Armodafinil is a new medication to improve wakefulness in patients with excessive daytime sleepiness. It is indicated for use in patients with narcolepsy, chronic shift work sleep disorder, and obstructive sleep apnoea-hypopnea syndrome.

Armodafinil is the (R)-enantiomer of modafinil; a racemic compound used for the same indication. Enantiomers are molecules that exist in two non-superimposable mirror images, designated (R)- and (S)- enantiomers. Each enantiomer of modafinil has similar pharmacological activity, yet significantly different pharmacokinetic properties. The (R)-enantiomer is eliminated approximately three times more slowly than the (S)-enantiomer. This may explain the higher peak plasma concentration and prolonged duration of activity observed with armodafinil.

There is insufficient evidence to suggest that armodafinil offers superior clinical efficacy when compared to modafinil. However, its prolonged duration of effect may be beneficial for patients who require high doses or twice daily dosing with modafinil. Armodafinil is not currently listed on the Pharmaceutical Benefits Scheme (PBS), while modafinil is subsidised for patients with narcolepsy.

The most common adverse effects reported in pre-approval studies were headache, nausea, dizziness, and insomnia. Armodafinil has not been specifically studied for its abuse potential, although it is assumed to be similar to modafinil. Studies have previously shown that the likelihood of abuse with modafinil is low compared to amphetamine-like agents used to promote wakefulness.

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