What is Dexamphetamine?
Dexamphetamine, or dextroamphetamine, is a powerful central nervous system (CNS) stimulant belonging to the amphetamine class of drugs. It is the dextro-isomer of the compound d,l-amphetamine sulfate. As a prescription medication, it is classified as a Schedule II controlled substance in the United States, indicating that it has a high potential for abuse and dependence, but also has accepted medical uses.
The drug works by speeding up the messages traveling between the brain and body. This action helps to improve concentration, reduce hyperactivity, and manage impulsive behaviors in individuals with ADHD, and promotes wakefulness in those with narcolepsy. Due to its potency and potential for misuse, it is tightly controlled and only available with a doctor's prescription.
How Does Dexamphetamine Work?
Dexamphetamine exerts its therapeutic effects by influencing several neurochemical pathways in the brain. Its primary mechanism of action involves increasing the levels of certain monoamine neurotransmitters in the brain, particularly dopamine and norepinephrine.
- Promoting Neurotransmitter Release: Dexamphetamine facilitates the release of dopamine and norepinephrine from nerve terminals in the brain. This flood of neurotransmitters into the synaptic cleft enhances chemical signaling between neurons.
- Blocking Reuptake: The drug also acts as a reuptake inhibitor, meaning it blocks the transporters that reabsorb dopamine and norepinephrine back into the nerve cell. This prolongs the presence of these neurotransmitters in the synapse, extending their effect.
- Inhibiting Monoamine Oxidase: In addition to releasing neurotransmitters and blocking their reuptake, dexamphetamine also inhibits monoamine oxidase (MAO), an enzyme that breaks down monoamines. This further increases the levels of circulating monoamines.
By increasing the availability of dopamine and norepinephrine, dexamphetamine can enhance brain functions related to attention, focus, and executive function. The specific effects on different brain regions, particularly the prefrontal cortex, are what lead to the therapeutic benefits observed in patients with ADHD and narcolepsy.
Uses and Medical Indications
Dexamphetamine is an important part of a comprehensive treatment plan for specific medical conditions. Its FDA-approved indications include:
- Attention-Deficit/Hyperactivity Disorder (ADHD): Used to help manage the core symptoms of ADHD in both adults and children, including distractibility, a short attention span, impulsivity, and hyperactivity. It is often used in combination with other remedial measures such as counseling and psychological interventions.
- Narcolepsy: Prescribed to treat narcolepsy, a chronic sleep disorder characterized by overwhelming daytime sleepiness and sudden attacks of sleep. By promoting alertness and wakefulness, dexamphetamine helps patients manage their symptoms throughout the day.
Forms of Dexamphetamine
Dexamphetamine is available in different formulations to accommodate varying treatment needs. These include:
- Immediate-release tablets: This form is designed for rapid onset of action.
- Extended-release capsules (e.g., Dexedrine Spansule): These are formulated to provide a longer duration of action. The contents can sometimes be sprinkled on food like applesauce if swallowing the capsule is difficult.
- Oral solution: A liquid form for oral administration.
The appropriate amount and timing of administration should always be determined by a physician to find the most effective and tolerable regimen for an individual patient. Patients should never change their regimen without consulting their healthcare provider.
Side Effects and Risks
As a potent stimulant, dexamphetamine can cause a range of side effects, from mild to severe. Common side effects often subside as the body adjusts to the medication, but more serious issues require immediate medical attention.
Common Side Effects:
- Nervousness or restlessness
- Headache
- Dry mouth
- Loss of appetite and weight loss
- Trouble sleeping
- Stomach pain, nausea, or vomiting
- Changes in sex drive
Serious Adverse Effects:
- Cardiovascular issues: Increased blood pressure and heart rate, heart palpitations, and, in rare cases, more serious heart problems like heart attack, stroke, or sudden death, especially in individuals with pre-existing heart conditions.
- Psychiatric symptoms: New or worsened behavioral or thought problems, agitation, hallucinations, mania, or psychosis.
- Circulation problems: Raynaud's phenomenon, which can cause fingers or toes to feel numb, cool, or painful and change color.
- Abuse and Dependence: Dexamphetamine has a high potential for abuse and psychological dependence. Misuse can lead to tolerance, addiction, and severe withdrawal symptoms upon discontinuation.
Dexamphetamine vs. Other Stimulants
When comparing dexamphetamine to other CNS stimulants, a few key distinctions, particularly regarding chemical makeup and effect profile, are important. This comparison table highlights the differences between Dexedrine (dextroamphetamine) and Adderall (a combination of amphetamine salts).
| Feature | Dexedrine (Dextroamphetamine) | Adderall (Amphetamine/Dextroamphetamine Salt Combo) |
|---|---|---|
| Chemical Composition | Contains only dextroamphetamine, the more potent, d-isomer of amphetamine. | A combination of four amphetamine salts, including both the dextroamphetamine (d-amphetamine) and levoamphetamine (l-amphetamine) isomers. |
| Potency | Generally considered stronger on a milligram-for-milligram basis due to its pure d-isomer composition. | The inclusion of the milder l-amphetamine isomer can create a more balanced effect, which some people may perceive as less intense than Dexedrine. |
| Effect Profile | Focuses more on mental alertness and attention. | Offers a broader range of effects, including increased physical energy, due to the presence of the l-amphetamine isomer. |
| Duration of Action | Available in both immediate-release and extended-release forms. | Available in immediate-release (IR) and extended-release (XR) forms. The XR form has a unique delivery system. |
Precautions and Warnings
Before taking dexamphetamine, it is essential to discuss your full medical history and all current medications with your doctor.
- Contraindications: Dexamphetamine should not be used in patients with known hypersensitivity to stimulants, moderate to severe hypertension, advanced arteriosclerosis, symptomatic cardiovascular disease, hyperthyroidism, glaucoma, or severe anxiety/agitation.
- Drug Interactions: Dangerous interactions can occur with monoamine oxidase inhibitors (MAOIs). Certain other medications, including antidepressants, blood pressure medication, and over-the-counter cold/allergy remedies, can also interact.
- Dietary Interactions: Vitamin C and fruit juices can interfere with the body's absorption of the medication.
- Monitoring: Patients should be regularly monitored for blood pressure, heart rate, and any changes in mood or behavior. Growth should be monitored in children and adolescents.
Withdrawal Symptoms
Abruptly stopping dexamphetamine, particularly after prolonged use or misuse, can lead to withdrawal symptoms as the body physiologically adapts. The severity of withdrawal depends on the duration of use.
Symptoms can include:
- Intense cravings
- Extreme fatigue
- Depression, anxiety, or irritability
- Increased appetite
- Restless sleep or vivid, unpleasant dreams
- Psychomotor agitation or retardation
Under medical supervision, the medication regimen can be gradually adjusted to minimize withdrawal effects.
Conclusion
What is dexamphetamine? It is a potent CNS stimulant that is an effective and critical part of treatment for ADHD and narcolepsy when used as prescribed. Its mechanism of action, which increases key neurotransmitters like dopamine and norepinephrine, helps to manage symptoms of these conditions effectively. However, due to its high potential for abuse and significant side effect profile, it is a Schedule II controlled substance. Patients and healthcare providers must be diligent in following prescribing instructions, monitoring for adverse effects, and being aware of the risks of misuse and dependence. For more comprehensive patient information, the MedlinePlus drug information page is a valuable resource.
