Effect of diphenylhydantoin on insulin secretion in man

Fetal hypoxia and hyperglycemia in the formation of phenytoin-induced cleft lip and maxillary hypoplasia

OBJECTIVE

Phenytoin exposure during the first trimester of pregnancy increases the risk of maxillary hypoplasia and cleft lip. The etiology of phenytoin embryopathy is unknown. Interestingly, phenytoin is also known to induce hyperglycemia in humans as well as rats. This study uses a rat model of fetal phenytoin syndrome to examine the role of hyperoxia, hyperglycemia, and arachidonic acid deficiency in the development of cleft lip and maxillary hypoplasia.

METHODS

Pregnant rats were dosed with phenytoin during the critical period of lip development (day 11 of pregnancy) with or without supplemental oxygen, insulin, or arachidonic acid. The fetuses from all studies were examined at term.

RESULTS

The frequency of cleft lip and maxillary hypoplasia was reduced by treating dams at the time of phenytoin exposure with either increased oxygen or insulin. However, in fetuses from phenytoin-treated dams dosed with arachidonic acid, the incidence of severe lip deformities remained the same although there was an increase in normal and mildly affected fetuses. Interestingly, this occurred in embryos from hyperglycemic dams.

SIGNIFICANCE

Together, the results from these experiments suggest phenytoin-induced malformations may be a multifactorial process as malformations were not solely linked to a hyperglycemic state of the dam.

Regulation of hepatic energy metabolism by the nuclear receptor PXR

The pregnane X receptor (PXR) is a nuclear receptor that is traditionally thought to be specialized for sensing xenobiotic exposure. In concurrence with this feature PXR was originally identified to regulate drug-metabolizing enzymes and transporters. During the last ten years it has become clear that PXR harbors broader functions. Evidence obtained both in experimental animals and humans indicate that ligand-activated PXR regulates hepatic glucose and lipid metabolism and affects whole body metabolic homeostasis. Currently, the consequences of PXR activation on overall metabolic health are not yet fully understood and varying results on the effect of PXR activation or knockout on metabolic disorders and weight gain have been published in mouse models. Rifampicin and St. John's wort, the prototypical human PXR agonists, impair glucose tolerance in healthy volunteers. Chronic exposure to PXR agonists could potentially represent a risk factor for diabetes and metabolic syndrome. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

Homonymous hemianopia in nonketotic hyperglycemia is an ictal phenomenon

Extended video-EEG or ¹⁸F-fluorodeoxyglucose PET (FDG-PET) was obtained in 3 adult patients with hemianopia secondary to nonketotic hyperglycemia. Two male patients presented with left hemianopia and episodic left gaze deviation and one male patient presented with right hemianopia and visual hallucinations. None of the 3 patients had a history of seizures or known epilepsy risk factors. All 3 patients were found to have elevated serum glucose (267 mg/dL, 320 mg/dL, and 487 mg/dL) without acidosis or urine ketones. In all 3 patients, video-EEG recorded recurrent ictal discharges originating from the posterior quadrant contralateral to their hemianopia. In 2 patients, FDG-PET demonstrated corresponding focal areas of hypermetabolism. Resolution of visual symptoms was achieved with antiepileptic drugs, hydration, and tight glycemic control.

Impaired metabolism-secretion coupling in pancreatic beta-cells: role of determinants of mitochondrial ATP production

Glucose-induced insulin secretion from beta-cells is often impaired in diabetic condition and by exposure to diabetogenic pharmacological agents. In pancreatic beta-cells, intracellular glucose metabolism regulates exocytosis of insulin granules, according to metabolism-secretion coupling in which glucose-induced mitochondrial ATP production plays an essential role. Impaired glucose-induced insulin secretion often results from impaired glucose-induced ATP elevation in beta-cells. Mitochondrial ATP production is driven by the proton-motive force including mitochondrial membrane potential (DeltaPsi(m)) generated by the electron transport chain. These electrons are derived from reducing equivalents, generated in the Krebs cycle and transferred from cytosol by the shuttles. Here, roles of the determinants of mitochondrial ATP production in impaired glucose-induced insulin secretion are discussed. Cytosolic alkalization, H(+) leak in the inner membrane by uncoupler (e.g. free fatty acid exposure), decrease in the supply of electron donors including NADH and FADH(2) to the respiratory chain, and endogenous mitochondrial ROS (e.g. Na(+)/K(+)-ATPase inhibition) all reduce hyperpolarlization of DeltaPsi(m) and ATP production, causing decresed glucose-induced insulin release. The decrease in the supply of NADH and FADH(2) to the respiratory chain derives from impairments in glucose metabolism including glycolysis (e.g. MODY2 and exposure to NO) and the shuttles (e.g. diabetic state and exposure to ketone body).

Diphenylhydantoin suppresses glucose-induced insulin release by decreasing cytoplasmic H+ concentration in pancreatic islets

Diphenylhydantoin (DPH), which is clinically used in the treatment of epilepsy, inhibits glucose-induced insulin release from pancreatic islets by a mechanism that remains unknown. In the present study, DPH is shown to suppress glucose-induced insulin release concentration-dependently. In dynamic experiments, 20 microm DPH suppressed 16.7 mm glucose-induced biphasic insulin release. DPH also suppressed insulin release in the presence of 16.7 mm glucose, 200 microm diazoxide, and 30 mm K+ without affecting the intracellular Ca2+ concentration. DPH suppressed ATP content and mitochondrial membrane hyperpolarization in the presence of 16.7 mm glucose without affecting glucose utilization, glucose oxidation, and reduced nicotinamide adenine dinucleotide phosphate fluorescence. DPH increased cytoplasmic pH in the presence of high glucose, but the increase was abolished under Na+ -deprived conditions and HCO3- -deprived conditions, suggesting that Na+ and HCO3- transport across the plasma membrane are involved in the increase in cytoplasmic pH by DPH. Alkalization by adding NH4+ to the extracellular medium also suppressed insulin release, ATP content, and mitochondrial membrane hyperpolarization. Because ATP production from the mitochondrial fraction in the presence of substrates was decreased by increased pH in the medium, DPH suppresses mitochondrial ATP production by reducing the H+ gradient across mitochondrial membrane. Using permeabilized islets, the increase in pH was shown to decrease Ca2+ efficacy at a clamped concentration of ATP in the exocytotic system. Taken together, DPH inhibits glucose-induced insulin secretion not only by inhibiting mitochondrial ATP production, but also by reducing Ca2+ efficacy in the exocytotic system through its alkalizing effect on cytoplasm.

Risperidone-associated new-onset diabetes

BACKGROUND

Weight gain, and its associated complications such as the development of diabetes, is becoming increasingly recognized as an important potential side effect of the novel antipsychotic drugs.

METHODS

Two retrospective cases are described in which patients with schizophrenia developed diabetes while taking the antipsychotic medication risperidone.

RESULTS

Both patients had preexisting risk factors for diabetes and developed insulin resistance in the context of weight gain. Both cases necessitated medical intervention and one patient requires ongoing treatment with insulin.

CONCLUSIONS

Although the exact mechanism of antipsychotic induced diabetes remains obscure, weight gain appears to be a significant risk factor. Careful monitoring of weight and fasting glucoses is recommended for any patient taking novel antipsychotic medications.

Insulin-dependent diabetes mellitus presenting in children as frequent, medically unresponsive, partial seizures

Severe partial seizures may be the presenting feature of nonketotic hyperglycemia in older adults, but cases in children are rare. We report three teenagers with well-controlled epilepsy who suddenly developed intractable partial seizures poorly responsive to anticonvulsants. Blood glucose levels were measured only after several days of hospitalization for frequent seizures when mild polyuria and polydipsia were first noted. Glucose levels were high with mild ketosis and acidosis in one patient and no ketosis in two. With institution of insulin, there was prompt cessation of seizures. The patients were diagnosed as having type I insulin-dependent diabetes mellitus and require ongoing insulin treatment. Hyperglycemia should be considered in children with epilepsy who develop intractable seizures.

Phenytoin-induced hyperglycaemia may confound rat cerebroprotection models

1. The anticonvulsant phenytoin (PHT) has been used with variable success in animal models of cerebral ischaemia. Although PHT has been reported to alter glucose regulation in man, this potential effect has been largely ignored in animals. Because hyperglycaemia strongly influences the outcome of cerebral ischaemia, we sought to systematically delineate the effects of PHT on serum glucose in several rat strains. 2. We studied the PHT dose-response curve for serum PHT and glucose concentrations and several physiological variables. Phenytoin induces a significant, concentration-dependent hyperglycaemia, even in the ranges commonly used for humans and in animal models. 3. Hypothermia of several degrees was observed during PHT administration, but no hypotension or bradycardia was found. 4. Both hyperglycaemia and hypothermia must be considered when PHT is studied as a neuroprotective agent in animal models.

Drug-induced diabetes

The only drugs which commonly cause diabetes during therapeutic use are the anti-hypertensive vasodilator diazoxide, and corticosteroids in high doses such as those used to palliate intracranial tumours. Thiazide diuretics have in the past been used in higher doses than necessary to treat hypertension, and the lower doses now used probably carry only a slight risk of inducing diabetes. The risk from beta-blockers is also quite small, but there is some evidence that thiazides combined with beta-blockers may be more likely to cause diabetes than either drug alone. The combination is probably best avoided in patients with a family history of non-insulin-dependent diabetes. The effect of the low-oestrogen combined oral contraceptive pill seems to be slight, and it presents a risk only to women who have had gestational diabetes. Bodybuilders who take enormous doses of anabolic-androgens can develop impaired glucose tolerance. Several drugs, including theophylline, aspirin, isoniazid and nalidixic acid can cause transient hyperglycaemia in overdosage, but only streptozotocin, alloxan and the rodenticide Vacor are likely to cause permanent diabetes.

Focal seizures and non-ketotic hyperglycaemia

The clinical features of seven patients with non-ketotic hyperglycaemia who developed focal seizures are presented. All patients were alert except one who was mildly confused. Glucose values varied from 17.8 to 55.1 mmol/l, while calculated osmolarity values were elevated in all cases to a mild or moderate extent (299.1 to 346.5 mmol/l). In three cases diabetes mellitus was a new diagnosis. Four patients had recurrent episodes of focal seizures when glycaemic control was lost. Movement induced or kinesigenic seizures were seen in three cases and epilepsia partialis continua in one case. Seizures associated with hyperglycaemia are resistant to anticonvulsant treatment and respond best to insulin and rehydration. Focal seizures in adults may indicate diabetes mellitus.

Phenytoin-induced insulin insensitivity

Phenytoin is known to induce hyperglycaemia. The mechanism has generally been considered primarily an inhibition of insulin release. We have recently treated a patient who became hyperglycaemic on phenytoin and whose markedly increased insulin requirements suggested an insulin resistant state. Reduction of the phenytoin dose resulted in amelioration of the hyperglycaemia. In vitro studies of phenytoin in a primary culture system of adipocytes that allowed assessment of both insulin receptor binding and post-binding function showed a 57% reduction in maximum [14C]3-0-methylglucose transport in the presence of phenytoin while having no effect on maximum insulin binding. These results suggest that phenytoin administration can result in insulin insensitivity by inducing a post-binding defect in insulin action.

Effects of antiepileptic drugs on hormones

A hormone is an intrinsic substance carried via the blood to a target organ which is then functionally stimulated. Similar to extrinsically administered medications, the metabolism and function of the hormones may be altered by antiepileptic drugs (AEDs). The proposed mechanisms are (a) enhanced metabolism (natural steroids, synthetic steroids, e.g., decadron and birth control pills, thyroxine, and vitamin D3), (b) altered protein bonding (thyroxine, sex hormones), (c) impaired release into the systemic circulation (calcitonin, insulin, vitamin K clotting factors) and (d) altered end-organ effect. The AEDs most likely to interact with hormones are barbiturates, carbamazepine, and phenytoin.

Hyperglycemia presenting with occipital seizures

Seizures are common in hyperglycemia and are often the first manifestation, particularly in nonketotic hyperglycemia (NKH). Published reports emphasize partial motor seizures almost exclusively. In a 3-year period, we observed three patients in whom occipital seizures, documented by ictal EEG recording, were the initial symptom of hyperglycemia. One patient was mildly ketotic at first. Seizures were visual in two patients and visual and adversive in the third. Seizures regressed with correction of abnormal glucose levels and did not recur during follow-up of less than or equal to 1 year despite discontinuation of antiepileptic drugs (AEDs) in two. Computed tomography (CT) scans did not show correlative abnormalities. Although published reports suggest that frontal lobe structures are particularly susceptible to the epileptogenic effects of NKH, our experience indicates that in NKH epileptic foci may originate in other cortical areas, such as occipital.

Movement disorders as a manifestation of nonketotic hyperglycemia

Movement disorders are well-known presenting signs of metabolic disorders. Focal motor abnormalities may be the chief initial presentation of diabetes mellitus in the nonketotic hyperglycemic state in 6% of patients. Nonketotic hyperglycemia (NKH), in particular, may manifest any of a wide variety of movement disorders. These have been described as focal seizures, epilepsia partialis continua, myoclonus, and opsoclonia. There are descriptions of movement disorders in hyperglycemia that are similar to the coarse flapping tremor of asterixis, the posturing of paroxysmal kinetogenic choreoathetosis, and of "fencing (stance) seizures." Disorders of facial motor function including aphasia, facial muscle twitching and jerking, and disorders of muscular tone have been described. These may include hemiparesis and hemiplegias as well as increased tone, in some cases mimicking the nuchal rigidity of meningitis. The movement disorders in NKH may mimic cerebral vascular accidents, meningitis, or psychiatric disorders, as well as various types of seizures. Clinicians may be able to avoid expensive and time-consuming diagnostic evaluations to rule out NKH in patients with movement disorders. We present two patients with focal motor abnormalities associated with nonketonic hyperglycemia and review the pertinent literature.

The risk-benefit ratio of anticonvulsant drugs

The concepts underlying the notion of a risk-benefit ratio for anticonvulsant therapy have determined the development of the drug treatment of epilepsy over many years. The risk element in the ratio arises from the various possible physical and psychological adverse effects of anticonvulsant therapy; the benefit is derived from the capacity of therapy to prevent seizures and thus reduce the disadvantages which result from having epilepsy. The physical adverse effects of anticonvulsant therapy may involve many tissues and organs. The drugs tend to depress cerebral, cerebellar and brain stem function, and may slow peripheral nerve conduction. Prolonged intake may cause hypocalcaemia and osteoporosis, folate depletion, various haematological and immunological abnormalities, and overgrowth of subcutaneous and gingival tissues. Idiopathic reactions may involve the skin, lymph nodes, liver, pancreas, kidney and thyroid, and cause electrolyte disturbances, while maternal anticonvulsant intake during pregnancy may be associated with an increased incidence of fetal malformations. Local reactions may occur at drug administration sites, and anticonvulsants may interact pharmacokinetically and pharmacodynamically with co-administered drugs. The taking of anticonvulsants sometimes has undesirable psychological effects on both the patient and his or her family. Epilepsy itself often results in adverse psychological consequences which emanate from the uncertainty and insecurity that is imposed by the unpredictable occurrence of seizures, from the limitations epilepsy sets on the patient's lifestyle and employment prospects, and from unfavourable community attitudes towards the disorder. Contemporary anticonvulsant therapy is not fully effective in all patients, but to the extent that it can control seizures it may help alleviate these emotional burdens that are a result of epilepsy. The consensus of present day medical opinion is that, in the great majority of clinical situations, the benefits of anticonvulsant therapy outweigh the disadvantages. However, to provide optimal management for individual patients, the risk-benefit ratio of therapy must be repeatedly assessed at all stages of a patient's treatment, and therapeutic decisions taken in the light of the ratio as it applies to the individual.

Effect of diazoxide or glucagon on hepatic glucose production rate during extreme neonatal hypoglycaemia

The relation between hepatic glucose production rate (HGPR) and plasma concentrations of insulin and glucagon was investigated in four term neonates who had severe hypoglycaemia. The hepatic glucose production rate was less than 20% of normal for fasting term neonates in all four babies and yet insulin concentrations were never greater than 12 microU/ml; two babies had very low glucagon concentrations (less than 60 ng/l). Two further neonates with similar histories also had plasma glucagon concentrations that were also extremely low (less than 20 ng/l). A single intravenous bolus of glucagon caused a rapid rise in hepatic glucose production rate towards the normal range, which was sustained for many hours after the bolus had been given. Diazoxide given to one baby suppressed previously 'normal' insulin concentrations still further (4.2 to less than 1.6 microU/ml) and thereby restored the hepatic glucose production rate to normal. In view of the normal plasma insulin concentrations at a time when the hepatic glucose production rate was reduced, we feel that the absolute concentration of insulin may be less important than the insulin/glucagon molar ratio in the control of glucose homeostasis in this group of infants. The changing of this ratio by means of boluses of glucagon may be useful in preventing rebound hypoglycaemia, which so often occurs when dextrose infusions are reduced either accidentally or in an attempt to restart oral feeds.

Effect of long-term anticonvulsant therapy on glucose metabolism in humans

This study was undertaken to evaluate the effect of anticonvulsants on glucose metabolism in humans. Tissue sensitivity to insulin (euglycemic clamp technique) and liver microsomal enzyme activity (oral antipyrine test) were measured in six subjects with epilepsy plus type 1 diabetes mellitus. They had received anticonvulsant drugs for greater than 8 years. Three groups--type 1 diabetics, persons with epilepsy, and healthy subjects--matched for sex, and weight, served as controls. Glucose disposal rate (M) was faster in subjects on anticonvulsant therapy as compared with the corresponding control group (p less than 0.01) and in nondiabetics as compared with diabetics (p less than 0.001). Antipyrine metabolism was rapid among patients on anticonvulsants and high normal in diabetics. Liver microsomal enzyme activity and glucose metabolism were related among diabetic (r = 0.593) and nondiabetic (r = 0.649) groups, respectively. Anticonvulsants with liver microsomal enzyme-inducing properties appear to enhance insulin sensitivity. These findings may serve to understand the long-term effect of anticonvulsants on glucose metabolism in humans.

Mortality from ischaemic heart disease among patients using anticonvulsive drugs: a case-control study

Patients who use phenytoin and some other anticonvulsive drugs have been shown to have raised concentrations of plasma high density lipoprotein. As this lipoprotein is known to be inversely associated with the incidence of ischaemic heart disease the causes of death of all patients with epilepsy known to be taking anticonvulsive drugs who died during 1978-80 were studied. Of 1399 deaths of anticonvulsant users, 258 (18.4%) were caused by ischaemic heart disease. This was significantly less (p less than 0.001) than the 382 deaths from ischaemic heart disease (27.3%) observed among paired controls matched for sex, age, and date of death. The total cardiovascular mortality was also lower among patients with epilepsy than among controls (p less than 0.02) despite there being more deaths due to cerebrovascular disease among patients. The difference in mortality from ischaemic heart disease was significant for both sexes and was not accounted for by excess deaths due to any other single cause. Users of phenytoin, carbamazepine, and barbiturates (alone or in combination) showed 29% less mortality due to ischaemic heart disease than respective controls (p less than 0.001).

The effect of diphenylhydantoin on metabolic and growth hormone changes during and after exercise

Metabolic and human growth hormone responses to exercise were investigated in six normal healthy subjects on two occasions with and without an oral dose of diphenylhydantoin (500 mg). Serum diphenylhydantoin concentrations were similar in all subjects and were just below the accepted therapeutic range for epileptic patients. There was no significant difference in blood lactate, pyruvate or glucose concentrations with diphenylhydantoin. Plasma free fatty acids, and blood glycerol and total ketone concentrations were greater after exercise following diphenylhydantoin. Significantly greater concentrations of human growth hormone occurred during exercise with diphenylhydantoin. Further investigation of the mechanisms by which diphenylhydantoin alters lipolysis and human growth hormone release would be of value as these metabolic and hormonal effects could influence exercise tolerance in athletics and other pursuits.

Focal seizures and systemic metabolic disorders

Repetitive focal seizures were associated with hyperglycemia in three patients, and with hypoxia in another patient. Autopsy in one case and computed tomography (CT) scans in two patients failed to reveal relevant focal cerebral disease. Awareness of the occurrence of focal seizures in metabolic disorders, especially non-ketotic hyperglycemia, should be increased as early recognition is vital for successful treatment. Metabolic encephalopathies can cause focal seizures with or without underlying focal cerebral pathology.

[Islet cell cancer with organic hyperinsulinism. Clinical aspects, diagnosis and therapy]

About 8%-15% of the patients with organic hyperinsulinism have an islet cell carcinoma (13% in our series). In addition to a history of complaints of relatively recent onset, the patients present clinically the typical intermittent neurologic-psychiatric symptoms concurrently associated with hypoglycemia. The diagnosis is established biochemically on the basis of hypoglycemia, with inadequate incrementation of the insulin concentration subsequent to suppression and provocation tests. Elevated serum proinsulin and, in most patients, an increased insulin secretion rate are usually found after administration of agents such as glucose or leucine. Localization of the tumors is achieved by selective coeliacography as well as abdominal computerized axial tomography. The islet cell carcinoma is found most frequently in the tail of the pancreas, less frequently in the body and head of the pancreas. Metastatic spread is seen early into adjacent lymph nodes and especially in the liver. The treatment of choice is surgical resection of the tumor. Even in cases with advanced metastatic involvement, surgical intervention appears indicated. Medical treatment includes the administration of diazoxide, long-acting glucagon as well as the cytostatic agent streptozotocin. The average survival time is 30-40 months after diagnosis (in our series 79 months). Thus, the prognosis of patients with islet cell carcinoma appears relatively favorable, especially when compared with adenocarcinoma of the pancreas.

Hepatic microsomal glucose-6-phosphatase of normal and alloxan-diabetic rats. Thermotropic effects on kinetics and interaction with deoxycholate and 1-anilino-8-naphthalene sulfonate

Thermotropic effects on the kinetics of glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9) activity of hepatic microsomes from normal and alloxan-diabetic rat liver were investigated by determining V, Km and Ki (substrate inhibition) values. Influence of deoxycholate (0.1%) and 1-anilino-8-naphthalene sulfonate (2.5 mM) on the kinetics was also evaluated. 1. Substrate inhibition occurred at 0.06 M for the enzyme from normal rats and at 0.0-0.025 M for the enzyme from diabetic rats. 2. The enzyme from diabetic rats showed a transition that extended between 22.7 and 27 degrees C in the Arrhenius plot (log V vs. T-1) instead of at 19.5 degrees C. 3. Deoxycholate increased the V value of both enzymes without affecting substrate inhibition at all the temperatures but did not completely abolish the transition in the Arrhenius plot of the enzyme from diabetic rats. 4. 1-Anilino-8-naphthalene sulfonate eliminated substrate inhibition and activated the enzyme of normal rats above 27.5 degrees C by increasing both V and Km values. Below this temperature, the enzyme showed biphasic or allosteric kinetics. At low substrate concentrations it was activated as both V and Km values were increased. The enzyme from diabetic rats, on the other hand, was activated at all the temperatures and exhibited linear kinetics. 5. Binding of 1-anilino-8-naphthalene sulfonate to the microsomal fraction increased with decreasing temperature as revealed by the increase of relative fluorescence. The microsomal fraction of diabetic rats showed a more anomalous fluorescence response between 13-18 degrees C. 6. Enthalpy changes for glucose 6-phosphate binding to the inhibition site were slightly larger than binding to the active site. Calculated entropies of activation for transition state complex of glucose-6-phosphatase reaction were fairly large and negative. The free energy of activation (28-30 kcal/mol) was independent of temperature and experimental conditions. 7. In the microsomal fraction (total as well as rough), phospholipid content and fatty acid unsaturation index of phospholipids were decreased after diabetes. The level of free cholesterol remained unchanged but the molar ratio of cholesterol to phospholipid increased. The different thermal response and 1-anilino-8-naphthalene sulfonate interaction to the enzyme from diabetic rat and liver could be ascribed to the altered lipid environment of the enzyme on the endoplasmic reticulum membrane.

Influence of diphenylhydantoin on lysosomal enzyme release during bone resorption in vitro

The effect of diphenylhydantoin (DPH) on the release of lysosomal enzymes during resorption of cultured mouse calvarial bone was studied. The enzyme activities of beta-glucuronidase and beta-galactosidase in the culture medium was taken as indicators for lysosomal enzyme release. In concentrations 50 micrograms/ml or higher, DPH inhibited the release of beta-glucuronidase and beta-galactosidase in parallel with bone resorption as indicated by reduced release of 45Ca, Ca2+, Pi and hydroxyproline. The release of the cytosolic enzyme lactate dehydrogenase was not influenced by concentrations of DPH up to 50 micrograms/ml but higher concentrations caused an increased release indicating cell injury. When bone resorption was stimulated by prostaglandin E2, DPH (50 micrograms/ml) also reduced the mobilization of bone mineral and the release of beta-glucuronidase without influencing the release of lactate dehydrogenase. It is suggested that DPH by interfering with cellular release processes reduces the resorption of bone.

Hyperglycemia produced in mice by administration of acetazolamide and diphenylhydantoin

Isolated mouse islets exposed to 3mM glucose released an increased amount of insulin in the presence of acetazolamide (AZM) (10 mM) and diphenylhydantoin (DPH) (0.35 or 3.5 mM), whereas insulin secretion due to 20 mM glucose was decreased in the presence of AZM (10 mM) and DPH (0.35, 0.70 or 3.5 mM). The serum insulin concentration was increased 1 h after AZM injection, but was not significantly altered 1 h after combined administration of AZM and DPH. A moderate transient hyperglycemia was found 1 and 2 h after DPH injection (100 mg/kg b.w.) in fed mice, and a slight, transient hyperglycemic response was observed 24 h after administration of AZM (1.5 g/kg b.w.) to fed mice. A steadily increasing, marked hyperglycemia was seen in both fed and starved mice when AZM was given shortly before or after DPH. All animals subjected to this kind of treatment died within 48 h after the injections. Ketones were found in urine and serum of the hyperglycemic animals, and the hyperglycemia was abolished and the survival of the animals was prolonged by insulin administration, suggesting that ketoacidosis contributed to the death. Light microscopy disclosed degeneration and necrosis of some B-cells, and occasionally insulitis after combined treatment with AZM and DPH. Pretreatment with AZM inhibited the hyperglycemic response to p-hydroxymercuribenzoate in fed mice, but did not affect the hyperglycemic response of fed mice to D-mannoheptulose. The findings indicate that AZM and DPH, when given to mice in combination and in sufficient amount, cause impaired B-cell function with an inhibited glucose-induced insulin release and a severe, fatal hyperglycemia. The B-cell changes are believed to be due to intracellular ionic alterations.

The effect of long-term diphenylhydantoin therapy on glucose tolerance and insulin secretion: a controlled trial

The influence of long-term administration of diphenylhydantoin (DPH) on glucose tolerance and insulin secretion was studied in a random controlled trial in non-epileptic patients receiving the drug for 2 years following recovery from myocardial infarction. While receiving DPH, insulin response to glucose was less than that in the control group, both in absolute terms and when related to the blood glucose level. Despite this, glucose tolerance did not differ from the control group. One month after cessation of DPH, the plasma insulin response had returned to the levels found in the control group, and glucose tolerance had improved to be significantly better than that found in the control group. Thus, the tendency of DPH to impair the insulin response to glucose has been confirmed in this controlled study. However, this does not result in significantly impaired glucose tolerance; it is suggested that the decreased insulin secretion is accompanied by improved insulin sensitivity.

The effects of toxic and non-toxic serum phenytoin levels on carbohydrate tolerance and insulin levels

The effect of toxic and non-toxic phenytoin levels on carobhydrate tolerance and insulin levels was studied in 18 patients with epilepsy and 17 control subjects. Toxic levels were defined as a serum level greater than 20 microgram/ml. Toxic levels occurred in 11 patients and nontoxic levels in seven patients. Blood glucose and insulin levels were measured at 30-min intervals for a period of 3 h following the ingestion of 50 g glucose. Blood glucose levels were measured by the ferricyanide method, and serum insulin levels by immunoassay of insulin with insulin antibody precipitate. Serum phenytoin levels were measured by gas liquid chromatography. The insulin profiles were the same for all three groups, but there was a significant delay in reaching peak glucose concentrations in patients with toxic levels of phenytoin. It was therefore confirmed that non-toxic levels of phenytoin do not affect carbohydrate tolerance or insulin levels when phenytoin is used in the routine treatement of epilepsy, and it has also been shown that toxic levels of phenytoin do not affect carbohydrate tolerance when the high levels are detected at an early stage.

Assessment of diabetogenic drug activity in the rat: 5,5-diphenyl-2-thiohydantoin

The diabetogenic activity of 5,5-diphenyl-2-thiohydantoin (DPTH) via oral administration was assessed in both normal and streptozotocin diabetic rats. Rats were fed powdered chow diet with and without 0.1% (w/w) DPTH. Food consumption and body weight were recorded every other day; whole blood glucose concentrations were determined at the start of the study and at the midpoint. At sacrifice, liver and pancreas were excised and blood samples were collected. Protein and lipid levels were determined in liver; insulin in pancreas; and glucose, insulin, and lipid in blood. DPTH treatment caused decreased food consumption and body weight gain. The drug dose, calculated from the food consumption data, was 76.5 mg/kg/day for the normal rats and 107 mg/kg/day for the diabetic rats. DPTH increased liver weight and liver lipid content in both normal and diabetic rats, and markedly lowered serum triglyceride concentration in normal rats but not in diabetic rats. Serum fatty acid concentration was not altered by DPTH. DPTH produced a significant elevation of blood glucose concentration of the diabetic rats that was not, however, correlated with altered pancreatic insulin concentration. In vitro, DPTH infusion inhibited insulin secretion by the perfused pancreas.

Secretion of human growth hormone and insulin in levodopa test during carbamazepine therapy

The effect of oral administration of carbamazepine for a period of three weeks on serum growth hormone, serum immunoreactive insulin, and blood glucose was studied in healthy volunteers using a levodopa stimulation test. Serum growth hormone rose significantly from 1.3 +/- 0.3 ng/ml to 16.3 +/- 3.4 ng/ml in 60 minutes after levodopa administration (1000 mg orally) before carbamazepine, and almost similarly from 2.3 +/- 0.5 ng/ml to 15.1 +/- 4.0 ng/ml after carbamazepine during the test. No consistent changes were found in blood glucose concentrations in the levodopa test before or after carbamazepine. Levels of serum IRI were also normal throughout the test and no impairment in insulin secretion was seen during carbamazepine treatment. It is suggested that carbamazepine does not lead to an altered anterior pituitary function or to an impairment in insulin secretion. This is of advantage when growing children or subjects with a risk factor for diabetes are treated.

Effect of diphenylhydantoin on patterns of insulin secretion in obese subjects

The effect of short-term treatment with diphenylhydantoin (DPH) on the insulin secretion patterns during OGTT and on the daily insulin profile was studied in obese patients. DPH treatment for 3 days with a dose of 300 mg/die (100 mg, 3 times daily) significantly decreased the insulin release after glucose ingestion, but did not alter the basal insulin level. No effect on the fasting glucose concentration as well as on the glucose profiles during OGTT was observed after short-term DPH treatment. A smaller decrease of plasma free fatty acid concentration during OGTT performed after DPH administration confirmed the inhibitory effect of the drug on insulin release. Short-term DPH treatment was also shown to decrease markedly the postpradial insulin release in obese patients. No difference was noted between plasma 11-OHCS and serum HGH concentrations during OGTT before and after DPH treatment. The possible therapeutic role of DPH in obesity is discussed.

Morphologic effects of diazoxide and diphenylhydantoin on insulin secretion and biosynthesis in B cells of mice

The action of diazoxide, an antidiuretic agent, and diphenylhydantoin, an antiepileptic (DPH), both with strong hyperglycemic side effects on the pancreatic B cells, was examined by electron microscopy and cytochemistry, with the following findings. 1. Effects on secretory apparatus: the severe hyperglycemic syndrome following a single injection of diazoxide (200 mg/kg) or DPH (150 mg/kg) did not change the granularity of the B cells. Ultrastructurally a marked increase of lysosomal digestion of secretory granules (crinophagy) was observed in almost all B cells. Crinophagy may be regarded as a result of an impaired discharge of secretory granules during simultaneous maintenance of biosynthesis. It is also possible that changes of the electrophysical properties of the granule surfaces may play an additional role in crinophagy. 2. Effect on synthesizing apparatus: in B cells subtotally degranulated by the injection of anti-insulin serum (AIS), regranulation occurred more rapidly after the additional administration of diazoxide or DPH than without these compounds. This fact may imply that, under the hyperglycemic conditions tested, diazoxide or DPH have no effect on the synthesizing capacity of the B cells.

Neurologic manifestations of diabetic comas: correlation with biochemical alterations in the brain

Coma and other neurologic abnormalities are present in patients with either diabetic ketoacidosis (DKA) or nonketotic coma (NKC), and the cause of such phenomena are not known. Patients with NKC also manifest seizures and focal neurologic changes. Treatment of diabetic coma with insulin may induce cerebral edema by as yet undefined mechanism(s). In patients with DKA, cerebral oxygen utilization is impaired, and there is hyperviscosity of the blood. A substantial part of the brain's energy source is derived from ketones, which in themselves can depress sensorium. Extracellular hyperosomolality is present, which may also contribute to the genesis of coma. In addition, most ketoacidotic patients have associated medical conditions, which may further impair consciousness. Biochemical changes in the brains of animals with DKA include impairment of both phosphofructokinase activity and pyruvate oxidation, and accumulation of citrate. The net effect upon sensorium in ketoacidotic patients probably represents the interaction of most of the above factors and differs markedly among individuals. Patients with NKC manifest not only depression of sensorium, but also focal motor seizures, hemiparesis, and other neurologic changes, such as aphasia, hypereflexia, sensory defects, autonomic changes, and brainstem dysfunction. Most of the aforementioned changes revert to normal after correction of hyperosomolality. Gamma amino butyric acid, which has been shown to elevate the seizure threshold, is normal in brains of ketoacidotic animals, but may be low in nonketotic coma. Also, hyperosomolality per se may produce seizures. Cerebral edema may complicate the treatment of either DKA or NKC. The available experimental evidence suggests that many of the commonly held theories for the production of such brain swelling probably do not occur. There is no breakdown of the sodium pump, sorbitol or fructose do not accumulate in brain, and brain glucose is only about 25 percent of that in plasma; Cerebral edema is probably produced largely by a direct action of insulin on brain at a time when plasma glucose is approaching normal values. Cerebral edema can thus theoretically be avoided by stopping insulin when plasma glucose has been lowered to values approaching normal.

Somatostatin blockade of acute and chronic stimuli of the endocrine pancreas and the consequences of this blockade on glucose homeostasis

The nature and extent of somatostatin-induced inhibition of pancreatic endocrine secretion were studied by administration of a number of stimuli of either glucagon or insulin to over night fasted baboons with and without an infusion of linear somatostatin. The stimuli for acute-phase insulin release were intravenous pulses of glucose, tolbutamide, isoproterenol, and secretin. When given 15 min after the start of a somatostatin infusion, these agents were essentially unable to stimulate insulin secretion. Chronic insulin secretion was stimulated by infusions of either glucose or glucagon. Within 10 min of the start of a super-imposed infusion of somatostatin, insulin levels fell to less than 40 percent of prestimulus control and remained suppressed for the duration of the somatostatin infusion. Stimulation of glucagon secretion by insulin-induced hypoglycemia was also blocked by somatostatin. Plasma glucose decreased during somatostatin infusions except when superimposed upon an infusion of glucagon. Somatostatin had no effect on glucose production in a rat liver slice preparation. We conclude: (a) Somatostatin is a potent and so far universally effective inhibitor of both acute and chronic phases of stimulated insulin and glucagon secretion (b) The inhibitory effect is quickly reversible and the pattern of recovery of secretion is appropriate to prevailing signals; (c) Present evidence suggests that the effect of somatostatin on blood glucose is mediated through its effect on blood glucagon; (d) In the overnight-fasted baboon both in the basal state and 45 min into a 4-mg/kg-min glucose infusion, a somatostatin-induced fall in serum insulin levels appears to be unable to prevent a decrease in hepatic glucose production.

Idiosyncratic reactions to the antiepileptic drugs

Idiosyncratic drug reactions can be defined as those adverse drug effects caused by genetically determined enzymatic abnormalities. For the clinician, however, this definition is too limited, and other rare and unusual adverse reactions to the antiepileptic drugs are discussed, including drug interactions, drug allergies, and organ toxicities, as well as true idiosyncrasies. Responsibility for initial recognition and later diagnosis of these reactions falls heavily upon the clinician. In addition to discussing the more common or serious rare reactions, the epidemiology and general mechanisms underlying the reactions are discussed. Treatment involves drug withdrawal, plus general supportive and specific therapy determined by the type and severity of the individual reaction. If primum non nocere should guide the treatment in general, then secundum non plus nocere should guide the treatment of adverse drug reactions.