Test ID: MEPHS
Mephobarbital and Phenobarbital, Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Monitoring of mephobarbital and phenobarbital therapy
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| MBARS | Mephobarbital, S | No | Yes |
| PHBRS | Phenobarbital, S | No | Yes |
Method Name A short description of the method used to perform the test
Gas Chromatography-Mass Spectrometry (GC-MS)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Mebaral (Mephobarbital)
Luminal (Phenobarbital)
Barbita (Phenobarbital)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Red top
Specimen Volume: 2 mL
Collection Instructions: Spin down within 2 hours of draw.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross reject |
| Icterus | Mild OK; Gross reject |
| Other | Serum gel tube |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 14 days |
| Ambient | 14 days | |
| Frozen | 14 days |
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)
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.
MEPHOBARBITAL
Therapeutic range: 1.0-7.0 mcg/mL
Toxic concentration: > or =15.0 mcg/mL
PHENOBARBITAL
Therapeutic range
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.
Interpretation Provides information to assist in interpretation of the test results
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.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Teitz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th 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. 7th edition. Edited by RC Baselt. Foster City, CA, Biomedical Publications, 2004, pp 1254
Method Description Describes how the test is performed and provides a method-specific reference
Barbiturates are extracted from serum using solid-phase extraction techniques. The serum is buffered and eluted with organic solvent. The organic phase is dried, reconstituted, and analysis is performed by gas chromatography-mass spectrometry, using selected ion monitoring. The assay utilizes deuterated barbiturates as internal standards. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Wednesday; 8 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
80184-Phenobarbital
82205-Barbiturates
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 89706 | Mephobarbital, S | 3750-7 |
| 84582 | Phenobarbital, S | 3948-7 |
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