Drilldown: Medicines

Dextromethorphan / Quinidine (1)

Nuedexta (1)

None (1)

'"`UNIQ--vote-00001580-QINU`"' First FDA-approved treatment for PBA. The 10 mg quinidine daily dose is far below antiarrhythmic levels but sufficient to nearly fully inhibit CYP2D6, the basis of the combination's pharmacokinetic rationale'"`UNIQ--ref-00001581-QINU`"'. (1)

'"`UNIQ--vote-00001582-QINU`"' (1)

1 capsule (20/10 mg dextromethorphan/quinidine) PO once daily × 7 days, then 1 capsule BID (1)

20 mg dextromethorphan HBr / 10 mg quinidine sulfate capsules (1)

None · Indication-specific · 40 mg/d · 10 mg/d · 20 mg/d · 80 mg/d · 10 mg/d (adults) · 100 mg/d · 4 g/d · 400 mg/d · 40 mg/d typical; up to 240 mg/d for Zollinger-Ellison · 5 mg/d · 50 mg/d · 600 mg/d · No fixed ceiling; titrate to clinical effect and tolerability with CDC opioid prescribing guidance constraints on morphine-milligram-equivalent (MME) totals · No fixed maximum; titrated to TSH target · TID per eye · Titrated to glucose; no fixed ceiling · Titrated to glucose; no fixed maximum · '''20 mg/day in adults >60 years''' per FDA's 2011-2012 QT-prolongation warning; 40 mg/day in adults ≤60

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Oral (1)

PBA episode reduction within 1-2 weeks (1)

12 hours (1)

Dextromethorphan substantially prolonged by quinidine's CYP2D6 inhibition (typical extensive metabolizers see ~10× higher AUC); quinidine ~6-8 hours'"`UNIQ--ref-00001583-QINU`"' (1)

None · 100% (IV) · ~100% from subcutaneous depot · ~80% (oral)'"`UNIQ--ref-00000027-QINU`"' · 70–90% (oral) · ~100% (oral)'"`UNIQ--ref-0000001C-QINU`"' · ~50% (oral)'"`UNIQ--ref-00000021-QINU`"' · ~95% · '''Saturable''' via the LAT-1 amino-acid transporter, producing nonlinear pharmacokinetics: ~60% at 300 mg single dose, falling to ~35% at 1200 mg single dose'"`UNIQ--ref-0000002A-QINU`"' · 10-20% (oral; reduced by food, calcium, antacids, PPIs, tea/coffee; enhanced by ascorbate) · 100% (IV); essentially complete (oral) · 100% (IV); rapidly neutralized by gastric acid (oral) · 16-21% capsule, 25% suspension (oral; iron and antacids reduce absorption substantially)'"`UNIQ--ref-000009E5-QINU`"' · 25 mg: ~29%; 50 mg: ~35%; food reduces absorption'"`UNIQ--ref-00000C4F-QINU`"' · 30-40% (oral; increases with repeated dosing as gastric pH rises)'"`UNIQ--ref-000000DF-QINU`"' · 40-45% (oral; not significantly affected by food)'"`UNIQ--ref-0000025C-QINU`"' · 40-80% (oral); reduced by food, calcium, iron, PPIs, fiber; take fasting with water'"`UNIQ--ref-00000037-QINU`"' · 42-58% (oral; dose-dependent)'"`UNIQ--ref-00000AEF-QINU`"' · 50-60% (oral; decreased with food, but food given anyway for GI tolerance)'"`UNIQ--ref-00000019-QINU`"' · 60-70% PO at low doses; saturable at high doses (parenteral routes preferred above 15-25 mg/week)'"`UNIQ--ref-000007C9-QINU`"'

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Limited data; quinidine has been used in pregnancy as antiarrhythmic.<sup class="pcp-cn" title="This claim needs a citation.">&#91;[[Pharmacopedia:Citation needed|citation&nbsp;needed]]&#93;</sup> (1)

[[USLegal:Prescription only|Rx-only]] in US. Caution with QT-prolonging medicines (quinidine itself is class IA antiarrhythmic, and the dose here, though sub-antiarrhythmic, still contributes to QT)'"`UNIQ--ref-00001585-QINU`"' (1)