Modafinil

# Modafinil ## Overview Modafinil is a wakefulness-promoting agent with a mechanism distinct from stimulants, primarily acting as a selective dopamine reuptake inhibitor. Schedule IV controlled substance. ## Primary Indications - **Narcolepsy**: Excessive daytime sleepiness - **Obstructive sleep apnea (OSA)**: Residual sleepiness despite optimal CPAP - **Shift work sleep disorder (SWSD)** - Note: Off-label use for ADHD, fatigue in MS, or depression; limited evidence supports these uses. ## Adult Dosing - **Narcolepsy / OSA**: 200 mg once daily in the morning. - Max: 400 mg/day (less commonly needed) - **SWSD**: 200 mg once daily ~1 hour before shift start. - May reduce dose for tolerability (e.g., 100 mg/day). ## Pediatric Dosing - **Narcolepsy (≥16 years)**: Per adult dosing; safety/efficacy <16 years not established. - **ADHD (off-label, limited data)**: 100–200 mg once daily; not FDA-approved. Use only under specialist guidance. Max: 400 mg/day. ## Dose Adjustments - **Hepatic impairment (severe, Child-Pugh C)**: Reduce dose by 50% (e.g., 100 mg once daily). - **Renal impairment**: No adjustment needed for mild-moderate. Severe not studied. - **Elderly**: Start at lower dose (100 mg/day) due to slower clearance. ## Contraindications - Hypersensitivity to modafinil or armodafinil - History of left ventricular hypertrophy, valvular heart disease, or arrhythmias (especially if on CNS stimulants) - Uncontrolled hypertension ## Adverse Effects - **Common**: Headache, nausea, nervousness, anxiety, insomnia, decreased appetite. - **Serious (rare)**: Severe rash (Stevens-Johnson syndrome), angioedema, psychiatric symptoms (mania, psychosis), arrhythmias, blood pressure elevation. ## Key Drug Interactions - **CYP3A4 inducer**: Reduces efficacy of hormonal contraceptives (pill, implant, IUD) during therapy and for 1 month after stopping. Use backup non-hormonal contraception. - **CYP2C19 inhibitor**: Increases levels of modafinil; may increase side effects. - **Warfarin, SSRIs, benzodiazepines**: Modafinil may reduce levels via CYP induction; monitor effects. - **Sympathomimetics (e.g., amphetamines)**: Additive pressor effects. ## Monitoring - Baseline: Blood pressure, heart rate, ECG if cardiac history. - At follow-up: Assess for excessive sleepiness persistence, adverse effects (rash, mood changes, insomnia), blood pressure at each visit. ## Clinical Pearls - Take early morning (or before shift) to minimize insomnia. - Avoid driving or operating machinery until effect known. - Hormonal contraception failure is a critical counseling point. - Tolerance may develop over weeks; taper if discontinuing. - Lower doses often adequate; 400 mg rarely improves efficacy. --- *This information is for educational purposes only and does not replace clinical judgment. Always verify current prescribing information from official drug monographs and institutional guidelines, as national protocols and evidence may vary.*