Mephobarbital and Phenobarbital, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Mephobarbital is an orally administered, methylated barbiturate used for the treatment of epilepsy.(1,2) It is demethylated by hepatic microsomal enzymes to generate its major metabolite, phenobarbital. During long-term use, most of mephobarbital's activity can be attributed to the accumulation of phenobarbital. Consequently, mephobarbital's pharmacological properties, toxicity, and clinical uses are the same as phenobarbital's.(1,2) The use of mephobarbital is uncommon as it offers no significant advantage over phenobarbital alone.(1,2)
Monitoring of mephobarbital and phenobarbital therapy
The therapeutic range for mephobarbital is 1.0 to 7.0 mcg/mL.
In children, the therapeutic range for phenobarbital is 15.0 to 30.0 mcg/mL; in adults the therapeutic range is 20.0 to 40.0 mcg/mL.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Concentration at which toxicity occurs varies; results should be interpreted in light of the clinical situation.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Therapeutic range: 1.0-7.0 mcg/mL
Toxic concentration: > or =15.0 mcg/mL
Children: 15.0-30.0 mcg/mL
Adults: 20.0-40.0 mcg/mL
Toxic concentration: > or =60.0 mcg/mL
Concentration at which toxicity occurs varies and should be interpreted in light of clinical situation.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Teitz Textbook of Clinical Chemistry and Molecular Diagnostics. Fourth edition. Edited by CA Burtis, ER Ashwood, DE Bruns. St. Louis, MO, Elsvier Saunders, 2006, pp 1091
2. Disposition of Toxic Drugs and Chemicals in Man. Seventh edition. Edited by RC Baselt. Foster City, CA, Biomedical Publications, 2004, pp 1254