Carbamazepine and methylphenidate in ADHD

Drugs for patients with epilepsy and excessive daytime sleepiness

Excessive daytime sleepiness (EDS) and attentional deficits are often observed in people with epilepsy. They may be the consequence of seizures and subclinical discharges as well as of comorbid conditions as obstructive sleep apnea/hypopnea syndrome (OSAS), attention deficit hyperactivity disorder (ADHD), or other less frequent disorders. Excessive daytime sleepiness may also be caused or worsened by antiseizure medications (ASMs). Several meta-analyses suggested that lamotrigine, lacosamide, and perhaps eslicarbazepine are less sedative than other traditional and new ASMs and, in patients prone to somnolence, might be preferred over ASMs with more sedative properties. In patients with severe EDS and/or ADHD, advantages and risks of a treatment with a psychostimulant need to be considered. Methylphenidate, modafinil, armodafinil, pitolisant, and solriamfetol are authorized for use in ADHD and EDS in patients with narcolepsy and some of them also in OSAS. These agents are off-label for the treatment of EDS associated with epilepsy. They do not have proconvulsant effects, although there are several possible risks for patients with epilepsy. The risks of cardiovascular events and psychiatric symptoms should be carefully evaluated as such disorders can coexist with epilepsy and be triggered by these agents. Finally, combination of psychostimulants with ASMs may be associated with several pharmacokinetic drug-drug interactions.

Clinically Significant Drug-Drug Interactions with Agents for Attention-Deficit/Hyperactivity Disorder

This article provides an overview of the pharmacokinetic drug-drug interactions (DDIs) for agents prescribed for attention-deficit/hyperactivity disorder (ADHD). Polypharmacy in the treatment of patients with ADHD leads to high exposures to DDIs and possibly adverse safety outcomes. We performed a systematic search of DDI reports for ADHD agents in Embase and Medline. We also searched for agents in the pharmacological pipeline, which include (1) mazindol, molindone and viloxazine, which were previously prescribed for other indications; (2) centanafadine and AR-08, never before approved; and (3) two extracts (Polygala tenuifolia extract and the French maritime pine bark extracts). The identified literature included case reports, cross-sectional, cross-over and placebo-controlled studies of patient cohorts and healthy volunteers. The DDIs were classified as follows: ADHD agents acting as perpetrators, i.e., affecting the clearance of co-prescribed agents (victim drugs), or ADHD agents being the victim drugs, being affected by other agents. Ratios for changes in pharmacokinetic parameters before and after the DDI were used as a rough estimate of the extent of the DDI. Alcohol may increase plasma dextroamphetamine concentrations by presystemic effects. Until studies are done to orient clinicians regarding dosing changes, clinicians need to be aware of the potential for cytochrome P450 (CYP) 2D6 inhibitors to increase amphetamine levels, which is equivalent to increasing dosages. Atomoxetine is a wide therapeutic window drug. The CYP2D6 poor metabolizers who do not have CYP2D6 activity had better atomoxetine response, but also an increased risk of adverse effects. CYP2D6 inhibitors have been used to increase atomoxetine response in CYP2D6 extensive metabolizers. Guanfacine is mainly metabolized by CYP3A4, which can be induced and inhibited. The package insert recommends that in guanfacine-treated patients, after adding potent CYP3A4 inducers, the guanfacine dose should be doubled; after adding potent CYP3A4 inhibitors the guanfacine dose should be halved. Based on a phenobarbital case report and our experience with CYP3A4-metabolized antipsychotics, these correction factors may be too low. According to two case reports, carbamazepine is a clinically relevant inducer of methylphenidate (MPH). A case series study suggested that MPH may be associated with important elevations in imipramine concentrations. Due to the absence of or limitations in the data, no comments for clinicians can be provided on the pharmacokinetic DDIs for clonidine, centanafadine, mazindol, molindone, AR-08, P. tenuifolia extract and the French maritime pine bark extracts. According to currently available data, clinicians should not expect that ADHD drugs modify each other's serum concentrations. A summary table for clinicians provides our current recommendations on pharmacokinetic DDIs of ADHD agents based on our literature review and the package inserts; whenever it was possible, we provide information on serum concentrations and dose correction factors. There will be a need to periodically update these recommendations and these correction factors as new knowledge becomes available.

An evaluation of the pharmacokinetics of methylphenidate for the treatment of attention-deficit/ hyperactivity disorder

INTRODUCTION

Methylphenidate (MPH) plays a principal role in the multimodal treatment of attention-deficit/hyperactivity disorder (ADHD). Controlled studies have demonstrated an effective reduction in the core symptoms of the disorder following MPH therapy, although long-term studies also demonstrate that the therapeutic benefits dissipate in the absence of combined psychosocial interventions.

AREAS COVERED

This review article focuses on the pharmacological characteristics of MPH, examining its effects on brain metabolism and the neurotransmitter system. Neuropsychological and clinical effects of different immediate and extended release MPH formulations are discussed to aid clinicians in choosing the appropriate formulation. The drug's addictive potency and abuse potential is also discussed. Data came from a literature search of relevant studies performed using the PubMed database up to June 2013.

EXPERT OPINION

MPH is effective in the treatment of the core symptoms of ADHD. Considerable clinical expertise is required to identify an individually well-adapted dosage which will produce the optimal clinical effects with potential side effects minimized. Due to low adherence to medication, especially in adolescents, motivation to treatment and attentive clinical monitoring is mandatory, as is the consideration of risks of abuse or the presence of a comorbid addictive disorder.

Treatment of epilepsy in children with developmental disabilities

Children with developmental disabilities are at increased risk for epilepsy with a prevalence rate higher than the general population. Some of the more common developmental disorders in childhood and the features of epilepsy in these conditions are discussed. Specifically, autism, cerebral palsy, mental retardation, and attention deficit and hyperactivity disorder are reviewed. Ideal treatment for developmentally-disabled children with epilepsy entails maximal seizure control without any significant adverse effects from the anti-epileptic drugs and good quality of life. Antiepileptic drugs' cognitive and behavioral adverse effects tend to occur more frequently in these children. Careful selection of the appropriate medication and close monitoring for drug adverse effects is important. The specific adverse effects of the older and newer antiepileptic drugs are also reviewed.

Association between attention-deficit/hyperactivity disorder and epilepsy in pediatric populations

There is a bidirectional relationship between attention-deficit/hyperactivity disorder (ADHD) and epilepsy. ADHD increases seizure risk, while patients with epilepsy have an increased prevalence of ADHD. The reasons explaining this association are not fully understood. Proposed mechanisms include effects of antiepileptic medications, underlying neurodevelopmental vulnerability, the effects of chronic seizures and subclinical epileptiform activity on cognitive functions and adrenergic dysfunction. There may also be a common genetic defect underlying both disorders in some families. Antiepileptics associated with ADHD-like side effects include phenobarbital, gabapentin, vigabatrin and topiramate. Methylphenidate has been studied in a double-blind setting against placebo for treatment of ADHD comorbid with epilepsy, and has a good risk-benefit ratio. Amphetamine, atomoxetine, clonidine and guanfacine only have case series to support their use and bupropion should be avoided.

Attention deficit hyperactivity disorder in children with epilepsy

Attention deficit hyperactivity disorder (ADHD) is more frequent in children with epilepsy than in general pediatric population. Several factors may contribute to this comorbidity, including the underlying brain pathology, the chronic effects of seizures and of the epileptiform EEG discharges, and the effects of antiepileptic drugs. Symptoms of ADHD are more common in some specific types of epilepsies, such as frontal lobe epilepsy, childhood absence epilepsy and Rolandic epilepsy, and may antedate seizure onset in a significant proportion of cases. In epileptic children with symptoms of ADHD, treatment might become a challenge for child neurologists, who are forced to prescribe drugs combinations, to improve the long-term cognitive and behavioral prognosis. Treatment with psychotropic drugs can be initiated safely in most children with epilepsy and ADHD symptoms.

An expert opinion on methylphenidate treatment for attention deficit hyperactivity disorder in pediatric patients with epilepsy

Methylphenidate (MPH) is one of the most commonly prescribed medications to treat attention deficit hyperactivity disorder (ADHD). Despite the elevated rates of ADHD in children with epilepsy, few studies have examined the use of MPH in this population. Case reports have warned about new-onset seizures in patients treated with MPH, and drug-drug interactions between MPH and antiepileptic drugs (AEDs), as well as antidepressants. However, retrospective chart reviews, open-label trials and controlled trials of MPH in patients with epilepsy and ADHD have noted significant improvements in ADHD symptoms without an exacerbation of seizures or an adverse effect on AED serum levels. This paper reviews the chemistry and mechanisms of action of MPH, as well as preclinical, premarketing clinical trials and postmarketing data relevant to its use in patients with ADHD and epilepsy.

Attention-deficit/hyperactivity disorder in pediatric patients with epilepsy: review of pharmacological treatment

Attention-deficit/hyperactivity disorder (ADHD) in children with epilepsy is a common source of impairment. Based on review of Medline indexed articles, meeting abstracts, and data requested from drug manufacturers, a summary of evidence that might guide treatment and research is presented. Methylphenidate (MPH) has shown high response rates and no increase in seizures in small trials. However, low baseline seizure rates, small numbers of subjects, and short observation periods limit the power of these studies to detect increases in seizure risk. Although longer-term effects of MPH and its effects in children with frequent seizures need to be studied, the evidence available at this time best supports use of MPH for the treatment of ADHD not amenable to changes in antiepileptic drugs or improvements in seizure control. This treatment should be part of a biopsychosocial approach. Other agents show promise. Preclinical, retrospective and open-label studies on amphetamines and atomoxetine support undertaking randomized controlled studies of these agents in patients with ADHD plus epilepsy. In contrast, additional data on guanfacine and modafinil should be gathered before undertaking randomized controlled studies with these agents.

Pharmacodynamic and pharmacokinetic interactions of psychotropic drugs with antiepileptic drugs

Co-morbid psychiatric disorders are relatively frequent in patients with epilepsy. The prevalence rates of mood and anxiety disorders, psychotic disorders and attention deficit/hyperactivity disorder have been found to be significantly higher in patients with epilepsy than in the general population. While co-morbid psychiatric disorders have frequently been considered as complications of the seizure disorder, there is an increasing body of literature that points to a complex relationship between psychiatric and seizure disorders. Because of this, it is crucial that clinicians consider the presence of co-morbid psychiatric disorders when planning the treatment of patients with epilepsy. Having a clear understanding of the pharmacodynamic and pharmacokinetic interactions between antiepileptic drugs and psychotropic drugs is of the essence to avert unnecessary adverse events and loss of efficacy of psychotropic drugs. This chapter provides a practical review on the use of psychotropic drugs for the treatment of these psychiatric co-morbidities in patients with epilepsy.

Pharmacokinetic and pharmacodynamic drug interactions in the treatment of attention-deficit hyperactivity disorder

The psychostimulants methylphenidate, amphetamine and pemoline are among the most common medications used today in child and adolescent psychiatry for the treatment of patients with attention-deficit hyperactivity disorder. Frequently, these medications are used in combination with other medications on a short or long term basis. The present review examines psychostimulant pharmacology, summarises reported drug-drug interactions and explores underlying pharmacokinetic and pharmacodynamic considerations for interactions. A computerised search was undertaken using Medline (1966 to 2000) and Current Contents to provide the literature base for reports of drug-drug interactions involving psychostimulants. These leads were further cross-referenced for completeness of the survey. Methylphenidate appears to be more often implicated in pharmacokinetic interactions suggestive of possible metabolic inhibition, although the mechanisms still remain unclear. Amphetamine was more often involved in apparent pharmacodynamic interactions and could potentially be influenced by medications affecting cytochrome P450 (CYP) 2D6. No published reports of drug interactions involving pemoline were found. The alpha2-adrenergic agonists clonidine and guanfacine have been implicated in several interactions. Perhaps best documented is their antagonism by tricyclic antidepressants and phenothiazines. In additional, concurrent beta-blocker use, or abrupt discontinuation, can lead to hypertensive response. Although there are few published well-controlled interaction studies with psychostimulants and alpha2-adrenergic agonists, it appears that these agents may be safely coadministered. The interactions of monoamine oxidase inhibitors with psychostimulants represent one of the few strict contraindications.