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Study on the Safety and Effectiveness of Guanfacine Hydrochloride and Atomoxetine Hydrochloride for Children and Adolescents with ADHD Aged 6 to 17 Years

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the safety and effectiveness of a medication called Guanfacine Hydrochloride in children and adolescents aged 6 to 17 years who have been diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD). ADHD is a condition that affects attention, self-control, and the ability to sit still. The study is designed to help understand how well Guanfacine Hydrochloride works and how safe it is for long-term use in young people who cannot use stimulant medications due to various reasons such as intolerance or ineffectiveness.

The trial will compare Guanfacine Hydrochloride with another medication called Atomoxetine Hydrochloride, which is also used to treat ADHD. Participants will be randomly assigned to receive either Guanfacine Hydrochloride, Atomoxetine Hydrochloride, or a placebo. The study will begin with a phase where the best dose for each participant is determined, followed by a period where the medication is taken regularly. The trial will last for a total of 12 months, during which the participants' attention and reaction times will be monitored using a computer-based test called the Cambridge Automated Neuropsychological Test Battery (CANTAB).

The main goal of the study is to evaluate the long-term safety of Guanfacine Hydrochloride and its effects on attention and psychomotor speed, which refers to the coordination between thinking and physical movement. The study will also look at other health indicators such as weight, height, and vital signs like blood pressure and heart rate. This research aims to provide valuable information on the use of Guanfacine Hydrochloride for managing ADHD in children and adolescents.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, the participant will be informed about the trial's purpose and procedures. Consent from a parent or legally authorized representative is required, along with the participant's assent if applicable.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to confirm eligibility. This includes checking intellectual functioning, ability to swallow tablets, and ensuring blood pressure is within the required range.

  3. Step 3

    Randomized treatment phase

    Participants will be randomly assigned to receive either guanfacine hydrochloride or atomoxetine hydrochloride. The medication will be taken orally once daily. The dosage will be optimized based on individual response and tolerance.

  4. Step 4

    Dose optimization

    During this phase, the dosage of the medication will be adjusted to find the most effective and tolerable dose for each participant. This process ensures the best possible outcome for managing symptoms.

  5. Step 5

    Double-blind evaluation

    In this part of the study, neither the participants nor the researchers will know which medication is being administered. This helps to ensure unbiased results when assessing the medication's effectiveness and safety.

  6. Step 6

    Open-label evaluation

    Following the double-blind phase, all participants will receive guanfacine hydrochloride in an open-label manner, meaning both participants and researchers will know the medication being taken. This phase allows for further assessment of the medication's long-term safety and efficacy.

  7. Step 7

    Safety and efficacy assessments

    Throughout the study, regular assessments will be conducted to monitor safety and efficacy. This includes measuring reaction time, attention, and other cognitive functions using specific tests. Vital signs, weight, and other health indicators will also be monitored.

  8. Step 8

    Completion of the study

    Upon completing the study, participants will undergo a final assessment to evaluate the overall impact of the treatment. This includes a review of any changes in symptoms and any side effects experienced during the trial.

Who can join the trial?

11 criteria

  • The participant must be a boy or girl aged 6 to 17 years old.
  • The participant should be able to think and understand at a level appropriate for their age, as judged by the study doctor.
  • The participant must be able to swallow whole tablets.
  • If the participant is a girl who can have children, she must have a negative pregnancy test before starting the study and agree to use birth control if required by the study rules. This applies to girls aged 9 years or older, or younger if they have started menstruating.
  • The participant's blood pressure must be within the normal range for their age, sex, and height when lying down and standing up.
  • The participant must have a main diagnosis of ADHD according to a detailed psychiatric evaluation.
  • The participant must have tried stimulant medications for ADHD that were not suitable, not tolerated, or did not work, as determined by the study doctor.
  • The participant must have a certain score on the ADHD Rating Scale, which measures the severity of ADHD symptoms.
  • The participant must have a certain score on the Clinical Global Impressions-Severity (CGI-S) scale, which measures the severity of the participant's condition.
  • The participant's parent or legal guardian must sign a consent form agreeing to the participant's involvement in the study. The participant must also agree to take part in the study and understand what it involves.
  • The participant and their parent or guardian must be willing and able to follow all the study requirements, including taking the study medication each morning.

Who cannot join the trial?

10 criteria

  • Patients who have a medical condition other than ADHD that might interfere with the study.
  • Patients who are currently taking medications that could affect the study results.
  • Patients who have a history of severe allergies or reactions to medications.
  • Patients who have a history of drug or alcohol abuse.
  • Patients who have a serious mental health condition, such as severe depression or anxiety.
  • Patients who are pregnant or breastfeeding.
  • Patients who have participated in another clinical trial within the last 30 days.
  • Patients who have a family history of certain heart conditions.
  • Patients who have a history of seizures or epilepsy.
  • Patients who have a significant medical condition that the study doctor believes would make participation unsafe.
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Investigated drugs

  • Guanfacine Hydrochloride Prolonged-release

    is a medication used in this trial to help manage symptoms of Attention-deficit/Hyperactivity Disorder (ADHD) in children and adolescents. It works by affecting certain parts of the brain to improve attention, focus, and impulse control. This medication is designed to release slowly over time, providing a steady effect throughout the day.

  • Atomoxetine

    is another medication being studied in this trial. It is used to treat ADHD by increasing the levels of certain chemicals in the brain that help with attention and impulse control. Unlike some other ADHD medications, atomoxetine is not a stimulant, which means it works differently and may be suitable for those who cannot tolerate stimulant medications.

What is already known about the treatment

Guanfacine Hydrochloride Prolonged-release (SPD503) – This medication is taken orally in the form of a prolonged-release tablet, which means it is designed to release the active ingredient slowly over time. It is currently being studied in clinical trials for its safety and effectiveness in treating children and adolescents aged 6 to 17 years with Attention-deficit/Hyperactivity Disorder (ADHD), especially for those who cannot use stimulant medications. Guanfacine works by affecting receptors in the brain to help improve attention and reduce hyperactivity and impulsiveness. It is classified as an alpha-2 adrenergic agonist, which means it helps calm certain parts of the brain.

Investigated diseases

Attention-deficit/hyperactivity disorder (ADHD) – ADHD is a neurodevelopmental disorder characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. Inattention may manifest as wandering off task, lacking persistence, having difficulty sustaining focus, and being disorganized. Hyperactivity involves excessive movement, fidgeting, or an inability to stay still, while impulsivity refers to hasty actions that occur without forethought and have a high potential for harm. The symptoms typically appear before the age of 12 and can continue into adulthood. The disorder can lead to difficulties in academic, occupational, and social settings. The severity and specific symptoms can vary widely among individuals.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase IIITrial ID2022-502630-71-00Protocol codeSPD503-401Estimated enrolment287 patientsSponsorTakeda Development Center Americas Inc.

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