Some users lose efficacy with modafinil over time, although not all. The body may develop a tolerance to the medication, reducing its wakefulness-promoting effects with repeated usage. Modafinil has less tolerance than amphetamines or caffeine. If you think modafinil isn't working, see a doctor. You may have sleep deprivation, stress, or other health issues. If necessary, your doctor may change your dose or offer alternate treatments.
Does modafinil lose effectiveness?