Research and Clinical Trials on Guanfacine (Tenex)

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By Dr Greg Mulhauser

This list of current clinical research trials on Guanfacine (Tenex) is followed by a short set of abstracts from the most recent research articles published on the drug.

Article Contents

Guanfacine (Tenex) Clinical Research Trials

From our searchable database at ClinicalTrialsFeeds.org, this list includes all the latest information about clinical trials involving Guanfacine (Tenex).

 

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Current Research Literature on Guanfacine (Tenex)

Here are abstracts for some of the latest research articles to have appeared on Guanfacine (Tenex):

Guanfacine extended release in the treatment of attention-deficit/hyperactivity disorder.

Curr Psychiatry Rep. 2009 Oct; 11(5): 339-40
Rostain AL

Mapping the central effects of methylphenidate in the rat using pharmacological MRI BOLD contrast.

Neuropharmacology. 2009 Sep 4;
Easton N, Marshall FH, Marsden CA, Fone KC
Methylphenidate (Ritalin((R))) is a selective dopamine reuptake inhibitor and an effective treatment for attention deficit hyperactivity disorder (ADHD) however the anatomical foci and neuronal circuits involved in these therapeutic benefits are unclear. This study determines the temporal pattern of brain regional activity change produced by systemic administration of a therapeutically relevant dose of methylphenidate in anaesthetised Sprague-Dawley rats using BOLD MRI and a 2.35T Bruker magnet. Following 60 min basal recording separate rats received saline (n = 9) or +/- methylphenidate hydrochloride (2 mg/kg, i.p., n = 9) and BOLD changes were recorded for 90 min using statistical parametric maps. Methylphenidate produced significant positive random BOLD effects in the nucleus accumbens, substantia nigra, entorhinal cortex and medial orbital cortex. Negative random BOLD effects were more widespread and intense, occurring in the motor and somatosensory cortices, caudate putamen, lateral globus pallidus and bed nucleus of the stria terminalis, without accompanying changes in blood pressure or respiratory rate. Methylphenidate-induced negative BOLD in the striatum, and other dopamine terminal areas, may reflect post-synaptic changes produced by blockade of the neuronal dopamine reuptake transporter. While increased positive BOLD in the medial orbital cortex may reflect altered dopamine and/or noradrenaline release indirectly altering striatal activity. The overall pattern of BOLD changes is comparable to that seen in previous studies using guanfacine, amphetamine and atomoxetine, and suggests that although these compounds operate through distinct pharmacological mechanisms the BOLD changes may represent a 'fingerprint pattern' predictive of therapeutic benefit in ADHD.

Alpha-2 adrenergic agonists in children with inattention, hyperactivity and impulsiveness.

CNS Drugs. 2009; 23 Suppl 1: 43-9
Scahill L
Although originally developed for the treatment of hypertension, alpha(2)-agonists have been used to treat Tourette's syndrome, attention-deficit hyperactivity disorder (ADHD), developmental disorders and substance abuse for nearly three decades. Based on studies of clonidine, alpha(2)-agonists were presumed to reduce arousal by decreasing the firing of noradrenaline neurons in locus ceruleus. Accumulated preclinical evidence indicates that guanfacine has features in common with clonidine, in addition to other pharmacological effects. Clonidine binds to the three subtypes of alpha(2)-receptors, A, B and C, whereas guanfacine binds more selectively to alpha(2A)-receptors, which appears to enhance prefrontal function. Several reports on the use of the alpha(2)-agonists show improvements in children with ADHD and improvements in hyperactivity, impulsiveness and inattention in children with tic disorders and pervasive developmental disorders. Both clonidine and guanfacine are associated with sedation, fatigue and somnolence. Reductions in heart rate and blood pressure are modest and rarely lead to discontinuation of treatment across these trials.

Toward a new understanding of attention-deficit hyperactivity disorder pathophysiology: an important role for prefrontal cortex dysfunction.

CNS Drugs. 2009; 23 Suppl 1: 33-41
Arnsten AF
Recent advances in neurobiology have aided our understanding of attention-deficit hyperactivity disorder (ADHD). The higher-order association cortices in the temporal and parietal lobes and prefrontal cortex (PFC) interconnect to mediate aspects of attention. The parietal association cortices are important for orienting attentional resources in time/space, while the temporal association cortices analyse visual features critical for identifying objects/places. These posterior cortices are engaged by the salience of a stimulus (its physical characteristics such as movement and colour). Conversely, the PFC is critical for regulating attention based on relevance (i.e. its meaning). The PFC is important for screening distractions, sustaining attention and shifting/dividing attention in a task-appropriate manner. The PFC is critical for regulating behaviour/emotion, especially for inhibiting inappropriate emotions, impulses and habits. The PFC is needed for allocating/planning to achieve goals and organizing behaviour/thought. These regulatory abilities are often referred to as executive functions. In humans, the right hemisphere of the PFC is important for regulating distractions, inappropriate behaviour and emotional responses. Imaging studies of patients with ADHD indicate that these regions are underactive with weakened connections to other parts of the brain. The PFC regulates attention and behaviour through networks of interconnected pyramidal cells. These networks excite each other to store goals/rules to guide actions and are highly dependent on their neurochemical environment, as small changes in the catecholamines noradrenaline (NA) or dopamine (DA) can have marked effects on PFC function. NA and DA are released in the PFC according to our arousal state; too little (during fatigue or boredom) or too much (during stress) impairs PFC function. Optimal amounts are released when we are alert/interested. The beneficial effects of NA occur at postsynaptic alpha(2A)-receptors on the dendritic spines of PFC pyramidal cells. Stimulation of these receptors initiates a series of chemical events inside the cell. These chemical signals lead to the closing of special ion channels, thus strengthening the connectivity of network inputs to the cell. Conversely, the beneficial effects of moderate amounts of DA occur at D(1) receptors, which act by weakening irrelevant inputs to the cells on another set of spines. Genetic linkage studies of ADHD suggest that these catecholamine pathways may be altered in some families with ADHD, e.g. alterations in the enzyme that synthesizes NA (DA beta-hydroxylase) are associated with weakened PFC abilities. Pharmacological studies in animals indicate catecholamine actions in the PFC are highly relevant to ADHD. Blocking NA alpha(2A)-receptors in the PFC with yohimbine produces a profile similar to ADHD: locomotor hyperactivity, impulsivity and poor working memory. Conversely, drugs that enhance alpha(2)-receptor stimulation improve PFC function. Guanfacine directly stimulates postsynaptic alpha(2A)-receptors in the PFC and improves functioning, while methylphenidate and atomoxetine increase endogenous NA and DA levels and indirectly improve PFC function via alpha(2A)- and D(1) receptor actions. Methylphenidate and atomoxetine have more potent actions in the PFC than in subcortical structures, which may explain why proper administration of stimulant medications does not lead to abuse. Further understanding of the neurobiology of attention and impulse control will allow us to better tailor treatments for specific patient needs.

Efficacy and safety limitations of attention-deficit hyperactivity disorder pharmacotherapy in children and adults.

CNS Drugs. 2009; 23 Suppl 1: 21-31
Wigal SB
There have been major advances in the treatment and understanding of attention-deficit hyperactivity disorder (ADHD) in the last decade. Among these are the availability of newer stimulant formulations, an appreciation of the combined effects of medication and behavioural therapies, and a better understanding of the neurobiology of the disorder in children (aged 6-12 years), adolescents and adults. This article focuses on the evaluation of the efficacy and safety profiles of medications used for the management of ADHD. In assessing the various medical treatments for ADHD, certain issues and analyses have become important to address. The diagnosis, characterization and quantification of ADHD symptoms are crucial to assessing treatment effectiveness. A standardized setting for measuring the severity of ADHD symptoms is the laboratory school protocol, which simulates a school environment with tightly controlled timing of measurements. This method has been adapted successfully to the adult workplace environment to help with the evaluation of adult ADHD symptoms. Statistical analyses, such as effect size and number needed to treat, may aid in the comparison and interpretation of ADHD study results. Although an objective approach to evaluating the efficacy and safety profiles of the available medications provides necessary details about the medical options, typical clinical decisions are often based on trial and error and may be individualized based on a patient's daily routine, comorbidities and risk factors. Stimulants remain the US FDA-approved medical treatment of choice for patients with ADHD and are associated with an exceptional response rate. Findings of the Multimodal Treatment of Children With ADHD study suggest that the combination of behavioural and medical therapy may benefit most patients. Nonstimulant agents, such as atomoxetine (FDA-approved), and several non-approved agents, bupropion, guanfacine and clonidine, may offer necessary alternatives to the stimulants. This is especially important for patients who have comorbidities that are contraindicated for stimulant use based on medical issues and/or risk for stimulant abuse. Typical psychiatric comorbidities in patients with ADHD include oppositional defiant disorder, conduct disorder, major depressive disorder, bipolar disorder, anxiety, substance abuse disorder, tic disorder, and Tourette's syndrome. Although relatively safe, both stimulants and atomoxetine have class-related warnings and contraindications and are associated with adverse effects that require consideration when prescribing. Polypharmacy is a common psychiatric approach to address multiple symptoms or emergent adverse effects of necessary treatments. Future research may provide an improved understanding of polypharmacy and better characterization of the factors that influence the diagnosis and successful treatment of patients with ADHD.

 

This page was last reviewed by Dr Greg Mulhauser, Monday, 1 June 2009.

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