How to Read Carbamazepine (Tegretol) Test Report

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Carbamazepine Test:

Carbamazepine is a drug that is used to treat seizure disorders like epilepsy, stabilize moods of people with bipolar disorder, ease alcohol withdrawal, and treat some types of nerve pain. This Carbamazepine test measures the amount of carbamazepine in the blood. The test is also used to monitor the amount to determine whether the range is within the therapeutic limit.

Factors involved to understand the normal range of Carbamazepine (Tegretol) levels:

  1. What is the normal range of Carbamazepine test?
  2. What do high levels of Carbamazepine mean?
  3. Symptoms of high levels of Carbamazepine
  4. What do low levels of Carbamazepine mean?
  5. Symptoms of low levels of Carbamazepine
  6. Causes of high levels of Carbamazepine
  7. Causes of low levels of Carbamazepine
  8. Precautions to be taken to maintain normal levels of Carbamazepine
  9. Are there any risks associated with Carbamazepine test?
  10. What other tests are ordered along with Carbamazepine test?

What is the normal range of Carbamazepine test?

Normal range of carbamazepine is in the range of 4-12 mcg/mL or 17 to 51 micromol/L. The results are given in micrograms per milliliter (mcg/mL) or micromoles per liter (micromol/L), depending upon the laboratory. Carbamazepine toxicity occurs at levels higher than 40 mg/L.

What do high levels of Carbamazepine mean?

Higher than 15 mcg/mL of carbamazepine in blood indicates carbamazepine toxicity. High levels of carbamazepine requires immediate medical care.

Symptoms of high levels of Carbamazepine

Symptoms are often associated with higher concentrations of carbamazepine in blood. These include:

  • Dizziness
  • Uncoordinated movement
  • Sleepiness
  • Blurred or double vision
  • A red itchy rash
  • Gastrointestinal problems such as diarrhea, constipation, nausea, and vomiting
  • Headache and confusion
  • Irregular heartbeat
  • Bleeding gums
  • Nosebleeds

Some of the severe symptoms include:

  • Congestive heart failure
  • Edema
  • Aggravation of hypertension
  • Severe arrhythmia
  • Respiratory depression and trouble breathing
  • Renal dysfunction and failure, etc.

In some cases, higher concentration of carbamazepine can also cause liver dysfunction, low sodium levels, a decrease in WBCs, or an increase in eosinophils.

What do low levels of Carbamazepine mean?

Too low levels of carbamazepine in the blood can indicate that the drug dosage is ineffective. In patients with low levels of carbamazepine, a recurrence of symptoms such as seizures, mania, or pain, is observed.

Symptoms of low levels of Carbamazepine

Low levels of carbamazepine results in recurrence of the symptoms. Some people experience or show certain severe symptoms on the lower side of therapeutic range. These include:

  • Recurrence of seizures
  • Mood swings
  • Nerve pain
  • Pain
  • Mania

Causes of high levels of Carbamazepine

Certain medications can cause an increase in the levels of carbamazepine. These medications interfere with the drug and also elevate its effectiveness. Some of these medications are as follows:

  • Mood stabilizer and anti-seizure medication
  • Certain antibiotics like ciprofloxacin, erythromycin, etc.
  • Heartburn or reflex medications
  • Antifungal medications
  • Certain heart medications
  • Certain medications used to treat mood swings or sleep issues

Grapefruit juice also causes an increase in the levels of carbamazepine.

Causes of low levels of Carbamazepine

Some of the drugs used to treat convulsions or seizures increase the metabolism of carbamazepine, thereby decreasing its concentration in the blood. This leads to lower than required therapeutic levels of the drug in the blood which in turn causes recurrence of symptoms. Some of these drugs include:

  • Phenobarbital
  • Primidone
  • Phenytoin

Precautions to be taken to maintain normal levels of Carbamazepine

Normal levels of carbamazepine is a very narrow range. Hence, precautions must be taken to maintain a required range. Monitoring of blood levels helps in deciding and adjusting the dosage. Administering a low dosage initially and gradually increasing it is advised. Medications should be taken with meals. Combining tegretol suspension with other liquid medications or diluents should not be done.

If the medication of a patient is being shifted from tablets to suspension, it advised to administer the same number of ‘mg’ per day to avoid an increase or decrease in the levels of carbamazepine. Dosages should be adjusted carefully to achieve a steady concentration.

Are there any risks associated with Carbamazepine test?

Carbamazepine estimation requires a blood sample and is a simple test. There are some risks associated with using a needle for the test. These may include bleeding, infection, bruising, or pain at the time of puncture. Sometimes, a person may also feel lightheaded. Site of puncture may become sore. However, these side effects fade on their own and do not cause any complications.

What other tests are ordered along with Carbamazepine test?

A patient undergoing a carbamazepine drug treatment should be monitored closely and regularly. Since carbamazepine affects different parameters in the body, a series of investigative tests are ordered along with this test. CBC test is ordered as levels of platelet and white blood cells are observed to be decreased during high levels of carbamazepine.

Period estimation of liver function tests is ordered when there is evidence of liver dysfunction, liver damage, or severe liver disease. Eye examinations are also ordered as some drugs can cause eye changes. Thyroid function tests are also ordered as the levels of thyroid hormones have been shown to decrease with Tegretol administration. Blood urea nitrogen (BUN) and creatinine tests are ordered to check the functioning of kidneys. Electrolyte test is ordered to measure the levels of certain minerals in your blood.

Estimation and monitoring of other medications that a patient may be taking and pregnancy tests are also ordered. The health care provider may also order genetic testing before the administration of the drug to determine the likeliness of a reaction to it.

Test results often vary depending upon certain factors such as age, gender, health history, test method, etc. Test results does not necessarily indicate a problem and it is important to talk to your health care provider about the results. Timing for this test is an important aspect and hence, the test is ordered just before a dose is scheduled. There are no specific preparations required.

Adjusting a steady dose may require different amount of the drug in different patients. Patients are advised not to increase, decrease, or stop the medications without consulting the doctor first. It is also important to let your health care provider know about the prescription drugs, over-the-counter medications, or herbs that you may be taking. These may interact with the carbamazepine in a dangerous way.


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