Mechanism of Action
Dextroamphetamine acts primarily by promoting the release of
dopamine and
norepinephrine from presynaptic nerve terminals. It also inhibits their reuptake, leading to increased concentrations of these neurotransmitters in the synaptic cleft. This dual action enhances neurotransmission and stimulates the CNS, resulting in heightened alertness and energy.
Therapeutic Uses
Besides ADHD and narcolepsy, dextroamphetamine is sometimes used off-label for conditions such as treatment-resistant depression and certain types of obesity. However, its use should be carefully monitored due to its high potential for
abuse and addiction.
Toxicity and Dosage
The therapeutic dosage of dextroamphetamine varies depending on the condition being treated. For ADHD, the typical starting dose is 2.5 to 5 mg per day for children and 5 to 10 mg per day for adults. The dose can be gradually increased based on the patient's response. However, exceeding the prescribed dosage can lead to
toxicity, characterized by symptoms such as restlessness, tremors, hyperreflexia, and rapid breathing.
Signs and Symptoms of Overdose
An overdose of dextroamphetamine can be life-threatening and requires immediate medical attention. Symptoms may include severe agitation, confusion, hallucinations, panic states, hyperthermia, and
rhabdomyolysis. In extreme cases, it can lead to cardiovascular collapse, seizures, and coma.
Management of Toxicity
The management of dextroamphetamine toxicity involves supportive care and symptomatic treatment. Activated charcoal may be administered if the overdose is recent. Benzodiazepines can be used to control agitation and seizures, while antihypertensive agents may be necessary to manage severe hypertension. Continuous cardiac monitoring and intravenous fluids are often required to stabilize the patient.Drug Interactions
Dextroamphetamine can interact with several other medications, increasing the risk of adverse effects or toxicity. For example, concurrent use with monoamine oxidase inhibitors (MAOIs) can result in a hypertensive crisis. It can also potentiate the effects of other CNS stimulants and certain antidepressants, leading to increased risk of serotonin syndrome.Long-Term Effects
Chronic use of dextroamphetamine can lead to psychological dependence and addiction. Long-term abuse has been associated with cardiovascular problems, such as hypertension and arrhythmias, as well as mental health issues, including anxiety, paranoia, and psychosis. It may also result in cognitive deficits and impaired social functioning.Conclusion
While dextroamphetamine is an effective medication for certain conditions, its potential for abuse and toxicity cannot be overlooked. Proper dosing, monitoring, and awareness of drug interactions are crucial to minimize the risks associated with its use. Prompt recognition and management of overdose symptoms are essential to prevent severe complications and ensure patient safety.
