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Test ID: PENTS Pentobarbital, Serum

Reporting Name

Pentobarbital, S

Useful For

Monitoring of pentobarbital therapy treatment

Clinical Information

Pentobarbital is a short-acting barbiturate with anticonvulsant and sedative-hypnotic properties. Uses include sedation induction; relief of preoperative anxiety; control of status epilepticus or seizures resulting from meningitis, tetanus, alcohol withdrawal, poisons, chorea, or eclampsia; and induction of coma in the management of cerebral ischemia and increased intracranial pressure that may follow stroke or head trauma.(1,2)


Pentobarbital is administered orally, parenterally, and rectally. The duration of hypnotic effect is about 1 to 4 hours. The drug distributes throughout the body with about 35% to 45% of a dose bound to plasma proteins in the blood. Metabolism takes place in the liver via oxidation to the inactive metabolite, hydroxypentobarbital. Elimination is biphasic; half-life is about 4 hours in the first phase, and 35 to 50 hours in the second phase. Excretion occurs through the urine, mainly as glucuronide conjugates of metabolites, with only about 1% excreted as unchanged drug.(1,2) Tolerance to the hypnotic effects of pentobarbital occurs after about 2 weeks of continuous dosing.


Pentobarbital concentrations above 10 mcg/mL have been associated with toxicity.

Report Available

3 to 9 days

Day(s) Performed


Clinical Reference

1. NEMBUTAL Sodium Solution (pentobarbital sodium injection). Package insert: Ovation Pharmaceuticals Inc; October 2007

2. Physician's Desk Reference (PDR): 61st edition. Thomson PDR; 2007

3. Baselt RC: Disposition of Toxic Drugs and Chemicas in Man. 10th ed. Biomedical Publications; 2014:2211

4. Milone MC, Shaw LM: Therapeutic drugs and their management. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:800-831

5. Langman LJ, Bechtel LK, Meier BM, Holstege C: Clinical toxicology. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:832-887

6. Mihic SJ, Mayfield J, Harris RA: Hypnotics and sedatives. In: Brunton LL, Hilal-Dandan R, Knollmann BC, eds. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill Education; 2017

Method Name

Gas Chromatography-Mass Spectrometry (GC-MS)

Specimen Type

Serum Red

Specimen Required

Collection Container/Tube: Red top (Serum gel/SST are not acceptable)

Submission Container/Tube: Plastic vial

Specimen Volume: 1.2 mL

Collection Instructions:

1. Draw blood immediately before next scheduled dose.

2. Centrifuge and aliquot serum in plastic vial within 2 hours of collection.

Specimen Minimum Volume

0.7 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reference Values

Therapeutic range

Hypnotic: 1-5 mcg/mL

Therapeutic coma: 20-50 mcg/mL

Reducing intracranial pressure: 30-40 mcg/mL

This degree of sedation requires artificial respiratory support.

Toxic concentration: >10 mcg/mL

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


G0480 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PENTS Pentobarbital, S 3924-8


Result ID Test Result Name Result LOINC Value
8239 Pentobarbital, S 3924-8


If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Epilepsy, mml-Neuro-oncology