From the Guidelines
Taking modafinil twice a day is not recommended due to its long half-life and potential to disrupt sleep patterns. Modafinil is typically prescribed as a once-daily medication, usually taken in the morning, with doses ranging from 100-200mg for most conditions 1. The drug has a long half-life of approximately 15 hours, which means a single morning dose can maintain therapeutic levels throughout the waking day. Taking a second dose later in the day can significantly disrupt sleep patterns as the medication's effects may persist well into the night, potentially causing insomnia.
Some key points to consider when taking modafinil include:
- The typical dosage range is 100-200mg per day, with some studies using higher doses of 200-400mg for sleepiness 1
- Modafinil has a novel mechanism of action and has less abuse potential compared to other psychostimulants 1
- Common side effects include headache, nausea, nervousness, and insomnia 1
- The medication has been shown to be effective in reducing fatigue in patients with cancer, multiple sclerosis, and other conditions 1
If you feel your current modafinil regimen is not adequately controlling your symptoms, it's better to consult with your healthcare provider about adjusting your single daily dose rather than splitting it into two doses. They might consider increasing your morning dose or exploring alternative medications rather than adding a second dose that could interfere with your sleep-wake cycle and potentially lead to tolerance issues.
From the FDA Drug Label
The recommended dosage of modafinil tablets for each indication are as follows: (2) Narcolepsy or OSA: 200 mg once a day in the morning. (2.1) SWD: 200 mg once a day, taken approximately one hour prior to start of the work shift The FDA drug label does not answer the question.
From the Research
Dosage and Administration
- The recommended dosage of modafinil is 200 or 400 mg/day, given once or twice daily (morning and midday) to patients with narcolepsy 2.
- A study compared the efficacy of modafinil 400 mg once daily, 400 mg given in a split dose, or 200 mg once daily for maintaining wakefulness throughout the day in patients with narcolepsy, and found that the 400-mg split-dose regimen improved wakefulness significantly in the evening compared with the 200-mg and 400-mg once-daily regimen 3.
Efficacy and Safety
- Modafinil is effective in the treatment of excessive daytime sleepiness (EDS) in patients with narcolepsy, although it is not effective against cataplexy 2.
- Modafinil is generally well tolerated in patients with obstructive sleep apnoea/hypopnoea syndrome (OSA/HS) or shift work sleep disorder (SWSD), and has a low abuse potential 4.
- Common adverse events with modafinil include insomnia, headache, nausea, nervousness, and hypertension 5.
Pharmacokinetics
- Peak plasma concentrations of modafinil were reached 2.3 hours after a single 200mg oral dose in healthy volunteers 2.
- The pharmacokinetics of modafinil are not affected to a clinically significant extent by volunteer age or food intake, but both the maximum plasma concentration and the elimination half-life of the drug are increased in patients with hepatic or renal impairment 2.
Clinical Use
- Modafinil is approved for use in patients with excessive sleepiness associated with narcolepsy, OSA/HS, or SWSD 4.
- Modafinil may be beneficial for patients with attention deficit hyperactivity disorder (ADHD), but its use in this population is not approved by the FDA due to concerns about serious dermatological toxicity 5.