Test
Carbamazepine (Tegretol)
Other Test Request Name
- Tegretol
- Total Carbamazepine
Test Composition
Not Applicable
Intended Use
To determine the concentration of carbamazepine in the blood to establish an appropriate dose and maintain a therapeutic level
Methodology
Immunoassay (IA)
Laboratory Section
Special Test
Special Instructions/Patient Preparations
Levels should be drawn before next oral dose with patient at steady state.
Collection/Sample Container
Red tube (DO NOT USE GOLD TUBE or any other type of tube with gel separator)
Specimen and Volume Requirement
Note:Follow tube manufacturer recommendation.
3 mL Serum
Alternative Specimen and Volume Requirement
Not Applicable
Specimen Stability
• Room Temperature (15-25°C)
Not Applicable
• Refrigerated Temperature (2-8°C)
3 Days
• Freezer Temperature (-20°C)
Not Applicable
Transport Temperature
Transport specimen at 2°C - 8°C (with cold packs)
Rejection Criteria
- Quantity Not sufficient
- Improperly labeled specimen
- Exceeded sample stability requirement
- Hemolyzed specimen
- Markedly lipemic
Running Day
Monday to Friday
Cut Off Time
Monday to Friday, 7:00 AM
TAT/Releasing of Results
3 days aftre (excluding Saturdays, Sundays and Holidays
Reference Interval/Result Interpretation
Available upon request
Limitations/Interferences
None Specified.
Frequently Asked Questions (FAQs)
Q: When to get tested?
A:At regular intervals to monitor the drug's level; when indicated to detect low or excessive (potentially toxic) concentrations
Q: What is being tested?
A:Carbamazepine is a drug that is primarily used to treat certain seizure disorders (also called epilepsy) but is also prescribed to stabilize the moods of people with bipolar disease, to ease alcohol withdrawal, and to help alleviate some types of nerve pain. It may be prescribed by itself or in combination with other antiepileptic drugs. This test measures the level of carbamazepine in the blood.
Carbamazepine levels are monitored because the drug must be maintained within a narrow therapeutic range. If the level is too low, the drug may not be effective and the person may experience a recurrence of symptoms (i.e., seizures, mania, or pain); if the level is too high, the person may experience toxic side effects. Maintaining a therapeutic level of this drug can be a challenge to achieve for several different reasons:
- Oral doses of carbamazepine are absorbed in the gastrointestinal tract at widely variable rates.
- Since carbamazepine is metabolized by the liver, anything that affects liver function can affect blood levels of the drug.
- Upon a long-term administration, carbamazepine induces its own metabolism.
- Much of the drug is bound to plasma protein, but it is the free portion of the drug that is active. Conditions that affect protein binding of the drug may affect therapeutic effectiveness. This may occur when someone has low blood albumin, kidney failure, or when they are very young (newborn) or elderly.
- The metabolite of carbamazepine, carbamazepine-10,11-epoxide, is also therapeutically active and contributes to the overall effect of the medication.
- Several drugs, if taken in conjunction with carbamazepine, may interact or affect its metabolism and blood levels.
Dosages of carbamazepine must be adjusted carefully in order to reach a steady concentration in the blood. The actual amount of drug required to reach this steady state will vary from person to person and may change over time.
Carbamazepine is usually monitored long-term because it is prescribed to treat the chronic conditions epilepsy, bipolar disorder, trigeminal neuralgia, and nerve pain from diabetes.
Epilepsy affects the brain's ability to transmit electrical impulses and to regulate nerve activity. During a seizure, a person may experience changes in consciousness, alterations in sight, smell, and taste, and may experience convulsions. The frequency of seizures varies from a single episode, to occasional seizures, to recurrent seizures. Carbamazepine is prescribed to help prevent specific types of recurrent seizures.
Bipolar disorder is a mental condition that is characterized by cycles of depression and mania that may last for days, weeks, months, or years. During a depressive episode, those affected may feel sad, hopeless, worthless, and have thoughts of suicide. During a manic episode, those affected may be euphoric, irritable, use poor judgment, and participate in risky behaviors. Carbamazepine is prescribed to help even out the moods of the person with bipolar disorder, especially mania.
Trigeminal neuralgia, a condition associated with facial nerve pain and muscle spasms, and paroxysmal choreoathetosis, a movement disorder that causes involuntary movements of the limbs, trunk, and facial muscles, are also sometimes treated with carbamazepine. So is diabetic peripheral neuropathic pain, which affects the functionality, mood, and sleep patterns of approximately 10-20% of people with diabetes mellitus. (For more on this, see the Neuropathy article.)
Q: How it is used?
A:The carbamazepine test is used to measure and monitor the amount of carbamazepine in the blood to determine whether the level of drug is within the therapeutic range. Carbamazepine is primarily used to treat certain seizure disorders (also called epilepsy) but is also prescribed to stabilize the moods of people with bipolar disease, to ease alcohol withdrawal, and to help alleviate some types of nerve pain.
Initially, the test may be used to establish the appropriate dose for an individual. Depending on the results of the blood test, the dose of drug may be adjusted up or down until the blood level reaches the therapeutic range. Subsequent tests are then used to ensure that the level remains in the therapeutic range. If a person's health changes or if, for example, they begin taking other drugs, the test may be used to determine whether an adjustment to the prescribed dose is necessary.
A healthcare practitioner may use a carbamazepine test to help evaluate someone who is experiencing side effects or adverse reactions or a recurrence of symptoms.
A routine carbamazepine test measures total carbamazepine, both protein-bound and free portions of the drug. Sometimes a test to measure free carbamazepine or the biologically active metabolite, carbamazepine-10,11-epoxide, is ordered along with the total carbamazepine test to evaluate their contribution to a person's therapy.
Q: When it is ordered?
A:Carbamazepine tests are ordered frequently at first, then at regular intervals and as needed to ensure that therapeutic blood concentrations are maintained.
Additional total carbamazepine tests may be ordered if dosages of the drug are changed or if the treated person starts or stops taking additional medications to judge their effect, if any, on the carbamazepine level. Once blood concentrations of carbamazepine have stabilized, concentrations are monitored at regular intervals to ensure that they remain within therapeutic range.
The carbamazepine test may be ordered when a person does not appear to be responding to therapy and has a recurrence of symptoms such as seizure, nerve pain, or bipolar mood swings. The blood level may not be high enough, the person may not be taking the medication regularly, or the drug may be ineffective for that person.
Carbamazepine tests may also be ordered when a person experiences a troublesome level of side effects and/or develops complications. Side effects that may be seen at any dose but that are related to higher concentrations include:
- Dizziness
- Uncoordinated movement
- Sleepiness
- Blurred or double vision
- Involuntary back and forth movement of the eyeball
Other side effects may include:
- Red, itchy rash
- Nausea
- Diarrhea
- Constipation
- Headache
- Confusion
A healthcare practitioner should be contacted immediately if someone has serious side effects, including:
- Pale skin, rapid heart rate, trouble concentrating
- Fever, chills, or sore throat
- Mouth and throat ulcers
- Easy bruising or bleeding
- Severe tingling, numbness, pain, muscle weakness
- Confusion, agitation, vision problems, or hallucinations
- Shortness of breath
- Swelling of the ankles or feet
- Urinating less than usual
- Yellowing of the skin or eyes
- Severe skin reaction
Carbamazepine can also sometimes cause liver dysfunction, low sodium levels, a decrease in white blood cells, or an increase in eosinophils (a type of white blood cell). In some cases, the severity of side effects may necessitate use of a different anti-seizure, bipolar, or nerve pain medication.
A free carbamazepine test and/or a carbamazepine-10,11-epoxide test may also be ordered along with the total carbamazepine test when a healthcare practitioner wants to evaluate the contribution of the free drug and/or its metabolite to drug therapy. The healthcare practitioner may choose to do so when the result from a total carbamazepine test is within the therapeutic range but the treated person is experiencing side effects. Sometimes results are evaluated as a percentage of free to total carbamazepine.
Related Words/Test
Valproic Acid Phenytoin Therapeutic Drug Monitoring Emergency and Overdose Drug Testing Pharmacogenetic Tests.
