Pharmacology of drugs frequently used in ICUs: midazolam and flumazenil

Comparison of short-term effects of midazolam and lorazepam in the intra-amygdala kainic acid model of status epilepticus in mice

Benzodiazepines remain as the first-line treatment for status epilepticus (SE), but debate continues as to the choice and delivery route of pharmacotherapy. Lorazepam is currently the preferred anticonvulsant for clinical use, but midazolam has become a popular alternative, particularly as it can be given by nonintravenous routes. Anticonvulsants are also commonly used to terminate SE in animal models. Here, we aimed to compare the efficacy of midazolam with that of lorazepam in an experimental model of focal-onset SE. Status epilepticus was induced by intra-amygdala microinjection of kainic acid in 8week old C57Bl/6 mice. Forty minutes later, mice were treated with an intraperitoneal injection of either lorazepam or midazolam (8mg/kg). Electroencephalogram (EEG) activity, histology, and behavioral tests assessing recovery of function were evaluated and compared between groups. Intraperitoneal injection of either lorazepam or midazolam resulted in similar patterns of reduced EEG epileptiform activity during 1-hour recordings. Damage to the hippocampus and presentation of postinsult anxiety-related behavior did not significantly differ between treatment groups at 72h. However, return of normal behaviors such as grooming, levels of activity, and the evaluation of overall recovery of SE mice were all superior at 24h in animals given midazolam compared with lorazepam. Our results indicate that midazolam is as effective as lorazepam as an anticonvulsant in this model while also providing improved animal recovery after SE. These data suggest that midazolam might be considered by researchers as an anticonvulsant in animal models of SE, particularly as it appears to satisfy the requirements of refining procedures involving experimental animals at early time-points after SE.

Sedation for critically ill or injured adults in the intensive care unit: a shifting paradigm

As most critically ill or injured patients will require some degree of sedation, the goal of this paper was to comprehensively review the literature associated with use of sedative agents in the intensive care unit (ICU). The first and selected latter portions of this article present a narrative overview of the shifting paradigm in ICU sedation practices, indications for uninterrupted or prolonged ICU sedation, and the pharmacology of sedative agents. In the second portion, we conducted a structured, although not entirely systematic, review of the available evidence associated with use of alternative sedative agents in critically ill or injured adults. Data sources for this review were derived by searching OVID MEDLINE and PubMed from their first available date until May 2012 for relevant randomized controlled trials (RCTs), systematic reviews and/or meta-analyses and economic evaluations. Advances in the technology of mechanical ventilation have permitted clinicians to limit the use of sedation among the critically ill through daily sedative interruptions or other means. These practices have been reported to result in improved mortality, a decreased length of ICU and hospital stay and a lower risk of drug-associated delirium. However, in some cases, prolonged or uninterrupted sedation may still be indicated, such as when patients develop intracranial hypertension following traumatic brain injury. The pharmacokinetics of sedative agents have clinical importance and may be altered by critical illness or injury, co-morbid conditions and/or drug-drug interactions. Although use of validated sedation scales to monitor depth of sedation is likely to reduce adverse events, they have no utility for patients receiving neuromuscular receptor blocking agents. Depth of sedation monitoring devices such as the Bispectral Index (BIS©) also have limitations. Among existing RCTs, no sedative agent has been reported to improve the risk of mortality among the critically ill or injured. Moreover, although propofol may be associated with a shorter time to tracheal extubation and recovery from sedation than midazolam, the risk of hypertriglyceridaemia and hypotension is higher with propofol. Despite dexmedetomidine being linked with a lower risk of drug-associated delirium than alternative sedative agents, this drug increases risk of bradycardia and hypotension. Among adults with severe traumatic brain injury, there are insufficient data to suggest that any single sedative agent decreases the risk of subsequent poor neurological outcomes or mortality. The lack of examination of confounders, including the type of healthcare system in which the investigation was conducted, is a major limitation of existing pharmacoeconomic analyses, which likely limits generalizability of their results.

Value and Safety of Midazolam Anesthesia during Transrectal Ultrasound-Guided Prostate Biopsy

PURPOSE

Although transrectal ultrasound-guided prostate biopsy is useful for diagnosing prostate cancer, it is a painful procedure. There are many methods for providing pain relief and for treating discomfort during the procedure, but occasionally these are reported to be of limited use. We aimed to evaluate the value and safety of midazolam-induced anesthetic transrectal ultrasound-guided prostate biopsy.

MATERIALS AND METHODS

From August 2008 to December 2009, 104 male patients, who were examined with transrectal ultrasound-guided prostate 12-core biopsy, were randomly assigned to two groups. Group 1 (n=51) received ketorolac (Tarasyn®) 30 mg. Group 2 (n=53) was treated with midazolam (Dormicum®) 3 mg, which was increased to 5 mg if necessary. Immediately after the procedure, the patients were asked to rate their comfort level by using a 10-point visual analog self-assessment pain scale.

RESULTS

The pain scale in group 2 was significantly lower than that in group 1 (p<0.05). The patients assigned to group 2 experienced no side-effects from midazolam and were more satisfied than the patients in group 1 (p<0.05).

CONCLUSIONS

Midazolam anesthesia relieves pain effectively, and the patient's satisfaction is better than with conventional transrectal ultrasound-guided prostate biopsy. Midazolam-induced anesthetic transrectal ultrasound-guided prostate biopsy is useful and safe.

Midazolam anesthesia during rigid and flexible cystoscopy

The objective of this study was to investigate the usefulness and safety of midazolam-induced anesthesia for cystoscopy. From September 2005 to March 2006, 80 patients scheduled for regular outpatient follow-up cystoscopy participated in this study. The patients were randomized and classified according to the cystoscope type and midazolam use as follows: group 1 (10 men and 10 women), flexible cystoscopy + midazolam; group 2 (10 men and 10 women), flexible cystoscopy + no midazolam; group 3 (10 men and 10 women), rigid cystoscopy + midazolam; and group 4 (10 men and 10 women), rigid cystoscopy + no midazolam. Immediately after the procedure, the patients were asked to rate their comfort level using a ten-point visual linear analog self-assessment pain scale. The patients assigned in the midazolam group experienced no side-effects from the midazolam. Blood pressure and pulse rate did not change significantly during the procedure. The degree of pain experienced by group 1 was lower than other groups (P < 0.05) and group 4 had a significantly greater pain score than other groups (P < 0.05). No difference was evident between group 2 and 3 regarding the pain score. Midazolam anesthesia may relieve pain during rigid and flexible cystoscopy. Our findings suggest that midazolam anesthesia during cystoscopy is useful and safe.

Population plasma pharmacokinetics of 11C-flumazenil at tracer concentrations

OBJECTIVE

The objectives of the study were to develop a population pharmacokinetic model for (11)C-flumazenil at tracer concentrations, to assess the effects of patient-related covariates and to derive an optimal sampling protocol for clinical use.

METHODS

A population pharmacokinetic model was developed using nonlinear mixed effects modelling (NONMEM) with data obtained from 51 patients with either depression or epilepsy. Each patient received approximately 370 MBq (1-4 microg) of (11)C-flumazenil. The effects of selected covariates (gender, weight, type of disease and age) were investigated. The model was validated using a bootstrap method. Finally, an optimal sampling design was established.

RESULTS

The population pharmacokinetics of tracer quantities of (11)C-flumazenil were best described by a two compartment model. Type of disease and weight were identified as significant covariates (P < 0.002). Mean population pharmacokinetic parameters (percent coefficient of variation) were: CL 1530 mL min(-1) (6.6%), V(1) 24.8 x 10(3) mL (3.8%), V(2) 27.3 x 10(3) mL (5.4%), and Q 2510 mL min(-1) (6.5%). CL was 20% lower in patients with epilepsy, and the influence of weight on V(1) was 0.55% kg(-1). For the prediction of the AUC, a combination of two time points at t = 30 and 60 min post injection was considered optimal (bias -0.7% (95% CI -2.2 to 0.8%), precision 5.7% (95% CI 4.5-6.9%)). The optimal sampling strategy was cross-validated (observed AUC = 296 MBql(-1) min(-1) (95% CI 102-490), predicted AUC = 288 MBql(-1) min(-1) (95% CI 70-506)).

CONCLUSIONS

The population pharmacokinetics of tracer quantities of (11)C-flumazenil are well described by a two-compartment model. Inclusion of weight and type of disease as covariates significantly improved the model. Furthermore, an optimal sampling procedure may increase the feasibility and applicability of (11)C-flumazenil PET.

Sleep-related nocturnal erections and erections during midazolam-induced sedation in healthy young men

This study was performed to evaluate the characteristics of penile erection during midazolam-induced sedation after nocturnal sleep deprivation (NSD) and to determine the effect of NSD on erectile episodes in healthy, sexually functional young men. This procedure might possibly prove to be a brief office-based method of assessing whether erectile dysfunction is psychogenic or biogenic. Nineteen volunteers between the ages of 20 and 29 years participated in this study. We measured the morning penile erection after midazolam (3-5 mg) administration intravenously and all subjects completed 42 tests. Of 42 test, 28 tests revealed erectile episodes, whereas no erectile episodes were observed in 14 tests. Nocturnal sleep deprivation rate was significantly higher in tests with erectile episodes than in tests without erectile episode (P=0.030). Test order or duration of test was not different between two test results. Number of erectile episodes (r=0.374, P=0.015), tip radial rigidity (r=0.412, P=0.007), base radial rigidity (r=0.366, P=0.017) and tip tumescence (r=0.447, P=0.003) correlated with the degree of NSD. When we determined whether NSD was discriminative with regard to erectile episodes, the area under the receiver operating characteristic curve was calculated at 0.705 (95% confidence interval, 0.527-0.883; P=0.032) for the possibility of erectile episodes. Nocturnal sleep deprivation might recover the inhibited rapid eye movement sleep during midazolam-induced sedation. Our findings suggest that erection monitoring during midazolam-induced sedation after NSD may be convenient. However, validation of midazolam-induced morning penile tumescence monitoring with a large population is mandatory.

Propofol vs midazolam for ICU sedation : a Canadian multicenter randomized trial

STUDY OBJECTIVES

To determine whether sedation with propofol would lead to shorter times to tracheal extubation and ICU length of stay than sedation with midazolam.

DESIGN

Multicenter, randomized, open label.

SETTING

Four academic tertiary-care ICUs in Canada.

PATIENTS

Critically ill patients requiring continuous sedation while receiving mechanical ventilation.

INTERVENTIONS

Random allocation by predicted requirement for mechanical ventilation (short sedation stratum, < 24 h; medium sedation stratum, > or = 24 and < 72 h; and long sedation stratum, > or = 72 h) to sedation regimens utilizing propofol or midazolam.

MEASUREMENTS AND RESULTS

Using an intention-to-treat analysis, patients randomized to receive propofol in the short sedation stratum (propofol, 21 patients; midazolam, 26 patients) and the long sedation stratum (propofol, 4 patients; midazolam, 10 patients) were extubated earlier (short sedation stratum: propofol, 5.6 h; midazolam, 11.9 h; long sedation stratum: propofol, 8.4 h; midazolam, 46.8 h; p < 0.05). Pooled results showed that patients treated with propofol (n = 46) were extubated earlier than those treated with midazolam (n = 53) (6.7 vs 24.7 h, respectively; p < 0.05) following discontinuation of the sedation but were not discharged from ICU earlier (94.0 vs 63.7 h, respectively; p = 0.26). Propofol-treated patients spent a larger percentage of time at the target Ramsay sedation level than midazolam-treated patients (60.2% vs 44.0%, respectively; p < 0.05). Using a treatment-received analysis, propofol sedation either did not differ from midazolam sedation in time to tracheal extubation or ICU discharge (sedation duration, < 24 h) or was associated with earlier tracheal extubation but longer time to ICU discharge (sedation duration, > or = 24 h, < 72 h, or > or = 72 h).

CONCLUSIONS

The use of propofol sedation allowed for more rapid tracheal extubation than when midazolam sedation was employed. This did not result in earlier ICU discharge.

Critical care pharmacotherapy: issues and approaches

Critically ill patients are a unique group with potentially altered pharmacokinetic and pharmacodynamic characteristics. The provision of optimal care to these patients is best accomplished via an intensivist-led multidisciplinary team. Included on this team should be a pharmacist specifically trained in critical care. The presence of a critical care pharmacist has been documented to not only decrease the cost of drug use in this setting but to improve the quality of care as well. Further investigations should focus on the impact of these interventions on outcomes. These will include pharmacoeconomic outcomes as well as their impact on other parts of the healthcare system in order to avoid cost shifting and improve morbidity and mortality.

Continuous infusion of lorazepam versus medazolam in patients in the intensive care unit: sedation with lorazepam is easier to manage and is more cost-effective

OBJECTIVE

To evaluate the effectiveness of lorazepam and midazolam for long-term sedation of critically ill, mechanically ventilated patients.

DESIGN

Double-blind, randomized, controlled study.

SETTING

Medical intensive care unit in a university teaching hospital.

PATIENTS

Sixty-four evaluable adult patients admitted to the intensive care department requiring mechanical ventilation for >3 days.

INTERVENTIONS

Patients were randomized to receive blinded solutions of either lorazepam or midazolam by continuous infusion. The lowest dose that achieved an adequate sedation was infused. The maximum dose allowed for each drug was 60 mg/hr for midazolam and 4 mg/hr for lorazepam. Sedation was assessed initially and at least every 8 hrs thereafter on a seven-point scale if the sedation was adequate and every 2 hrs if it was not.

MEASUREMENTS AND MAIN RESULTS

Measurements included the score on the sedation scale, the time between determination of the desired level of sedation and the achievement of that level, and plasma concentrations. It is significantly easier to reach a desired level of sedation with lorazepam than with midazolam. No difference in recovery was found in the 24 hrs after discontinuation of therapy. The fact that there are many factors influencing midazolam pharmacokinetics may explain the more difficult management of desired sedation levels. The equipotent dose of 10 mg of midazolam proved to be 0.7 mg of lorazepam in long-term sedation. The average cost for therapy with midazolam was approximately ten times more than that with lorazepam.

CONCLUSIONS

Lorazepam is a useful alternative to midazolam for the long-term sedation of patients in the medical intensive care unit and provides easier management of the sedation level. Sedation with lorazepam offers a significant cost-savings.

Use of intramuscular midazolam for status epilepticus

Although intravenous (i.v.) administration of antiepileptic drugs is the preferred route of therapy in status epilepticus, intramuscular (i.m.) delivery may provide a valuable alternative when there are obstacles to venous access. Compared to other treatment options such as rectal drug administration, which is as challenging as the i.v. route in a convulsing patient, the i.m. route is easier and less invasive. The two most commonly used first-line anticonvulsants, diazepam and lorazepam, may be administered i.m., but are absorbed from the i.m. site more slowly than midazolam. Midazolam, a fairly new benzodiazepine, is a potent anticonvulsant with a fast onset of effect. Because of its water solubility, midazolam is rapidly absorbed from the injection site and has excellent local tolerability. The pharmacodynamic effects of midazolam can be seen within seconds of its administration, and seizure arrest is usually attained within 5 to 10 min. Case reports and a recent randomized trial that demonstrate the successful use of i.m. midazolam in the termination of epileptic seizures are reviewed.

Use of midazolam for refractory status epilepticus in pediatric patients

Status epilepticus is more common among children than young adults. Children might be less likely to die and might be resistant to permanent neurologic damage due to status epilepticus, but significant sequelae also have been demonstrated. Aggressive intervention and rapid termination of seizures contribute significantly to better prognosis and reduced mortality from status epilepticus. Initial treatment of status epilepticus typically consists of either diazepam or lorazepam, immediately followed by phenytoin or phenobarbital. However, approximately 100% to 15% of status epilepticus episodes are refractory to these conventional therapies. Traditionally, refractory status epilepticus is treated with barbiturate coma or general anesthetics, both of which require invasive cardiorespiratory and hemodynamic monitoring and are associated with significant complications. Midazolam is a water-soluble benzodiazepine with a fast onset of action, a short half-life, and inactive metabolites that has been very effective in terminating seizures refractory to diazepam, lorazepam, phenytoin, and phenobarbital in pediatric patients. Midazolam is a valuable treatment option for refractory status epilepticus, especially in pediatric patients.

Opioid and benzodiazepine tolerance and dependence: application of theory to critical care practice

Critical care clinicians frequently manage patient pain and agitation and promote ventilator stability through use of opioids and benzodiazepines. Often, doses of these drugs must be increased considerably over time as they lose their effectiveness-an indication of drug tolerance. Furthermore, patients can experience negative physiologic responses to withdrawal of these drugs-an indication of drug dependence. Withdrawal symptoms due to abrupt discontinuation of drug therapy can be profound and dangerous. It is important that clinicians understand the mechanisms of drug therapies and their potential negative sequelae. The purpose of this article is to present physiologic theories of opioid and benzodiazepine actions, as well as drug tolerance and dependence, as a basis of knowledge for clinical practice. A clinical scenario of an intensive care unit patient is presented, and a care plan is offered, to provide guidance to practitioners who care for patients experiencing the consequences of long-term opioid and benzodiazepine use.

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.

Midazolam: a review of therapeutic uses and toxicity

Midazolam is a familiar agent commonly used in the emergency department to provide sedation prior to procedures such as laceration repair and reduction of dislocations. Midazolam is also effective in the treatment of generalized seizures, status epilepticus, and behavioral emergencies, particularly when intravenous access is not available. Midazolam is often employed as an induction agent for rapid sequence endotracheal intubation. Midazolam has a rapid onset of action following intravenous, intramuscular, oral, nasal, and rectal administration. Only 50% of an orally administered dose reaches the systemic circulation due to extensive first-pass metabolism. Midazolam is metabolized by the cytochrome P450 enzyme system to several metabolites including an active metabolite, alpha-hydroxymidazolam. Cytochrome P450 inhibitors such as cimetidine can profoundly reduce the metabolism of midazolam. Midazolam has a half-life of approximately 1 h, but this half-life may be prolonged in patients with renal or hepatic dysfunction. Midazolam has been associated with respiratory depression and cardiac arrest when used in combination with an opioid, particularly in the elderly, although all ages are at risk for respiratory depression. Midazolam is relatively free of side effects when used alone and offers several advantages over traditional pharmacological agents such as chloral hydrate and the combination of meperidine, chlorpromazine, and promethazine. Hiccups, cough, nausea, and vomiting are the most commonly reported adverse effects. Many of the adverse effects associated with midazolam can be reversed rapidly by the administration of flumazenil, a competitive benzodiazepine receptor antagonist. Midazolam is a safe and effective agent for providing sedation in the emergency department.

Cardiovascular effects of intravenous midazolam after open heart surgery

Midazolam is the sedating agent of choice in many paediatric intensive care units, and is usually administered as a continuous intravenous infusion with or without a preceding bolus dose. Ten haemodynamically stable children, ventilated in the early postoperative period after cardiac surgery and receiving intravenous morphine infusions, were given an intravenous bolus followed by a continuous infusion of midazolam. Haemodynamic data were recorded before the bolus, and 15 minutes and one hour later. A bolus of midazolam lowered the cardiac output by 24.1%. Arterial blood pressure, oxygen consumption, and mixed venous oxygen content fell significantly. There was a tendency for all variables subsequently to recover towards baseline values, within one hour, during a continuous infusion. An intravenous bolus of midazolam causes a transient but unwanted fall in cardiac output. It is suggested that in children who are receiving intravenous opiates, its use in the early postoperative period be limited to a continuous infusion.

Failure of intravenous low dose midazolam to influence memory recall in drug paralysed post-operative patients sedated with papaveretum

Sedation of ventilated patients in the Intensive Care Unit generates a tension between adequate sedation to maintain comfort and ease of ventilation and over sedation with undesirable prolongation of ventilation and delays in discharge. Studies in animals suggest very low dose midazolam, but not higher doses, potentiate the sedative effects of opiates. We undertook a trial of opiate sedation versus opiate sedation plus low dose midazolam (1 mg/hour) to determine whether a similar effect could be demonstrated in man. Although ventilator time and the duration of admission to Intensive Care was not prolonged by the addition of midazolam, we were unable to demonstrate any statistically significant benefit with regard to memory recall.

New anticonvulsant drugs. Focus on flunarizine, fosphenytoin, midazolam and stiripentol

In the past decade, several new antiepileptic drugs have been tested. Most recently, 5 new antiepileptic drugs have been launched onto European and US markets. These include vigabatrin, oxcarbazepine and lamotrigine in Europe, and felbamate and gabapentin in the US. In addition to these, 3 additional drugs are in the clinical investigational stage: flunarizine, fosphenytoin and stiripentol. A fourth agent is midazolam, which was originally introduced in 1986, but recently has shown effectiveness in the treatment of status epilepticus. Flunarizine is a selective calcium channel blocker that has shown anticonvulsant properties in both animal and human studies. It is a long-acting anticonvulsant that clinical studies have shown to have effects similar to those of phenytoin and carbamazepine in the treatment of partial, complex partial and generalised seizures. Fosphenytoin was developed to eliminate the poor aqueous solubility and irritant properties of intravenous phenytoin. It is rapidly converted to phenytoin after intravenous or intramuscular administration. In clinical studies, this prodrug showed minimal evidence of adverse events and no serious cardiovascular or respiratory adverse reactions. It may have a clear advantage over the present parenteral formulation of phenytoin. Midazolam is a benzodiazepine that is more potent than diazepam as a sedative, muscle relaxant and in its influence on electroencephalographic measures. It has been shown to be an effective treatment for refractory seizures in status epilepticus. Stiripentol has anticonvulsant properties as well as the ability to inhibit the cytochrome P450 system. There are significant metabolic drug interactions between stiripentol and phenytoin, carbamazepine and phenobarbital (phenobarbitone). Stiripentol has been studied in patients with partial seizures, refractory epilepsy and refractory absence seizures with some efficacious results.

Flumazenil as a diagnostic tool in the differential diagnosis of coma in a critically ill patient

The purpose of this report is to describe the use of flumazenil as a diagnostic aid in the differential diagnosis of coma in a patient with an inadvertent overdose of benzodiazepines. We report a patient with suspected septic encephalopathy whose level of consciousness markedly improved following flumazenil administration. Subsequent analysis revealed the presence of benzodiazepines and their metabolites in the blood and urine although the patient had not received benzodiazepines for over two weeks. The critically ill patient with multiorgan failure may have considerable derangement of benzodiazepine metabolism; therefore, if an obtunded patient's level of consciousness improves following flumazenil administration, benzodiazepine intoxication must be considered.