An Overview of ADHD Stimulant Medications: How Do They Work?

Three Main Types of ADHD Stimulant Medications

The majority of medications that are approved for treating ADHD are stimulants. Of these, there are three main types:

  • Methylphenidate (MPH)
  • Dextroamphetamine (DEX or d-Amph)
  • Mixed Amphetamine Salts (AMP or MAS)

There are a variety of ADHD stimulant medications which administer these drugs in various doses and through different mechanisms of release.

Instant Release vs. Time Release

The two main methods for administering ADHD stimulant medications are instant release and time release pills.

At first, ADHD stimulants were only available in instant release form. These generally last for only a few hours, and so ADHD patients needed to take multiple doses throughout the day in order to maintain the effects of the drug. Since people with ADHD tend to be forgetful, and because multiple doses are inconvenient, pharmaceutical companies began to develop drugs which last longer.

For example, Concerta is an MPH which has a coating of medicine that is released within an hour of ingestion. After that, there are two additional doses that take effect later in the day. Other time release medications do not have a medicated coating. Instead, they may contain a powder or tiny beads which cause the drug to be released at different times throughout the day. Examples include Vyvanse, which uses powder, and Adderall XR, which uses beads.

How the Brain Communicates

In order to understand how these medications treat ADHD symptoms, it is important to know a little bit about how the brain communicates. It does this through cells called neurons which send signals to each other by releasing chemicals called neurotransmitters.

When a neuron receives a signal to fire, it transmits this signal through its axon (nerve fiber). Once the signal reaches the end of the neuron, neurotransmitters are released into a tiny space (the synaptic cleft) between the first neuron and the second. The outside of the second neuron has receptors, which tell it when these neurotransmitters have been received. It then sends this signal down its axon and releases its own neurotransmitters in order to communicate with the next neuron.

After the signal has been sent, the neurotransmitters that have been used are usually broken down by enzymes or taken back up into the first neuron through a process called reuptake.

How do ADHD Stimulant Medications Treat Symptoms of ADHD?

There is a strong evidence which suggests that ADHD symptoms are caused by problems in how the brains of people with ADHD communicate. Specifically, ADHD patients have problems with the production and transmission of the neurotransmitters dopamine and norepinephrine.

Research on ADHD stimulant medications shows that they work by blocking the reuptake of dopamine. This means that there is a greater amount of dopamine available between the neurons, making it easier for signals to be sent.

The neural effects which have been observed are consistent with the therapeutic uses of ADHD stimulant medications. In particular, from looking at how these drugs work in the brain, one would expect that they would decrease distractibility and improve the patient's motivation to perform required tasks. (Volkow, et. al., 2002) Other research also suggests that drugs which increase dopamine levels would result in decreased impulsivity.

Are Stimulant Medications Effective?

As one would expect based on the predictions made by these findings, research has repeatedly found that ADHD stimulant medications significantly improve symptoms for most patients diagnosed with ADHD. In fact, roughly 80% of patients respond positively to this form of treatment and demonstrate measurable improvements in sustaining attention, controlling impulsive behavior, and feeling motivated to fulfill their obligations. (Brown, 2005; Faraone, 2009)

Stimulant medications are not "one size fits all." As mentioned earlier, there is a wide variety of dosages and methods of administration among these drugs. Studies have found a high degree of variability in effective dosage levels between patients – even between those with similar physical characteristics. For example, some small children require high doses in order for the drug to be effective, whereas some heavier and older individuals may need very low amounts of the same drug in order to achieve the same effect.

For this reason, doctors who prescribe ADHD stimulant medications tailor their treatment plans to each specific individual. Treatment usually begins with low doses of the prescribed drug, which are incrementally raised over time until an effective dosage has been found for that specific patient.

Stimulant Medications are not for Everyone

Although it is generally agreed that usage of ADHD stimulant medications is safe under the careful supervision of a qualified medical professional, there are some downsides to this treatment option.

Despite the significant improvements experienced by the majority of patients diagnosed with ADHD, stimulant medications are not effective for everyone. Roughly 20% of patients do not find relief of their symptoms through the usage of stimulants. For these people, it is necessary to pursue alternative treatments.

ADHD Stimulant Medication Side Effects

Aside from cases where these drugs are not effective, there are additional reasons why people choose not to take stimulants to improve their ADHD symptoms.

There are a number of side effects which are associated with these medications. Some of them include: dry mouth, loss of appetite, sleeplessness, clenching of teeth (bruxism), jitteriness and reduced emotional responses, among others. When patients experience these side effects, they may become nervous about continuing to take the medication, and some even stop pursuing this form of treatment.

While these side effects are common, it is important to point out that many of them dissipate throughout the course of the treatment. It takes time for the brain to adjust to stimulants, and this should be kept in mind by people who are considering discontinuing the treatment.

Disclaimer

The content of this article is for information purposes only and is not intended to replace sound medical advice and opinion.

References

Brown, Thomas E. Attention Deficit Disorder: The Unfocused Mind in Children and Adults, Yale University Press, 2005, 246 – 295.

Faraone, Stephen V. "Using Meta-analysis to Compare the Efficacy of Medications for Attention-Deficit/Hyperactivity Disorder in Youths", P&T, 2009, vol. 34, no. 12, pp. 678 – 694.

Volkow, Nora D., Folwer, Joanna S., et. al., "Mechanism of Action of Methylphenidate: Insights from PET Imaging Studies", Journal of Attention Disorders, 2002, vol. 6 (Supplement I): S31 – S43.

"Stimulant Medications and ADHD – Fact Sheet", National Center for Gender Issues and AD/HD.

Image Credits

"Synapse diag1", Wikimedia Commons/(CC) Vectorization: Mouagip; Drawn by fr:Utilisateur:Dake; Corrections of original PNG by en:User:Nrets.