Dextroamphetamine

Stimulants are first-line drugs for children and adults diagnosed with attention-deficit hyperactivity disorder (ADHD). But how do they actually work?

First, let’s look at the brain

• Medical imaging indicates people with ADHD may have slight differences in their brain’s structure, the way their brain regions work together to perform tasks, and how their brain’s chemical messengers, called neurotransmitters, pass on information.
• These brain differences are associated with the symptoms of ADHD, including inattention, impulse control and problems with memory.

What stimulants are prescribed in Australia?

• The three main stimulants prescribed for ADHD in Australia are dexamfetamine, methylphenidate (sold under the brand names Ritalin and Concerta) and lisdexamfetamine (sold as Vyvanse).
• Dexamfetamine and methylphenidate have been around since the 1930s and 1940s respectively.

So how do they work for ADHD?

• Stimulants increase the amount of dopamine and noradrenaline in the tiny gaps between neurons, known as synapses.
• They do this by predominantly blocking a transporter that then prevents their re-uptake back into the neuron that released them.
• Amphetamines also increase the amount of dopamine the neuron releases into the synapse (the tiny gaps between neurons).

What effect do they have on ADHD symptoms?

We still don’t fully understand the underlying brain mechanisms that change behaviour in people with ADHD. But research shows stimulants that modulate noradrenaline and dopamine can improve brain processes such as:
They can also improve general behaviour, such as self-control, not talking over the top of others, and concentration. These behaviours are important for social interactions. Stimulants reduce ADHD symptoms in about 70% to 80% of children and adults who take them. Some people will notice their symptoms improve right away. Other times, these improvements will be more noticeable to parents, carers, teachers, colleagues and partners.

Not everyone gets the same dose

The optimal stimulant dose varies between individuals, with multiple dosage options available. This enables a “start low, go slow” approach, where the stimulant can be gradually increased to the most effective dose for the individual.

• Dexamfetamine and methylphenidate are available in immediate-release preparations.
• As these have short half-lives (meaning they act quickly and wear off rapidly), they are often taken multiple times a day – usually in the morning, lunch and afternoon.
• Methylphenidate is also available in long-acting tablets (Concerta) and capsules (Ritalin LA).

What are the side effects?

The most common side effects are sleep problems and decreased appetite. A recent study showed children and young people taking methylphenidate for ADHD were around 2.6 times more likely to have sleep problems and 15 times more likely to have a decreased appetite than those not taking methylphenidate. Headache and abdominal pain are also relatively common.

Can someone without ADHD take a stimulant to improve productivity?

• As stimulants increase dopamine, they can cause euphoria and a heightened sense of wellbeing.
• A common myth about stimulant medicines is they can improve the concentration and productivity of people without ADHD.
• At each of the sessions, participants were given either a placebo or a stimulant before completing the task.
• Read more:
  ADHD medications have doubled in the last decade – but other treatments can help too

Mary Bushell does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.