section name header

Synonym

Tubes

Recommended sample collection time:

DrugRoute of
Administration
Recommended
Collection
Time
PhenobarbitalIV
  • Peak: 30 minutes to 1 hour after a dose
  • Trough: Just prior to when next dose is due
PhenobarbitalPOFor therapeutic monitoring (steady state after 4 half-lives) after initiating therapy, change in dosing regimen, adding a second drug, or change in the patient's liver or GI function
  • Newborn: Frequently
  • Children: 10-15 days, then every 3-4 months
  • Adults: 15-25 days, then every 6 months
  • For suspected toxicity: Immediately, then 6 hrs after last dose

Additional information

Info

This section covers Antiseizure medication levels - Phenobarbital. Other sections provide detailed information on other components of Antiseizure medication levels.

Clinical

Additional information

This section covers Antiseizure medication levels - Phenobarbital. Other sections provide detailed information on other components of Antiseizure medication levels.

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

PhenobarbitalConv. Units
(µg/mL)
SI Units
(µmol/L)
Adult/Child (Therapeutic)15-4065-172
Neonate (Therapeutic)15-3065-129
Toxic (Adult/Child)>50>216
Toxic (Neonate)>40>172

This section covers Antiseizure medication levels - Phenobarbital. Other sections provide detailed information on other components of Antiseizure medication levels.

High Result

Elevated serum Phenobarbital level is associated with incorrect dosing, overdose, poisoning and toxicity.

Drugs that may increase phenobarbital levels or increase risk of toxicity include:

This section covers Antiseizure medication levels - Phenobarbital. Other sections provide detailed information on other components of Antiseizure medication levels.

Low Result

Decreased Phenobarbital levels are associated with decreased therapeutic effect, inadequate dosing or non-compliance.

Drugs that may decrease phenobarbital levels include:

This section covers Antiseizure medication levels - Phenobarbital. Other sections provide detailed information on other components of Antiseizure medication levels.

References