PMID- 23666567
OWN - NLM
STAT- MEDLINE
DCOM- 20131126
LR  - 20191210
IS  - 1536-3694 (Electronic)
IS  - 0163-4356 (Linking)
VI  - 35
IP  - 3
DP  - 2013 Jun
TI  - Improved method for therapeutic drug monitoring of 6-thioguanine nucleotides and 
      6-methylmercaptopurine in whole-blood by LC/MSMS using isotope-labeled internal 
      standards.
PG  - 313-21
LID - 10.1097/FTD.0b013e318283ed5d [doi]
AB  - OBJECTIVES: Thiopurine drugs (azathioprine, 6-mercaptopurine) show wide 
      interindividual variability and a narrow therapeutic range thus making 
      therapeutic monitoring of their active metabolite 6-thioguanine nucleotides 
      (6-TGN) desirable. We improved the currently available laborious and complex 
      methodology of therapeutic drug monitoring of 6-TGN and the metabolite 
      6-methylmercaptopurine (6-MMP) in washed erythrocytes (ery) based on a 
      whole-blood method. METHODS: The analytes were hydrolyzed and extracted from 
      25-microL ethylenediaminetetraacetic acid-anticoagulated whole-blood spiked with 
      isotope labeled 6-TG-C2N and 6-MMP-d3 internal standards. Chromatography was 
      performed in 5.1 minutes on a C18 reverse phase column followed by detection via 
      electrospray interface-coupled API 4000 mass spectrometer set up in the positive 
      multiple reaction monitoring mode. The hemoglobin concentration was measured in 
      20 microL of the original sample (AHD575 method), and the results were standardized 
      to 120 g/L of hemoglobin. RESULTS: Calibration curves were linear with r > 0.999 
      (6-TGN and 6-MMP up to 10,000 pmol/0.2 mL). The limit of quantification was 30 
      pmol/0.2 mL for 6-TGN and 6-MMP. Intraassay and interassay imprecision was <7.5% 
      at 3 tested levels for 6-TGN and 6-MMP, respectively. Method comparisons were as 
      follows: Ery 6-TGN: y = 1.3x - 11 and ery 6-MMP y = 1.1x - 124. CONCLUSIONS: The 
      new method compares favorably with established ones, allowing for rapid single 
      run determination of 6-TGN and 6-MMP from <50 microL of fresh or frozen whole blood. 
      Linearity and limits of quantification cover the clinically relevant range. 
      Variability during sample preparation and matrix effects are compensated by the 
      use of isotope-labeled internal standards. The whole-blood method is hemoglobin 
      standardized to avoid falsely low results in the case of anemia. The method 
      correlates well with 6-TGN measured in washed erythrocytes, but it requires 
      significantly less hands-on time. Preliminary therapeutic ranges for the most 
      common indications of azathioprine and 6-MP are provided.
FAU - Kirchherr, Hartmut
AU  - Kirchherr H
AD  - Medizinisches Labor Bremen, Bremen, Germany.
FAU - Shipkova, Maria
AU  - Shipkova M
FAU - von Ahsen, Nicolas
AU  - von Ahsen N
LA  - eng
PT  - Comparative Study
PT  - Journal Article
PT  - Validation Study
PL  - United States
TA  - Ther Drug Monit
JT  - Therapeutic drug monitoring
JID - 7909660
RN  - 0 (Guanine Nucleotides)
RN  - 0 (Thionucleotides)
RN  - 15867-02-4 (6-thioguanylic acid)
RN  - 6V404DV25O (6-methylthiopurine)
RN  - E7WED276I5 (Mercaptopurine)
SB  - IM
MH  - Calibration
MH  - Chromatography, High Pressure Liquid/*methods
MH  - Drug Monitoring/methods
MH  - Erythrocytes/metabolism
MH  - Guanine Nucleotides/*blood
MH  - Humans
MH  - Limit of Detection
MH  - Mercaptopurine/*analogs & derivatives/blood
MH  - Tandem Mass Spectrometry/*methods
MH  - Thionucleotides/*blood
MH  - Time Factors
EDAT- 2013/05/15 06:00
MHDA- 2013/12/16 06:00
CRDT- 2013/05/14 06:00
PHST- 2013/05/14 06:00 [entrez]
PHST- 2013/05/15 06:00 [pubmed]
PHST- 2013/12/16 06:00 [medline]
AID - 10.1097/FTD.0b013e318283ed5d [doi]
PST - ppublish
SO  - Ther Drug Monit. 2013 Jun;35(3):313-21. doi: 10.1097/FTD.0b013e318283ed5d.