Status epilepticus associated with the combination of valproic acid and clomipramine

Pharmacokinetic Interactions Between Antiseizure and Psychiatric Medications

Antiseizure medications and drugs for psychiatric diseases are frequently used in combination. In this context, pharmacokinetic interactions between these drugs may occur. The vast majority of these interactions are primarily observed at a metabolic level and result from changes in the activity of the cytochrome P450 (CYP). Carbamazepine, phenytoin, and barbiturates induce the oxidative biotransformation and can consequently reduce the plasma concentrations of tricyclic antidepressants, many typical and atypical antipsychotics and some benzodiazepines. Newer antiseizure medications show a lower potential for clinically relevant interactions with drugs for psychiatric disease. The pharmacokinetics of many antiseizure medications is not influenced by antipsychotics and anxiolytics, while some newer antidepressants, namely fluoxetine, fluvoxamine and viloxazine, may inhibit CYP enzymes leading to increased serum concentrations of some antiseizure medications, including phenytoin and carbamazepine. Clinically relevant pharmacokinetic interactions may be anticipated by knowledge of CYP enzymes involved in the biotransformation of individual medications and of the influence of the specific comedication on the activity of these CYP enzymes. As a general rule, these interactions can be managed by careful evaluation of clinical response and, when indicated, individualized dosage adjustments guided by measurement of drugs serum concentrations, especially if pharmacokinetic interactions may cause any change in seizure control or signs of toxicity. Further studies are required to improve predictions of pharmacokinetic interactions between antiseizure medications and drugs for psychiatric diseases providing practical helps for clinicians in the clinical setting.

The pharmacological management of psychiatric comorbidities in patients with epilepsy

Psychiatric disorders represent a frequent comorbidity in patients with epilepsy affecting quality of life, morbidity and mortality. Evidence-based data on the management of these conditions are limited but a number of recommendations are now available to guide clinical practice. The present paper reviews the pharmacological treatment of psychiatric problems in epilepsy with special attention to data coming from randomised controlled trials (RCTs), pharmacological interactions with AEDs and the issue of seizure worsening during treatment with psychotropic drugs. Epidemiologically or clinically relevant psychiatric conditions are discussed namely mood and anxiety disorders, psychoses and attention deficit hyperactivity disorder.

Pharmacokinetic and pharmacodynamic interactions between antiepileptics and antidepressants

INTRODUCTION

Antiepileptic-antidepressant combinations are frequently used by clinicians; their pharmacokinetic (PK) and pharmacodynamic (PD) drug interactions (DIs) have not been well studied but are frequently likely to be clinically relevant.

AREAS COVERED

This article provides a comprehensive review of PK DIs between antiepileptics and antidepressants. In the absence of PD DI studies, PD information on pharmacological mechanisms and studies on efficacy and safety of individual drugs are reviewed.

EXPERT OPINION

The clinical relevance of the inductive properties of carbamazepine, phenytoin, phenobarbital and primidone and the inhibitory properties of valproic acid and some antidepressants are well understood; correction factors are provided if appropriate DI studies have been completed. More PK studies are needed for: i) antiepileptics with potent inductive effects for all recently approved antidepressants; ii) high doses of mild CYP3A4 inducers, such as clobazam, eslicarbazepine, oxcarbazepine, rufinamide and topiramate for reboxetine and vilazodone; iii) valproate as a possible inhibitor, mild inducer or both a mild inducer and competitive inhibitor of some antidepressants; and iv) inhibitory effects of long-term fluoxetine use on clobazam, lacosamide, phenobarbital, primidone, carbamazepine, felbamate, tiagabine and zonisamide. Possible synergistic or additive beneficial PD DIs in generalized anxiety disorder, chronic pain, migraine prophylaxis, weight control and menopausal symptoms need study.

Interaction of valproic acid and the antidepressant drugs doxepin and venlafaxine: analysis of therapeutic drug monitoring data under naturalistic conditions

Valproic acid and the antidepressants doxepin and venlafaxine are frequently used psychotropic drugs. In the literature, an influence of valproic acid on serum levels of antidepressants has been described, although studies have focused on amitriptyline. The authors assessed their therapeutic drug monitoring (TDM) database for patients receiving a combination of doxepin or venlafaxine and valproic acid and compared these samples with matched controls without valproic acid comedication in terms of the serum concentration of antidepressants. The mean dose-corrected serum concentration of doxepin+N-doxepin in 16 patients who received valproic acid comedication was higher (2.171±1.482 ng/ml/mg) than that in the matched controls (0.971±0.857 ng/ml/mg, P<0.003). We also found a significant correlation between valproic acid serum level and dose-corrected doxepin+N-doxepin serum level (Spearman's ρ r=0.602, P<0.014). The mean dose-corrected serum level of venlafaxine+O-desmethylvenlafaxine in 41 patients who received valproic acid comedication did not differ significantly from that of the matched controls (P<0.089), but there was a significant difference between both groups in the dose-corrected serum level of O-desmethylvenlafaxine (1.403±0.665 vs. 1.102±0.444, P<0.017). As a consequence, if a combination of valproic acid with doxepin or venlafaxine is administered, cautious dosing is advisable and TDM should be performed.

Interaction of valproic acid and amitriptyline: analysis of therapeutic drug monitoring data under naturalistic conditions

Amitriptyline (AMI) and valproic acid (VPA) are common psychotropic drugs which are frequently used in psychiatry and also administered in neurology or anesthesia in the absence of a psychiatric indication. On the basis of the case of a 73-year-old man with therapy-resistant major depressive episode who experienced anticholinergic delirium after adding VPA to AMI, we retrospectively analyzed therapeutic drug monitoring data of the years 2008 to 2010. We assessed cases receiving a combination of AMI and VPA, and obtained a control sample of AMI patients without VPA which were matched for sex, age, daily dose, and comedication. Both samples were compared regarding the serum levels of AMI and nortriptyline (NOR) as well as the ratio of NOR and AMI with the Mann-Whitney U test. The combination of AMI and VPA led to a remarkable increase of AMI and NOR serum levels. When comparing 33 patients who received comedication with VPA versus 33 matched controls, the total concentration by combining mean AMI and NOR serum levels (237.1 [119.9] vs 126.4 [52.8] ng/mL) and NOR/AMI ratio (1.300 [0.905] vs 0.865 [0.455]) was significantly higher. Both AMI and VPA are widely prescribed drugs. A combination of both is common for psychiatric or neurologic patients. A cautious dosing of AMI with VPA comedication is advisable, and therapeutic drug monitoring should be performed because this combination may lead to a remarkable increase of AMI and NOR serum levels.

One-year seizure prognosis in epilepsy patients treated with antidepressants

To investigate the clinical effects of antidepressants on seizure frequency of patients with epilepsy treated with antiepileptic drugs, we retrospectively evaluated the 1-year course of seizure frequency. One hundred twenty-one patients with epilepsy treated with antidepressants and 300 patients with epilepsy not treated with antidepressants (controls) were the subjects of this study. Seizure frequency over the 1-year period of administration of antidepressants was retrospectively evaluated and compared with that for controls. In the patients with epilepsy taking antidepressants, seizure frequencies at four observation points (1, 3, 6, and 12 months after starting antidepressants) were equivalent to those of the control group. There was no significant difference in seizure frequency between first- and second-generation antidepressants. Patients with epilepsy treated with antiepileptic drugs can take antidepressants without a significant risk of exacerbation of seizures. Most antidepressants can be used for psychiatric treatment of patients with epilepsy.

Consensus statement: the evaluation and treatment of people with epilepsy and affective disorders

Affective disorders in people with epilepsy (PWE) have become increasingly recognized as a primary factor in the morbidity and mortality of epilepsy. To improve the recognition and treatment of affective disorders in PWE, an expert panel comprising members from the Epilepsy Foundation's Mood Disorders Initiative have composed a Consensus Statement. This document focuses on depressive disorders in particular and reviews the appearance and treatment of the disorder in children, adolescents, and adults. Idiosyncratic aspects of the appearance of depression in this population, along with physiological and cognitive issues and barriers to treatment, are reviewed. Finally, a suggested approach to the diagnosis of affective disorders in PWE is presented in detail. This includes the use of psychometric tools for diagnosis and a stepwise algorithmic approach to treatment. Recommendations are based on the general depression literature as well as epilepsy-specific studies. It is hoped that this document will improve the overall detection and subsequent treatment of affective illnesses in PWE.

Disposition of valproic acid in self-poisoned adults

Acute intoxication with valproic acid is increasingly being observed in clinical practice. In Poland, such intoxication frequently occurs as a result of mixing different drugs or alcohol. We studied the pharmacokinetics of valproic acid in five intoxicated patients. Apart from valproic acid, barbiturates, chlorprotixene, tricyclic antidepressants, tetrahydrocannabinols and alcohol were detected and measured. The absorption of the drug was rapid and the maximum concentration was observed after the period of 3.5-5.6 hr. The lowering of the valproic acid level in plasma was biphasic, with terminal half-life ranging between 8.8-30.9 hr. The calculated apparent volume of distribution was 0.17-0.72 l/kg and could be affected by varied levels of doses as well as time of drug intake (data from interviews of patients) used for calculation and reduction in plasma protein binding at higher concentration of valproic acid. Frequent multiple drug poisonings oblige toxicological laboratories not only to monitor valproic acid concentration in serum, but also to perform the toxicological screenings.

Clinically relevant drug interactions with antiepileptic drugs

Some patients with difficult-to-treat epilepsy benefit from combination therapy with two or more antiepileptic drugs (AEDs). Additionally, virtually all epilepsy patients will receive, at some time in their lives, other medications for the management of associated conditions. In these situations, clinically important drug interactions may occur. Carbamazepine, phenytoin, phenobarbital and primidone induce many cytochrome P450 (CYP) and glucuronyl transferase (GT) enzymes, and can reduce drastically the serum concentration of associated drugs which are substrates of the same enzymes. Examples of agents whose serum levels are decreased markedly by enzyme-inducing AEDs, include lamotrigine, tiagabine, several steroidal drugs, cyclosporin A, oral anticoagulants and many cardiovascular, antineoplastic and psychotropic drugs. Valproic acid is not enzyme inducer, but it may cause clinically relevant drug interactions by inhibiting the metabolism of selected substrates, most notably phenobarbital and lamotrigine. Compared with older generation agents, most of the recently developed AEDs are less likely to induce or inhibit the activity of CYP or GT enzymes. However, they may be a target for metabolically mediated drug interactions, and oxcarbazepine, lamotrigine, felbamate and, at high dosages, topiramate may stimulate the metabolism of oral contraceptive steroids. Levetiracetam, gabapentin and pregabalin have not been reported to cause or be a target for clinically relevant pharmacokinetic drug interactions. Pharmacodynamic interactions involving AEDs have not been well characterized, but their understanding is important for a more rational approach to combination therapy. In particular, neurotoxic effects appear to be more likely with coprescription of AEDs sharing the same primary mechanism of action.

Encephalopathy and myoclonus triggered by valproic acid

In recent years, the use of valproic acid (VPA) as a mood-stabilizing agent has continuously increased. Although VPA usually is well tolerated, its use in combination with other psychotropic compounds might bear an elevated risk of adverse reactions. Here, we present the case of a 42-year-old male suffering from treatment-resistant psychotic depression, who was prescribed VPA additionally to lithium, clomipramine, flupentixol and risperidone. By doing so, he developed myoclonus, tremor and encephalopathy with sedation and marked EEG background slowing. Most notably, these side effects occurred in the presence of normal VPA and ammonia serum concentrations. On VPA discontinuation, all symptoms vanished and EEG normalized. We thus suggest that direct VPA-induced encephalopathy in the absence of ammonemia does exist, in this case probably facilitated by psychotropic polypharmacy.

Antiepileptic drug-induced pharmacodynamic aggravation of seizures: does valproate have a lower potential?

Thirty-five years since its introduction into clinical use, valproate (valproic acid) has established itself as one of the most widely used antiepileptic drugs (AEDs). In recent years, there has been a growing awareness of the potential aggravation of seizure disorders by AEDs. Such aggravation may be due to a variety of factors that include a paradoxical pharmacodynamic effect. In order to address this important safety aspect of AED treatment, we reviewed all available published evidence in search of factors related to seizure aggravation during valproate therapy. We analysed the 20 available publications, which outline about 99 case reports (in some papers, the exact number was not specified) of aggravation of seizures associated with valproate. Almost all of these cases occurred in a specific clinical context known to be linked to seizure aggravation, such as overdose, encephalopathy, hepatopathy or metabolic disorders. However, we found no consistent evidence of pure pharmacodynamic aggravation in the absence of any of the above quoted factors. In view of the large number of patients treated worldwide with valproate, the number of reported cases of seizure aggravation in patients taking the drug in the literature is low. Conditions in which worsening of seizures as a result of valproate use may occur are well known and often avoidable. Thus, unlike most AEDs, including the newer ones, valproate appears to have a very low potential for pharmacodynamic paradoxical seizure aggravation. This knowledge is in accordance with long-standing clinical experience and practice.

Clinically important drug interactions in epilepsy: interactions between antiepileptic drugs and other drugs

Antiepileptic drugs (AEDs) are commonly prescribed for long periods, up to a lifetime, and many patients will require treatment with other agents for the management of concomitant or intercurrent conditions. When two or more drugs are prescribed together, clinically important interactions can occur. Among old-generation AEDs, carbamazepine, phenytoin, phenobarbital, and primidone are potent inducers of hepatic enzymes, and decrease the plasma concentration of many psychotropic, immunosuppressant, antineoplastic, antimicrobial, and cardiovascular drugs, as well as oral contraceptive steroids. Most new generation AEDs do not have clinically important enzyme inducing effects. Other drugs can affect the pharmacokinetics of AEDs; examples include the stimulation of lamotrigine metabolism by oral contraceptive steroids and the inhibition of carbamazepine metabolism by certain macrolide antibiotics, antifungals, verapamil, diltiazem, and isoniazid. Careful monitoring of clinical response is recommended whenever a drug is added or removed from a patient's AED regimen.

Effects of psychotropic drugs on seizure threshold

Psychotropic drugs, especially antidepressants and antipsychotics, may give rise to some concern in clinical practice because of their known ability to reduce seizure threshold and to provoke epileptic seizures. Although the phenomenon has been described with almost all the available compounds, neither its real magnitude nor the seizurogenic potential of individual drugs have been clearly established so far. In large investigations, seizure incidence rates have been reported to range from approximately 0.1 to approximately 1.5% in patients treated with therapeutic doses of most commonly used antidepressants and antipsychotics (incidence of the first unprovoked seizure in the general population is 0.07 to 0.09%). In patients who have taken an overdose, the seizure risk rises markedly, achieving values of approximately 4 to approximately 30%. This large variability, probably due to methodological differences among studies, makes data confusing and difficult to interpret. Agreement, however, converges on the following: seizures triggered by psychotropic drugs are a dose-dependent adverse effect; maprotiline and clomipramine among antidepressants and chlorpromazine and clozapine among antipsychotics that have a relatively high seizurogenic potential; phenelzine, tranylcypromine, fluoxetine, paroxetine, sertraline, venlafaxine and trazodone among antidepressants and fluphenazine, haloperidol, pimozide and risperidone among antipsychotics that exhibit a relatively low risk. Apart from drug-related factors, seizure precipitation during psychotropic drug medication is greatly influenced by the individual's inherited seizure threshold and, particularly, by the presence of seizurogenic conditions (such as history of epilepsy, brain damage, etc.). Pending identification of compounds with less or no effect on seizure threshold and formulation of definite therapeutic guidelines especially for patients at risk for seizures, the problem may be minimised through careful evaluation of the possible presence of seizurogenic conditions and simplification of the therapeutic scheme (low starting doses/slow dose escalation, maintenance of the minimal effective dose, avoidance of complex drug combinations, etc.). Although there is sufficient evidence that psychotropic drugs may lower seizure threshold, published literature data have also suggested that an appropriate psychotropic therapy may not only improve the mental state in patients with epilepsy, but also exert antiepileptic effects through a specific action. Further scientific research is warranted to clarify all aspects characterising the complex link between seizure threshold and psychotropic drugs.

Clinical significance of pharmacokinetic interactions between antiepileptic and psychotropic drugs

As antiepileptic drugs (AEDs) and psychotropic agents are increasingly used in combination, the possibility of pharmacokinetic interactions between these compounds is relatively common. Most pharmacokinetic interactions between AEDs and psychoactive drugs occur at a metabolic level, and usually involve changes in the activity of the cytochrome P450 mixed-function oxidases (CYP) involved in their biotransformation. As a consequence of CYP inhibition or induction, plasma concentrations of a given drug may reach toxic or subtherapeutic levels, and dosage adjustments may be required to avoid adverse effects or clinical failure. Enzyme-inducing AEDs, such as carbamazepine (CBZ), phenytoin (PHT), and barbiturates, stimulate the oxidative biotransformation of many concurrently prescribed psychotropics. In particular, these AEDs may decrease the plasma concentrations of tricyclic antidepressants, many antipsychotics, including traditional compounds, i.e., haloperidol and chlorpromazine, and newer agents, i.e., clozapine, risperidone, olanzapine, quetiapine, and ziprasidone, and some benzodiazepines. Conversely, new AEDs appear to have a lower potential for interactions with all psychotropic drugs. While antipsychotics and anxiolytics do not significantly influence the pharmacokinetics of most AEDs, some newer antidepressants, such as viloxazine, fluoxetine, and fluvoxamine, may lead to higher serum levels of some AEDs, namely CBZ and PHT, through inhibition of CYP enzymes. No significant pharmacokinetic interactions have been documented between AEDs and lithium. Information about CYP enzymes responsible for the biotransformation of individual agents and about the effects of these compounds on the activity of specific CYP enzymes may help in predicting and avoiding clinically significant interactions. Apart from careful clinical observation, serum level monitoring of AEDs and psychotropic drugs can be useful in determining the need for dosage adjustments, especially if there is any change in seizure control, or possible toxicity.

Antidepressant drugs and seizure susceptibility: from in vitro data to clinical practice

The use of antidepressant drugs (ADs) in patients with epilepsy still raises uncertainties because of the widespread conviction that this class of drugs facilitates seizures. A detailed knowledge of this issue in its various aspects may help in optimal management of patients suffering concurrently from epilepsy and depression. This article reviews the available data in vitro in animals and humans concerning the known potential of various ADs to induce epileptic seizures. Emphasis has been placed on those variables that may generate confusion in interpreting the results of the various studies. Most ADs at therapeutic dosages exhibit in nonepileptic patients a seizure risk close to that reported for the first spontaneous seizure in the general population (i.e., <0.1%). In patients taking high AD doses, seizure incidence rises markedly and may reach values up to 40%. With a patient history of epilepsy and/or concomitant drugs that act on neuronal excitability, low or therapeutic AD doses may be sufficient to trigger seizures. Experimental data are in partial conflict with human data on the relative potential seizure risk of the various ADs. Therefore, a reliable scale for assigning a relative value to an individual AD or to single AD classes cannot be made. It appears fair to say that maprotiline and amoxapine exhibit the greatest seizure risk, whereas trazodone, fluoxetine, and fluvoxamine exhibit the least. Some ADs may also display antiepileptic effects, especially in low doses, in experimental models of epilepsy and in humans, but the mechanism of this action is largely unknown. The available data suggest that ADs may display both convulsant and anticonvulsant effects and that the most important factor in determining the direction of a given compound in terms of excitation/inhibition is drug dosage. It is probable that drugs that increase serotonergic transmission are less convulsant or, even, more anticonvulsant than others. Because of mutual pharmacokinetic interactions between antiepileptic drugs and ADs, with consequent marked changes in plasma concentrations, it remains to be established whether or not plasma AD levels that are effective against depression also facilitate seizures. Finally, exploring the mechanisms through which ADs modulate neuronal excitability might open new possibilities in antiepileptic drug development.

Changing presentation of seizures with aging: clinical and etiological factors

BACKGROUND

The historically higher incidence of seizures in children has changed, the elderly now have a higher incidence than any age-group, 2-3 times of that found in children. Classical teachings on etiologies, clinical presentation and progression of seizures are based on observations of a younger population and need to be revised in view of features unique to this age-group. The findings of two large VA cooperative studies show that even in sophisticated medical environments, up to 30% of patients 60 years and older with recurrent partial seizures go undiagnosed for more than 1 year of seizure onset.

OBJECTIVE

(a) To characterize the manifestations of auras, seizures and postictal states in the elderly and the relevance of various etiologies to these presentations. (b) To identify and discuss factors that contribute to the difficulties in the diagnosis of seizures in this population.

METHODS

A review of our experience in treating a large population of elderly patients in a university epilepsy center and a review of the literature relating to the problem.

CONCLUSIONS

Seizures in the elderly are both overdiagnosed and underdiagnosed: either situation can have serious adverse consequences. Diversity of etiologies and atypical presentations make recognition of seizures difficult. Histories are frequently inadequate: complaints of multiple physical symptoms confuse the picture, unwillingness of elderly patients to admit to problems they believe are physiological in nature by the fear others may think they are 'losing their mind' and high staff turnover result in erratic identification of problems. The significant morbidity and mortality associated with poorly controlled seizures in this population are in large part preventable since excellent response to treatment can be achieved in more than 80% of individuals. The correct diagnosis of seizures is more likely if both physician and patients are familiar with the nuances of epilepsy in the elderly.

Drug-drug interactions in pediatric psychopharmacology

Serious consequences caused by drug-drug interactions continue to plague contemporary pharmacotherapy. The possibility of a drug-drug interaction should be suspected anytime a new or unexpected effect occurs that complicates the clinical management of a patient in the setting where the patient is receiving more than one drug. In this article, the authors address the mechanisms of pharmacokinetic-based drug-drug interactions focusing on important interactions that may occur with the common medications a pediatrician may prescribe to the child receiving psychoactive medication(s) prescribed by a child psychiatrist.