Behaviour | August 8, 2014 | Author: The Super Pharmacist
Attention deficit/hyperactivity disorder (ADHD) is a neuropsychiatric disorder that may also present with symptoms such as inconsistent focus and performance in completing tasks, poor motivation and drowsiness. ADHD diagnosis is strongly associated with male children under 18, but may also have an onset in adult patients. This condition is associated with brain regions that control aspects of cognition, social interaction and impulse control.
ADHD primary treatment is mostly based on pharmacotherapy that improves the availability and/or activity of the neurotransmitters dopamine and norepinephrine. These are classed as either 'stimulant' or 'non-stimulant' drugs. Many of these are established as being ADHD long term success treatments. The main factors affecting adherence to these treatment options are adverse effects and patient concerns about the nature or effects of ADHD medications.
Attention deficit/hyperactivity disorder is a neuropsychiatric disorder commonly characterised by poor impulse control, hyperactivity, and chronic inattention.
Estimates suggest that approximately 10% of children from 7 to 12 years exhibit symptoms that satisfy the DSM-5 criteria for ADHD and 40 to 60% of these may experience symptoms that persist beyond adolescence.
ADHD is typically diagnosed in those aged three to seventeen, although adult onset is also possible and males 3 times more likely than females.
This condition is associated with specific differences in areas of the brain that control working memory, cognition, response inhibition, social interaction and sleep compared to healthy individuals of the same age.
ADHD may present as a variety of symptoms beyond those typically associated with the disorder, such as poor focus, motivational deficits, inconsistent task performance, drowsiness and/or sleep disorders. These areas are mainly associated with the neurotransmitters dopamine, serotonin and norephinephrine. Therefore, pharmacotherapy that affects the availability of one or more of these molecules is often the basis of ADHD treatment.
Methylphenidate (Ritalin®, Concerta®): This is the standard ADHD treatment. It acts by inhibiting the dopamine transporter protein in the brain, which leads to increased availability of dopamine and norepinephrine.
Methylphenidate is associated with a range of side-effects, including insomnia, mood disorders, abdominal and chest pain, anorexia, sweating, lethargy and drowsiness.
This drug may be associated with an increased risk of serious psychiatric disorder (e.g. psychosis) development. It is also popularly associated with growth retardation, but recent reviews have found no significant associaton between this and methylphenidate administration in children or adolescents.
Dexamphetamine: This is an analogue of amphetamine. It increases dopamine availability by binding a receptor called TAAR1 in certain nerve cells. It is similar to methylphenidate in terms of side-effects, and may also cause euphoric effects in some patients. Both of these drugs are thought to be equal in terms of ADHD symptom reduction.
Amphetamine and dexamphetamine (not available in Australia): This combination of the two most well-known forms of amphetamine is also popular in ADHD treatment. It is associated with the same side-effect profile of dexamphetamine, and may also be associated with an increased risk of anxiety disorder development. It is very established in the management of symptoms in children, but trials in adults with ADHD are limited.
Atomoxetine (Strattera®): This is a non-stimulant drug (a selective norepinephrine uptake inhibitor) that is approved for ADHD treatment. It has demonstrated significant improvements on symptoms scores and quality of life metrics compared to placebo in adult patients. It is also associated with a range of side-effects, which include dyspepsia, decreased appetite, dizziness, insomnia, irritability, dry mouth and nausea.
Guanfacine (not marketed in Australia): This is an agonist (or activator) of the alpha-2 receptor, which responds to the neurotransmitter noradrenaline. It is associated with significant improvements in inattention and behavioural symptoms of ADHD in children. Guanfacine is approved for use in patients under; however, a recent review showed no effect of the drug on symptoms in adolescent patients. There is little data on the effects of this drug on adult ADHD. The side-effects of guanfacine are simliar to those of atomoxetine, and may also cause sedation.
Treatment is often initiated soon after a diagnosis of ADHD. In a review of pharmacotherapy practice for this condition, approximately 80% of patients aged three to seventeen were prescribed medication within 12 months of diagnosis.
Early treatment is associated with positive outcomes, but may not achieve 'normalisation' of child ADHD patients in all cases. There is a paucity of research on the long-term outcomes of ADHD treatment in adults. One study indicates that long-term stimulant treatment was associated with limited occupational improvement, unless the patient had significantly severe symptoms at diagnosis.
There are indicatations that both stimulant and non-stimulant drugs are associated with positive outcomes for up to 24 months of treatment.
A small-scale trial of methylphenidate combined with dexamphetamine in adult patients over 16 weeks showed some positive outcomes, but also a relatively high (38%) proportion of non-responders, and also indicated a high probability of anxiety disorder exacerbation, if patients have this pre-existing condition.
Clinical trials of atomoxetine have demonstrated significant improvements at 10 weeks, 12 weeks and 6 months. Adherence to atomoxetine treatment may be affected by side-effects, however; one trial with 233 patients was subject to nearly 16% dropout due to adverse events.
ADHD treatment is also affected by non-compliance in general.
For example, another 23.9% of the participants dropped out of this same trial simply due to the fact that it was open-label; i.e. the patients knew which type of drug they were taking.
A review of the long-term safety of methylphenidate, atomoxetine and amphetamines in children showed that up to 78% of patients documented experienced side-effects, which led to discontinuation in up to 25% of these.
A review of twelve studies of guanfacine showed that 26% of the patients documented discontinued treatment due to adverse events.
Non-adherence to treatment may also be based on other reasons, such as patient (or parent) fears about stimulants, their side-effects and potential for addiction.
Treatment is generally associated with positive outcomes in social function and psychological well-being for all age groups.
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