ADVERSE REACTIONS The following adverse reactions and their incidence were compiled from surveillance of thousands of hospitalized patients. Because such patients may be less aware of certain of the milder adverse effects of barbiturates, the incidence of these reactions may be somewhat higher in fully ambulatory patients. Nervous System Somnolence, agitation, confusion, hyperkinesia, ataxia, CNS depression, nightmares, nervousness, psychiatric disturbance, hallucinations, insomnia, anxiety, dizziness, thinking abnormality Respiratory System Hypoventilation, apnea Cardiovascular System Bradycardia, hypotension, syncope Digestive System Nausea, vomiting, constipation Dermatologic Reactions Exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermic necrolysis. Other Reported Reactions Headache; injection site reactions; hypersensitivity reactions, including but not limited to angioedema and skin rashes; fever; liver damage and megaloblastic anemia following chronic phenobarbital use.