In some cases, to determine the concentration of levetiracetam in the blood to establish an individualised dose; to detect toxicity or verify that a person is taking the medication as prescribed (compliance /adherence); to monitor changes that may affect drug clearance and/or kidney function
In some cases, at the start of treatment when establishing dosage; when indicated to detect low or excessive (potentially toxic) concentrations; when a person has decreased kidney function; occasionally to verify compliance /adherence
A blood sample taken from a vein in your arm
Levetiracetam is a drug that is used to treat certain seizure disorders (also called epilepsy). It is prescribed either as primary therapy or as an adjunctive (secondary) treatment in combination with other antiepileptic drugs. This test measures the amount of levetiracetam in the blood.
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. Seizures are categorised by the parts of the brain and body that are affected. Levetiracetam is prescribed to help prevent specific types of recurrent seizures.
Levetiracetam is one of several newer second-generation antiepileptic drugs. It has a wider therapeutic range than many existing first-generation seizure medications. That is, the range of concentration in the blood in which the drug is effective without being toxic is broader, making it somewhat safer. It is also associated with fewer severe side effects and does not interact with as many other drugs. Since it is relatively new, however, it has less of a ‘use history’ – its long-term safety and efficacy and its appropriate therapeutic range are less well established.
Because levetiracetam has a wider therapeutic range, it does not need to be monitored in the same manner as first-generation antiepileptic drugs. (For further discussion of this, see the article on Therapeutic Drug Monitoring.) However, there are circumstances in which it is useful and sometimes necessary to measure blood levels. Some of these include:
- To establish the range that is therapeutic for an individual; after treatment has started and the individual has relief from symptoms (no seizures) and suffers no side effects, the concentration of the drug in the blood is determined. The range around this value is considered therapeutic for the person and may be used to evaluate their treatment in the future if their health status or other factors change.
- To verify that a person's symptoms (seizures or side effects) are not due to too little or too much drug; to verify that a person is taking the medication as prescribed
- To evaluate and adjust the dose as necessary in certain conditions such as:
- Kidney disease—levetiracetam is cleared from the body by the kidneys, so anything that affects kidney function can affect blood levels of the drug.
- A change or addition of other drugs
- Aging—people typically are prescribed seizure medications for life and, as they age, the amount of drug needed to be effective may change.
- Pregnancy—this condition can temporarily affect drug metabolism and clearance.
At the start of therapy, doses of levetiracetam may be gradually increased until a standard amount is reached. Once a stable dose is achieved, a blood level may sometimes be measured to ensure that it is within the therapeutic range. If levetiracetam is being used as an adjunctive (secondary) medication, the doctor will also consider the effectiveness of other drugs that are prescribed and may adjust them as necessary.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
This test is used to measure the amount of levetiracetam in the blood to determine whether the level of drug is within the therapeutic range. Initially, the test may be requested to help establish the appropriate dose for an individual. Since the therapeutic range is relatively wide and not well established, the doctor will evaluate the effectiveness of the dose in controlling seizures and the presence and severity of side effects in the individual. Depending on these clinical findings and the results of the blood test, the dose of drug may be adjusted up or down.
Routine periodic monitoring is usually not required, but levetiracetam tests may be requested to adjust the dosage as necessary if the treated person becomes pregnant or if there is a health change, a decrease in kidney function, or any other condition that may affect the rate of clearance of the drug. In some cases, a levetiracetam blood test may be requested if someone begins taking other drugs in order to determine whether an adjustment to the prescribed dose is necessary.
A doctor may use a levetiracetam test to help evaluate someone who is experiencing side effects or adverse reactions or experiencing a recurrence of seizures or symptoms. Rarely, testing may be requested to verify that the person is taking the medication as prescribed (compliance/adherence).
When is it requested?
Levetiracetam tests may occasionally be requested after a person begins taking the drug and a stable dose is achieved. Additional levetiracetam blood tests may occasionally be requested when dosages of the drug are changed or when the treated person starts or stops taking additional medications in order to judge their effect, if any, on the concentration of levetiracetam in the bloodstream.
Tests may be requested periodically when a person has decreased kidney function, has an underlying condition that may affect kidney function, and/or has significant liver dysfunction.
It may be requested when a person does not appear to be responding to therapy and has a recurrence of seizures. The blood level may not be high enough, the person may not be taking the medication as prescribed, or the drug may be ineffective for that person.
Levetiracetam tests may also be requested when a person experiences a troublesome level of side effects and/or develops complications. Leveteracetam has a good safety profile, but side effects that may be seen at any dose but that are related to higher concentrations include:
- Blocked nose/itchy throat
- Allergic reactions (rare but may be severe)
- Lack of coordination
- Loss of appetite
- Memory problems
- Numbness, tingling, or burning in the hands or feet
- Skin reactions
- Thoughts of suicide
- Weakness/lack of energy (asthenia)
People who take levetiracetam should talk to their doctor about the timing of the sample collection. Normally, the recommended time for having the blood test is just before the next dose is taken (trough level).
What does the test result mean?
The therapeutic range for levetiracetam is wide, approximately 12.0 - 46.0 mg/L. Levels above 46 mg/L are considered potentially toxic. Quoted ranges vary slightly from laboratory to laboratory. Doctors and people tested should use the therapeutic ranges and units established by the laboratory that performs the testing.
Within the therapeutic range, most people will respond to the drug without excessive side effects; however, response varies with each individual. Some people will experience seizures at the low end of the therapeutic range, some will experience excessive side effects at the upper end, and some will require dosages outside of the established range for effectiveness and/or freedom from side effects. People who use this medication should work closely with their doctor to find the dosage that works the best for them.
In general, if levetiracetam test results are within the therapeutic range (or at an individually established level) and the treated person is not having recurrent seizures and is not experiencing significant side effects, then the drug dosage is considered adequate. A level that is outside the therapeutic range may mean an individual is not taking the drug as prescribed by the doctor. This is important to know, as this may put the person at increased risk of experiencing symptoms.
Is there anything else I should know?
How long will I need to be on levetiracetam?
People who have epilepsy will typically take levetiracetam or other medications throughout their lifetime. If levetiracetam ceases to be effective or causes adverse effects, then the person may need to be given different drug(s).
What other antiepileptic drugs (AEDs) are there?
There is a broad range of AEDs available that have different forms of action and are used to treat different types of seizures. First-generation AEDs that have been use for a long period of time include: phenobarbital (since the early 1900s), phenytoin, carbamazepine, ethosuximide, and valproate (valproic acid). Newer, second-generation AEDs include drugs such as: gabapentin, lamotrigine, oxcarbazepine, topiramate, and levetiracetam. Some of these are used by themselves, but most of the newer AEDs are used in combination with other drugs.
Elsewhere On The Web
Epilepsy Society: Medication
NHS: Epilepsy treatment
British National Formulary: Levetiracetam
Medicines for Children information leaflet: Levetiracetam in preventing seizures