Dextroamphetamine

Introduction Overview

Generic Name

dextroamphetamine

Brand Name

Xelstrym

Dosage Form

transdermal skin patch

Drug Class

CNS stimulants

Pharmacokinetics

Absorption:
Dextroamphetamine delivered via the Xelstrym transdermal patch is absorbed through the skin at a controlled rate. After application to clean, dry, hairless skin, peak plasma concentrations are typically achieved within several hours, with the patch designed to deliver medication over a 9-hour wear period. The transdermal route circumvents first-pass metabolism in the liver, resulting in more consistent systemic drug levels compared to oral administration. Factors such as skin thickness, hydration, temperature, and integrity can influence absorption rates. Bathing, showering, or swimming does not significantly affect drug absorption as the patch remains adhered during these activities if applied correctly.

Distribution:
Once absorbed, dextroamphetamine distributes widely throughout body tissues, including the central nervous system. It is lipophilic allowing penetration of the blood-brain barrier, where it exerts its pharmacological effects. Dextroamphetamine is moderately bound to plasma proteins (~15-40%). The volume of distribution is approximately 3-6 L/kg, indicating extensive tissue uptake. Distribution can be influenced by factors such as age, body fat content, and concomitant medications that alter plasma protein binding.

Metabolism:
Dextroamphetamine undergoes hepatic metabolism primarily through oxidative deamination and aromatic hydroxylation catalyzed by cytochrome P450 enzymes including CYP2D6. Metabolites include 4-hydroxyamphetamine and norephedrine, which have some pharmacologic activity but are less potent. Genetic polymorphisms affecting CYP2D6 may alter metabolism rates, influencing plasma levels and clinical response. Transdermal administration avoids the extensive first-pass metabolism seen with oral forms, potentially resulting in altered metabolite profiles.

Elimination:
The elimination half-life of dextroamphetamine from the transdermal patch is approximately 8-12 hours, with variability depending on urine pH and renal function. The drug and its metabolites are predominantly excreted renally via glomerular filtration and tubular secretion. Acidic urine increases ionization of amphetamines, reducing reabsorption and accelerating elimination. In contrast, alkaline urine prolongs elimination half-life. Renal impairment can significantly affect clearance, necessitating dosage adjustments. Sweat and fecal elimination are minor routes. The patch should be removed after 9 hours to prevent drug overexposure and accumulation.

Dosage Forms

Available Dosage Forms:
- Transdermal skin patch containing dextroamphetamine as the active ingredient.
- Specific strengths: 4.5 mg, 9 mg, 13.5 mg, and 18 mg per 9 hours of wear.

Dosages for Adults and Adolescents:
- Pediatric patients aged 6 to 17 years: Starting dose typically 4.5 mg/9 hours patch applied once daily.
- Dosage may be titrated upward weekly by 4.5 mg increments based on clinical response and tolerability, up to a maximum recommended dose of 18 mg/9 hours.
- Adults: Starting dose usually 9 mg/9 hours patch applied once daily with similar titration increments and a maximum dose of 18 mg/9 hours.

Specific Patient Populations:
- Pediatric use is approved for children 6 years and older.
- Caution advised for patients with cardiovascular disease, hypertension, severe agitation, history of substance abuse, or psychiatric disorders due to risk of adverse effects.
- Not recommended in patients with glaucoma, hyperthyroidism, or moderate to severe hypertension.
- Use during pregnancy may increase risks of premature birth and neonatal withdrawal; breastfeeding is contraindicated while using Xelstrym.
- Patients with renal impairment may require dose adjustment or monitoring given renal elimination characteristics.

Clinical guidelines emphasize applying the patch to different sites on the body each day, avoiding application on the same skin area within seven days to prevent irritation. The patch should be worn for no more than 9 hours per day, applied approximately two hours before symptom control is needed, and removed promptly after the wear period to minimize systemic accumulation and adverse reactions.

Mechanism Of Action

Dextroamphetamine, the active component of Xelstrym, is a potent central nervous system (CNS) stimulant belonging to the amphetamine class. Its primary molecular mechanism involves increasing synaptic concentrations of monoamine neurotransmitters, principally dopamine and norepinephrine, through multiple pathways. It enters presynaptic neurons via uptake transporters and promotes release of stored monoamines from vesicles into the synaptic cleft.

At the cellular level, dextroamphetamine reverses the direction of dopamine and norepinephrine transporters (DAT and NET), facilitating non-exocytotic release of neurotransmitters. It also inhibits the action of monoamine oxidase (MAO), the enzyme responsible for catabolism of these neurotransmitters, thereby prolonging their synaptic availability. This combined effect leads to enhanced neurotransmission in brain regions implicated in attention, alertness, and executive function.

Biochemically, dextroamphetamine interacts with trace amine-associated receptor 1 (TAAR1), modulating intracellular signaling cascades including cyclic AMP pathways. These effects contribute to increased neuronal firing rates and enhanced catecholaminergic tone. Such neurochemical modulation underlies the clinical efficacy of Xelstrym in reducing symptoms of attention deficit hyperactivity disorder (ADHD), by improving attention span, decreasing impulsivity, and mitigating hyperactivity.

Compared with other stimulants like methylphenidate, which primarily inhibits dopamine and norepinephrine reuptake, dextroamphetamine uniquely facilitates neurotransmitter release and inhibits monoamine degradation, offering a distinct pharmacodynamic profile. Clinical studies have confirmed the effectiveness of transdermal dextroamphetamine patches in sustained symptom control in both pediatric and adult populations with ADHD, highlighting favorable pharmacokinetics and steady drug delivery via the skin patch system.

Pharmacological Actions

Central nervous system stimulant with enhanced dopaminergic and noradrenergic neurotransmission.
Increases synaptic release of dopamine and norepinephrine by reversing VMAT2 and monoamine transporters.
Inhibits monoamine oxidase activity thereby reducing neurotransmitter breakdown.
Promotes increased neuronal firing and cortical arousal through activation of trace amine-associated receptor 1 (TAAR1).
Improves attention, focus, and impulse control in individuals with ADHD.
Produces sympathomimetic effects including increased heart rate and blood pressure.
Exhibits appetite suppressant properties mediated via hypothalamic pathways.
Enhances wakefulness and reduces fatigue by stimulating CNS alertness centers.
Demonstrates a prolonged and consistent systemic exposure profile due to transdermal delivery.
Potential for abuse and dependence due to euphoric effects linked to dopaminergic activation.
May precipitate mood changes including euphoria or irritability in sensitive patients.
Modulates motor function and behavior by impacting basal ganglia circuits.
Exerts peripheral vasoconstrictor effects contributing to potential cardiovascular side effects.
Increases release of serotonin to a lesser extent, contributing to complex neurotransmitter interactions.

Therapeutic Or Clinical Uses

Treatment of attention deficit hyperactivity disorder (ADHD) in children aged 6 years and older and adults.
Improves symptoms of inattention, hyperactivity, and impulsivity associated with ADHD.
Adjunctive therapy in narcolepsy to promote wakefulness and reduce excessive daytime sleepiness (off-label use).
Potential utility in treatment-resistant depression as an augmenting agent (clinical discretion required).
Useful in managing fatigue related to various medical conditions due to CNS stimulation.
Alternative delivery method for patients who have difficulty with oral stimulant administration.
May improve executive function and cognitive processing speed in individuals with ADHD.
Provides steady medication delivery with reduced peak-trough fluctuations compared to oral forms.
Appropriate for patients with gastrointestinal absorption issues who benefit from transdermal administration.
FDA-approved for once-daily dosing with controlled drug exposure over a 9-hour period.
Effective for patients requiring flexible dosing schedules and site rotation for patch application.
May facilitate improved adherence through simplified administration in appropriate patients.
An option for patients with swallowing difficulties or aversion to oral medications.
Suitable for long-term pharmacotherapy as part of a comprehensive ADHD management plan.
May be integrated into multi-modal treatment including behavioral therapies.

Side Or Adverse Effects

Mild to moderate skin irritation or contact dermatitis at the site of patch application.
Dry mouth, which may impact oral comfort and dental health.
Insomnia or difficulty initiating and maintaining sleep.
Headache and dizziness due to central stimulant effects.
Loss of appetite leading to weight loss, particularly in pediatric patients.
Nausea and occasional vomiting related to gastrointestinal stimulation.
Increased blood pressure and tachycardia with potential cardiovascular implications.
Mood changes including irritability, agitation, or anxiety.
Muscle twitching or tics, which may exacerbate pre-existing motor disorders.
Risk of serious cardiovascular events such as chest pain, arrhythmias, or hypertension exacerbation.
Potential for seizures in susceptible individuals or those with seizure disorders.
Psychotic symptoms including hallucinations, paranoia, or mania in rare cases.
Serotonin syndrome when combined with serotonergic agents.
Dependence and withdrawal manifestations upon abrupt discontinuation.
Rare but serious hypersensitivity reactions including rash, swelling, or anaphylaxis.

Precautions

Use with caution in patients with a history of cardiovascular disease or hypertension.
Monitor for the emergence or worsening of psychiatric symptoms such as psychosis, mania, or aggression.
Avoid use in patients with glaucoma or hyperthyroidism due to potential exacerbation.
Assess for history of drug or alcohol abuse given the potential for dependence.
Ensure proper skin site rotation to minimize irritation and dermatitis.
Regular cardiovascular monitoring including blood pressure and heart rate assessment is recommended.
Evaluate growth parameters in pediatric patients during prolonged therapy.
Caution advised when used concomitantly with serotonergic drugs to prevent serotonin syndrome.
Avoid use within 14 days of monoamine oxidase inhibitors to prevent hypertensive crisis.
Pregnancy risk requires weighing benefits against potential fetal harm; register patients for pregnancy exposure monitoring.
Not recommended during breastfeeding due to excretion in breast milk and potential adverse effects in infants.
Monitor for signs of peripheral vasculopathy including Raynaud's phenomenon.
Adjust dose carefully in patients with renal impairment or other comorbidities.
Educate patients about the risk of abuse and proper patch storage to prevent misuse.
Advise patients against activities requiring full alertness until response to therapy is established.

Warnings

Increased risk of addiction, misuse, and dependence with dextroamphetamine-containing products.
Potential for serious cardiovascular events including sudden death, stroke, and myocardial infarction, especially in patients with pre-existing cardiac conditions.
Possible exacerbation of hypertension necessitating close monitoring.
Risk of severe psychiatric adverse reactions such as psychosis, mania, hallucinations, and aggression.
Contraindicated in patients with known hypersensitivity to amphetamines or stimulant medications.
Severe allergic skin reactions and contact dermatitis may require discontinuation.
Risk of serotonin syndrome if combined with other serotonergic agents; discontinue immediately if symptoms occur.
Do not use concurrently with or within 14 days of using monoamine oxidase inhibitors (MAOIs) due to risk of hypertensive crisis.
Use with caution in patients with motor tics or Tourette's syndrome as it may worsen symptoms.
May impair ability to perform tasks requiring alertness; avoid driving until effects are known.
Avoid exposure to external heat sources (e.g., saunas, heat lamps) with patch application to prevent increased drug absorption.
Careful dose titration and patient monitoring essential to minimize overdose and toxicity risk.
Potential for fetal harm including premature birth, low birth weight, and neonatal withdrawal symptoms when used during pregnancy.
Not recommended in moderate to severe agitation or severe anxiety due to drug’s stimulating properties.
Strict adherence to prescribed dosing and patch application guidelines required to prevent overdose.

Contraindication

Known hypersensitivity or allergy to dextroamphetamine, amphetamines, or any component of Xelstrym patch.
Patients with glaucoma or increased intraocular pressure.
Severe hypertension or moderate to severe high blood pressure uncontrolled by therapy.
Severe heart disease including coronary artery disease, arrhythmias, or significant structural cardiac abnormalities.
History of drug or alcohol dependence or addiction.
Patients with severe agitation, anxiety, or tension where stimulant therapy may exacerbate symptoms.
Concurrent or recent use (within 14 days) of monoamine oxidase inhibitors (MAOIs).
Known or suspected psychosis or bipolar disorder not stabilized.
Peripheral vascular disease or Raynaud’s phenomenon may be a contraindication depending on severity.
Use in patients with motor tics or Tourette’s syndrome requiring careful consideration and often contraindicated.
Pregnancy and breastfeeding are contraindicated unless benefits outweigh risks and under strict medical supervision.
Severe renal impairment without ability to monitor plasma concentrations or adjust dose appropriately.
Use is contraindicated in patients with known hypersensitivity to adhesives or excipients of the patch that cause severe skin reactions.
Patients with seizure disorders not adequately controlled may be contraindicated or require close monitoring.
Any condition where increased sympathetic stimulation would be harmful is generally contraindicated.

Drug Interactions

Coadministration with monoamine oxidase inhibitors (MAOIs) is contraindicated due to risk of hypertensive crisis.
Concomitant use with serotonergic drugs (e.g., SSRIs, SNRIs, triptans, tramadol) may increase risk of serotonin syndrome.
Drugs that alter urinary pH (e.g., ammonium chloride, sodium bicarbonate) affect amphetamine elimination and plasma levels.
Antacids may modify absorption and renal excretion of dextroamphetamine.
Interaction with antihypertensives may reduce their effectiveness due to stimulant-induced blood pressure elevation.
Concomitant use of other CNS stimulants or vasoconstrictors increases risk of cardiovascular or CNS adverse events.
Ovulation-inducing agents or hormonal contraceptives may have altered efficacy when used simultaneously.
Co-administration with lithium may increase risk of agitation and neurotoxic effects.
Tramadol and fentanyl interactions may enhance CNS excitation leading to increased side effects.
Acetazolamide may increase excretion of amphetamines leading to modified therapeutic effects.
Use with diuretics may alter electrolyte and fluid balance, increasing risk of side effects.
Vitamin C or acidic products can increase renal clearance of amphetamines, potentially decreasing efficacy.
Buspirone interaction with dextroamphetamine may increase central nervous system stimulation.
Other seizure medications may alter plasma levels or increase seizure risk when combined with stimulants.
Methenamine and other urinary antiseptics may affect urinary excretion and pharmacokinetics of dextroamphetamine.

Preparations Of The Drug

Xelstrym transdermal skin patch containing dextroamphetamine.
Patch available in doses delivering 4.5 mg, 9 mg, 13.5 mg, and 18 mg of dextroamphetamine over 9 hours.
Patch composed of acrylic adhesives, green ink, polyester/polyurethane backing, and polyester release liner.
Provided as a single-use, disposable patch to be applied once daily.
Transdermal system designed to adhere to clean, dry, and hairless skin surfaces such as the upper arm, chest, or back.
Supplied in a protective pouch to maintain patch integrity until application.
Packaged in original sealed containers to prevent contamination and preserve drug stability.
Each patch is individually labeled with strength and directions for safe disposal.
Patch instructions include applying approximately two hours before activity requiring symptom control and removal after 9 hours.
Not to be cut or altered to ensure dose accuracy and controlled drug delivery.
Manufactured by Noven Pharmaceuticals, Inc. in Miami, FL, USA.
Patient information leaflet includes detailed guide on usage, warnings, storage, and disposal.
Storage conditions recommend room temperature away from moisture, heat, and light.
Unused or discarded patches should be disposed of per local regulations to prevent accidental exposure.
Provided alongside medication guides emphasizing abuse potential and safe handling.