PMID- 19371318
OWN - NLM
STAT- MEDLINE
DCOM- 20091009
LR  - 20211020
IS  - 1365-2125 (Electronic)
IS  - 0306-5251 (Print)
IS  - 0306-5251 (Linking)
VI  - 67
IP  - 4
DP  - 2009 Apr
TI  - In vitro and in vivo glucuronidation of midazolam in humans.
PG  - 445-54
LID - 10.1111/j.1365-2125.2009.03386.x [doi]
AB  - AIMS: Midazolam (MDZ) is a benzodiazepine used as a CYP3A4 probe in clinical and 
      in vitro studies. A glucuronide metabolite of MDZ has been identified in vitro in 
      human liver microsome (HLM) incubations. The primary aim of this study was to 
      understand the in vivo relevance of this pathway. METHODS: An authentic standard 
      of N-glucuronide was generated from microsomal incubations and isolated using 
      solid-phase extraction. The structure was confirmed using proton nuclear magnetic 
      resonance (NMR) and (1)H-(13)C long range correlation experiments. The metabolite 
      was quantified in vivo in human urine samples. Enzyme kinetic behaviour of the 
      pathway was investigated in HLM and recombinant UGT (rUGT) enzymes. Additionally, 
      preliminary experiments were performed with 1'-OH midazolam (1'-OH MDZ) and 
      4-OH-midazolam (4-OH MDZ) to investigate N-glucuronidation. RESULTS: NMR data 
      confirmed conjugation of midazolam N-glucuronide (MDZG) standard to be on the 
      alpha-nitrogen of the imidazole ring. In vivo, MDZG in the urine accounted for 
      1-2% of the administered dose. In vitro incubations confirmed UGT1A4 as the 
      enzyme of interest. The pathway exhibited atypical kinetics and a substrate 
      inhibitory cooperative binding model was applied to determine K(m) (46 microM, 64 
      microM), V(max) (445 pmol min(-1) mg(-1), 427 pmol min(-1) mg(-1)) and K(i) (58 
      microM, 79 microM) in HLM and rUGT1A4, respectively. From incubations with HLM 
      and rUGT enzymes, N-glucuronidation of 1'-OH MDZ and 4-OH MDZ is also inferred. 
      CONCLUSIONS: A more complete picture of MDZ metabolism and the enzymes involved 
      has been elucidated. Direct N-glucuronidation of MDZ occurs in vivo. 
      Pharmacokinetic modelling using Simcyp illustrates an increased role for UGT1A4 
      under CYP3A inhibited conditions.
FAU - Hyland, Ruth
AU  - Hyland R
AD  - Pharmacokinetics Dynamics and Metabolism, Pfizer Global R&D, Ramsgate Road, 
      Sandwich, Kent, CT13 9NJ, UK. ruth.hyland@pfizer.com
FAU - Osborne, Toby
AU  - Osborne T
FAU - Payne, Anthony
AU  - Payne A
FAU - Kempshall, Sarah
AU  - Kempshall S
FAU - Logan, Y Raj
AU  - Logan YR
FAU - Ezzeddine, Khaled
AU  - Ezzeddine K
FAU - Jones, Barry
AU  - Jones B
LA  - eng
PT  - Journal Article
PL  - England
TA  - Br J Clin Pharmacol
JT  - British journal of clinical pharmacology
JID - 7503323
RN  - 0 (Anti-Anxiety Agents)
RN  - 0 (Glucuronides)
RN  - EC 1.14.14.1 (Cytochrome P-450 CYP3A)
RN  - EC 1.14.14.55 (CYP3A4 protein, human)
RN  - R60L0SM5BC (Midazolam)
SB  - IM
MH  - Anti-Anxiety Agents/*metabolism
MH  - Cytochrome P-450 CYP3A
MH  - Glucuronides/isolation & purification/*metabolism/urine
MH  - Humans
MH  - Magnetic Resonance Spectroscopy
MH  - Microsomes, Liver/metabolism
MH  - Midazolam/chemistry/*metabolism
PMC - PMC2679108
EDAT- 2009/04/18 09:00
MHDA- 2009/10/10 06:00
PMCR- 2010/04/01
CRDT- 2009/04/18 09:00
PHST- 2009/04/18 09:00 [entrez]
PHST- 2009/04/18 09:00 [pubmed]
PHST- 2009/10/10 06:00 [medline]
PHST- 2010/04/01 00:00 [pmc-release]
AID - BCP3386 [pii]
AID - 10.1111/j.1365-2125.2009.03386.x [doi]
PST - ppublish
SO  - Br J Clin Pharmacol. 2009 Apr;67(4):445-54. doi: 
      10.1111/j.1365-2125.2009.03386.x.