Test Details
Methodology
Immunoassay
Result Turnaround Time
2 - 3 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Use
This deoxybarbiturate is closely related chemically to the barbiturates. It is converted to two active metabolites, phenobarbital and phenylethylmalonamide (PEMA). Primidone is used principally in generalized tonic-clonic and complex and simple partial seizures; some clinicians believe that the drug has specific usefulness for complex partial seizures. It is as effective as carbamazepine or phenytoin in controlling partial or generalized tonic-clonic seizures, although a greater incidence of adverse reactions, especially during initial therapy, limits patient acceptance. Primidone is commonly given with phenytoin but monotherapy is preferred. The conversion of primidone to phenobarbital is significantly increased when this drug is used with other antiepileptic medication. It is not effective in absence seizures.
Footnotes
References
Custom Additional Information
Plasma half-life of primidone usually ranges from six to eight hours with rapid elimination (24 to 40 hours). Since phenobarbital requires a longer interval (48 hours) to achieve therapeutic blood levels, checking both levels can be used to determine chronic compliance. The phenobarbital:primidone ratio normally is 2.5, can be higher (4.3 mean) in patients on other anticonvulsants (phenytoin, carbamazepine) and lower than normal among patients discontinued from those medicines or who are chronically noncompliant. Primidone decreases the effects of oral anticoagulants, carbamazepine, valproate, ethosuximide, felbamate, lamotrigine, topiramate, and oxcarbazepine.1
Specimen Requirements
Specimen
Serum or plasma
Volume
1 mL
Minimum Volume
0.3 mL
Container
Red-top tube or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.
Collection Instructions
Transfer separated serum or plasma to a plastic transport tube. Collect specimen immediately prior to next dose.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Reference Range
Therapeutic: primidone: 5.0−12.0 μg/mL, phenobarbital: 15−40 μg/mL
Storage Instructions
Room temperature
Causes for Rejection
Gel-barrier tube; severe hemolysis; lipemia; icteric specimen
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 007856 | Primidone (Mysoline(R)), Serum | 3978-4 | 018713 | Primidone, Serum | ug/mL | 3978-4 |
| 007856 | Primidone (Mysoline(R)), Serum | 3978-4 | 007830 | Phenobarbital, Serum | ug/mL | 3948-7 |
| Order Code | 007856 | |||||
| Order Code Name | Primidone (Mysoline(R)), Serum | |||||
| Order Loinc | 3978-4 | |||||
| Result Code | 018713 | |||||
| Result Code Name | Primidone, Serum | |||||
| UofM | ug/mL | |||||
| Result LOINC | 3978-4 | |||||
| Order Code | 007856 | |||||
| Order Code Name | Primidone (Mysoline(R)), Serum | |||||
| Order Loinc | 3978-4 | |||||
| Result Code | 007830 | |||||
| Result Code Name | Phenobarbital, Serum | |||||
| UofM | ug/mL | |||||
| Result LOINC | 3948-7 |