Dexmethylphenidate: Difference between revisions

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 | classes           = Psychostimulant, CNS stimulant, NDRI
 | mechanism         = Norepinephrine–dopamine reuptake inhibition (DAT, NET) — d-threo enantiomer of methylphenidate
-| uses              = ADHD
+| uses              = Inattention, Productivity
 | formula           = C<sub>14</sub>H<sub>19</sub>NO<sub>2</sub>
 | routes            = Oral
@@ Line 98: / Line 98: @@
 | seealso           = [[Methylphenidate]], [[Mixed amphetamine salts]], [[Dextroamphetamine]], [[Lisdexamfetamine]], [[Modafinil]], [[Atomoxetine]], [[Viloxazine]]
 | references        =
-}}
+}}<h2 id="Pharmacokinetics">Pharmacokinetics</h2><span></span>
+'''Absorption:''' Rapid oral absorption; peak plasma in ~1–1.5 h (IR) or ~6.5 h (XR, which has a biphasic release profile with an initial peak around 1.5 h and a second peak ~6.5 h). Bioavailability ~22–25% due to extensive first-pass metabolism. '''Distribution:''' Volume of distribution similar to racemic methylphenidate (~13 L/kg); plasma protein binding ~15%. '''Metabolism:''' Like the racemate, dexmethylphenidate is metabolized primarily by '''carboxylesterase 1 (CES1)''' to ritalinic acid (inactive). This non-CYP metabolic pathway means dexmethylphenidate, like its racemate, has '''few clinically significant CYP-mediated drug interactions'''. '''Elimination:''' Predominantly renal as ritalinic acid; parent half-life 2.2 h (IR) and ~3 h (XR parent). Multi-dose-daily IR dosing or once-daily XR is required for sustained therapeutic effect.<h2 id="Pharmacodynamics">Pharmacodynamics</h2>
+Mechanistically identical to racemic methylphenidate at the molecular level — competitive inhibition of the dopamine and norepinephrine transporters (DAT, NET), increasing synaptic catecholamine concentrations without acting as a transporter substrate (i.e., no reverse transport or vesicular displacement; '''reuptake inhibition only'''). The functional difference is purely stereochemical: dexmethylphenidate provides the same effective amount of pharmacologically active material at half the milligram dose. Minimal effect on serotonin; no MAO inhibition; no significant binding at 5-HT, histamine, or muscarinic receptors.<h2 id="Indications">Indications</h2>
+*Attention-deficit hyperactivity disorder (children ≥6 y, adolescents, and adults)
+*Off-label: same off-label uses as racemic methylphenidate (treatment-resistant depression augmentation, cancer/HIV/MS fatigue)
+*Not FDA-approved for narcolepsy (use racemic methylphenidate or an amphetamine for that indication)<h2 id="Dosing">Dosing and titration</h2>
+<span></span>
+'''Focalin IR:''' Start 2.5 mg PO twice daily (separate doses by at least 4 h). Titrate by 2.5–5 mg/week. Max 20 mg/day (adults and children).
+'''Focalin XR:''' Start 5 mg PO once daily AM (children), 10 mg PO once daily AM (adults). Titrate weekly. Max 30 mg/day (children); 40 mg/day (adults).
+'''Conversion from racemic methylphenidate:''' use approximately '''half''' the total daily dose (e.g., Ritalin 20 mg/day → Focalin 10 mg/day).
+<span></span>
+'''Renal/hepatic impairment:''' caution; reduce dose and monitor.<h2 id="Effects">Effects</h2><span></span>
+====Therapeutic====
+*<effect slug="attention" label="Attention and focus">Improved attention, executive function, and working memory. Many patients report a cleaner subjective effect than racemic methylphenidate at equivalent therapeutic doses.</effect>
+*<effect slug="reduced-impulsivity" label="Reduced impulsivity and hyperactivity" />
+*<effect slug="wakefulness" label="Wakefulness" />
+<span></span>
+====Common====
+*<effect slug="decreased-appetite" label="Decreased appetite">Often dose-limiting; may produce weight loss over time.</effect>
+*<effect slug="insomnia" label="Insomnia">Especially with late-afternoon dosing.</effect>
+*<effect slug="headache" label="Headache" />
+*<effect slug="abdominal-pain" label="Abdominal pain" />
+*<effect slug="irritability" label="Irritability" />
+*<effect slug="dry-mouth" label="Dry mouth" />
+*<effect slug="hr-bp-elevation" label="Elevated heart rate / blood pressure">Usually mild but dose-dependent.</effect>
+*<effect slug="weight-loss" label="Weight loss" />
+<span></span>
+====Cardiovascular====
+*<effect slug="palpitations" label="Palpitations / tachycardia" />
+*<effect slug="cardiac-event" label="Serious cardiac event">Rare reports of sudden cardiac death in patients with structural heart disease (FDA warning).</effect>
+<span></span>
+====Psychiatric====
+*<effect slug="anxiety" label="Anxiety" />
+*<effect slug="agitation" label="Agitation" />
+*<effect slug="psychosis" label="Psychosis">Rare; higher risk in patients with bipolar predisposition.</effect>
+*<effect slug="mania" label="Mania">Rare; higher risk in patients with bipolar predisposition.</effect>
+*<effect slug="hallucinations" label="Hallucinations">Visual or tactile; rare, more common at higher doses or in predisposed patients.</effect>
+<span></span>
+====Other adverse====
+*<effect slug="tics" label="Tics">May emerge or worsen; comorbid Tourette syndrome is a traditional relative contraindication.</effect>
+*<effect slug="dependence" label="Dependence / misuse">Schedule II controlled substance; abuse liability similar to racemic methylphenidate per milligram of active material. Crushed/insufflated/IV misuse is the major risk pattern.</effect>
+*<effect slug="tolerance" label="Tolerance">To therapeutic effects, with chronic high-dose use.</effect>
+*<effect slug="growth-suppression" label="Growth suppression">Modest reduction in growth velocity in chronically-treated children.</effect>
+*<effect slug="priapism" label="Priapism">Rare but documented; FDA warning, especially in adolescents.</effect>
+*<effect slug="vasculopathy" label="Peripheral vasculopathy">Raynaud-like phenomenon, rare digital ischemia.</effect>
+*<effect slug="seizure" label="Lowered seizure threshold">Caution in epilepsy.</effect>
+*<effect slug="withdrawal" label="Withdrawal /" crash""="">Fatigue, rebound hyperactivity, dysphoria on dose offset.</effect><h2 id="Contraindications">Contraindications</h2>
+*Hypersensitivity to dexmethylphenidate or methylphenidate
+*Concurrent MAOI use, or within 14 days of MAOI discontinuation
+*Symptomatic cardiovascular disease, advanced atherosclerosis, moderate–severe hypertension, recent MI
+*Hyperthyroidism
+*Glaucoma
+*Pheochromocytoma
+*Severe anxiety, tension, or agitation
+*'''Relative:''' Tourette syndrome / tic disorders, history of substance use disorder, bipolar disorder, psychotic disorders, structural cardiac abnormalities<h2 id="Interactions">Interactions</h2>
+*'''MAOIs''' — hypertensive crisis risk; contraindicated within 14 days
+*'''Tricyclic antidepressants''' — possible elevation of TCA levels; additive cardiovascular effects
+*'''Warfarin''' — possible elevation of INR
+*'''Phenytoin, phenobarbital, primidone''' — possible elevation of anticonvulsant levels
+*'''Antihypertensives''' — pressor effect of dexmethylphenidate may partially antagonize
+*'''Other sympathomimetics''' (pseudoephedrine, phenylephrine, decongestants) — additive cardiovascular effects
+*'''Antipsychotics''' — mutual pharmacologic antagonism
+*'''Alcohol''' — may mask effects; possible increased exposure via altered metabolism
+*'''Caffeine''' — additive stimulant and anxiogenic effects
+Like racemic methylphenidate, '''few CYP-mediated interactions''' due to CES1-dominated metabolism.<h2 id="Pregnancy">Pregnancy and lactation</h2>
+Category C. Crosses the placenta. Reproductive data limited and largely extrapolated from racemic methylphenidate; overall not clearly teratogenic but cohort studies suggest a small increase in cardiac malformations. Third-trimester exposure can produce transient neonatal withdrawal. Risk-benefit decision; many patients defer ADHD treatment during pregnancy. Excreted in breast milk in low amounts; breastfeeding generally compatible at therapeutic doses with infant monitoring.<h2 id="Monitoring">Monitoring</h2>
+*Baseline: cardiovascular history (including family history of sudden cardiac death), blood pressure, heart rate, weight/height, mental health history, history of tics or substance use
+*Consider ECG if cardiac risk factors are present
+*At each visit: blood pressure, heart rate, weight (and height in children), efficacy, side effects, signs of misuse/diversion, tic emergence
+*Sleep quality and timing of last dose
+*Periodically reassess continued need; consider drug holidays in children<h2 id="Counseling">Patient counseling</h2>
+*Take in the morning (XR) or twice daily 4+ hours apart (IR); avoid late-afternoon dosing to minimize insomnia.
+*'''Focalin XR capsules:''' may be swallowed whole or opened and sprinkled on applesauce; '''do not crush or chew the beads inside.'''
+*Eat regular meals despite appetite suppression; weigh periodically.
+*Stay well-hydrated.
+*Do not combine with significant alcohol or other stimulants.
+*Do not share or sell — Schedule II controlled substance.
+*Report chest pain, palpitations, severe agitation, hallucinations, prolonged erection, or new/worsening tics.
+*If switching from racemic methylphenidate, dose conversion is roughly half — confirm with prescriber.
+*<nowiki>Plan for the "crash" when the dose wears off, especially with IR.{{#if:</nowiki><h2 id="Anecdotes">Personal experience</h2>
+<span></span>
+''The following are personal accounts and not medical advice.''
+<span></span><discuss slug="personal-experience" />

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