A double-blind, randomized comparison of i.v. lorazepam versus midazolam for sedation of ICU patients via a pharmacologic model

BACKGROUND

Benzodiazepines, such as lorazepam and midazolam, are frequently administered to surgical intensive care unit (ICU) patients for postoperative sedation. To date, the pharmacology of lorazepam in critically ill patients has not been described. The aim of the current study was to characterize and compare the pharmacokinetics and pharmacodynamics of lorazepam and midazolam administered as continuous intravenous infusions for postoperative sedation of surgical ICU patients.

METHODS

With Institutional Review Board approval, 24 consenting adult surgical patients were given either lorazepam or midazolam in a double-blind fashion (together with either intravenous fentanyl or epidural morphine for analgesia) through target-controlled intravenous infusions titrated to maintain a moderate level of sedation for 12-72 h postoperatively. Moderate sedation was defined as a Ramsay Sedation Scale score of 3 or 4. Sedation scores were measured, together with benzodiazepine plasma concentrations. Population pharmacokinetic and pharmacodynamic parameters were estimated using nonlinear mixed-effects modeling.

RESULTS

A two-compartment model best described the pharmacokinetics of both lorazepam and midazolam. The pharmacodynamic model predicted depth of sedation for both midazolam and lorazepam with 76% accuracy. The estimated sedative potency of lorazepam was twice that of midazolam. The predicted C50,ss (plasma benzodiazepine concentrations where P(Sedation > or = ss) = 50%) values for midazolam (sedation score [SS] > or = n, where n = a Ramsay Sedation Score of 2, 3, ... 6) were 68, 101, 208, 304, and 375 ng/ml. The corresponding predicted C50,ss values for lorazepam were 34, 51, 104, 152, and 188 ng/ml, respectively. Age, fentanyl administration, and the resolving effects of surgery and anesthesia were significant covariates of benzodiazepine sedation. The relative amnestic potency of lorazepam to midazolam was 4 (observed). The predicted emergence times from sedation after a 72-h benzodiazepine infusion for light (SS = 3) and deep (SS = 5) sedation in a typical patient were 3.6 and 14.9 h for midazolam infusions and 11.9 and 31.1 h for lorazepam infusions, respectively.

CONCLUSIONS

The pharmacology of intravenous infusions of lorazepam differs significantly from that of midazolam in critically ill patients. This results in significant delays in emergence from sedation with lorazepam as compared with midazolam when administered for ICU sedation.

Interactive effects of subanesthetic ketamine and subhypnotic lorazepam in humans

Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist with psychotogenic and dissociative effects in healthy humans. These cognitive and perceptual effects in humans are reportedly reduced by benzodiazepine premedication. This study assessed the interactive effects of a ketamine (i.v. bolus of 0.26 mg/kg followed by an infusion of 0.65 mg/kg per hour) and lorazepam 2 mg., PO, in humans. Twenty-three healthy subjects completed 4 test days involving the oral administration of lorazepam or matched placebo 2 h prior to the i.v. infusion of ketamine or placebo. Ketamine: 1) produced behaviors similar to the positive and negative symptoms of schizophrenia as assessed by the Brief Psychiatric Rating Scale (BPRS); 2) evoked perceptual alterations as measured by the Clinician-Administered Dissociative States Scale (CADSS); 3) impaired performance on the Wisconsin Card Sorting Test (WCST) and other tests sensitive to frontal cortical impairment; and 4) had amnestic effects. Lorazepam produced attention impairments, concrete proverb interpretations, and recall impairments. Lorazepam reduced ketamine-associated emotional distress and there was a non-significant trend for it to decrease perceptual alterations produced by ketamine. However, it failed to reduce many cognitive and behavioral effects of ketamine, including psychosis. Further, lorazepam exacerbated the sedative, attention-impairing, and amnestic effects of ketamine. There was no evidence of pharmacokinetic interaction between these medications. These data suggest that subhypnotic lorazepam and ketamine show a spectrum of interactive effects, ranging from antagonism to potentiation.

Effect of the genotype on the pharmacokinetics, pharmacodynamics, and drug interactions of intravenous lorazepam in healthy volunteers

OBJECTIVE

Our objective was to investigate the effect of the uridine 5'-diphosphate-glucuronosyltransferase (UGT) 2B15 genetic polymorphism on the pharmacokinetics and pharmacodynamics of lorazepam in basal, inhibited, and induced metabolic states in healthy normal volunteers.

METHODS

Twenty-four healthy subjects were enrolled and grouped into UGT2B15*1/*1 or UGT2B15*2/*2 genotype groups. The pharmacokinetic and pharmacodynamic profiles of intravenous lorazepam were characterized before and after inhibition with 600 mg valproate once daily for 4 days and after induction with rifampin (INN, rifampicin) pretreatment (600 mg once daily for 10 days), with a washout period of 10 days between. The plasma concentrations of lorazepam and lorazepam glucuronide were analyzed before and at 0.25, 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, and 48 hours after lorazepam administration by liquid chromatography-tandem mass spectrometry. Visual analog scale assessments and psychomotor coordination tests were administered before and up to 12 hours after drug administration.

RESULTS

The UGT2B15*2/*2 group showed 0.58-fold (95% confidence interval, 0.43-0.72; P < .0001) lower systemic clearance during the basal state and 1.37-fold (95% confidence interval, 1.05-1.88; P = .037) higher area under the visual analog scale-time curve during the induced state compared with the UGT2B15*1/*1 group. The mean systemic clearance of lorazepam decreased by 20% in the inhibited state and increased by 140% in the induced state. During the inhibited or induced state, absolute values of clearance were consistently lower in the *2/*2 group, but the percent changes from baseline did not differ significantly by genotype.

CONCLUSIONS

Our results suggest that the UGT2B15*2 polymorphism is a major determinant of interindividual variability with respect to the pharmacokinetics and pharmacodynamics of lorazepam.

Pharmacokinetic and Pharmacodynamic Interaction of Lorazepam and Valproic Acid in Relation to UGT2B7 Genetic Polymorphism in Healthy Subjects

Pharmacokinetic and pharmacodynamic profiles of lorazepam and valproate were analyzed according to uridine 5'-diphosphate-glucuronosyltransferase (UGT)2B7 genotype in 14 healthy subjects with UGT2B15*2/*2 genotype. Systemic clearance of lorazepam (2 mg intravenously) and area under the concentration-time curve (AUC) of valproate (600 mg once daily for 4 days) were analyzed as pharmacokinetic parameters, and area under the effect-time curve (AUEC) of psychomotor coordination tests (Vienna) was used for pharmacodynamic parameter. No significant differences were found in systemic clearances of lorazepam by UGT2B7 genotype. AUCs of valproate showed an increasing tendency as the number of UGT2B7*2 alleles increased, but the difference was insignificant. Psychometric results were significant among the UGT2B7 genotype group (AUEC_tracking 261.5+/-298.9 in *1/*1, and 3,396.8+/-947 in *2/*2, P=0.047) when the two drugs were coadministered. Our study suggests that the UGT2B7 genotype probably affects lorazepam-valproate pharmacodynamic interaction, especially in subjects who have homovariant genotypes of UGT2B7 and UGT2B15, although the effects on the pharmacokinetics are less significant.

Pharmacodynamic and pharmacokinetic effects of TPA023, a GABA(A) alpha(2,3) subtype-selective agonist, compared to lorazepam and placebo in healthy volunteers

TPA023, a GABA(A) alpha2,3 alphasubtype-selective partial agonist, is expected to have comparable anxiolytic efficacy as benzodiazepines with reduced sedating effects. The compound lacks efficacy at the alpha1 subtype, which is believed to mediate these effects. This study investigated the effects of 0.5 and 1.5 mg TPA023 and compared them with placebo and lorazepam 2 mg (therapeutic anxiolytic dose). Twelve healthy male volunteers participated in this placebo-controlled, double-blind, double-dummy, four-way, cross-over study. Saccadic eye movements and visual analogue scales (VAS) were used to assess the sedative properties of TPA023. The effects on posturaL stability and cognition were assessed using body sway and a standardized battery of neurophysiological memory tests. Lorazepam caused a significant reduction in saccadic peak velocity, the VAS alertness score and impairment of memory and body sway. TPA023 had significant dose dependent effects on saccadic peak velocity (85 deg/sec maximum reduction at the higher dose) that approximated the effects of lorazepam. In contrast to lorazepam, TPA023 had no detectabLe effects on saccadic latency or inaccuracy. Also unlike lorazepam, TPA023 did not affect VAS alertness, memory or body sway. These results show that the effect profile of TPA023 differs markedly from that of lorazepam, at doses that were equipotent with regard to effects on saccadic peak veLocity. Contrary to lorazepam, TPA023 caused no detectable memory impairment or postural imbalance. These differences reflect the selectivity of TPA023 for different GABA(A) receptor subtypes.

Bioavailability and pharmacokinetics of lorazepam after intranasal, intravenous, and intramuscular administration

The purpose of this study was to evaluate the pharmacokinetic profile of intranasal lorazepam in comparison to currently established administration routes. Eleven healthy volunteers completed this randomized crossover study. On three occasions, each separated by a 1-week washout, subjects received a 2 mg dose of lorazepam via the intranasal, intravenous, or intramuscular route. Blood samples were collected serially from 0 to 36 hours. Noncompartmental methods were used to determine pharmacokinetic parameters. Lorazepam was well absorbed following intranasal administration with a mean (%CV) bioavailability of 77.7(11.1). Intranasal administration resulted in a faster absorption rate than intramuscular administration. Elimination profiles were comparable between all three routes. The concentration-time profile for intranasal delivery demonstrated evidence of a double peak in several subjects, suggesting partial oral absorption. Females were found to have significantly higher AUC values than males for all three delivery routes. Overall, this study demonstrated favorable pharmacokinetics of intranasal lorazepam in relation to standard administration methods. Intranasal delivery could provide an alternative, noninvasive delivery route for lorazepam.

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.

Comparative population pharmacokinetics of lorazepam and midazolam during long-term continuous infusion in critically ill patients

AIMS

It is well established that there is a wide intra- and interindividual variability in dose requirements for lorazepam and midazolam in intensive care patients. The objective of this study was to compare the population pharmacokinetics of lorazepam and midazolam after long-term continuous infusion in mechanically ventilated critically ill patients.

METHODS

Forty-nine critically ill patients randomly received either lorazepam (n = 28) or midazolam (n = 21) by continuous infusion for at least 24 h. Multiple blood samples were obtained for determination of the drug and metabolite concentrations by HPLC. Population pharmacokinetic models were developed using the Non-Linear Mixed Effect Modelling (NONMEM) program. The influence of selected covariates was investigated. The prospective performance of the models was evaluated on the basis of results in separate groups of patients for lorazepam (n = 31) and midazolam (n = 33).

RESULTS

The pharmacokinetics of lorazepam were best described by a two-compartment model. Alcohol abuse, positive end expiratory pressure (PEEP) and age were identified as significant covariates. Total body clearance for patients without alcohol abuse was 4.13 - (PEEP - 5) x 0.42 l h-1, and 0.74 l h-1 for patients with alcohol abuse. The volume of distribution was 0.74 l, the steady state volume of distribution was 56 - (age - 58) x 2.1 l and the intercompartmental clearance was 10 l h-1. The proportional residual error was 15% and the median absolute prediction error was 13.6% with a bias of 1.5%. The pharmacokinetics of midazolam were best described by a two-compartment model with alcohol abuse, APACHE score and age as significant covariates. Total body clearance for patients without alcohol abuse was 11.3 - (age - 57) x 0.14 l h-1, and 7.27 - (age -57) x 0.14 l h-1 for patients with alcohol abuse. The volume of distribution was 7.15 l, the steady state volume of distribution was 431 l, and the intercompartmental clearance was 40.8 - (APACHE score - 26) x 2.75 l h-1. The proportional residual error was 31% with an additive residual error of 32 ng ml-1. The median absolute prediction error was 12.9% with a bias of 1.2%. The prospective performance in the lorazepam evaluation group was better with the covariate adjusted model, but in the midazolam evaluation group it was not better than with the simple model. In all models a tendency to overestimate the lower plasma concentrations was observed.

CONCLUSIONS

The pharmacokinetics of both lorazepam and midazolam were well described by a two-compartment model. Inclusion of alcohol abuse and age as covariates improved both models. PEEP was identified as an additional covariate for lorazepam, and the APACHE score for midazolam. For both drugs there is a large interindividual variability in their pharmacokinetics when used for long-term sedation in critically ill patients. However, the intra-individual variability is much lower for lorazepam.

Propylene Glycol–Associated Renal Toxicity from Lorazepam Infusion

OBJECTIVES

Using data from patients who developed elevations in serum creatinine concentrations while receiving continuous-infusion lorazepam, we sought to determine the correlations between the magnitude of serum creatinine concentration rise and each of the following variables: serum propylene glycol level, cumulative lorazepam dose, and duration of lorazepam administration. An additional objective was to identify clinical markers for propylene glycol toxicity.

DESIGN

Retrospective chart review.

SETTING

Medical-surgical intensive care unit and burn unit at a university hospital.

PATIENTS

Eight patients who developed elevations in serum creatinine concentrations while receiving continuous-infusion lorazepam (range 2-28 mg/hr).

MEASUREMENTS AND MAIN RESULTS

The mean cumulative dose of lorazepam was 4305 mg (range 1200-10,920 mg), and the mean propylene glycol level determined at the time of peak serum creatinine concentration was 1103 microg/ml (range 186-3450 microg/ml). Serum creatinine concentrations increased in all eight patients during lorazepam infusion and decreased in seven within 3 days after stopping infusion. A weak-to-moderate correlation existed between the magnitude of the rise in serum creatinine concentration and propylene glycol level (r=0.53). A weak-to-moderate correlation also was identified between cumulative lorazepam dose and magnitude of serum creatinine concentration rise (r=0.43), and a strong-to-moderate correlation was found between duration of lorazepam infusion and magnitude of serum creatinine concentration rise (r=0.60). Propylene glycol levels were strongly correlated with both serum osmolality and osmol gap.

CONCLUSION

The patients' increased serum creatinine concentrations are likely to have resulted from exposure to propylene glycol as a result of lorazepam infusion. Serum osmolality and osmol gap may be useful markers for propylene glycol toxicity.

Can a rapidly-eliminated hypnotic cause daytime anxiety?

To test further the conclusions of preliminary reports that regular use of a rapidly-eliminated hypnotic might cause daytime anxiety, 82 women and 38 men, mean age 53, who claimed to be poor sleepers, took a capsule nightly for 45 nights. On 25 consecutive nights the capsule contained triazolam 0.5 mg (40 subjects), lormetazepam 2 mg (40 subjects) or continued placebo (40 subjects). Both drugs improved sleep, but compared with placebo or lormetazepam-takers, triazolam-takers became more anxious on self-ratings, were judged more often to have had a bad response by an observer, more often wrote down complaints of distress, and suffered weight loss. After about 10 days of regular triazolam they tended to develop panics and depression, felt unreal, and sometimes paranoid. The very short life of triazolam, leading to daytime withdrawal symptoms, may account for some of the observations, but enhancement of benzodiazepine inverse agonist activity is also hypothesized.

Ischemic preconditioning activates phosphatidylinositol-3-kinase upstream of protein kinase C

The present study is designed to test whether phosphatidylinositol 3-kinase (PI3-kinase) has a role in the signaling pathway in ischemic preconditioning (PC) and whether it is proximal or distal to protein kinase C (PKC). Before 20 minutes of global ischemia, Langendorff-perfused rat hearts were perfused for 20 minutes (control); preconditioned with 4 cycles of 5-minute ischemia and 5-minute reflow (PC); treated with either wortmannin (WM) or LY 294002 (LY), each of which is a PI3-kinase inhibitor, for 5 minutes before and throughout PC; treated with 1,2-dioctanoyl-sn-glycerol (DOG), an activator of PKC for 10 minutes (DOG); treated identically to the DOG group except with WM added 10 minutes before and during perfusion with DOG; or treated with either WM or LY for 25 minutes. Recovery of left ventricular developed pressure (LVDP; percentage of initial preischemic LVDP), measured after 30 minutes of reflow, was improved by PC (72+/-2% versus 36+/-4% in control; P<0.001), and this was blocked by WM and LY (41+/-4% and 43+/-5%, respectively; P<0.05 compared with PC). DOG addition improved postischemic LVDP (67+/-6%; P<0.001 compared with control), but in contrast to its effect on PC, WM did not completely eliminate the protective effect of DOG (52+/-4%; P>0.05 compared with DOG; P<0.05 compared with control). PC induced phosphorylation of protein kinase B and translocation of PKC epsilon, and it increased NO production, and these effects were blocked by WM, which suggests a role for PI3-kinase in PC upstream of PKC and NO.

Symptom-driven lorazepam protocol for treatment of severe alcohol withdrawal delirium in the intensive care unit

STUDY OBJECTIVE

To compare outcomes of treating alcohol withdrawal delirium (AWD) with a symptom-driven benzodiazepine protocol versus nonprotocol benzodiazepine infusions in the intensive care unit (ICU).

DESIGN

Retrospective observational study of a quality improvement project.

SETTING

Medical intensive care unit at a Veterans Affairs medical center.

PATIENTS

Thirty-six patients who had 40 ICU admissions for AWD between January 1, 1994, and May 31, 2003. Sixteen episodes (15 patients [historical controls]) occurred before implementation of the symptom-driven protocol in 1998, and 24 episodes (21 patients) occurred after implementation.

MEASUREMENTS AND MAIN RESULTS

Outcomes evaluated were time to reach symptom control, total dose of benzodiazepine, amount of time receiving continuous benzodiazepine infusion, length of ICU and hospital stay, polypharmacy (use of multiple benzodiazepines), and complications of treatment. The historical control group was treated according to physician preference, which consisted of continuous-infusion midazolam without a protocol. The symptom-driven protocol used lorazepam administered initially as intermittent intravenous doses, progressing to a continuous intravenous infusion according to a locally developed symptom scale. The mean +/- SD values for the outcomes in the historical control group versus the protocol group were as follows: time to control symptoms 19.4 +/- 9.7 versus 7.7 +/- 4.9 hours (p=0.002), cumulative benzodiazepine dose in lorazepam equivalents 1677 +/- 937 versus 1044 +/- 534 mg (p=0.014), time receiving benzodiazepine continuous infusion 122.1 +/- 64.4 versus 52.0 +/- 35.1 hours (p=0.001), length of stay in the ICU 7.7 +/- 6.3 versus 5.6 +/- 1.7 days (p=0.21), and length of hospital stay 15.3 +/- 8.9 versus 11.2 +/- 3.4 days (p=0.43).

CONCLUSIONS

Use of a symptom-driven protocol was associated with significantly decreased time to symptom control, amount of sedative required, and time spent receiving benzodiazepine infusion compared with historical controls. The use of the protocol is effective but requires close monitoring to ensure protocol compliance and to avoid potential propylene glycol toxicity.

Comparative single-dose kinetics and dynamics of lorazepam, alprazolam, prazepam, and placebo

Thirty-nine healthy volunteers received single oral doses of either alprazolam (1 mg), lorazepam (2 mg), prazepam (20 mg), or placebo in a randomized, double-blind, parallel group study. Plasma drug concentrations, subjective self-ratings, and the digit symbol substitution test (DSST) were evaluated during 24 hours after dosage. Alprazolam was absorbed rapidly and produced correspondingly rapid sedation and impaired DSST performance. These effects also resolved rapidly, being similar to placebo by 4 to 6 hours after dosage. Sedative and DSST-impairing effects of lorazepam were of slower onset but longer duration than those of alprazolam. After oral prazepam, appearance of desmethyldiazepam in plasma was slow, with minimal sedative and DSST-impairing effects. Twenty-four hours after dosage, both alprazolam and lorazepam significantly impaired recall of a list of 16 words learned previously 3 hours after dosage. Thus benzodiazepines with approximately equivalent clinical anxiolytic properties may have different sedative, performance-impairing, and amnesic profiles after single doses in healthy volunteers; these differences are explained at least in part by pharmacokinetic variations.

Osmol Gap as a Surrogate Marker for Serum Propylene Glycol Concentrations in Patients Receiving Lorazepam for Sedation

STUDY OBJECTIVES

To correlate serum propylene glycol concentration with osmol gap, serum lactate concentration, and amount of propylene glycol administered to mechanically ventilated patients receiving continuous infusions of lorazepam (80% propylene glycol by weight), and to characterize the prevalence of hyperosmolality and range of serum propylene glycol concentrations in this patient population.

DESIGN

Prospective, controlled, observational study.

SETTING

Adult surgical and cardiothoracic intensive care units (ICUs) of a 1200-bed, urban, tertiary care, teaching hospital.

PATIENTS

Sixty-four consecutively enrolled intensive care patients requiring mechanical ventilation and pharmacologic sedation.

INTERVENTION

Thirteen patients received continuous infusions of high-dose lorazepam (> or = 6 mg/hr) for a minimum of 36 hours, and 26 received continuous infusions of low-dose lorazepam (2-5.99 mg/hr) for 36 hours. Twenty-five control patients received sedatives that did not contain propylene glycol.

MEASUREMENTS AND MAIN RESULTS

Serum propylene glycol and lactate concentrations, osmolality, and basic metabolic profiles were obtained 72-108 hours after ICU admission. Clinical data, drug administration, and severity of illness scores were recorded. Osmol gap and the amount of propylene glycol administered before serum sampling predicted propylene glycol concentrations (r(2)=0.692, p<0.05). Osmol gap alone also predicted serum propylene glycol concentrations (r(2)=0.532, p<0.05). Serum lactate concentrations did not correlate with serum propylene glycol concentrations. Unlike the low-dose and control patients, eight (62%) of 13 high-dose patients had osmol gaps above 10. All 13 high-dose patients had serum propylene glycol concentrations previously associated with toxicity.

CONCLUSION

Osmol gap can be used as a surrogate marker for serum propylene glycol concentration. In critically ill patients receiving lorazepam for sedation, an osmol gap above 10 was associated with concentrations previously reported to cause toxicity.

Propylene glycol accumulation associated with continuous infusion of lorazepam in pediatric intensive care patients

OBJECTIVE

To determine if propylene glycol accumulates in children receiving continuous lorazepam infusion and, if accumulation occurs, to determine if it is associated with significant laboratory abnormalities.

DESIGN

Prospective study.

SETTING

A tertiary care pediatric intensive care unit.

PATIENTS

Eleven intubated pediatric intensive care patients receiving continuous lorazepam infusion for sedation.

INTERVENTIONS

Propylene glycol accumulation was determined by comparing concentrations at baseline, after 48 hrs, and at end of therapy. Laboratory abnormalities were determined by comparing serum lactate and osmolar gap at baseline, after 48 hrs, and at end of therapy. Correlation between the cumulative dose of lorazepam received and the propylene glycol concentration measured at the end of therapy was determined.

MEASUREMENTS AND MAIN RESULTS

Patients aged 1-15 months were studied. Lorazepam infusion rates ranged from 0.1 to 0.33 mg.kg.hr and lasted 3-14 days. Propylene glycol accumulated significantly in patients receiving continuous infusion of lorazepam. The propylene glycol concentration increased during the study from 86 +/- 93 microg/mL at baseline to 763 +/- 660 microg/mL at the end of the study ( p=.038). A statistically significant correlation between the cumulative dose of lorazepam received and propylene glycol concentration at the end of therapy was demonstrated ( r(2)=.65, p<.005). However, the propylene glycol accumulation was not associated with significant laboratory abnormalities. Neither serum lactate concentrations nor osmolar gap were significantly elevated over baseline.

CONCLUSION

Propylene glycol accumulated significantly in pediatric intensive care patients receiving continuous lorazepam infusion, and propylene glycol concentration correlated with the cumulative lorazepam dose the patient received. However, significant laboratory abnormalities due to propylene glycol accumulation were not observed.

Pharmacokinetics of lorazepam in critically ill neonates with seizures

Pharmacokinetic data were evaluated in 10 term neonates with seizures after intravenous administration of lorazepam, 0.05 mg/kg or 0.1 mg/kg. All seizure activity ceased, with no adverse effects. Pharmacokinetic data revealed a decreased volume of distribution and clearance, and a prolonged half-life in comparison with data from older children and adults. These findings are consistent with physiologic differences in the neonate.

Windows of detection of lorazepam in urine, oral fluid and hair, with a special focus on drug-facilitated crimes

The purported lowering of sex opposition, coupled with a possible abrupt unconsciousness-inducing effect and ease of administration in spiked drinks have resulted in the use of hypnotics in cases of drug-facilitated offense. Among these compounds, lorazepam possesses amnesic properties and can impair an individual rapidly. The chances to detect this substance increase if the most sensitive methods are used and if the biological fluid which allows the longest possible detection time is available. In order to document the window of detection of lorazepam, we have orally administered 2.5 mg of the drug to three volunteers and collected oral fluid (n = l) over 8 h, urine (n = 2) over 144 h and hair (n = 3) 4 weeks after exposure. Lorazepam was analyzed by LC-MS/MS after alkalinisation (to pH 8.4 with phosphate buffer) and extraction by dichloromethane/diethyl ether in presence of diazepam-d5, used as internal standard. Reversed-phase separation on a XTerra C18 column was achieved in 12 min, under gradient conditions. Molecular ions (m/z 321 and 290 for lorazepam and the IS, respectively) were selected in Ql and the corresponding daughter ions (m/z 303 and 275 for lorazepam and m/z 154 and 198 for the IS) were detected in Q3 after collision with argon. Urine tested positive for lorazepam over 144 h (2-4 ng/ml), with a peak detected after 24 h exposure (411-880 ng/ml). Oral fluid tested positive for lorazepam over 8 h (0.7 ng/ml). Despite a limit of quantitation at 1 pg/mg, we were unable to detect a single lorazepam dose in hair, contrarily to most other benzodiazepines that are detectable. Therefore, in case of drug-facilitated crimes involving lorazepam, urine appears as the best specimen to document exposure, particularly if LC-MS/MS is used.

Pharmacokinetics and clinical use of benzodiazepines in the management of status epilepticus

Benzodiazepines are potent and effective drugs for the management of acute seizures and status epilepticus. Lorazepam, diazepam, and clonazepam have been the most widely studied of the benzodiazepines in the treatment of status epilepticus. In 47 studies of these drugs involving 1,455 patients, lasting control of status epilepticus was achieved in 79% of the patients. None of these benzodiazepines is clearly superior to another for the effective control of status epilepticus. Differences in pharmacokinetic parameters, therefore, will influence the choice of drug. All three benzodiazepines are lipid-soluble and enter the brain within seconds to minutes after intravenous administration. Diazepam, however, is very lipid-soluble and highly protein-bound and thus has a very large volume of distribution of unbound drug. As a result, the effective duration of action of diazepam in status epilepticus is only 20 to 30 min, whereas that of lorazepam, which has a much smaller volume of distribution of unbound drug, is at least several hours after a single intravenous injection. This allows the orderly administration of an antiepileptic drug for long-term seizure control after status epilepticus has been controlled. For this reason, lorazepam is preferable for the initial management of status epilepticus. Continuous intravenous infusion of diazepam has been used successfully in the management of some patients with status epilepticus refractory to initial treatment.

Pharmacokinetic alterations after severe head injury. Clinical relevance

Pharmacological therapy, present and future, will undoubtedly continue to play a large role within the overall management of patients with severe head injury. Nevertheless, limited clinical data are available to evaluate the effect of severe head injury on pharmacokinetics. The disruption of the blood-brain barrier secondary to trauma and/or subsequent hyperosmolar therapy can be expected to result in higher than expected brain drug concentrations. Aggressive dietary protein supplementation may result in increased oxidative drug metabolism. These effects may counterbalance inhibitory influences on drug metabolism secondary to cytokine release during the acute phase response. Alterations in protein binding can also be anticipated with the hypoalbuminaemia and increases in alpha 1-acid glycoprotein typically observed in these patients. Based on studies in other patient populations, moderate hypothermia, a treatment strategy in patients with head injury, can decrease drug metabolism. The pharmacokinetics of the following drugs in patients with severe head injury have been studied: phenytoin, pentobarbital (pentobarbitone), thiopental (thiopentone), tirilazad, and the agents used as marker substrates, antipyrine, lorazepam and indocynanine green (ICG). Several studies have documented increase in metabolism over time with phenytoin, pentobarbital, thiopental, antipyrine and lorazepam. Increases in tirilazad clearance were also observed but attributed to concurrent phenytoin therapy. No changes in the pharmacokinetics of ICG were apparent following head injury. With the frequent use of potent inhibitors of drug metabolism (e.g., cimetidine, ciprofloxacin) the potential for drug interaction is high in patients with severe head injury. Additional pharmacokinetic investigations are recommended to optimise pharmacological outcomes in patients with severe head injury.

Effect of valproate on the pharmacokinetics and pharmacodynamics of lorazepam

The pharmacokinetic-pharmacodynamic interaction between valproate and lorazepam was evaluated in this randomized, double-blind, placebo-controlled crossover study. Sixteen healthy male volunteers enrolled in the study to receive either divalproex sodium (500 mg every 12 hours) or matching placebo for 12 days in the first period, and then to receive the other regimen for an identical second 12-day period. In both periods, lorazepam (1 mg every 12 hours) was administered on days 6 through 9 and on the morning of day 10. Concomitant administration of divalproex sodium with lorazepam resulted in an 8%, 20%, and 31% increase in steady-state maximum plasma concentration, area under the concentration-time curve, and trough plasma concentrations of lorazepam, respectively. The apparent clearance of lorazepam through the formation of lorazepam glucuronide was reduced by 31% during coadministration of divalproex sodium. Pharmacokinetic properties of valproate did not change significantly in the ten available participants during coadministration of lorazepam. Sedation scales revealed no statistically significant differences in sedation between the two regimens. It is concluded that valproate increases plasma concentrations and reduces clearance of lorazepam, most likely by impairing hepatic glucuronidation, and that coadministration of lorazepam does not affect the steady-state pharmacokinetic properties of valproate.

Effect of neurotrauma on hepatic drug clearance

Lorazepam, antipyrine, and indocyanine green were administered to 10 patients with severe head injuries as marker substrates of hepatic glucuronidation, oxidation, and hepatic blood flow, respectively. Pharmacokinetic parameter estimates were determined at baseline (20 to 80 hours after injury) and up to three additional times thereafter (study days 4, 7, and 14). Antipyrine clearance was increased significantly from baseline (0.50 +/- 0.31 ml/min/kg) on study days 4, 7, and 14 (p less than 0.0001). Increases in antipyrine clearance from baseline to the last study day were observed in all study patients ranging from 14% to 207%. A significant increase was also observed in lorazepam clearance on study day 14 relative to baseline (1.39 +/- 0.56 ml/min/kg) (p less than 0.005). Increases in lorazepam clearance occurred in seven of nine patients over time ranging from 9% to 130%. The unbound fraction of lorazepam did not change significantly over the study period. Likewise, no significant change was observed in the clearance of indocyanine green over time. Antipyrine clearance and alpha 1-acid glycoprotein (r = 0.41), and lorazepam clearance and C-reactive protein (r = -0.38) were significantly correlated (p less than 0.05). Similarly, antipyrine and lorazepam clearances were significantly correlated with injury severity based on the Acute Physiologic and Chronic Health Evaluation (APACHE II) score (r = -0.43 and r = -0.37, respectively). These findings suggest that hepatic oxidative and conjugative metabolism increase significantly over time in patients after acute head injury. An awareness of the potential for pharmacokinetic alterations in similarly metabolized drugs used for patients with severe head injuries is recommended.

Age-related differences in hepatic drug clearance in children: studies with lorazepam and antipyrine

The disposition of intravenous antipyrine and lorazepam, administered as model substrates for hepatic oxidative metabolism and conjugation, was evaluated in 50 children (mean age, 7.8 years; range, 2.3 to 17.8 years) with acute lymphocytic leukemia in complete remission and compared with a group of ten healthy adults. Antipyrine clearance normalized to body weight was significantly greater in children than in adults (0.91 versus 0.59 ml/min/kg; p = 0.012), but was not different when normalized to body surface area. In contrast, lorazepam total clearance (CL) and unbound clearance (CLu) normalized to body weight were not significantly different between children and adults but were smaller in children when normalized to body surface area (CL = 31.9 versus 40.6 ml/min/m2, p = 0.036; CLu = 352 versus 485 ml/min/m2, p = 0.010). The mean lorazepam fraction unbound in children was 0.087, which was not different from adult volunteers (0.084). This study has identified significant differences between children and adults in the disposition of these two compounds, with higher milliliter per minute per kilogram clearance for antipyrine but not lorazepam.

Clorazepate and lorazepam: clinical improvement and rebound anxiety

Sixty-two anxious patients were treated under double-blind conditions for 4 weeks with either clorazepate or lorazepam. Two-thirds of each treatment group were then switched abruptly to placebo for 2 weeks, while one-third continued to receive active medication. Two major findings were obtained. About 70% of the patients maintained improvement during the 2-week placebo period. Some patients, however, experienced rebound anxiety, which appeared to be more intense and occurred earlier when placebo was substituted for a benzodiazepine with a short half-life (lorazepam) than for one with a long half-life (clorazepate). The clinical relevance of these findings is discussed.

Thermo-sensitive gels containing lorazepam microspheres for intranasal brain targeting

Thermo-sensitive gels containing lorazepam microspheres were developed and characterized for intranasal brain targeting. Pluronics (PF-127 and PF-68) have been selected since they are thermo-reversible polymers with the property of forming a solution at low temperatures (4-5 °C), and a gel at body temperature (37 °C). This property makes them an interesting material to work with, especially in case of controlled release formulations. The present study focuses on the development of an intranasal formulation for lorazepam, as an alternative route of drug delivery to the brain. Direct transport of drugs to the brain circumventing the brain barrier, following intranasal administration, provides a unique feature and better option to target brain. The presence of mucoadhesive microspheres in the gel vehicle via nasal route can achieve a dual purpose of prolonged drug release and enhanced bioavailability. To optimise the microsphere formulation, Box Behnken design was employed by investigating the effect of three factors, polymer concentration (chitosan), emulsifier concentration (Span 80) and cross-linking agent (glutaraldehyde) on the response variable which is the mean particle size. The concentration of 21% PF-127 and 1% PF-68 were found to be promising gel vehicles. The results showed that the release rate followed a prolonged profile dispersion of the microspheres in the viscous media, in comparison to the microspheres alone. Histopathological studies proved that the optimised formulation does not produce any toxic effect on the microscopic structure of nasal mucosa.

Evaluation of in vitro percutaneous absorption of lorazepam and clonazepam from hydro-alcoholic gel formulations

Clonazepam and lorazepam are two anxiolytics, antidepressant agents, having suitable features for transdermal delivery. The objectives of this study were to evaluate the in vitro percutaneous absorption of these drugs through excised human skin (stratum corneum and epidermis, SCE) and to determine their in vitro permeation behavior from a series of hydro-alcoholic gel formulations containing various enhancing agents. The best permeation profile was obtained for both drugs applying them together with Azone in combination with propylene glycol (PG): these enhancers were able to increase the clonazepam and lorazepam percutaneous fluxes at steady-state about threefold, compared to the free enhancer formulations (Control). To explain the mechanism of the used promoters, the benzodiazepine diffusion and partitioning coefficients from the gel containing the enhancers were calculated. The results indicated that the Azone in combination with PG could act by increasing the benzodiazepine diffusion coefficients, Transcutol increased only the SC/vehicle partition coefficients, limonene in combination with PG appeared to increase both partition and diffusion coefficients moderately, while PG did not increase both the parameters. Furthermore, to evaluate the potential application of tested benzodiazepine formulations containing Azone in combination with PG using the flux values from the in vitro experiments, the corresponding steady-state plasma concentrations (C(SS)) were calculated. The obtained calculated C(SS) values are within the lorazepam therapeutic range and suggest that transdermal delivery of this drug could be regarded as feasible.