Modafinil 400mg is a high dose of the drug modafinil, which is a stimulant of alertness. Modafinil is mainly used for improving alertness in people suffering from narcolepsy, obstructive sleep apnea syndrome, and excessive daytime sleepiness due to shift work sleep disorder. The drug affects different brain signals that affect alertness, though its mode of action is not completely understood.

The dose of 400mg per day is higher than the standard dose for many approved purposes; therefore, the right dose for the treatment depends on the specific condition of the patient. Modafinil may produce side effects, such as headaches, nausea, nervousness, dizziness, insomnia, or lack of appetite. Severe skin reactions and other serious allergic reactions are rare but require medical intervention immediately.

Modafinil may have interactions with other medications and may lower the efficacy of hormonal contraceptives. People with existing illnesses or taking other medications should consult their doctor about taking this drug.