--- Query Results --- | |||||||
| Organization: | Alberta Precision Laboratories | ||||||
| Message Alert: | PLEASE NOTE: This Test Directory is in an interim state and due to changes pertaining to the DynaLIFE transition, performing site for routing has not been updated. Please refer to Laboratory Information System for appropriate routing. | ||||||
| Test Name/Synonym: | Phenytoin Level, Free (Synonym: Dilantin, PHENY FREE) | ||||||
| Clinical Indications: | Phenytoin is commonly used to treat several types of seizures and, occasionally, ventricular arrhythmias. Typically about 90% of the total phenytoin in the blood is bound to proteins, primarily albumin. Only the unbound ("free") drug is pharmacologically active. The presence of other drugs and several clinical conditions (e.g. hypoalbuminemia, uremia, pregnancy, burns and liver failure) can affect the extent of protein binding, thus altering the free drug concentration without changing the total drug concentration. Order if decreased plasma protein binding is suspected (e.g. low albumin, high creatinine, high bilirubin).
Phenytoin (PTN) must also be ordered to determine % free.
Phenytoin reaches steady state 1-5 weeks post dose adjustment. Free levels, like total levels, should not be ordered daily or even every second day. | ||||||
| Test Includes: |
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| Ordering Alert: | Record time of last dose on requisition or in electronic ordering system. | ||||||
| Collection Alert: | For oral therapy, collection time should be consistent for a given patient (Trough levels are not imperative because of long half-life). For IV therapy, collect greater than 2 hours after end of dose. Best practice is to not draw from an intravenous line through which the drug has been administered as it can produce erroneous results and impact patient care. If best practice is not possible, prior consultation with the most responsible health practitioner is required. | ||||||
| LABID (Connect Care): | LAB32 | ||||||
| Primary Container: | Calgary: MINT LIHEP PST Edmonton: GOLD SST | ||||||
| Alternate Containers: | Calgary: GOLD SST Edmonton: MINT LIHEP PST | ||||||
| Minimum Collection Volume: | 1.5 mL serum | ||||||
| Test Resources: |
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| Transportation: | Calgary: Transport at room temperature. | ||||||
| Method: | Kinetic Interaction of Microparticles in Solution (KIMS) assay | ||||||
| Testing Schedule: | Daily | ||||||
| Reference Interval: | Target range: 4.0 - 8.0 µmol/L
based on 90% protein binding | ||||||
| Critical Value: | Greater than 12 µmol/L | ||||||
| Performing Site: | Calgary: Foothills Medical Centre Edmonton: University of Alberta Hospital | ||||||
| Additional Test Information: | Steady state: 1-5 weeks (zero order kinetics)
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| Last Updated On: | Tuesday, April 30, 2024 | ||||||
