The pharmacokinetics of midazolam in patients with congestive heart failure

Midazolam Ameliorates Hyperglycemia-Induced Glomerular Endothelial Dysfunction by Inhibiting Transglutaminase 2 in Diabetes

Midazolam is an anesthetic widely used for anxiolysis and sedation; however, to date, a possible role for midazolam in diabetic kidney disease remains unknown. Here, we investigated the effect of midazolam on hyperglycemia-induced glomerular endothelial dysfunction and elucidated its mechanism of action in kidneys of diabetic mice and human glomerular microvascular endothelial cells (HGECs). We found that, in diabetic mice, subcutaneous midazolam treatment for 6 weeks attenuated hyperglycemia-induced elevation in urine albumin/creatinine ratios. It also ameliorated hyperglycemia-induced adherens junction disruption and subsequent microvascular leakage in glomeruli of diabetic mice. In HGECs, midazolam suppressed high glucose-induced vascular endothelial-cadherin disruption and endothelial cell permeability via inhibition of intracellular Ca²⁺ elevation and subsequent generation of reactive oxygen species (ROS) and transglutaminase 2 (TGase2) activation. Notably, midazolam also suppressed hyperglycemia-induced ROS generation and TGase2 activation in glomeruli of diabetic mice and markedly improved pathological alterations in glomerular ultrastructure in these animals. Analysis of kidneys from diabetic Tgm2^−/− mice further revealed that TGase2 played a critical role in microvascular leakage. Overall, our findings indicate that midazolam ameliorates hyperglycemia-induced glomerular endothelial dysfunction by inhibiting ROS-mediated activation of TGase2.

Scaling clearance in paediatric pharmacokinetics: All models are wrong, which are useful?

Linked Articles

This article is commented on in the editorial by Holford NHG and Anderson BJ. Why standards are useful for predicting doses. Br J Clin Pharmacol 2017; 83: 685–7. doi: 10.1111/bcp.13230

Aim

When different models for weight and age are used in paediatric pharmacokinetic studies it is difficult to compare parameters between studies or perform model‐based meta‐analyses. This study aimed to compare published models with the proposed standard model (allometric weight^0.75 and sigmoidal maturation function).

Methods

A systematic literature search was undertaken to identify published clearance (CL) reports for gentamicin and midazolam and all published models for scaling clearance in children. Each model was fitted to the CL values for gentamicin and midazolam, and the results compared with the standard model (allometric weight exponent of 0.75, along with a sigmoidal maturation function estimating the time in weeks of postmenstrual age to reach half the mature value and a shape parameter). For comparison, we also looked at allometric size models with no age effect, the influence of estimating the allometric exponent in the standard model and, for gentamicin, using a fixed allometric exponent of 0.632 as per a study on glomerular filtration rate maturation. Akaike information criteria (AIC) and visual predictive checks were used for evaluation.

Results

No model gave an improved AIC in all age groups, but one model for gentamicin and three models for midazolam gave slightly improved global AIC fits albeit using more parameters: AIC drop (number of parameters), –4.1 (5), –9.2 (4), –10.8 (5) and –10.1 (5), respectively. The 95% confidence interval of estimated CL for all top performing models overlapped.

Conclusion

No evidence to reject the standard model was found; given the benefits of standardised parameterisation, its use should therefore be recommended.

Dosing of Vancomycin in Patients with Continuous-Flow Left Ventricular Assist Devices: A Clinical Pharmacokinetic Analysis

Purpose

To describe the pharmacokinetics of vancomycin in patients with continuous-flow left ventricular assist devices (CF-LVADs).

Methods

Eligible patients were ≥18 years old, implanted with a Heart Mate II CF-LVAD during January 2008-April 2012, and treated with vancomycin ≥48 hours for infection. Key exclusion criteria were unstable renal function, acute heart failure exacerbation, hemodynamic instability, and recent surgery. First-order elimination rate constant (Ke) and volume of distribution (Vd) were estimated using ideal (IBW), adjusted (AdjBW), actual (ABW), and fixed body weights. Estimated parameters were compared with measured pharmacokinetic parameters, which were calculated from steady state peak and trough vancomycin levels using one-compartment model equations.

Results

Twelve patients were included (age 44.9 ± 15 years, 91.7% male, 58.3% obese, CLcr 79.2 ± 27 mL · min-1). Common treatment indications were health-care associated pneumonia (41.7%), driveline infection (25%), and sepsis (16.7%). All methods of predicting Ke provided overestimates (p<0.05), ranging from 47 to 79%, depending on body habitus. Methods of predicting Vd using ABW in obese patients yielded overestimates of 74.5% (p<0.05), where IBW predictive Vd equations provided accurate assessments regardless of body habitus.

Conclusions

General population methods may not accurately estimate the pharmacokinetic parameters of vancomycin for compensated heart failure patients implanted with CF-LVADs.

Monitoring of anesthetic depth during surgical correction of acquired valvular disorders: single center, randomized trial

OBJECTIVE

The authors' primary objective was to test the hypothesis that Cerebral State Index (CSI)-guided control of anesthetic depth might reduce the consumption of anesthetics and shorten the duration of ICU and hospital stays after surgical correction of combined valve disorders.

DESIGN

Single center, randomized trial.

SETTING

City Hospital Number 1 of Arkhangelsk, Russian Federation.

PARTICIPANTS

Fifty adult patients with combined valve disorders requiring surgical correction.

INTERVENTIONS

The patients were randomized into 2 groups. In the CSI group, anesthetic depth was monitored, and the rate of infusion of propofol was titrated to maintain the depth of anesthesia corresponding to a CSI of 40-60. In the control group, the depth of anesthesia was monitored clinically, and the dosage of propofol was administered according to the recommendations of the manufacturer.

MEASUREMENTS AND MAIN RESULTS

All patients received standard perioperative monitoring. Consumption of anesthetics and length of ICU and hospital stays were recorded. Preoperative patient characteristics did not differ significantly between the groups. In the CSI group, average intraoperative doses of midazolam and propofol were reduced by 41% and 19%, respectively (p<0.01). Maintenance of anesthesia guided by CSI shortened the time until fit for ICU discharge by 50% and reduced the lengths of ICU and postoperative hospital stays by 35% and 25%, respectively (p< 0.05).

CONCLUSIONS

Monitoring of anesthetic depth reduces the requirements for midazolam and propofol, resulting in a faster recovery and a shorter postoperative ICU and hospital stay after surgical correction of combined valve disorders.

Effect of chronic hypoxic hypoxia on oxidation and glucuronidation of carvedilol in rats

Heart failure is accompanied with tissue (circulatory) hypoxia, and the metabolism of several drugs has been reported to be reduced in heart failure. The aim of this study was to investigate the effect of another type of respiratory hypoxia, hypoxic hypoxia (FiO2 15 % for 24 h followed by FiO2 10 % for 9 days) on the metabolism of carvedilol enantiomers in rats. Oxidation of carvedilol in rat liver microsomes was evaluated in the presence of reduced nicotinamide adenine dinucleotide phosphate, whereas glucuronidation was evaluated in the presence of UDP-glucuronic acid. Both oxidation and glucuronidation activities for two carvedilol enantiomers in hypoxic rat liver microsomes were similar to those in control rat liver microsomes. We also performed pharmacokinetic analysis of carvedilol enantiomers following intraportal infusion in control and hypoxic rats. The mean (±S.E.) portal clearance value of R- and S-carvedilol in control rats was 72 ± 16 and 156 ± 31 ml/min/kg, respectively, whereas that of the R- and S-enantiomers in hypoxic rats was 68 ± 8 and 113 ± 14 ml/min/kg, respectively. These findings indicated that the metabolism of carvedilol enantiomers was not significantly diminished in rats with chronic hypoxic hypoxia, and that other factor(s) besides hypoxia may be responsible for the reduced drug metabolism in heart failure.

Drug structure-transport relationships

Malcolm Rowland has greatly facilitated an understanding of drug structure–pharmacokinetic relationships using a physiological perspective. His view points, covering a wide range of activities, have impacted on my own work and on my appreciation and understanding of our science. This overview summarises some of our parallel activities, beginning with Malcolm’s work on the pH control of amphetamine excretion, his work on the disposition of aspirin and on the application of clearance concepts in describing the disposition of lidocaine. Malcolm also spent a considerable amount of time developing principles that define solute structure and transport/pharmacokinetic relationships using in situ organ studies, which he then extended to involve the whole body. Together, we developed a physiological approach to studying hepatic clearance, introducing the convection–dispersion model in which there was a spread in blood transit times through the liver accompanied by permeation into hepatocytes and removal by metabolism or excretion into the bile. With a range of colleagues, we then further developed the model and applied it to various organs in the body. One of Malcolm’s special interests was in being able to apply this knowledge, together with an understanding of physiological differences in scaling up pharmacokinetics from animals to man. The description of his many other activities, such as the development of clearance concepts, application of pharmacokinetics to the clinical situation and using pharmacokinetics to develop new compounds and delivery systems, has been left to others.

Cardiovascular manifestations of sedatives and analgesics in the critical care unit

There are numerous sedatives and analgesics used in critical care medicine today; these medications are used on critically ill patients, many of whom have heart disease, including coronary artery disease or congestive heart failure. The purpose of this review is to recognize the effects of these medications on the heart. Studies that evaluated the effects of sedatives and analgesics on normal individuals or on those with heart disease were reviewed. Current choices for sustained sedation in the critically ill include the benzodiazepines, morphine, propofol, and etomidate. Each of these medications has their particular advantages and disadvantages. Benzodiazepines provide the greatest amnesia and cardiovascular safety but they can cause significant hypotension in the hemodynamically unstable patient. Morphine provides analgesia and cardioprotective activity after ischemia, although the large observational study CRUSADE showed increased mortality rate in those patients with non-ST segment elevation myocardial infarction who received morphine. Propofol is the most easily titratable drug with cardioprotective features, but its use must be accompanied with great attention to possible development of propofol infusion syndrome, which is a deadly disease, especially in patients with head injury and those with septic shock receiving vasopressors. Etomidate has a rapid onset effect and short period of action with great hemodynamic stability even in patients with shock and hypovolemia, but the incidence of adrenal insufficiency during infusion, not bolus doses, may cause deterioration in the circulatory stability. In conclusion, the sedatives and analgesics mentioned here have characteristics that give them a cardiovascular safety profile useful in critically ill patients. However, use of these drugs on an individual basis is dependent on each agent's safety and efficacy.

Insomnia and chronic heart failure

Insomnia is highly prevalent in patients with chronic disease including chronic heart failure (CHF) and is a significant contributing factor to fatigue and poor quality of life. The pathophysiology of CHF often leads to fatigue, due to nocturnal symptoms causing sleep disruption, including cough, orthopnea, paroxysmal nocturnal dyspnea, and nocturia. Inadequate cardiac function may lead to hypoxemia or poor perfusion of the cerebrum, skeletal muscle, or visceral body organs, which result in organ dysfunction or failure and may contribute to fatigue. Sleep disturbances negatively affect all dimensions of quality of life and is related to increased risk of comorbidities, including depression. This article reviews insomnia in CHF, cardiac medication side-effects related to sleep disturbances, and treatment options.

Hepatic venous stenosis-related reduction of cyclosporin clearance in a pediatric patient after liver transplantation

A 20-month-old girl with Alagille syndrome developed stenosis of hepatic venous anastomosis after living related-donor liver transplantation. Cyclosporin (a microemulsion formulation) was given orally at a dose of 50 mg twice daily, and the trough blood concentration was relatively stable. Before balloon angioplasty of the hepatic vein, trough cyclosporin blood concentrations became elevated and consequently, the dosage was reduced to 15 mg twice daily. On the day of angioplasty, the calculated elimination rate constant of cyclosporin was 0.036 hr(-1), while its apparent basal value was 0.078 hr(-1). The cyclosporin trough concentration to dosage (C/D) ratio gradually increased reaching the maximum on the day after angioplasty. Thereafter, the C/D ratio promptly decreased. Thus, it is speculated that the increase in cyclosporine C/D ratio was mainly dependent on reduction of hepatic clearance of cyclosporin due to hepatic congestion caused by the stenosis of the hepatic venous anastomosis.

Clinical pharmacology of midazolam in infants and children

Midazolam is a parenteral benzodiazepine with sedative, amnesic, anxiolytic, muscle relaxant and anticonvulsant properties. The drug exerts its clinical effect by binding to a receptor complex which facilitates the action of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Midazolam has a faster onset and shorter duration of action than other benzodiazepines such as diazepam and lorazepam. The most serious adverse events associated with midazolam in children include hypoventilation, decreased oxygen saturation, apnoea and hypotension. It is water soluble in the commercially prepared formulation but becomes lipid soluble at physiological pH and can then cross the blood brain barrier. It is metabolised in the liver by the cytochrome P450 system, and its chief metabolite is 1-hydroxymethyl midazolam. The latter is conjugated to the glucuronide form, and it has only minimal biological activity. Midazolam is excreted primarily by the kidney. Its half-life in children over 12 months is reported to be 0.8 to 1.8 hours, with a clearance of 4.7 to 19.7 ml/min/kg. Doses given to children must be calculated on a mg/kg basis. For children 6 months to 5 years of age the initial dose is 0.05 to 0.1 mg/kg. A total dose up to 0.6 mg/kg titrated slowly may be necessary to achieve the desired endpoint. For children 6 to 12 years of age the initial dose is 0.025 to 0.05 mg/kg with a total dose up to 0.4 mg/kg to achieve the desired end-point.

A rapid high-performance liquid chromatographic method for the measurement of midazolam plasma concentrations during long-term infusion in ICU patients

A new high-performance liquid chromatographic method was developed for quantification of midazolam in plasma samples from intensive care unit patients on long-term intravenous infusion of this benzodiazepine. Plasma samples (0.5 ml) were mixed with 1 microgram flurazepam (internal standard), alkalinized with 2.5 N NaOH, and extracted with toluene. The organic phase was evaporated to dryness, and the residue was dissolved in the mobile phase (acetonitrile/0.05 M phosphate buffer pH 4.5) and injected into the analytical column (C18 Nova-Pak 3.9 x 150 mm, 4 microns, maintained at room temperature; mobile phase flow rate: 1.2 ml/minute). The eluate was monitored at 207 nm, which reduced the risk of interferences from concurrent medications. Retention times of flurazepam, 1'-hydroxymidazolam (an active metabolite) and midazolam were approximately 4.5, 6.1 and 13.5 minutes, respectively. The assay was linear over the range 100 to 3000 ng/ml. The coefficients of variation of the within-day and between-day assay for the 100 to 3000 ng/ml range were < 5% and < 7%, respectively. The developed method is fast, reproducible, and well suited to monitor steady state midazolam plasma concentrations in clinical samples.