Standard Dosing for Modafinil
The standard dose of modafinil is 200 mg once daily in the morning for narcolepsy or obstructive sleep apnea, and 200 mg taken approximately one hour before the start of work shift for shift work disorder. 1
Dosing Guidelines by Indication
Narcolepsy or Obstructive Sleep Apnea (OSA):
- 200 mg once daily in the morning 1
Shift Work Disorder (SWD):
- 200 mg once daily, taken approximately one hour prior to start of work shift 1
Special Population Considerations
Severe Hepatic Impairment:
- Reduce dose to half the recommended dose (100 mg daily) 1
Geriatric Patients:
- Consider lower dose due to potential changes in drug metabolism 1
Dosing Adjustments for Specific Situations
For patients experiencing late-day sleepiness despite morning dosing, a split-dose regimen may be more effective:
- 400 mg split dose (e.g., 200 mg in morning and 200 mg at midday) has been shown to be more effective than a single 400 mg dose for sustaining wakefulness throughout the entire day 2
- This split-dosing strategy significantly improves late-day wakefulness compared to once-daily dosing 2
Dose-Related Side Effects
Lower doses (50-200 mg/day) may produce fewer stress-related side effects compared to higher doses (200-400 mg/day), which are more likely to produce anxiety and stress-related symptoms 3. Common adverse reactions include:
- Headache
- Nausea
- Nervousness
- Anxiety
- Insomnia
- Dizziness 1
Important Considerations
- Modafinil is FDA-approved for excessive sleepiness associated with narcolepsy, OSA, and shift work disorder 1
- It is not FDA-approved for cancer-related fatigue, though some small studies have shown promise in this area 4
- For cancer-related fatigue, studies have used doses of 200 mg daily, but evidence is insufficient to recommend its use for this indication 4
- The medication reaches peak plasma concentrations approximately 2 hours after administration when taken on an empty stomach 5
- Food does not affect overall bioavailability but may delay peak concentration by 2-4 hours 5
Cautions and Monitoring
- Monitor for development or worsening of anxiety, sleep disturbances, and cardiovascular symptoms 3
- Contraindicated in patients with known hypersensitivity to modafinil or armodafinil 1
- Use with caution in patients with a history of psychosis, depression, or mania 1
- Consider increased monitoring in patients with known cardiovascular disease 1
Modafinil has a relatively low abuse potential compared to other stimulants like amphetamines and methylphenidate, making it a preferred option for many patients requiring wakefulness-promoting agents 6.