Side Effects of Modafinil
Modafinil commonly causes headache, insomnia, nausea, diarrhea, dry mouth, and anxiety as its main side effects, with more serious but rare adverse events including severe skin reactions, psychiatric symptoms, and cardiovascular effects. 1
Common Side Effects
- Headache - The most frequently reported side effect, occurring in approximately 50% of patients 1
- Insomnia - Difficulty falling or staying asleep, especially if taken too close to bedtime 1, 2
- Nausea and digestive issues - Including diarrhea, dyspepsia (indigestion), and dry mouth 1
- Anxiety and nervousness - Feelings of unease or restlessness 1, 2
- Dizziness - Sensation of lightheadedness or unsteadiness 1
- Upper respiratory tract infections - More commonly reported with armodafinil but also seen with modafinil 1
- Decreased appetite - May lead to weight loss, particularly in children and adolescents 1, 3
Serious Side Effects
Dermatological Reactions
- Severe skin reactions - Including rash, hives, and in rare cases, Stevens-Johnson Syndrome (SJS) 2
- Black box warning exists for pediatric patients due to reported cases of SJS 1, 3
- Stop taking immediately if skin rash, mouth sores, blistering or peeling skin develops 2
Psychiatric Effects
- Anxiety and depression - May worsen existing conditions 1, 4
- Psychosis - Rare but serious, especially in pediatric patients 1, 2
- Hallucinations - Seeing, hearing, or feeling things that aren't there 2
- Mania - Extreme increase in activity and talking 1, 2
- Suicidal thoughts - Particularly noted in pediatric populations 1, 3
Cardiovascular Effects
- Increased blood pressure - Monitoring recommended, especially in patients with hypertension 2, 4
- Increased heart rate - May be problematic for patients with pre-existing cardiac conditions 2, 4
- Chest pain - Requires immediate medical attention if it occurs 2
Special Populations and Considerations
Pregnancy and Breastfeeding
- Potential fetal harm - Animal data suggests risk; human data insufficient 1
- Higher rate of congenital anomalies reported in pregnancy registry 1
- Not recommended during pregnancy or breastfeeding as it's unknown if modafinil passes into breast milk 2
Drug Interactions
- Hormonal contraceptives - Modafinil may reduce effectiveness of birth control pills 2
- Potential for drug interactions due to effects on cytochrome P450 enzymes 5, 6
- Alcohol - Should be avoided while taking modafinil 2
Abuse Potential
- Schedule IV controlled substance due to potential for abuse or dependency 1, 2
- Lower abuse potential than amphetamines or methylphenidate 5, 6
- No significant withdrawal phenomena reported after discontinuation 5, 6
Monitoring and Management
- Start at lower doses and titrate slowly to minimize side effects 3, 6
- Take early in the day to avoid insomnia 2
- Reduce dose in elderly patients and those with hepatic impairment 5, 6
- Monitor blood pressure regularly, especially in patients with hypertension 2, 4
- Discontinue immediately if serious skin reactions or psychiatric symptoms develop 2
Rare or Unusual Side Effects
- Cataplexy-like symptoms have been reported in non-narcoleptic patients as a paradoxical effect 7
- Severe dermatologic effects more common in children, including erythema multiforme 4, 3
- Central sleep apnea has been reported in rare cases 1, 6
Understanding these side effects is crucial for safe use of modafinil, with particular attention needed for skin reactions, psychiatric symptoms, and cardiovascular effects which may require immediate discontinuation of the medication.