Methods of diagnosing sleepiness objectively, such as the Multiple Sleep Latency Test, do not confirm the symptom—objective sleepiness is not observed despite the complaint.Finally, on the opposite end of the spectrum, other patients may report feeling that they have slept much longer than is observed. It has been proposed that this experience be subclassified under sleep state misperception as "positive sleep state misperception", "reverse sleep state misperception", and "negative sleep state misperception". Diagnostic criteria
The patient has a complaint of insomnia while sleep quality and duration are normal. Polysomnographic monitoring demonstrates normal sleep latency, a normal number of arousals and awakenings, and normal sleep duration with or without a multiple sleep latency test that demonstrates a mean sleep latency of greater than 10 minutes. No medical or mental disorder produces the complaint. Other sleep disorders producing insomnia are not present to a degree that would explain the patient’s complaint. Detection and difficulties
Detecting sleep state misperception by objective means has been elusive.A 2011 study published in the journal Psychosomatic Medicine has shown that sleep misperception (i.e., underestimation of sleep duration) is prevalent among chronic insomniacs who sleep objectively more than 6 hours in the sleep lab. The psychological profile of these chronic insomniacs with objective normal sleep duration is characterized by depressive, anxious-ruminative traits and poor coping resources. Thus, it appears that not all chronic insomniacs underestimate their sleep duration, and that sleep misperception is a clinical characteristic of chronic insomniacs with objective normal sleep duration.
It was recommended that the drug remain available only for patients with severe epilepsy for whom the benefits outweigh the risks, and that changes be made to the products labelling to reflect the newly recognized risk. This redemption came with an additional warning since there had been 10 cases acute liver failure (4 of which were fatal). At this point, 10,000 to 12,000 people remained on the drug. United Kingdom
The drug is only available on a limited named-patient basis. Indications and usage
Adults: Monotherapy or adjunctive therapy in the treatment of partial seizures, with and without generalization. Children: Adjunctive therapy in the treatment of partial and generalized seizures associated with Lennox-Gastaut syndrome. Dosing
Felbamate is available in tablets (400 mg and 600 mg) and as a peach-coloured oral suspension (600 mg/5 mL). Adults (≥ 14 years): begin with 1,200 mg daily given every 6 to 8 hours
Children (2–14 years): 15 to 45 mg per kg per day given every 6 to 8 hours

Side effects
Adverse reactions include decreased appetite, vomiting, insomnia, nausea, dizziness, somnolence, and headache. Many patients report increased alertness with the drug. Two rare but very serious effects include aplastic anemia and serious liver damage. The risk of aplastic anemia is between 1:3,600 and 1:5,000, of which 30% of cases are fatal. The risk of liver damage is between 1:24,000 to 1:34,000, of which 40% of cases are fatal. Drug interactions
Felbamate is an inhibitor of CYP2C19 - an enzyme involved in the metabolism of several commonly used medications.