Midazolam

From PubPK

Jump to: navigation, search
IUPAC Name
8-chloro- 6-(2-fluorophenyl)- 1-methyl- 4H-imidazo[1,5-a] [1,4]benzodiazepine
Physicochemical Properties
CAS number 59467-70-8
PubChem 4192
DrugBank APRD00680
Molecular Formula C18H13ClFN3
Molecular Weight (g/mol) 325.767323
logP 2.68
H-Bond Donor 0
H-Bond Acceptor 4
Polar Surface Area (Å2) 30.2

Midazolam is a short-acting benzodiazepine widely used for preoperative sedation, induction, and maintenance of anesthesia.

Contents

Trade Names

  • Dormicum
  • Dormonid
  • Flormidal
  • Hypnovel
  • Versed

In Vitro Metabolism & Transport

Metabolism

CYP Substrate Inhibitor Inducer UGT Substrate Inhibitor Inducer
CYP1A1 UGT1A1
CYP1A2 UGT1A3
CYP1B1 UGT1A4
CYP2A6 UGT1A6
CYP2B6 UGT1A9
CYP2C8 UGT2A1
CYP2C9 UGT2A2
CYP2C19 UGT2A3
CYP2D6 UGT2B4
CYP2E1 UGT2B7
CYP2J2 UGT2B10
CYP3A4 Yes1 UGT2B11
CYP3A5 Yes1 UGT2B15
CYP3A7 UGT2B17

References:

Transport

ABC Substrate Inhibitor Inducer SLC Substrate Inhibitor Inducer
ABCB1 (MDR1) Yes1 SLC10A1 (NTCP)
ABCB4 (MDR3) SLC10A2 (NTCP2)
ABCB11 (BSEP) SLC15A1 (PEPT1)
ABCC1 (MRP1) SLC15A2 (PEPT2)
ABCC2 (MRP2) SLC16A1 (MCT1)
ABCC3 (MRP3) SLC16A4 (MCT5)
ABCC4 (MRP4) SLC22A1 (OCT1)
ABCC5 (MRP5) SLC22A2 (OCT2)
ABCC6 (MRP6) SLC22A3 (OCT3)
ABCC10 (MRP7) SLC22A4 (OCTN1)
ABCC11 (MRP8) SLC22A5 (OCTN2)
ABCG2 (BCRP) SLC22A6 (OAT1)
SLC22A7 (OAT2)
SLC22A8 (OAT3)
SLC22A9 (UST3)
SLC22A11 (OAT4)
SLC28A3 (CNT3)
SLCO1A2 (OATP-A)
SLCO1B1 (OATP-C)
SLCO1B3 (OATP8)
SLCO1C1 (OATP-F)
SLCO2B1 (OATP-B)
SLCO3A1 (OATP-D)
SLCO4A1 (OATP-E)
SLCO4C1 (OATP-H)

References: 1Tolle-Sander et al. 2003;

Pharmacokinetics

Summary of Pharmacokinetic Parameters

CLiv: total plasma clearance after iv administration; CLR: renal clearance of drug from the plasma; Vss: volume of distribution at steady state; t1/2: elimination half-life; Foral: oral bioavailability; fa: fraction of administered dose absorbed; EG: gut extraction ratio; EH: hepatic extraction ratio; fu: unbound fraction of drug in plasma; b/p: blood-to-plasma ratio
Mouse Rat Rabbit Dog Monkey Human
CLiv (mL/min/kg) 4.99 ± 1.531
CLR (mL/min/kg) 0.055
Vss (L/kg) 0.669 ± 0.2521
t1/2β (h) 2.0 ± 0.51
Foral (%) 28.2 ± 9.41
fa 1
EG (%) 46.9 ± 19.781
EH (%) 44.4 ± 13.61
fu (%) 1.68 ± 0.372
b/p 0.533

References: 1 Tateishi et al. 2001 (n=20, healthy European American men); 2 Pentikainen et al. 1989; 3 Obach 1999; 4 Calvo 1992; 5Thummel et al. 1996.

Midazolam kineitcs were also reported by many other papers include: Allonen et al., 1981; Greenblatt et al. 1984; Klotz and Ziegler, 1982; Heizmann et al., 1983; Schwagmeier et al., 1998; Thummel et al. 1996; Wandel et al., 2000).

Additional reported values of midazolam unbound fraction in human plasama (fu) include: 3.41 ± 0.11 and 3.74 ± 0.11 for young male and female, respectively (Greenblatt et al. 1984); 1.92 ± 0.69 (Thummel et al. 1996).

Pharmacokinetics in Preclinical Animals

Midazolam is metabolized almost completely by CYP3A4. Grapefruit juice reduces intestinal 3A4 and results in less metabolism and higher plasma concentrations, which could result in overdose.

Pharmacokinetics in Humans

Midazolam has a short elimination half-life of around 2 hours. Oral bioavailability is low (around 30%) and is associated with considerable interindividual variability, resulted from extensive first-pass metabolism in both the gut and the liver.

Absorption

Absorption of midazolam is complete and rapid, with peak plasma concentration being achieved at around 30 min after oral administration.

Distribution

Midazolam is lipophic at physiological pH. It crosses the placenta and is distributed into breast milk (Matheson et al., 1990). Nitsun et al. (2006) reported that an average of 0.005% (range, 0.002%-0.013%) of the maternal midazolam dose excreted into milk within 24 hours of induction of anesthesia.

Metabolism

Extensive first-pass metabolism in both the gut and the liver (Tateishi et al. 2001), mediated by CYP3A.

Excretion

Less than 1% of the administered midazolam was excreted in urine over 24 hours as unchanged drug (Thummel et al. 1996).

Factors Influencing Pharmacokinetics

Age

Midazolam half-life can be prolonged in neonates and in elderly (Greenblatt et al. 1984; Albrecht et al., 1999).

Gender

No significant gender-related differences were noted in the systemic or oral clearance values (Thummel et al. 1996).

Ethnicity

After intravenous injection plasma concentrations of midazolam were higher in Japanese subjects than those in European American men. This observation was associated with smaller initial and steady-state volumes of distribution in Japanese subjects. Normalization for body weight only modestly reduced these differences. The systemic clearance value of midazolam was 25% lower (in Japanese subjects, but this difference was not apparent after accounting for the smaller body weights of that group. No statistical differences were noted in the elimination half-life of midazolam between the two ethincity groups (Tateishi et al. 2001).

Diseases

  • Liver cirrhosis. The bioavoilability and AUC of oral midazolam were higher in liver cirrhosis patients than healthy volunteers (Pentikainen et al. 1989).
  • Renal impairment. Unbound fraction in plasma increased in renal patient (Calvo et al. 1992). Five patients with severe renal impairment experienced prolonged sedation when given midazolam; this was attributed to accumulation of conjugated metabolites (Bauer et al., 1995).
  • Obesity. Volume of distribution and half-life of midazolam increased significantly in obese volunteers compared to age and sex matched control subjects (Greenblatt et al. 1984).

Formulation

to be updated

Food

Significant changes in Cmax, tmax, and AUC were not found when midazolam was taken one hour before or with a meal as compared with the control condition. Significant changes in these parameters for both midazolam and its metabolite were seen when midazolam was ingested one hour after a meal: there was a delayed and reduced rate of absorption as well as a small reduction in the extent of absorption fa (Bornemann et al. 1986).

Drug Interactions

Effects on Other Drugs

Midazolam is not a known inhibitor of other drugs.

Effects by Other Drugs

Midazolam is exclusively metabolised by CYP3A. Drugs with potent CYP3A inhibitory properties can cause significant CYP3A-mediated drug-drug interactions.

  • Anacetrapib Anacetrapib (single daily oral doses of 150 mg) did not affect the pharmacokinetics of oral midazolam (Krishna et al. 2009).
  • Fluoxetine Fluoxetine (60mg per day) had no significant effect on the AUC of oral midazolam (Lam et al. 2003).
  • Fluvoxamine Fluvoxamine (200 mg daily) increased the AUC of oral midazolam by 66% on average (Lam et al. 2003).
  • Grapefruit juice
  • Itraconazole Itraconazole (100 mg daily) increased the AUC of oral midazolam 6-fold, Cmax 2.5-fold and the elimination half-life 2-fold (Ahonen et al. 1995).
  • Ketoconazole Ketoconazole (200 mg once daily) increased the AUC of oral midazolam by 772% on average (Lam et al. 2003). In another study, ketoconazole (200 mg daily) increased the AUC of midazolam to 5-fold after intravenous midazolam administration and to 16-fold after oral midazolam administration (Tsunoda et al. 1999).
  • Nefazodone Nefazodone (400 mg once daily) increased the AUC of oral midazolam by 444% on average (Lam et al. 2003).
  • Rifampicin Rifampicin (600 mg once daily) significantly increased the systemic and oral clearance of midazolam (Gorski et al. 2004).
  • Saquinavir In a double-blind, randomized, two-phase crossover study, 12 healthy volunteers received oral doses of either 1200 mg saquinavir or placebo three times a day for 5 days. On day 3, six subjects were given 7.5 mg oral midazolam and the other six subjects received 0.05 mg/kg intravenous midazolam. On day 5, the subjects who had received oral midazolam on day 3 received intravenously midazolam and vice versa. Saquinavir increased the bioavailability of oral midazolam from 41% to 90%, Cmax more than twofold, and the AUC more than fivefold. Saquinavir decreased the clearance of intravenous midazolam by 56% and increased its elimination half-life from 4.1 to 9.5 hours (Palkama et al. 1999).
  • Terbinafine Terbinafine (250 mg daily) did not significantly affect the pharmacokinetics of midazolam (Ahonen et al. 1995).
  • Voriconazole In a randomized, crossover study, ten healthy male volunteers were given either no pretreatment (control phase) or voriconazole (voriconazole phase) orally, 400 mg twice daily on the first day and 200 mg twice daily on the second day. Midazolam was given, either 0.05 mg/kg intravenously or 7.5 mg orally, 1 hour after the last dose of voriconazole and during the control phase. Voriconazole reduced the clearance of intravenous midazolam by 72% and increased its elimination half-life from 2.8 to 8.3 hours. The peak concentration and the area under the plasma concentration-time curve of oral midazolam were increased by 3.8- and 10.3-fold, respectively. The oral bioavailability of midazolam was increased from 31% to 84%. (Saari et al. 2006).

See also

External links

References

Retrieved from "http://www.pubpk.org/index.php?title=Midazolam"
Personal tools