Lamotrigine augmentation of serotonin reuptake inhibitors in treatment-resistant obsessive-compulsive disorder: a double-blind, placebo-controlled study

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.

Pharmacological treatment of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) affects up to 2.5% of the population of the course of a lifetime and produces substantial morbidity. Approximately 70% of patients can experience significant symptomatic relief with appropriate pharmacotherapy. Selective serotonin reuptake inhibitors are the mainstay of pharmacological treatment. These drugs are typically used at higher doses and for longer periods than in depression. Proven second-line treatments include the tricyclic clomipramine and the addition of low-dose neuroleptic medications. OCD refractory to available treatments remains a profound clinical challenge.

Management of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a common, often debilitating disorder characterized by the presence of obsessions and compulsions. Obsessions are repetitive thoughts or images which are experienced as intrusive and unwanted; they cause marked anxiety and distress. Compulsions (also known as rituals) are repetitive behaviors or mental acts that individuals with OCD perform in an attempt to decrease their anxiety. Patients tend to hide their symptoms due to shame; the amount of time between onset of symptoms and appropriate treatment is often many years. The disorder likely results from several etiological variables; functional imaging studies have consistently shown hyperactivity in the orbitofrontal cortex, anterior cingulate, thalamus, and striatum. The mainstays of treatment include cognitive-behavioral therapy in the form of exposure and response prevention (ERP) and serotonin reuptake inhibiting medications. Several pharmacological augmentation strategies exist for treatment-resistant OCD, with addition of antipsychotics being most commonly employed. Radio and neurosurgical procedures, including gamma knife radiation and deep brain stimulation, are reserved for severe, treatment-refractory disease that has not responded to multiple treatments, and some patients may benefit from transcranial magnetic stimulation.

The neurobiological link between OCD and ADHD

Obsessive compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) are two of the most common neuropsychiatric diseases in paediatric populations. The high comorbidity of ADHD and OCD with each other, especially of ADHD in paediatric OCD, is well described. OCD and ADHD often follow a chronic course with persistent rates of at least 40–50 %. Family studies showed high heritability in ADHD and OCD, and some genetic findings showed similar variants for both disorders of the same pathogenetic mechanisms, whereas other genetic findings may differentiate between ADHD and OCD. Neuropsychological and neuroimaging studies suggest that partly similar executive functions are affected in both disorders. The deficits in the corresponding brain networks may be responsible for the perseverative, compulsive symptoms in OCD but also for the disinhibited and impulsive symptoms characterizing ADHD. This article reviews the current literature of neuroimaging, neurochemical circuitry, neuropsychological and genetic findings considering similarities as well as differences between OCD and ADHD.

Evidence-based pharmacological treatment of anxiety disorders, post-traumatic stress disorder and obsessive-compulsive disorder: a revision of the 2005 guidelines from the British Association for Psychopharmacology

This revision of the 2005 British Association for Psychopharmacology guidelines for the evidence-based pharmacological treatment of anxiety disorders provides an update on key steps in diagnosis and clinical management, including recognition, acute treatment, longer-term treatment, combination treatment, and further approaches for patients who have not responded to first-line interventions. A consensus meeting involving international experts in anxiety disorders reviewed the main subject areas and considered the strength of supporting evidence and its clinical implications. The guidelines are based on available evidence, were constructed after extensive feedback from participants, and are presented as recommendations to aid clinical decision-making in primary, secondary and tertiary medical care. They may also serve as a source of information for patients, their carers, and medicines management and formulary committees.

Obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a common heterogeneous psychiatric disorder manifesting with obsessions and compulsions. Obsessions are intrusive, recurrent, and persistent unwanted thoughts. Compulsions are repetitive behaviors or mental acts that an individual feels driven to perform in response to the obsessions. The heterogeneity of OCD includes themes of obsessions, types of rituals, presence or absence of tics, etiology, genetics, and response to pharmacotherapy. Complications of OCD include interpersonal difficulties, unemployment, substance abuse, criminal justice issues, and physical injuries. Areas of the brain involved in the pathophysiology include the orbitofrontal cortex, anterior cingulate gyrus, and basal ganglia. Overall, OCD may be due to a malfunction in the cortico-striato-thalamo-cortical circuit in the brain. Neurotransmitters implicated in OCD include serotonin, dopamine, and glutamate. Numerous drugs such as atypical antipsychotics and dopaminergic agents can cause or exacerbate OCD symptoms. The etiology includes genetics and neurological insults. Treatment of OCD includes psychotherapy, pharmacotherapy, electroconvulsive therapy, transcranial magnetic simulation, and in extreme cases surgery. Exposure and response prevention is the most effective form of psychotherapy. Selective serotonin reuptake inhibitors (SSRIs) are the preferred pharmacotherapy. Higher doses than listed in the package insert and a longer trial are often needed for SSRIs than compared to other psychiatric disorders. Alternatives to SSRIs include clomipramine and serotonin/norepinephrine reuptake inhibitors. Treatment of resistant cases includes augmentation with atypical antipsychotics, pindolol, buspirone, and glutamate-blocking agents.

Obsessive compulsive disorder and the glutamatergic system

PURPOSE OF REVIEW

Evidence-based pharmacological interventions for obsessive compulsive disorder (OCD) are targeted mainly at the serotonergic and dopaminergic pathways, and are not always effective. It is timely to review the growing evidence from animal models and clinical research (e.g., brain imaging, genetics) on the role of the glutamatergic system in OCD.

RECENT FINDINGS

Emerging evidence from both animal models and clinical research (including brain imaging, neurogenetics) supports the glutamatergic system as a potential target for pharmacotherapy in OCD. Although there have been relatively few randomized controlled trials of glutamatergic agents in pediatric or adult OCD to date, there is some work on riluzole, memantine, ketamine, topiramate, lamotrigine, N-acetylcysteine, and D-cycloserine.

SUMMARY

Given the need for more efficacious treatments in OCD, and given emergent findings on the role of the glutamatergic system in this disorder, there is a need for additional pharmacotherapy trials on glutamatergic agents in OCD. Possible research designs for such trials might include stand-alone approaches, pharmacotherapy augmentation, or psychotherapy augmentation.

Commonly asked questions in the treatment of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a common and often a highly disabling condition that was considered untreatable before the 1960s. The advent of serotonin reuptake inhibitors and exposure and response prevention revolutionized the treatment of OCD. Although they are still the first line treatments for OCD, new treatments like augmentation strategies, brain stimulation techniques, psychosurgery, newer forms of psychotherapy (like cognitive therapy, acceptance and commitment therapy) have been added to the armamentarium. With the available treatment strategies, many patients can achieve at least partial remission of symptoms. Nevertheless, the plethora of information gives rise to many questions on their application for practicing clinicians. We provide evidence-based responses to these questions and suggest a broad guideline for treatment of OCD.

Long-term outcome in adults with obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a chronic condition that often produces lifelong morbidity, but few studies have examined long-term outcome (greater than 5 years) in adult patients. Available studies suggest that 32-74% of adult OCD patients will experience clinical improvement over the long term. However, these studies were conducted before validated OCD rating scales were established and the development of evidence-based treatments for OCD.

METHODS

We investigated the 10-20 year outcome of 83 of 165 eligible subjects previously enrolled after participation in placebo-controlled trials of serotonin reuptake inhibitor (SRI) medications for OCD. We examined the association between clinical characteristics at initial assessment and OCD symptom severity at follow-up. We hypothesized that primary OCD symptom dimension and initial response to pharmacotherapy with serotonin reuptake inhibitors would be associated with later symptom severity.

RESULTS

Only 20% (17 of 83) of subjects had experienced a remission of their OCD symptoms at follow-up (Y-BOCS ≤ 8). Forty-nine percent (41 of 83) of subjects were still experiencing clinically significant OCD symptoms. Response to initial SRI pharmacotherapy was significantly associated with long-term outcome: 31% (13 of 42) of subjects who responded (CGI < 3) to initial SRI pharmacotherapy were remitted at follow-up, compared to 12% (3 of 25) of partial responders and none of the 16 subjects who had no response to initial SRI pharmacotherapy. We did not find a significant association between long-term clinical outcome and any of the OCD symptom dimensions.

CONCLUSION

Despite the introduction and dissemination of several evidence-based treatments for OCD, most adult OCD patients do not achieve remission. Initial response to pharmacotherapy was strongly associated with long-term outcome.

A case series of patients with lamotrigine toxicity at one center from 2003 to 2012

INTRODUCTION

Lamotrigine is a phenyltriazine compound that inhibits voltage-gated sodium channels, decreasing release of glutamate and aspartate, and inhibits serotonin, norepinephrine and dopamine reuptake. Reports of toxicity in the literature are limited to case reports and primarily involve coingestants. This case series is intended to report the clinical manifestations of lamotrigine toxicity.

METHODS

This retrospective case series from 2003 to 2012 studies the effects of lamotrigine toxicity when not confounded by coingestants. Admission records at an inpatient toxicology center were reviewed for lamotrigine-only exposure based on history with supporting laboratory data when available. After identification, these charts were reviewed again to characterize vital signs, neurological examination findings, specific laboratory and electrocardiography parameters, and complications.

RESULTS

Fifty-seven patients were identified with possible lamotrigine toxicity. Nine patients, including three toddlers, had lamotrigine-only ingestions. Three of these patients had seizures, four were hypertensive, five were tachycardic, and four experienced tachypnea. Mental status was altered in all nine (depressed (n = 4), agitated (n = 5) or both (n = 3)). Five patients were hyperreflexic and experienced intermittent myoclonus, and two had inducible clonus. On electrocardiogram, two patients experienced QRS prolongation (114-116 ms), and four had QTc prolongation (463-586 ms). No patient had life-threatening symptoms or signs. Serum levels of lamotrigine were available in seven patients, and averaged 35.4 mg/L (17-90 mg/L). The therapeutic range for sLTG is 3-14 mg/L.

CONCLUSIONS

Lamotrigine toxicity manifested with minor-moderate neurologic and/or electrocardiographic effects. Toxicity reflects the known pharmacologic actions of lamotrigine: serotonin, norepinephrine and dopamine reuptake inhibition, and sodium channel blockade.

Lamotrigine augmentation of serotonin reuptake inhibitors in severe and long-term treatment-resistant obsessive-compulsive disorder

The treatment recommendations in obsessive-compulsive disorder (OCD) after lack of response to selective serotonin reuptake inhibitors (SSRIs) include augmentation with other drugs, particularly clomipramine, a more potent serotonin reuptake inhibitor (SRI), or antipsychotics. We present two cases of response to lamotrigine augmentation in treatment-refractory OCD; each received multiple SRI trials over a >10-year period. The first patient had eleven years of treatment with multiple combinations including clomipramine and SSRIs. She had a >50% decrease of Y-BOCS (from 29 to 14) by augmenting paroxetine (60 mg/day) with lamotrigine (100 mg/day). The second patient had 22 years of treatment with multiple combinations, including combinations of SSRIs with clomipramine and risperidone. She had an almost 50% decrease of Y-BOCS (from 30 to 16) and disappearance of tics by augmenting clomipramine (225 mg/d) with lamotrigine (200 mg/day). These two patients were characterized by lack of response to multiple treatments, making a placebo response to lamotrigine augmentation unlikely. Prospective randomized trials in treatment-resistant OCD patients who do not respond to combinations of SSRIs with clomipramine and/or antipsychotics are needed, including augmentation with lamotrigine. Until these trials are available, our cases suggest that clinicians may consider lamotrigine augmentation in such treatment-resistant OCD patients.