Nembutal Side Effects

Generic Name: pentobarbital

Note: This page contains side effects data for the generic drug pentobarbital. It is possible that some of the dosage forms included below may not apply to the brand name Nembutal.

It is possible that some side effects of Nembutal may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to pentobarbital: parenteral solution for injection

Side effects include:

Residual sedation, drowsiness, lethargy, vertigo, nausea, vomiting, headache.

For Healthcare Professionals

Applies to pentobarbital: compounding powder, injectable solution, oral capsule, oral elixir, rectal suppository

Nervous system

Behavioral problems, impaired memory, impaired cognition, decreased perceptuomotor performance, tics, dyskinesias, nystagmus, oculogyric crises, dystonic reactions, and ataxia have also been reported.

Nervous system side effects have been common and have included drowsiness, sedation, lethargy, and somnolence. Paradoxical stimulation has also been reported in the elderly.


Respiratory side effects including life threatening respiratory depression have been reported, particularly during acute intoxication.


Withdrawal symptoms may include hallucinations, sweating, insomnia, and hypertension.

An increased frequency of seizures may occur if barbiturate therapy is suddenly discontinued.

Other side effects from pentobarbital use have included physical and psychological dependence. Withdrawal symptoms have been reported when pentobarbital therapy has been discontinued suddenly.


Cardiovascular side effects including hypotension and bradycardia have been reported.


Musculoskeletal side effects including myopathy in association with anticonvulsant osteomalacia has been reported in patients taking other barbiturates. Reflex sympathetic dystrophy of the upper extremities, Dupuytren's contractures, Peyronie's disease, the "shoulder-hand syndrome" and other musculoskeletal and joint pains have been reported in as many as 5% of patients treated with other barbiturates.


Hypersensitivity side effects have included a variety of hypersensitivity reactions reported in association with use of pentobarbital (the active ingredient contained in Nembutal) and other barbiturates. The reactions frequently involved generalized rashes, fever, and hepatic derangements.


The more serious hepatic effects have often been reported in association with hypersensitivity reactions.

Hepatic side effects including elevated liver function tests, hepatitis, cholestasis, and fulminant hepatic failure have all been reported in association with use of other barbiturates.


Hematologic side effects including macrocytosis and, more rarely, megaloblastic anemia have been reported with use of other barbiturates.

Animal studies have suggested that pentobarbital may inhibit prostaglandin l2 and thereby promote platelet aggregation.


Endocrine side effects including alterations in vitamin D metabolism have been reported in patients taking barbiturates and other anticonvulsants. Hypocalcemia and osteomalacia have been specifically reported.


Oncologic side effects have been reported. Some investigators have reported a possible increased frequency of malignancy (particularly brain tumors, lung cancer, and liver cancer) in patients taking pentobarbital (the active ingredient contained in Nembutal) and other barbiturates chronically. Other investigators have not found an association with malignancy.

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