs and needs further investigations at both experimental and clinical levels.

Influence of chronic phenytoin administration on the pharmacokinetics and pharmacodynamics of vecuronium.

The duration of action of vecuronium is reduced in patients receiving phenytoin. In this study, the authors examined, simultaneously, the influence of phenytoin on both the pharmacokinetics and the pharmacodynamics of vecuronium. This study was approved by the institutional review board of the University of California, San Francisco, and patients gave written informed consent. Twenty-two patients, 11 taking phenytoin and all scheduled to undergo prolonged neurosurgical procedures with general anesthesia, participated in the study. In 12 patients (6 phenytoin, 6 control), vecuronium was infused at 7.5 microg x kg(-1) x min(-1) until the first response (T1) of each train-of-four decreased by 50%; in the remaining 10 patients (5 phenytoin, 5 control), 200 microg/kg vecuronium was infused over 10 min. Arterial blood samples were drawn at intervals over the next 5-7 h. Plasma concentrations of vecuronium and 3-desacetylvecuronium were measured by capillary gas chromatography. Pharmacokinetic and pharmacodynamic modeling was used to characterize the disposition of vecuronium and patient responses to it in the two groups. Clearance was typically increased by 138% (95% confidence interval, 93-183%) in patients taking phenytoin. The effect of vecuronium was well described using a sigmoid Emax model. The concentration of vecuronium giving 50% twitch depression was increased 124% (45-202%) in patients taking phenytoin. Chronic phenytoin therapy reduces the effect of vecuronium by mechanisms that include both increased vecuronium metabolism and reduced sensitivity of the patient to circulating concentrations of vecuronium.

Phenytoin promotes Th2 type immune response in mice.

The effects of chronic administration of phenytoin, a common anticonvulsive drug, on immune responses were studied in mice. Anti-keyhole limpet haemocyanin (KLH) IgE antibody response after KLH-immunization was enhanced in phenytoin-treated mice. Proliferative responses of spleen cells induced with KLH, concanavalin A (ConA), lipopolysaccharide and anti-CD3 antibody were reduced in phenytoin-treated mice. Accessory function of spleen adherent cells on ConA-induced T cell proliferative response was reduced in phenytoin-treated mice. KLH-induced IL-4 production of spleen cells was enhanced, while IFN-gamma production was reduced in phenytoin-treated mice. In addition, production of IL-1 alpha, but not IL-6 and IL-12 by spleen adherent cells from phenytoin-treated mice was reduced. Natural killer cell activity was reduced in phenytoin-treated mice. These results suggest that phenytoin treatment preferentially induces a Th2 type response. We also observed that plasma ACTH and corticosterone levels were increased in phenytoin-treated mice, and speculated that phenytoin might act directly and indirectly, through HPA axis activation, on the immune system to modulate Th1/Th2 balance.

Lipopigment in rat hippocampal and Purkinje neurones after chronic phenytoin administration

The accumulation of lipopigment may indicate ageing, certain diseases and cellular damage, while phenytoin, which has been claimed to cause selective clinical cerebellar dysfunction and degeneration, has been reported to produce increased lipopigment accumulation in rat Purkinje neurones. In the present study, 8 rats received phenytoin, 300 mg/kg/day for 20 weeks, and were compared with a control group of 9 rats in respect of lipopigment in Purkinje and hippocampal neurones. Neuronal lipopigment was identified by fluorescence microscopy. The results did not indicate that phenytoin administration was associated with an increase in the area corresponding to (i.e. within the outlines of) neuronal lipopigment in Purkinje neurones, although the relatively small number of animals limits the power of the study. However, in hippocampal neurones, a two-way analysis of variance for numbers of discrete regions of lipopigment demonstrated a significant interaction ( P = 0.003) between, firstly, size categories of discrete regions of lipopigment and, secondly, phenytoin administration or a control procedure. In hippocampal neurones, phenytoin administration was accompanied by a decrease in the numbers of discrete lipopigment regions in the smaller size categories and an increase in the numbers in the larger size categories. This finding indicates the need for further investigation into the effects of phenytoin on brain regions other than the cerebellum, as intellectual deterioration may be related to chronic use of this drug.

P-298 - Studies on the seizure susceptibility in the withdrawal periods after chronic administration of phenytoin in the amygdala-kindled rats

P-298 - Studies on the seizure susceptibility in the withdrawal periods after chronic administration of phenytoin in the amygdala-kindled rats

Immunological studies on delayed hypersensitivity to phenytoin — II. The delayed skin reaction induced by BSA-phenytoin conjugate

Remarkable swelling of the foot pad was induced in guinea pigs sensitized with BSA-phenytoin by challenging with BSA-phenytoin or EA-phenytoin. Forty-eight hours after local injection of a mixture of exudate cells obtained from the abdominal cavity of sensitized guinea pigs and BSA (EA)-phenytoin, both erythema and induration developed at the injection sites in normal guinea pigs. At the sites exhibiting these skin reactions, an exudation of mononuclear leukocytes was noted. In addition, macrophages obtained from the abdominal cavity of phenytoin-sensitized animals showed a low migration index in the presence of phenytoin. When phenytoin was administered to rats (p.o.), large amounts of the compound were detected in the gingiva and there was a good correlation between the tissue and serum phenytoin concentrations. These findings indicate that the etiology of gingival hyperplasia produced by chronic administration of phenytoin may be related in some way to a delayed-type hypersensitivity induced by the drug.

Degeneration of granule cells following chronic phenytoin administration: An electron microscopic investigation of the mouse cerebellum

Fifteen male mice ( C57 Bl6J ) were fed the liquid diet “Stardit” supplemented with vitamins together with phenytoin for 8 weeks; experimental animals and controls were pair-fed. After 8 weeks of treatment, the anesthetized animals were perfused with 3.5% glutaraldehyde. Tissue samples of the cerebral cortex (area 3), cerebellum (vermis), thalamus, hypothalamus, and liver were embedded in Araldite. All phenytoin-treated animals displayed a hepatomegaly. Semithin sections and ultrastructural investigations of the cerebellar vermis showed pyknoses of granule cells and an enlargement and swelling of parallel fibers in presynaptic areas in the molecular layer. The swollen axons showed an accumulation of tubular structures which represented proliferated smooth endoplasmic reticulum. Similar tubular structures were observed in hepatocytes of experimental animals. It is proposed that phenytoin caused an induction of the microsomal system of hepatocytes and granule cells which led to a proliferation of the smooth endoplasmic reticulum. The transport of these organelles to the axon terminals of parallel fibers via the axoplasmic flow is assumed to cause a swelling of the presynaptic area. A dying-back process may then lead to pyknosis of granule cells. Chronic phenytoin administration to mice is a new experimental model of neuroaxonal dystrophy.

Damage of Purkinje cell axons following chronic phenytoin administration: an animal model of distal axonopathy.

An animal model of central distal axonopathy following chronic administration of phenytoin is described. Male C57/BL6J mice received diphenylhydantoin (DPH) in the daily diet (liquid diet 'Stardit', supplemented with vitamins) over a period of 8 weeks. Control and experimental animals were pair-fed. Twelve mice of both groups were perfused via the left ventricle with glutaraldehyde. Representative samples of the cerebral cortex (area 3), cerebellum (vermis and deep cerebellar nuclei), thalamus, hypothalamus, and liver were embedded in araldite. Semi-thin sections and electron microscopy of the cerebellar vermis revealed marked dystrophic changes in the Purkinje cell axons. The presynaptic segments of Purkinje cell axons in the deep cerebellar nuclei showed massive enlargement and swelling due to accumulation of spherical particles and tubular structures in the axoplasm. These structures represent a proliferation of the smooth endoplasmic reticulum. Identical changes were found in hepatocytes of treated animals. Because phenytoin induces hepatic microsomal enzymes, we suggest that phenytoin-related Purkinje cell damage may be produced by an induction of Purkinje cell microsomes with proliferation of the smooth endoplasmic reticulum which causes a swelling and enlargement of presynaptic segments of Purkinje cell axons in deep cerebellar nuclei. Chronic phenytoin administration to mice is a new model of phenytoin-induced encephalopathy and of distal axonopathy of cerebellar neurons.

Chronic phenytoin administration alters the metabolic profile of superficial gastrocnemius muscle fibers in dystrophic mice

Phenytoin is known to reduce neural overactivity (pseudomyotonia) affecting the hind limb musculature in C57B1 6J dystrophic ( dy 2J dy 2J ) mice. This study reports a change in the metabolic profile of superficial gastrocnemius muscle fibers from dy 2J dy 2J animals after chronic phenytoin treatment. The superficial gastrocnemius muscle region from normal mice is composed of 98% fast-twitch glycolytic muscle fibers. In dystrophic mice these fibers (FG) show increased oxidative capacity without evidence of morphologic degeneration during the first few months ex utero. Many of these fibers also store abnormally large amounts of glycogen as determined by periodic acid-Schiff histochemistry. After 104 days of phenytoin treatment, the dy 2J dy 2J FG muscle fibers showed a reduction in abnormally high oxidative capacity as monitored by succinic dehydrogenase activity; there was also a reduction of glycogen storage in a number of dy 2J dy 2J fibers. One hypothesis suggests that the increase in oxidative capacity of the dy 2J dy 2J superficial gastrocnemius muscle fibers is the expected result of overstimulation by the pseudomyotonia. Our experiments indicated that the abnormal metabolic profile observed in those fibers can be altered simply by a reduction in pseudomyotonia. These results mimic those seen after short-term denervation of the same dy 2J dy 2J muscle. After phenytoin treatment the mean dy 2J dy 2J superficial gastrocnemius muscle fiber cross-sectional area was significantly increased compared with untreated animals. Cursory examination of the degenerated deep region of this same muscle suggested that similar changes did not occur after drug treatment. This suggests that the pseudomyotonia was partially different from the factor(s) causing early degeneration of the oxidative muscle fibers in the dy 2J dy 2J animals.

Chronic phenytoin administration and the hepatic mixed function oxidase system in female rats

1. 1. The long term effects of phenytoin administration on mixed function oxidase activities and serum estradiol in female rats were examined. 2. 2. No induction of hepatic mixed function oxidases was seen until 8 days after the administration of 100 mg phenytoin/kg/day either orally or intraperitoneally. 3. 3. Maximum increase in aniline hydroxylase, aryl hydrocarbon hydroxylase (AHH) and ethylmorphine- N-deethylase activities occurred between days 8 and 16 of treatment and decreased thereafter. No induction of lung or intestinal AHH activity was observed. 4. 4. Serum levels of estradiol were significantly decreased after 16 days of phenytoin treatment. 5. 5. Maximal increases in hepatic cytochrome P-450 and cytochrome c reductase occurred after 8–16 days of treatment. Furthermore, pentobarbital sleeping times were shortest after 16 days of phenytoin administration. The activities of all enzymes after 32 days of phenytoin treatment were less than at the peak activities at 8–16 days.

Phenytoinによる歯肉増殖症の発症機序に関する免疫学的検討

Phenytoinによる歯肉増殖症の発症機序に関する免疫学的検討

Decreased benzodiazepine receptor density in rat cerebellum following neurotoxic doses of phenytoin.

The effect of acute and chronic administration of phenytoin on [3H]flunitrazepam binding was examined in the rat cerebellum. There was no significant effect of phenytoin on [3H]flunitrazepam binding in the rat cerebellum 1 and 6 h after a single i.p. injection of 200 mg/kg of phenytoin. However, after 14 days and 28 days of chronic phenytoin administration, significant decreases in [3H]flunitrazepam receptor density were observed, with no changes in apparent affinity constants in the rat cerebellum. This effect of phenytoin was dose-dependent, as lower doses of phenytoin (100 mg/kg/day) for 14 or 28 days produced no alterations in [3H]flunitrazepam binding the the rat cerebellum. Light-microscopic examination of the rat cerebellum treated with 200 mg/kg/day of phenytoin for 14 days showed degeneration of the Purkinje cells, with edematous Bergmann astrocytes. These data provide evidence for the neuronal localization of benzodiazepine receptors on cerebellar Purkinje cells.