Modafinil Dosage for Adults
The recommended dosage of modafinil for adults is 200 mg once daily in the morning for narcolepsy or obstructive sleep apnea (OSA), and 200 mg taken approximately one hour before the start of work shift for shift work disorder. 1
Standard Dosing Guidelines
Modafinil dosing follows a clear protocol based on the FDA-approved indications:
- Narcolepsy or OSA: 200 mg once daily in the morning 1
- Shift Work Disorder: 200 mg once daily, taken approximately one hour prior to start of work shift 1
Special Population Considerations
Dosage adjustments are necessary for certain patient populations:
- Severe Hepatic Impairment: Reduce dose to half the recommended dose (100 mg daily) 1
- Geriatric Patients: Consider lower starting dose due to potential altered pharmacokinetics 1
- Patients with anxiety concerns: Lower doses (50-200 mg/day) may be better for managing concentration problems and fatigue with fewer stress-related side effects 2
Dosing Titration
While the standard dose is 200 mg daily, some clinical evidence suggests a titration approach may be beneficial:
- Start with 100 mg/day for the first 1-2 weeks
- Increase to 200 mg/day if needed and tolerated 3
This approach is supported by research in multiple sclerosis patients with fatigue, where 50% of patients responded adequately to 100 mg daily, 42% required 200 mg daily, and only 4% needed 300 mg daily 3.
Pharmacokinetic Considerations
- Peak plasma concentrations are reached approximately 2-3 hours after oral administration 4
- Elimination half-life is 9-14 hours 4
- The pharmacokinetics are linear and dose-dependent in the range of 200-600 mg 4
Monitoring and Side Effects
When initiating modafinil therapy, monitor for:
- Headache (most common side effect) 4
- Nervousness and anxiety 2
- Insomnia, especially with doses taken later in the day 4
- Nausea and gastrointestinal effects 4
Important Cautions
- Modafinil is classified as a Schedule IV controlled substance with low but present potential for dependence 5, 6
- Not approved for use in individuals under 17 years of age 5
- May reduce the efficacy of hormonal contraceptives 4
- Rare but serious side effects include Stevens-Johnson syndrome 5
Clinical Efficacy
At the recommended dose of 200 mg daily, modafinil has demonstrated:
- Significant increase in daytime sleep latency 4
- Reduction in excessive daytime sleepiness 4
- Improvement in fatigue levels in various conditions 5, 3, 7
The evidence consistently shows that the 200 mg daily dose provides optimal balance between efficacy and side effects for most adult patients with approved indications.