Search Test

Why Get Tested?
To monitor the phenobarbital level in your blood to ensure a therapeutic level while avoiding toxic side effects
When To Get Tested?
At the start of therapy and at a regular intervals during treatment; when someone has signs and symptoms of toxicity or is experiencing seizures
Sample Type:
SERUM (SST or Plain)
Fasting :
NO
Report Delivery:
3rd Day
Components:
1 Observations

Tests Detail

Observations Included

Phenobarbitone (Gardinal)

The Test marked with (*) are in our NABL Scope.

Sample Report

Test Name	Phenobarbital (Gardinal)
Report Availability	3rd Day
Code	C1142
Category	SA-Special Advance
Schedule	Daily
TAT*	2
Tested At*	NRL
Method	Chemiluminescence
Brief Description	Medication History/Monitor therapeutic level.

*Reporting TAT in days
for the samples recieved by 4PM

*0 = Same Day, 1 = Next Day, 2 = 2nd Day,
3 = 3rd Day So on from Schedule

*NPL : Tested @ nirAmaya Pathlabs
NRL : Tested @ NPL Outsource lab

Also Known As:
[Often referred to by brand name (see MedlinePlus Drug Information)]
Formal Name:
Phenobarbital
Sample Instructions:
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
What Is Being Tested?
Phenobarbital is a long-acting barbiturate, an anti-epileptic drug (AED) and sedating drug that depresses the nervous system. Health practitioners usually prescribe it to prevent seizures or to relieve anxiety. It is often prescribed to treat epilepsy and other seizure disorders because the drug stabilizes electrical activity in the brain. This test measures the level of phenobarbital in the blood. It is important to maintain a stable level of phenobarbital in the blood within the therapeutic range. If the level is too low, the person who is being treated may experience seizures or anxiety. If the level is too high, the individual could experience side effects or even toxicity. The toxic effects include drowsiness, confusion, and lack of voluntary coordination of muscle movement (ataxia), which can affect things like driving performance. Those who are chronically treated may also develop tolerance to the sedative effects of the drug and become dependent. Maintaining a constant, therapeutic level of phenobarbital in the blood can be difficult. The difference between the level at which the drug is therapeutic and the level at which toxic side effects can occur is very small. This is called a narrow therapeutic index and is a primary reason the drug requires close monitoring. Furthermore, phenobarbital is broken down (metabolized) by liver enzymes and eliminated in the urine at different rates, depending on a person's age and overall health. Depending on dose, age and health, elimination can take several days to weeks. Once the body has reached its capacity to metabolize phenobarbital, small increases in dose can result in large increases in levels of the drug in the blood. Side effects can become more severe and toxicity may occur. A healthcare provider will monitor an individual's response to phenobarbital to make sure that the desired level of the drug is maintained in the blood and to determine the dose that works best for the person treated. The health practit
How Is It Used?
This test is used to measure and monitor the amount of phenobarbital in the blood and to determine whether the drug level is within a therapeutic range. Phenobarbital is an anti-epileptic drug used to prevent seizures in people with epilepsy. This test is used to ensure that the blood level of phenobarbital is not too low so as to cause a recurrence of seizures or too high as to cause side effects. Depending on the result, a health practitioner may adjust the drug dose up or down. If the person being treated begins taking another medication, this test may be used to monitor the blood level because phenobarbital interacts with several other common drugs. Phenobarbital might increase or decrease a specific drug's effectiveness, and that medication may also affect the level of phenobarbital in the blood. The result could be decreased effectiveness from a level that is too low or severe side effects/toxicity if the level is too high.
When Is It Ordered
A health practitioner will usually order the test after the start of phenobarbital treatment and every few weeks thereafter. Testing may be more frequent any time the dose is adjusted up or down. Once a stable blood level of phenobarbital is achieved and is in the therapeutic range, then the health practitioner will typically monitor levels at regular intervals to ensure that they are stable. More frequent testing may be done if an individual begins taking or discontinues another medication that affects phenobarbital levels. A healthcare provider might also order phenobarbital levels if the person does not appear to be responding to the medication and continues to experience seizures. Testing may be ordered when an individual experiences side effects from phenobarbital. Most side effects are not serious and often go away with no further action. A person should notify their healthcare provider if any of the following persist or become severe: Drowsiness Headache, dizziness Depression Excitement (especially in children) Upset stomach, vomiting Nightmares, increased dreaming Constipation Joint or muscle pain If any of the following symptoms are present, the healthcare provider should be notified immediately: Seizures Mouth sores, sore throat Easy bruising, bloody nose, unusual bleeding Unexplained fever Difficulty breathing or swallowing Severe skin rash
What Does The Test Result Mean?
The therapeutic range for adults taking phenobarbital is 15-40 micrograms/milliliter (mcg/ml) (65-173 micromole/liter) for seizure treatment, and 5-15 micrograms/milliliter (mcg/ml) (22-65 micromole/liter) for sedative-hypnotic use. The therapeutic range for seizure treatment in children (younger than 5 years old) is narrower: 15-30 micrograms/milliliter (mcg/ml) (65-130 micromole/liter). Within these ranges, most people will respond to the drug without displaying symptoms of toxicity. However, each person's response to the drug and side effects is individual. A person may experience side effects even with blood levels at the low end of the therapeutic range or continue to have seizures at the upper end. As with other anti-epileptic drugs, the healthcare provider will work with the person who is being treated to find the dosage that works best.
Is There Anything Else I Should Known?
Phenobarbital has been used to treat epilepsy since the early 20th century and is still the most widely prescribed anti-epileptic drug worldwide, despite development of several others since then. Because the drug causes sedation and other side effects, it is now often a second- or third-line medication in developed countries. But phenobarbital is still a first-line drug in many developing nations. You should take phenobarbital exactly as your healthcare provder has prescribed it. Do not decrease the dose, increase it, or discontinue the medication on your own because doing so can increase your risk of having a seizure and can affect the levels of your other medications. Always consult your healthcare provider if you are having problems taking phenobarbital. Your healthcare provider might decide to order a test if you begin taking another medication because several common drugs can affect how your body responds to phenobarbital. The following drugs can have effects with phenobarbital: Oral blood-thinning medications like warfarin Antidepressants and tricyclics, including MAO inhibitor antidepressants Central nervous system depressants, sedatives, hypnotics and tranquilizers Antihistamines Alcohol Oral contraceptives Corticosteroids like prednisone Doxycycline used to treat bacterial infections Griseofulvin, a drug used to treat fungal infections Phenytoin, another medication often prescribed to treat seizures How long will it take for the medicine to work? It may take a number of weeks to find the right dose, and even more time for your healthcare provider to know how well the medicine works to control your seizures. How long this takes will be different for each person. It may require 14-21 days to achieve the steady therapeutic blood concentrations. Factors affecting dose optimization include how often you have seizures, what other medicines you may be taking, and how your body responds to phenobarbital. How long will my

Phenobarbital (Gardinal)

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