Armodafinil (Nuvigil) — R-Enantiomer Wakefulness Agent — Brain

Overview

Armodafinil (Nuvigil) is the R-enantiomer of racemic modafinil, approved by the FDA in 2007. Modafinil is a 1:1 racemic mixture of R- and S-enantiomers; armodafinil contains only the pharmacologically more active R-enantiomer. The R-enantiomer has a longer half-life (10-15 hours vs 3-4 hours for S-enantiomer) and higher plasma concentrations later in the day compared to racemic modafinil, potentially providing more sustained wakefulness throughout the waking period. At equivalent doses, armodafinil produces higher plasma levels in the latter half of the day. Clinical trials demonstrated that armodafinil 150 mg produces similar wakefulness effects to modafinil 200 mg but with better sustained late-day alertness. The mechanism of action is identical to modafinil — DAT inhibition with secondary effects on orexin, histamine, and norepinephrine systems. Armodafinil is FDA-approved for the same three indications as modafinil: narcolepsy, obstructive sleep apnea, and shift work sleep disorder. Side effects are similar to modafinil though some users report that armodafinil feels 'smoother' with less of a pronounced peak-and-trough effect. Like modafinil, it is Schedule IV.

Indications

• FDA-approved: Narcolepsy
• FDA-approved: Obstructive sleep apnea/hypopnea syndrome
• FDA-approved: Shift work sleep disorder
• Off-label: Cognitive enhancement
• Off-label: Fatigue management

Mechanism of Action

R-enantiomer inhibits the dopamine transporter with similar affinity but longer duration than the S-enantiomer

Dosing

Evidence Grade

GRADE A

Safety & Contraindications

• Headache, nausea, dizziness, and insomnia most common
• Rare: SJS/TEN, DRESS syndrome — same rash warning as modafinil
• CYP3A4 induction — may reduce oral contraceptive efficacy
• Schedule IV controlled substance
• Longer duration of action than modafinil — later dosing carries higher insomnia risk
• Anxiety at higher doses