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23397 Citalopram, Serum (CITAL)

Citalopram, Serum (CITAL)
Test Code: CITASO
Synonyms/Keywords
Escitalopram, S-citalopram, Celexa (Citalopram)
Useful For
Monitoring citalopram therapy
 
Identifying noncompliance, although regular blood level monitoring is not indicated in most patients
 
Identifying states of altered drug metabolism when used in conjunction with CYP2C19 and CYP3A4-5 genotyping​
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​0.5 mL ​0.4 mL
Collection Processing Instructions

​Draw blood before next scheduled dose.

Centrifuge and remove serum from cells within 2 hours of collection.

Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ ​Refrigerated (preferred) ​28 days
​Ambient ​28 days
​Frozen ​28 days
Rejection Criteria
Serum gel tube​ ​
Interference

Test interpretation requires knowledge of which enantiomers (R, S- or S-) are prescribed; this assay does not distinguish the enantiomers. Flagging is based off of the racemic R,S-enantiomeric citalopram reference range, not the S-enantiomer escitalopram reference range.

Specimens that are obtained from gel tubes are not acceptable.

Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
​Mayo Clinic LaboratoriesMonday, Wednesday​1 to 4 days
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
Test Information

Citalopram (Celexa) and S-citalopram (escitalopram, Lexapro) are approved for treatment of depression. Celexa is a racemic mixture containing equal amounts of R- and S-enantiomer. Metabolites of citalopram (N-desmethylcitalopram) are less active than citalopram and do not accumulate in serum to clinically significant concentration.

Citalopram metabolism is carried out by cytochrome P450 (CYP) 2C19 and 3A4-5. CYP 2D6 may play a minor role in citalopram metabolism. Citalopram is known to reduce CYP 2D6 activity. Citalopram clearance is significantly affected by reduced hepatic function, but only slightly by reduced renal function.

A typical Celexa dose administered to an adult is 40-mg per day. A typical Lexapro dose is 20-mg per day. Citalopram is 80% protein bound, and the apparent volume of distribution is 12 L/Kg. Bioavailability is 80% and protein binding is 56% for either form of the drug. Time to peak serum concentration is 4 hours, and the elimination half-life is 35 hours. Half-life is increased in the elderly. Dosage reductions may be necessary for patients who are elderly or have reduced hepatic function.

Reference Range Information
Citalopram: 50 - 110 ng/mL
Escitalopram: 15-80 ng/mL
Interpretation

Steady-state serum concentrations associated with optimal response to citalopram are in the range of 50 to 100 ng/mL when the patient is administered the R,S-enantiomeric mixture (Celexa).

The most common toxicities associated with excessive serum concentration are fatigue, impotence, insomnia, and anticholinergic effects. The toxic range for citalopram is greater than 220 ng/mL.

Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80299
Synonyms/Keywords
Escitalopram, S-citalopram, Celexa (Citalopram)
Ordering Applications
Ordering Application Description
​Centricity ​Citalopram, S (83730)
​Cerner ​Citalopram, S (83730)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​0.5 mL ​0.4 mL
Collection Processing

​Draw blood before next scheduled dose.

Centrifuge and remove serum from cells within 2 hours of collection.

Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ ​Refrigerated (preferred) ​28 days
​Ambient ​28 days
​Frozen ​28 days
Rejection Criteria
Serum gel tube​ ​
Interference

Test interpretation requires knowledge of which enantiomers (R, S- or S-) are prescribed; this assay does not distinguish the enantiomers. Flagging is based off of the racemic R,S-enantiomeric citalopram reference range, not the S-enantiomer escitalopram reference range.

Specimens that are obtained from gel tubes are not acceptable.

Useful For
Monitoring citalopram therapy
 
Identifying noncompliance, although regular blood level monitoring is not indicated in most patients
 
Identifying states of altered drug metabolism when used in conjunction with CYP2C19 and CYP3A4-5 genotyping​
Reference Range Information
Citalopram: 50 - 110 ng/mL
Escitalopram: 15-80 ng/mL
Interpretation

Steady-state serum concentrations associated with optimal response to citalopram are in the range of 50 to 100 ng/mL when the patient is administered the R,S-enantiomeric mixture (Celexa).

The most common toxicities associated with excessive serum concentration are fatigue, impotence, insomnia, and anticholinergic effects. The toxic range for citalopram is greater than 220 ng/mL.

For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
​Mayo Clinic LaboratoriesMonday, Wednesday​1 to 4 days
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80299
For most current information refer to the Marshfield Laboratory online reference manual.