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Interpretive Handbook

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Test 8654 :
Carbamazepine, Total, Serum

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Carbamazepine is used in the control of partial seizures with both temporal lobe and psychomotor symptoms, and for generalized tonic-clonic seizures. It is also used for analgesia in trigeminal neuralgia.

 

Carbamazepine exhibits a volume of distribution of 1.4 L/kg with an elimination half-life of 15 hours. Protein binding averages 75%.

 

Carbamazepine-10,11-epoxide (CBZ10-11) is an active metabolite that represents the predominant form of the drug in children. The volume of distribution of CBZ10-11 is 1.1 L/kg, and the half-life is 8 hours.

 

Aplastic anemia and agranulocytosis are rare side effects of treatment with carbamazepine; baseline hematologic data should be documented before treatment is initiated.

 

Toxicity associated with carbamazepine overdose occurs when the blood level is > or =15.0 mcg/mL and is typified by irregular breathing, muscle irritability, and hyperreflexia; followed by hyporeflexia, tachycardia, hypotension, and impaired consciousness with coma in severe toxicity; the higher the blood level, the more severe the symptoms.

Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring therapy

 

Determining compliance

 

Assessing toxicity

Interpretation Provides information to assist in interpretation of the test results

Dosage adjustments are usually guided by monitoring blood levels. Most patients respond well when the serum concentration is in the range of 4.0 to 12.0 mcg/mL. Toxicity often occurs when levels are > or =15.0 mcg/mL.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Carbamazepine-10,11-epoxide (CBZ10-11) is not reported. Optimal response occurs when the CBZ10-11 level is in the range of 0.4 to 4.0 mcg/mL.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Therapeutic concentration: 4.0-12.0 mcg/mL

Toxic concentration: > or =15.0 mcg/mL

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Cereghino JJ, Meter JC, Brock JT, et al: Preliminary observations of serum carbamazepine concentration in epileptic patients. Neurology 1973;23:357-366

2. Patsalos PN, Berry DJ, Bourgeois BF, et al: Antiepileptic drugs-best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia 2008;49(7):1239-1276


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