Modafinil Dosage and Treatment Regimen
The recommended dosage of modafinil is 200 mg once daily in the morning for narcolepsy and obstructive sleep apnea (OSA), or 200 mg taken approximately one hour before the start of a work shift for shift work disorder (SWD). 1
Standard Dosing Guidelines
- For narcolepsy and OSA: 200 mg once daily in the morning as a single dose 1
- For shift work disorder: 200 mg once daily, taken approximately one hour before the start of the work shift 1
- The maximum total daily dose is 400 mg per day, which can be administered as a single dose in the morning or divided into two doses 2
- While doses up to 400 mg/day have been well tolerated, there is no consistent evidence that this higher dose provides additional benefits beyond the standard 200 mg/day dose 1
Dosing for Special Populations
- For patients with severe hepatic impairment: Reduce the dose to one-half of the recommended dose (100 mg daily) 1
- For elderly patients: Consider lower starting doses (100 mg once upon awakening) with close monitoring 2, 1
- For elderly patients: Dose can be increased at weekly intervals as necessary based on response and tolerability 2
Condition-Specific Dosing Considerations
- Higher doses (200-400 mg/day) may be more effective for treating excessive sleepiness 2
- Lower doses (50-200 mg/day) may be more appropriate for concentration problems and fatigue 2
Pharmacokinetic Considerations
- Modafinil has a half-life of approximately 15 hours 2
- Steady state is typically reached after 2-4 days of dosing 2
- The drug's pharmacokinetics are linear and dose-dependent in the 200-600 mg range 3
Common Adverse Events
Important Clinical Considerations
- Modafinil has less abuse potential compared to traditional stimulants like amphetamines 2, 3
- For OSA patients, modafinil is indicated to treat excessive sleepiness but not as treatment for the underlying obstruction; continuous positive airway pressure (CPAP) should be used if indicated 1
- Long-term studies (40 weeks) show that modafinil maintains its efficacy without development of tolerance 4
- Quality of life improvements have been demonstrated with modafinil treatment in patients with shift work sleep disorder 6
Common Pitfalls and Caveats
- Modafinil does not benefit cataplexy symptoms in narcolepsy patients 3, 7
- Modafinil may reduce the efficacy of hormonal contraceptives; alternative or additional contraceptive methods should be used during treatment and for one month after discontinuation 1, 3
- Modafinil may interact with drugs metabolized by various cytochrome P450 enzymes 7
- Serious rash, including Stevens-Johnson Syndrome, has been reported with modafinil use, typically within 1-5 weeks of treatment initiation 1