This side effect is due to entacapone metabolism and excretion in the urine and shown to not be harmful. Sudden sleep onset
People have reported sudden sleep onset while engaging in daily activities without prior warning of drowsiness. In controlled studies, patients on entacapone had a 2% increased risk of somnolence compared to placebo. Low blood pressure
Episodes of orthostatic hypotension have been shown to be more common at the start of entacapone use due to increased levels of levodopa. Behavior problems
Post-marketing data shows that entacapone may change or worsen mental status, leading to behaviors such as delusions, agitation, confusion, and delirium.People taking entacapone may experience increased urges to participate in gambling, sexual activities, money spending, and other stimulating reward behaviors. Interactions
In studies, entacapone has shown a low potential for interaction with other drugs. In theory, it could interact with MAO inhibitors, tricyclic antidepressants and noradrenaline reuptake inhibitors because they also increase catecholamine levels in the body, with drugs being metabolized by COMT (for example  methyldopa, dobutamine, apomorphine, adrenaline, and isoprenaline), with iron because it could form chelates, with substances binding to the same albumin site in the blood plasma (for example diazepam and ibuprofen), and with drugs being metabolized by the liver enzyme CYP2C9 (for example warfarin). None of the medications tested in studies have shown clinically relevant interactions, except perhaps warfarin for which a 13% (CI90: 6–19%) increase in INR was seen when combined with entacapone. Pharmacology
Mechanism of action
Entacapone is a selective and reversible inhibitor of catechol-O-methyltransferase (COMT).
This occurs because the spinal cord in a child with Spina bifida is low lying and tethered at the bottom. At the time of birth the mylomeningocele is separated from the skin but the spinal cord is still stuck in the same place. As the child begins to grow the spinal cord remains in the same place becoming stretched out causing the tight cord and the tethering at the end. With this type of tethering there is an interference with the blood supply to the nerves and body which can then cause the deterioration of the body causing orthopedic, neurological, and urological problems. With milder forms of Spina bifida such as Occulta, may be related to the degree of strain on the cord which can become worse with physical activity, injury, pregnancy, bone spurs, or spinal stenosis. The tethered cord in this case might not be diagnosed until adulthood when it worsens and can still cause neurological, orthopedic, and urological dysfunctions. Mechanism
Tethered spinal cord syndrome is a clinical entity which is manifested by progressive motor and sensory changes in:

legs
incontinence
back of leg pain
scoliosisIn order to understand the pathophysiology that is involved in a tethered spinal cord, the reduction/oxidation ratio has to be used in vivo of cytochrome alpha and alpha 3 to signal the oxidative metabolic functioning in humans. Studies have found that marked metabolic and electrophysiological susceptibility to hypoxic stress to the lumbar and sacral portion of the spinal cord under traction with various weights.