Sample Type: Serum

Overview:
Carbamazepine, commonly known by the brand name Tegretol, is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy, bipolar disorder, and trigeminal neuralgia. It works by stabilizing hyperexcited nerve membranes, inhibiting repetitive neuronal firing, and reducing synaptic transmission.

Clinical Use:

Epilepsy: Effective for partial and generalized tonic-clonic seizures.

Bipolar Disorder: Used as a mood stabilizer, especially in patients who are resistant to lithium.

Trigeminal Neuralgia: First-line treatment to relieve nerve-related facial pain.

Other Uses: Sometimes used in neuropathic pain and alcohol withdrawal syndromes.

Serum Monitoring Purpose:
Carbamazepine has a narrow therapeutic index, making serum level monitoring essential to ensure efficacy while avoiding toxicity. It is metabolized in the liver and exhibits autoinduction, meaning its metabolism increases over time with continued use.

Therapeutic Range:

Typically: 4–12 µg/mL (may vary slightly by lab)

Below 4 µg/mL: Risk of subtherapeutic effects (e.g., seizure breakthrough, poor mood control)

Above 12 µg/mL: Risk of toxicity (e.g., dizziness, ataxia, drowsiness, confusion, cardiac arrhythmias)

Toxicity and Side Effects:

Common: Nausea, dizziness, blurred vision, fatigue

Serious: Liver dysfunction, aplastic anemia, Stevens-Johnson syndrome, hyponatremia, bone marrow suppression

Interactions: Carbamazepine can induce liver enzymes, affecting the metabolism of other drugs.

Testing Procedure:
A blood sample (serum) is taken, usually in the morning before the next dose (trough level), to assess steady-state concentration. Initial frequent monitoring is needed during dose titration or if interacting drugs are introduced.