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PubMed1994

Purification and characterization of cytochrome P450 3A enzyme from hepatic microsomes of untreated doguera baboons.

We isolated a form of cytochrome P450 (P450) from hepatic microsomes of untreated doguera baboons. The final preparation (referred to as P450 BLa) was apparently homogenous, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The estimated minimum molecular weight of P450 BLa was 50 kDa. The N-terminal amino acid sequence of P450 BLa (identified 10 residues) was identical with that of P450 3A8 purified from cynomolgus monkeys. This protein was cross-reactive with antibodies raised against P450 3A4 and P450 CMLc which were P450 3A enzymes purified from hepatic microsomes of humans and cynomolgus monkeys, respectively. P450 BLa was capable of catalyzing testosterone 6 beta-hydroxylation and zonisamide reduction. P450 BLa antibody inhibited the activity of testosterone 6 beta-hydroxylase, but not the activities of testosterone 16 alpha- and 16 beta-hydroxylases in liver microsomes of doguera baboons. From these lines of evidence we conclude that P450 BLa can be classified as part of the P450 3A subfamily and acts as a constitutive testosterone 6 beta-hydroxylase in hepatic microsomes of doguera baboons.

Amino Acid Sequence↗
PubMed1996

Population pharmacokinetics of phenytoin in Japanese patients with epilepsy: analysis with a dose-dependent clearance model.

The population pharmacokinetic parameters of phenytoin were estimated using routine therapeutic drug monitoring data from 116 epileptic patients. The 531 serum concentration values at steady-state after repetitive oral administration were analyzed using a nonlinear mixed effects model (NONMEM) program designed for estimation of population pharmacokinetic parameters. A one-compartment model with dose-dependent clearance was used for the pharmacokinetic analysis of phenytoin. The volume of distribution (V) was estimated to be 1.231/kg in a typical 42-kg patient, assuming that the bioavailability of orally administered phenytoin is 100%. The maximal elimination rate (V(max)) and the Michaelis-Menten constant (K(m)) were 9.80 mg/d/kg and 9.19 micrograms/ml, respectively. The parameter of power function of weight to adjust V and V(max) was estimated to be 0.463. In addition, K(m) for phenytoin appeared to be 16% increased in patients receiving zonisamide concurrently. The population pharmacokinetic parameters of phenytoin will be useful for designing dosage regimens in epileptic patients.

Adolescent↗
PubMed2006

Serum aminotransferase activity as a predictor for estimation of total clearance of hepatically metabolized drugs in rats with acute hepatic failure.

The levels of serum aminotransferase activity, including aspartate aminotransferase (AST), in rats with acute hepatic failure at 24 h after an oral administration of CCl4 (0.01-0.5 ml/kg) were about 15-50 times higher (up to nearly 5000 IU/l) than those of vehicle control rats (about 85 IU/l). The values of total clearance (CL(tot)) of cyclosporin A, doxorubicin, tacrolimus and zonisamide in the CCl4-treated rats were decreased to about 1/2-1/3 of those in control rats. There were good correlations between AST activity and hepatic intrinsic clearance (CL(int)) (r=0.733-0.949) for the above drugs, as well as for chlorzoxazone, caffeine, lidocaine and tolbutamide after the intravenous administration of each drug in rats with acute hepatic failure. However, the slope of the linear regression equation, i.e., the ratio of decrease of CL(int) against increase of AST activity, differed markedly among these drugs. We found that there is a good correlation (r=0.953) between the values of the slope and the CL(int) of normal rats for these drugs, except for caffeine. In summary, the linear regression equation enables us to predict the decrease of CL(tot) in rats with acute hepatic failure to be predicted from the increase in serum AST activity. This approach may be useful as a guide for the dose modification of drugs for patients with acute hepatic failure.

Animals↗
PubMed2006

Development of dosage design of hepatic metabolizing drugs using serum albumin level in chronic hepatic failure.

We have previously reported good correlations among serum aminotransferase (AST) activity, metabolic enzyme activity of CYPs, and total clearance (CL(tot)) of probe drugs in rats with acute hepatic failure induced by CCl4. In this study, we searched for new biochemical indicators that correlate with hepatic function and tried to simulate appropriate drug dosage in chronic hepatic failure. Model rats were prepared by administration of CCl4 (1 ml/kg, s.c., 3 times/week) and used at 48 h after the last administration. Serum albumin concentration was time-dependently decreased and correlated well with 3 major biologic determinants of drug clearance, hepatic blood flow (HBF), intrinsic clearance (CL(int)), and the unbound fraction of drugs in plasma (fp) after intravenous administration of cyclophosphamide, tolbutamide, zonisamide, and chlorzoxazone (as probe drugs for low hepatic extraction) and propranolol and lidocaine (as high-hepatic extraction drugs). By calculating these parameters based on prediction equations by the level of albumin, CL(tot) was obtained. As a result of having evaluated this model using administration of cyclosporin, there was a statistically significant relationship between predicted CL(tot) and observed CL(tot). In conclusion, the value of serum albumin level is a useful parameter that correlates well with chronic hepatic function. We have shown that this quantitative administering design using serum albumin level can predict appropriate dosages of hepatic metabolizing drugs in chronic hepatic failure.

Animals↗
PubMed2003

Effects of concomitant antiepileptic drugs on serum carbamazepine concentration in epileptic patients: quantitative analysis based on extracellular water volume as a transforming factor.

The effects of concomitant antiepileptic drugs on the serum carbamazepine concentration (C1) were analyzed quantitatively. Primidone (PRM), phenobarbital (PB), phenytoin (PHT), valproic acid (VPA), zonisamide (ZNS), clonazepam (CZP), and ethosuximide (ETS) were coadministered with carbamazepine (CBZ). Routine therapeutic drug monitoring data, obtained from epileptic patients who were treated with the repetitive oral administration of CBZ fine granules/tablets, were used for the analysis. A total of 119 patients were administered CBZ alone, and 91, 39, 19, and 6 patients were coadministered one, two, three, and more than four different antiepileptic drugs, respectively. Using the data obtained from the patients administered CBZ alone, Ct could be expressed approximately as a function of the daily dose per extracellular water volume (D/VECW) as Ct = A(D/VECW)B (A, B: parameter). By comparing the regression line on log Ct vs. log(D/VECW) for CBZ alone with that for CBZ plus another concomitant drug, Ct was thus found to be affected at each definite ratio by PB and PHT, but not by VPA and ZNS. We postulated a model showing that Ct is affected by each concomitant antiepileptic drug i at each definite ratio. We defined the parameter Ri(i = 1, 2, ..., 7) representing the effect of each concomitant antiepileptic drug on Ct. A linear polynomial expression, in which both members of this model are converted into common logarithms, was used for a multiple regression analysis. The analysis clarified that PB and PHT lowered Ct to 0.770 and 0.710 the value of CBZ alone, respectively. On the other hand, VPA and ZNS did not affect Ct. The number of patients coadministered PRM, CZP, and/or ETS was not sufficient to detect the effect on Ct based on a test of significance. In the case of the addition or discontinuation of concomitant antiepileptic drugs in the same patient, the estimated Ct values were calculated using the value of each Ri and compared with the measured Ct values. Both values were in good agreement, and thus our results appear valid.

Adolescent↗
PubMed2004

[Influence of coadministered antiepileptic drugs on serum antiepileptic drug concentrations in epileptic patients -quantitative analysis based on suitable transforming factor].

We conducted a study to clarify the most suitable transforming factor related to the daily dose of antiepileptic drugs (D) providing a steady-state serum concentration (C(t)) and analyzed the influences of the concomitant use of antiepileptic drugs on C(t) quantitatively. Data obtained by routine therapeutic drug monitoring from epileptic patients treated with the multiple oral administration of valproic acid (VPA), carbamazepine (CBZ), zonisamide (ZNS), phenobarbital (PB), and phenytoin (PHT) were used for the analysis. Employing the ideal body weight or the extracellular water volume as a transforming factor, allowed the level/dose (L/D) ratio to be independent of the patient's age and gender for monotherapy with VPA or CBZ, ZNS, PB, and PHT, respectively. Each C(t) was revealed to be dependent on only one variable in terms of the transformed daily dose (D'). C(t) was proportional to the power function of D' for VPA and CBZ and was linearly proportional to D' for ZNS and PB. The L/D ratio is expressed as a linear function of C(t) for PHT. For a detailed analysis of the influences of the coadministered antiepileptic drugs, we defined the parameter as an alteration ratio, representing the influence of each antiepileptic drug on the C(t) of VPA and CBZ alone, and on the L/D ratio of ZNS and PB alone, respectively. A model based on the assumption that each value of an alteration ratio was independent from one other and multiplicative for VPA, CBZ, and ZNS, and that the coadministered drug inhibited the drug-metabolizing enzyme competitively for PB, was adopted. The Michaelis-Menten kinetic model was adopted for PHT. The analysis clarified that CBZ, PB, and PHT significantly lowered (P<0.05) C(t) to 0.81, 0.88, and 0.83 compared with the value of VPA alone, that PB and PHT significantly lowered C(t) to 0.77 and 0.71 compared with the value of CBZ alone, and that VPA, CBZ, PB, and PHT significantly lowered the L/D ratio of ZNS alone to 0.87, 0.85, 0.85, and 0.80, respectively. VPA, CBZ, and PHT significantly increased (P<0.05) the L/D ratio of PB to 1.47, 1.18, and 1.19, respectively. The daily PHT dose was decreased to 0.89, 0.91, 0.90, and 0.84 the dose of PHT alone to maintain C(t) in the therapeutic range when VPA, CBZ, ZNS, and PB were coadministered, respectively. In the case of the addition or discontinuance of concomitant treatment with antiepileptic drugs in the same patient, the estimated C(t) values were calculated using the value of each alteration ratio and compared with the measured ones. Each mean of prediction error was about 20%. Our results appear valid and these alteration ratios should be available for clinical use.

Administration, Oral↗
PubMed2003

A case of adversive seizures induced by hyperventilation.

We report a case of adversive seizures featuring neck rotation and conjugate deviation induced by the hyperventilation maneuver. At the age of 6 years the patient suffered from conjugate deviation to the left. She herself felt no symptoms other than oculomotor symptoms. Hyperventilation induced an adversive seizure and ictal EEG showed sharp waves in the right frontal, central, and parietal areas. No brain image showed abnormal findings. Zonisamide completely attenuated her attacks. It is well known that hyperventilation induces absence seizures, and it has been reported that hyperventilation can induce complex partial seizures. However, no previous reports have described patients diagnosed as having adversive seizures with conjugate deviation induced by hyperventilation. We report the present case because, although its epileptogenesis is unknown, the patient is a rare case not only clinically but also electrophysiologically.

Child↗
PubMed2002

Newer GABAergic agents for pharmacotherapy of infantile spasms.

Infantile spasms is an age-specific epileptic syndrome in infants and young children. Although the exact mechanism is unknown, adrenocorticotrophic hormone (ACTH) has been the mainstay for the therapeutic management of infantile spasms and other developmental epilepsies. Clinical benefits of ACTH in infantile spasms could partially relate to its stimulatory effects on the release of adrenocorticosteroids and neurosteroids. Glucocorticoids, pyridoxine and ketogenic diet therapy have all been used for the treatment of refractory infantile spasms. Recent studies indicate that several newer anticonvulsant agents, which are positive allosteric modulators of GABA(A) receptors, are as effective as ACTH in acutely controlling infantile spasms. The efficacy of agents that enhance GABA-mediated inhibition (such as vigabatrin and benzodiazepines) for rapid and complete abolition of infantile spasms has been demonstrated in several clinical studies. Ganaxolone, a novel neuroactive steroid has, however, demonstrated outstanding efficacy and better tolerability in children with intractable infantile spasms. Zonisamide, topiramate, deoxycorticosterone and neurosteroids are emerging as effective treatment approaches. These new antiepileptic drugs represent a potential nonhormonal approach for infantile spasms, but additional studies are needed to verify their efficacy and tolerability. Future studies will hopefully identify rational antiseizure drugs that not only control infantile spasms but also abrogate its risk on the development of the brain.

Adrenocorticotropic Hormone↗
PubMed2005

Drug-induced weight gain.

Drug-induced weight gain is a serious side effect of many commonly used drugs leading to noncompliance with therapy and to exacerbation of comorbid conditions related to obesity. Improved glycemic control achieved by insulin, insulin secretagogues or thiazolidinedione therapy is generally accompanied by weight gain. It is a problematic side effect of therapy due to the known deleterious effect of weight gain on glucose control, increased blood pressure and worsening lipid profile. Weight gain may be lessened or prevented by adherence to diet and exercise or combination therapy with metformin. Weight gain is also common in psychotropic therapy. The atypical antipsychotic drugs (clozapine, olanzepine, risperidone and quetiapine) are known to cause marked weight gain. Antidepressants such as amitriptyline, mirtazapine and some serotonin reuptake inhibitors (SSRIs) also may promote appreciable weight gain that cannot be explained solely by improvement in depressive symptoms. The same phenomenon is observed with mood stabilizers such as lithium, valproic acid and carbamazepine. Antiepileptic drugs (AEDs) that promote weight gain include valproate, carbamazepine and gabapentin. Lamotrigine is an AED that is weight-neutral, while topiramate and zonisamide may induce weight loss.

Adrenergic beta-Antagonists↗
PubMed1999

Estrogen supplementation for bone dematuration in young epileptic man treated with anticonvulsant therapy; a case report.

We encountered a young man treated with anticonvulsant therapy who had greatly reduced bone mineral density. An 18-year-old man was admitted to our hospital for shoulder pain and further evaluation of decreased bone mineral density. He had been treated with anticonvulsants, including phenytoin, phenobarbital, valproic acid and zonisamide for seizures. Although testosterone was found within the normal range for adult men, the serum estrogen concentration was below the detection limit (< 10 pg/ml) and his wrist epiphyses were not yet closed. After 10 months of treatment with the conjugated estrogen, both his height and weight showed improvement, while his bone mineral density and bone age were increased. These findings suggested that estrogen therapy had a significant effect on his skeletal growth and bone maturation in man. This is the first report showing the beneficial effect of estrogen supplementation in an epileptic man receiving treatment with anticonvulsants.

Adult↗
PubMed2004

Therapeutic drug monitoring of old and newer anti-epileptic drugs.

The aim of the present paper is to provide information concerning the setting up and interpretation of therapeutic drug monitoring (TDM) for anti-epileptic drugs. The potential value of TDM for these drugs (including carbamazepine, clobazam, clonazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, pheneturide, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide) is discussed in relation to their mode of action, drug interactions and their pharmacokinetic properties. The review is based upon available literature data and on observations from our clinical practice. Up until approximately 15 years ago anti-epileptic therapeutics were restricted to a very few drugs that were developed in the first half of the 20th century. Unfortunately, many patients were refractory to these drugs and a new generation of drugs has been developed, mostly as add-on therapy. Although the efficacy of the newer drugs is no better, there is an apparent improvement in drug tolerance, combined with a diminished potential for adverse drug interactions. All new anticonvulsant drugs have undergone extensive clinical studies, but information on the relationship between plasma concentrations and effects is scarce for many of these drugs. Wide ranges in concentrations have been published for seizure control and toxicity. Few studies have been undertaken to establish the concentration-effect relationship. This review shows that TDM may be helpful for a number of these newer drugs.

Anticonvulsants↗
PubMed2000

New anti-epileptic drugs for the 21st century.

Prior to 1993, there were only six major drugs available in the US for the treatment of patients with epilepsy. These included phenobarbital (PB), phenytoin (PHT), carbamazepine (CBZ), primidone (PRIM), valproic acid/sodium valproate (VPA) and ethosuximide (ESX). Of these drugs, VPA has the broadest spectrum of activity and ESX the most limited. Despite these six agents, as well as several secondary drugs, it is estimated that over 30% of patients have inadequate seizure control, while others, whose disease is adequately controlled, suffer from bothersome adverse events (AEs). Since 1993, ten new drugs have entered the worldwide market (not all in the US). Those released include felbamate (FBM), gabapentin (GBP), lamotrigine (LTG), topiramate (TPM), tiagabine (TGB), oxcarbazepine (OXC), levetiracetam (LVT), zonisamide (ZNS), clobazam (CLB) and vigabatrin (VGB). The purpose of this article is to review each of the above drugs, looking at efficacy, safety, tolerability and where they may play a role in the current treatment of epilepsy.

Animals↗
PubMed2003

Infantile spasms.

Infantile spasms is a catastrophic form of epilepsy found only in infants and young toddlers, with the peak incidence between 4 - 7 months of age. Estimated prevalence is 1 in 2000 - 6000 live births. There are many causes of infantile spasms, including tuberous sclerosis, hypoxic-ischaemic injury, congenital infectious diseases, inborn errors of metabolism, malformations of cortical development, genetic syndromes such as Aicardi's syndrome and chromosomal abnormalities. A small percentage of patients have idiopathic infantile spasms, with normal growth and development prior to the onset of infantile spasms and no known aetiology. Because of the poor prognosis of infantile spasms, treatment is usually aggressive and immediate, with the hopes of altering the natural history of the disease. The majority of patients with infantile spasms have a poor prognosis with intractable epilepsy, severe developmental delays and/or significant cognitive impairments. Of all patients with infantile spasms, 70 - 90% have mental retardation. Furthermore, 20 - 50% of patients with infantile spasms develop Lennox-Gastaut syndrome with multiple seizure types, cognitive impairments and a markedly abnormal electroencephalogram, arguably one of the most difficult epilepsy syndromes to treat. Infantile spasms are resistant to most of the standard antiepileptic drugs. Adrenocorticotropin hormone (ACTH) or oral steroids result in a significant reduction of seizures, as well as an improvement in the electroencephalogram. Some studies have indicated that infants treated with ACTH within the first month of onset have a more favourable prognosis. Vigabatrin has also been shown to be effective in the treatment, although it is not yet FDA-approved in the US. Valproate has also been used in the treatment of infantile spasms, with an efficacy of approximately 25 - 40%. However, in the very young infant, it does carry a high risk of fatal hepatotoxicity. Surgical resection may be the treatment of choice for those infants with focal cortical dysplasia and intractable infantile spasms. Emerging therapeutic possibilities include topiramate, felbamate, lamotrigine, zonisamide and perhaps levetiracetam. With the advancements in molecular biology, genetics and neuroimaging, there is the hope of novel therapies in the future.

Anti-Inflammatory Agents↗
PubMed2004

Behavioural effects of the newer antiepileptic drugs: an update.

The negative and positive effects of the nine newer antiepileptic drugs that have received a product licence in the UK or in the US are reviewed. The importance of avoiding misinterpretation of the data because of confounding factors such as alternative psychosis, the release phenomenon or drug interactions is emphasised. Vigabatrin has been associated with both psychosis and depression. Due to the concentric visual field defects that may occur with vigabatrin, its use is now limited, although it remains the drug of choice for infantile spasms. Lamotrigine seems to be largely associated with improvement rather than deterioration of mood and behaviour. It may have a role in treating affective disorder. Gabapentin probably has relatively little effect on behaviour but may exacerbate behavioural problems in some children with pre-existing difficulties. Topiramate may precipitate both psychosis and depression, but these are less likely to occur if the currently recommended lower starting doses, escalation rates and target doses are used. The data for tiagabine are limited, but there is no clear evidence for psychosis or depression being caused by this drug. Oxcarbazepine may be of value in treating mood disorder, but the information is very limited. There are few reports of behavioural disturbances with levetiracetam, but the data suggest that there is no significant increase in psychosis or depression. There are some reports of psychosis and other behavioural disturbances with felbamate, but the use of this drug is limited by the serious adverse effects of hepatotoxicity and aplastic anaemia. There is some evidence for psychosis with zonisamide, but there is also a suggestion that this drug may be of benefit in treating psychiatric disorders. Careful individual assessment of each patient should enable the clinician to determine whether the medication or some other factor is responsible for any behavioural disturbance.

Anticonvulsants↗
PubMed2005

Bipolar mixed states and their treatment.

Bipolar mixed states remain a nosologic dilemma, diagnostic challenge and neglected area of therapeutic research. While the outcome of mixed states is generally poorer than that of pure manic and depressive episodes, little is known about how to treat such a condition. The aim of this report is to investigate the results of clinical trials, including mixed bipolar patients, in order to provide some hints on the efficacy of the different compounds on this specific subpopulation. As a result of this research, it becomes clear that only dysphoric mania has been reasonably addressed in clinical trials, and unfortunately very little is known about the treatment of other mixed states. There is some indirect evidence that mixed mania may be more responsive to anticonvulsants than to lithium. Divalproate, and to a lesser extent carbamazepine, may be used either in monotherapy or as adjuncts to lithium. Use of other anticonvulsants, such as gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate or zonisamide is not yet supported by controlled data. The use of antidepressants is largely discouraged, as they may worsen this condition. On the other hand, atypical antipsychotics may be effective and safe either in monotherapy or in combination with lithium or valproate. Further research is urgently needed in this neglected area of psychiatry.

Anticonvulsants↗
PubMed2003

New migraine preventive options: an update with pathophysiological considerations.

BACKGROUND: The pharmacological treatment of migraine may be acute or preventive. Frequent, severe and long-lasting migraine attacks require prophylaxis. Multiple threads of research over the last 15 years have led to the concept that migraine is generated from a hyperexcitable brain. A variety of causes for hyperexcitability of the brain in migraine have been suggested. These causes include low cerebral magnesium levels, mitochondrial abnormalities, dysfunctions related to increased nitric oxide or the existence of a P/Q type calcium channelopathy. The better knowledge about migraine pathophisiology led us to discuss new treatment options. OBJECTIVES: The aim of the present study is to present an evidence-based review of some new drugs or some agents that even though available for a long time, are not frequently used. METHODS/RESULTS: We present a review of anticonvulsants with various mechanisms of action such as lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam and zonisamide. We also review natural products, like riboflavin and magnesium, botulinum toxin A, a specific CGRP antagonist and the anti-asthma medication montelukast, with pathophysiological discussion. CONCLUSIONS: We aimed to present an update of newer or less frequently used preventive migraine therapies, drugs that might reduce the burden and the costs of a disease that should be considered as a public health problem all around the world.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2004

Natural antioxidants may prevent posttraumatic epilepsy: a proposal based on experimental animal studies.

Head injury or hemorrhagic cortical infarction results in extravasation of blood and breakdown of red blood cells and hemoglobin. Iron liberated from hemoglobin, and hemoglobin itself, are associated with the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS have been demonstrated to be involved in the mechanism of seizures induced by iron ions in the rat brain, an experimental animal model for posttraumatic epilepsy (PTE). ROS are responsible for the induction for peroxidation of neural lipids, i.e., an injury of neuronal membranes, and also could induce disorders in the excitatory and inhibitory neurotransmitters. Antioxidants, such as a phosphate diester of vitamin E and C (EPC-K1) and antiepileptic zonisamide, have been known to prevent the epileptogenic focus formation, or to attenuate seizure activities in the iron-injected rat brain. Natural antioxidants, such as alpha-tocopherol, and condensed tannins, including (-)-epigallocatechin and (-)-epigallocatechin-3-O-gallate, adenosine and its derivative, melatonin, uyaku (Lindera Strychnifolia), fermented papaya preparations, Gastrodia elata BI., and Guilingji, have been demonstrated to scavenge ROS and/or RNS and to be prophylactic for the occurrence of epileptic discharge in the iron-injected rat brain.

Animals↗
PubMed2000

Adverse reactions to new anticonvulsant drugs.

A lack of systematic pharmacoepidemiological studies investigating adverse drug reactions (ADRs) to anticonvulsants makes it difficult to assess accurately the incidence of anticonvulsant-related ADRs. Most of the available information in this regard stems from clinical trial experience, case reports and postmarketing surveillance, sources that are not, by any means, structured to provide precise data on adverse event epidemiology. For various ethical, statistical and logistical reasons, the organisation of structured clinical trials that are likely to provide substantial data on ADRs is extremely difficult. This review concentrates on current literature concerning serious and life-threatening ADRs. As with the older anticonvulsants, the majority of ADRs to newer anticonvulsants are CNS-related, although there are several that are apparently unique to some of these new drugs. Gabapentin has been reported to cause aggravation of seizures, movement disorders and psychiatric disturbances. Felbamate should only be prescribed under close medical supervision because of aplastic anaemia and hepatotoxicity. Lamotrigine causes hypersensitivity reactions that range from simple morbilliform rashes to multi-organ failure. Psychiatric ADRs and deterioration of seizure control have also been reported with lamotrigine treatment. Oxcarbazepine has a safety profile similar to that of carbamazepine. Hyponatraemia associated with oxcarbazepine is also a problem; however, it is less likely to cause rash than carbamazepine. Nonconvulsive status epilepticus has been reported frequently with tiagabine, although there are insufficient data at present to identify risk factors for this ADR. Topiramate frequently causes cognitive ADRs and, in addition, also appears to cause word-finding difficulties, renal calculi and bodyweight loss. Vigabatrin has been reported to cause seizure aggravation, especially in myoclonic seizures. There have been rare reports of other neurological ADRs to vigabatrin, such as encephalopathy, aphasia and motor disturbances. Vigabatrin-induced visual field constriction is the latest and most worrying ADR. Many questions regarding the nature of this potentially serious ADR remain unanswered, as no prospective controlled study examining the phenomenon has been published. Rare cases of behavioural ADRs and IgA and IgG2 deficiency associated with the use of zonisamide have been reported. However, relatively few patients so far have been exposed to this drug, and therefore more postmarketing information is required. The relatively late establishment of aplastic anaemia and hepatic failure as potentially fatal ADRs of felbamate, and of visual field constriction with vigabatrin, should serve as ample reminders that ADRs can appear at any time.

Animals↗