Pharmacokinetic and pharmacodynamic analysis of sedative and amnesic effects of lorazepam in healthy volunteers

Pharmacodynamic and pharmacokinetic profile of SM-1, a triple-drug combination to increase total sleep time

OBJECTIVE

The primary objective was to characterize the pharmacokinetics and pharmacodynamics of SM-1 after administration of a single oral dose to healthy volunteers in a placebo-controlled double-blind trial of daytime sedation. Secondary objectives were to determine the onset, duration, and offset of the sedative effects using subjective and objective measures of sedation. Safety and tolerability of SM-1 were also investigated.

METHODS

Males and females 18-45 years of age received SM-1, a combination drug product comprised of diphenhydramine, zolpidem (delayed release), and lorazepam (delayed release). The pharmacokinetic profile of each drug was determined from blood samples. Sedative effects were assessed by visual analog scale, digit symbol substitution test, memory test, and quantitative electroencephalography.

RESULTS

Similar number and severity of adverse events were observed following administration of SM-1 and placebo. Onset of sedation, as determined by subjective, performance, and electroencephalography measures, occurred 0.5-1 hr postdose, lasting about 7-7.5 hr. Plasma concentration curves for the two delayed-release components were altered compared with published data for unmodified drugs. Exposure values obtained with the combination product were in good agreement with published values of the drugs given individually.

CONCLUSIONS

SM-1 was well tolerated and has pharmacologic activity starting within an hour of ingestion, lasting approximately 7-8 hr. Sedative activity was seen with subjective, psychomotor, and electroencephalography assays.

An 8-Week, Randomized, Phase 2, Double-Blind, Sequential Parallel-Group Comparison Study of Two Dose Levels of the GABAA Positive Allosteric Modulator PF-06372865 Compared With Placebo as an Adjunctive Treatment in Outpatients With Inadequate Response to Standard of Care for Generalized Anxiety Disorder

BACKGROUND

Generalized anxiety disorder (GAD) is a common psychiatric disorder, but many patients experience only partial relief of symptoms with existing therapies. Benzodiazepines are effective in many cases but are limited by a number of significant adverse effects. PF-06372865 is a subtype-selective gamma-aminobutyric acid A (GABAA)-positive allosteric modulator lacking in functional activity at alpha 1-containing receptors that are believed to mediate many of these adverse effects.

METHODS

PF-06372865 was evaluated as an adjunct to current GAD treatment in a double-blind, placebo-controlled, sequential parallel comparison study in patients with GAD who showed an incomplete response to current standard-of-care pharmacotherapy. A total of 90 subjects (of the planned 384) were randomized into the study before the decision to terminate the study. Two doses of PF-06372865 (2.5 mg twice daily and 7.5 mg twice daily) were compared with placebo.

RESULTS

Neither dose of PF-06372865 differentiated from placebo on week 4 Hamilton Anxiety Inventory total (primary end point) or on the Sheehan Disability Scale total score (secondary end point). Adverse events including dizziness, headache, and somnolence were observed, and the 7.5 mg dose demonstrated some impairment on the Digit Symbol Substitution test and the Epworth Sleepiness Scale relative to placebo and the 2.5 mg dose.

CONCLUSIONS

Factors contributing to the negative results include the limited sample size and failure to explore a broader range of doses.

Population Pharmacokinetic/ Pharmacodynamic Modelling of Auditory-Evoked Event-Related Potentials with Lorazepam

Event-related potentials (ERPs) are commonly used in Neuroscience research, particularly the P3 waveform because it is associated with cognitive brain functions and is easily elicited by auditory or sensory inputs. ERPs are affected by drugs such as lorazepam, which increase the latency and decrease the amplitude of the P3 wave. In this study, auditory-evoked ERPs were generated in 13 older healthy volunteers using an oddball tone paradigm, after administration of single 0.5 and 2 mg doses of lorazepam. Population pharmacokinetics (PK)/pharmacodynamics (PD) models were developed using nonlinear mixed-effects methods in order to assess the effect of lorazepam on the latency and amplitude of the P3 waveforms. The PK/PD models showed that doses of 0.3 mg of lorazepam achieved approximately half of the maximum effect on the latency of the P3 waveform. For P3 amplitude, half the maximum effect was achieved with a dose of 1.2 mg of lorazepam. The PK/PD models also predicted an efficacious dose range of lorazepam, which was close to the recommended therapeutic range. The use of longitudinal P3 latency data allowed better predictions of the lorazepam efficacious dose range than P3 amplitude or aggregate exposure-response data, suggesting that latency could be a more sensitive parameter for drugs with similar mechanisms of action as lorazepam and that time course rather than single time-point ERP data should be collected. Overall, the results suggest that P3 ERP waveforms could be used as potential non-specific biomarkers for functional target engagement for drugs with brain activity, and PK/PD models can aid trial design and choice of doses for development of new drugs with ERP activity.

Lorazepam: a weapon of offence

The use of knock out drugs for perpetuation of crime has significantly increased in recent years. These drug facilitated crimes mainly involve robbery and sexual offences. Most of the drugs employed for these purposes affect the nervous system and bring a state of incapacitation and amnesia. The miscreants exploit these properties of drugs to commit such crimes. The unsuspecting travellers on public transport vehicles and women in disco parties are most vulnerable to such crimes. The unrestricted and unregulated sale of prescription drugs and general ignorance of such incidents is a challenge that needs to be addressed promptly.

A systematic review of amnestic and non-amnestic mild cognitive impairment induced by anticholinergic, antihistamine, GABAergic and opioid drugs

BACKGROUND

Mild cognitive deficits are experienced by 18% of community-dwelling older adults, many of whom do not progress to dementia. The effect of commonly used medication on subtle impairments in cognitive function may be under-recognized.

OBJECTIVE

The aim of the review was to examine the evidence attributing amnestic or non-amnestic cognitive impairment to the use of medication with anticholinergic, antihistamine, GABAergic or opioid effects.

METHODS

MEDLINE and EMBASE were searched for randomized, double-blind, placebo-controlled trials of adults without underlying central nervous system disorders who underwent detailed neuropsychological testing prior to and after oral administration of drugs affecting cholinergic, histaminergic, GABAergic or opioid receptor pathways. Seventy-eight studies were identified, reporting 162 trials testing medication from the four targeted drug classes. Two investigators independently appraised study quality and extracted relevant data on the occurrence of amnestic, non-amnestic or combined cognitive deficits induced by each drug class. Only trials using validated neuropsychological tests were included. Quality of the evidence for each drug class was assessed based on consistency of results across trials and the presence of a dose-response gradient.

RESULTS

In studies of short-, intermediate- and long-acting benzodiazepine drugs (n = 68 trials), these drugs consistently induced both amnestic and non-amnestic cognitive impairments, with evidence of a dose-response relationship. H(1)-antihistamine agents (n = 12) and tricyclic antidepressants (n = 15) induced non-amnestic deficits in attention and information processing. Non-benzodiazepine derivatives (n = 29) also produced combined deficits, but less consistently than benzodiazepine drugs. The evidence was inconclusive for the type of cognitive impairment induced by different bladder relaxant antimuscarinics (n = 9) as well as for narcotic agents (n = 5) and antipsychotics (n = 5). Among healthy volunteers >60 years of age, low doses of commonly used medications such as lorazepam 0.5 mg, oxybutynin immediate release 5 mg and oxycodone 10 mg produced combined deficits.

CONCLUSION

Non-amnestic mild cognitive deficits are consistently induced by first-generation antihistamines and tricyclic antidepressants, while benzodiazepines provoke combined amnestic and non-amnestic impairments. Risk-benefit considerations should be discussed with patients in order to enable an informed choice about drug discontinuation or substitution to potentially reverse cognitive adverse effects.

Drugs involved in drug-facilitated crimes: part I: alcohol, sedative-hypnotic drugs, gamma-hydroxybutyrate and ketamine. A review

SUMMARY

In recent years, there has been a notable increase in the number of reports of drug-facilitated crimes (DFCs). Usually, individuals report that they were robbed or assaulted while incapacitated by drugs. Most often, these cases have involved drugs that have the ability to produce an effect that leaves the victim in a semiconscious or unconscious state. It is reasonable to assume that the purpose of drug-induced incapacitation is probably largely unchanged with time. This covers the full range of property offences (particularly theft) and crimes against the person. What have changed are the drugs themselves: the number; type; their accessibility; effects and detection. The purpose of this review is to explore the different aspects related to the involvement and use of ethanol, sedative-hypnotics drugs, gamma-hydroxybutyrate (GHB) and ketamine in DFCs or offences, which may help people working in this field to expand their knowledge for better understanding of the nature of these crimes or offences.

[Drugs for status epilepticus treatment]

The pharmacokinetics and pharmacodynamics of major antiepileptic agents are presented. The onset of action and the factors leading to extraction across the blood brain barrier are described as well as the mechanism and extent of metabolism, and the main interactions with other drugs. For each class, the dosing scheme and practical issues related to administration are described, based on evidence when available in the literature.

Effects of lorazepam on visual perceptual abilities

OBJECTIVE

To evaluate the effects of an acute dose of the benzodiazepine (BZ) lorazepam in young healthy volunteers on five distinguishable visual perception abilities determined by previous factor-analytic studies.

METHODS

This was a double-blind, cross-over design study of acute oral doses of lorazepam (2 mg) and placebo in young healthy volunteers. We focused on a set of paper-and-pencil tests of visual perceptual abilities that load on five correlated but distinguishable factors (Spatial Visualization, Spatial Relations, Perceptual Speed, Closure Speed, and Closure Flexibility). Some other tests (DSST, immediate and delayed recall of prose; measures of subjective mood alterations) were used to control for the classic BZ-induced effects.

RESULTS

Lorazepam impaired performance in the DSST and delayed recall of prose, increased subjective sedation and impaired tasks of all abilities except Spatial Visualization and Closure Speed. Only impairment in Perceptual Speed (Identical Pictures task) and delayed recall of prose were not explained by sedation.

CONCLUSION

Acute administration of lorazepam, in a dose that impaired episodic memory, selectively affected different visual perceptual abilities before and after controlling for sedation. Central executive demands and sedation did not account for results, so impairment in the Identical Pictures task may be attributed to lorazepam's visual processing alterations.

Premedication with orally administered lorazepam in adults undergoing ERCP: a randomized double-blind study

BACKGROUND

Restlessness often complicates ERCP and may be a reason for premature termination of the procedure.

OBJECTIVE

Our purpose was to evaluate whether a premedication with orally administered lorazepam could reduce the need for sedatives and improve sedation quality.

DESIGN

Randomized double-blind trial.

SETTING

Therapeutic ERCP with an intravenous sedation containing midazolam, propofol, and S(+)-ketamine.

PATIENTS

95 inpatients (aged 20-91 years).

INTERVENTIONS

1 mg of lorazepam (n=47) or placebo (n=48) given orally before ERCP.

MAIN OUTCOME MEASUREMENT

Total amount of administered propofol.

RESULTS

Heart rate, blood pressure, number of oxygen desaturations, and states of restlessness did not differ between the groups. The same amount of midazolam was administered in both groups. There was no significant difference in the total amount of propofol to achieve adequate sedation (lorazepam vs placebo: 71+/-5 vs 63+/-4 microg/kg/min, mean+/-SE). Paradoxically, patients pretreated with lorazepam even needed more propofol in the early phase of sedation (275+/-39 vs 159+/-37 microg/kg in minutes 5-10, P<.05) and the total amount of ketamine administered was higher in this group as well (15.8+/-1.4 vs 11.3+/-1.2 microg/kg/min, P<.05). In both groups there were high rates of satisfaction with the course of the procedure evaluated both by the endoscopists and the patients.

CONCLUSION

The trial failed to show an advantage of an oral premedication with lorazepam. The amount of sedatives administered in the lorazepam group even tended to be higher. A premedication with lorazepam may be counterproductive when followed by sedation containing another benzodiazepine.

A triazolam/amphetamine dose-effect interaction study: dissociation of effects on memory versus arousal

RATIONALE

In addition to producing robust memory impairment, benzodiazepines also induce marked sedation. Thus, it is possible that the observed amnestic effects are secondary to more global sedative effects and do not reflect a specific primary benzodiazepine effect on memory mechanisms.

OBJECTIVE

The objective was to use the nonspecific stimulant d-amphetamine to dissociate the sedative and memory-impairing effects of the benzodiazepine triazolam.

MATERIALS AND METHODS

Single oral doses of placebo, triazolam alone (0.25, 0.50 mg/70 kg), d-amphetamine sulfate alone (20, 30 mg/70 kg), and triazolam (0.25, 0.50 mg/70 kg) and d-amphetamine sulfate (20, 30 mg/70 kg) conjointly (at all dose combinations) were administered to 18 healthy adult participants across nine sessions in a double-blind, staggered-dosing, crossover design. In addition to standard data analyses, analyses were also conducted on z-score standardized data, enabling effects to be directly compared across measures.

RESULTS

Relative to the sedative measures, the memory measures generally exhibited a pattern of less reversal of triazolam's effects by d-amphetamine. The memory measures ranged in degree of reversal such that the most reversal was observed for reaction time on the n-back working memory task, and the least reversal was observed for accuracy on the Sternberg working memory task, with most measures showing an overall pattern of partial reversal.

CONCLUSIONS

Benzodiazepines have specific effects on memory that are not merely a by-product of the drugs' sedative effects, and the degree to which sedative effects contribute to the amnestic effects varies as a function of the particular memory process being assessed.

Effects of the amnesic drug lorazepam on complete and partial information retrieval and monitoring accuracy

RATIONALE

In Koriat's accessibility model (Koriat, Psychol Rev, 100:609-639, 1993; Koriat, J Exp Psychol Gen, 124:311-333, 1995), when a person fails to recall a required target, he or she can nevertheless provide some partial information about the target. Moreover, individuals are able to provide feeling-of-knowing (FOK) judgments about the availability of the target in memory. The cues for the FOK evaluations reside in the products of the retrieval process itself. It was shown that the benzodiazepine lorazepam drug induces some impairment of memory.

OBJECTIVES

The effects of the amnesic benzodiazepine lorazepam on the total and partial recall of recently learned material and on FOK ratings were investigated in healthy volunteers.

METHODS

Twenty-eight healthy volunteers participated in the study: 14 of these received a capsule containing lorazepam (0.038 mg/kg) and 14 a placebo capsule. The material to be learned consisted of four-letter nonsense tetragrams with each letter providing partial information with regard to the four-letter target (Koriat, Psychol Rev, 100:609-639, 1993).

RESULTS

The number of incorrect letters reported was higher for the lorazepam than for the placebo condition. The FOK magnitude was higher for the placebo participants than for the lorazepam participants. The predictive value of FOK for recognition was preserved by the drug.

CONCLUSION

When studying four-letter nonsense letter strings, lorazepam participants present an impairment of episodic short-term memory and the drug has an effect on FOK estimates but not on the predictive accuracy of the FOK. The accessibility hypothesis of FOK was confirmed in this study and seems to retain some validity even under the effect of an amnesic drug.

Midazolam does not inhibit association formation, just its storage and strengthening

RATIONALE

Although there have been many studies examining the effects of benzodiazepines on memory performance, their effects on working memory are equivocal and little is known about whether they affect the efficacy of practice of already learned material.

OBJECTIVES

The objectives in two experiments were to examine (a) whether midazolam impairs performance on a working memory task designed to minimize mnemonic strategies such as rehearsal or chunking of information to be recalled and (b) the effect of midazolam on repeated practice of paired associates that were learned before drug administration.

MATERIALS AND METHODS

Both experiments involved subcutaneous administration of 0.03 mg of saline or midazolam per kilogram of bodyweight in within-subject, placebo-controlled designs, involving 23 subjects in (a) and 31 in (b).

RESULTS

The drug had no effect on the ability to recall the digits in serial order even though the encoding task prevented the digits from being rehearsed or maintained in an articulatory buffer. Paired associates that were learned before the injection showed a benefit of subsequent practice under saline but not under midazolam.

CONCLUSIONS

The results suggest that (a) midazolam does not affect the formation of new associations in short-term memory provided that the presentation rate is not too fast to form these associations when sedated, despite the evidence that the drug blocks long-term memory (LTM) retention of associations; and (b) the potential for over-learning with practice of learned associations in LTM is adversely affected by midazolam such that repeated exposures do not strengthen new learning.

Facilitating effect of 15-Hz repetitive transcranial magnetic stimulation on tactile perceptual learning

Recent neuroimaging studies have revealed that tactile perceptual learning can lead to substantial reorganizational changes of the brain. We report here for the first time that combining high-frequency (15 Hz) repetitive transcranial magnetic stimulation (rTMS) over the primary somatosensory cortex (SI) with tactile discrimination training is capable of facilitating operant perceptual learning. Most notably, increasing the excitability of SI by 15-Hz rTMS improved perceptual learning in spatial, but not in temporal, discrimination tasks. These findings give causal support to recent correlative data obtained by functional magnetic resonance imaging studies indicating a differential role of SI in spatial and temporal discrimination learning. The introduced combination of rTMS and tactile discrimination training may provide new therapeutical potentials in facilitating neuropsychological rehabilitation of functional deficits after lesions of the somatosensory cortex.

Efficacy of etifoxine compared to lorazepam monotherapy in the treatment of patients with adjustment disorders with anxiety: a double-blind controlled study in general practice

Adjustment Disorders With Anxiety (ADWA) account for almost 10% of psychologically motivated consultations in primary care. The aim of this double-blind randomised parallel group study was to compare (non-inferiority test) the efficacies of etifoxine, a non-benzodiazepine anxiolytic drug, and lorazepam, a benzodiazepine, for ADWA outpatients followed by general practitioners. 191 outpatients (mean age: 43, female: 66%) were assigned to receive etifoxine (50 mg tid) or lorazepam (0.5-0.5-1 mg /day) for 28 days. Efficacy was evaluated on days 7 and 28 of the treatment. The main efficacy assessment criterion was the Hamilton Rating Scale for Anxiety score (HAM-A) on Day 28 adjusted to Day 0. The anxiolytic effect of etifoxine was found not inferior to that of lorazepam (HAM-A score decrease: 54.6% vs 52.3%, respectively, p=0.0006). The two drugs were equivalent on Day 28. However, more etifoxine recipients responded to the treatment (HAM-A score decreased by >or=50%, p=0.03). Clinical improvement (based on Clinical Global Impression scale CGI, Social Adjustment Scale Self-Report SAS-SR, and Sheehan scores) was observed in both treatment arms, but more etifoxine patients improved markedly (p=0.03) and had a marked therapeutic effect without side effects as assessed by CGI, p=0.04. Moreover, 1 week after stopping treatment, fewer patients taking etifoxine experienced a rebound of anxiety, compared to lorazepam (1 and 8, respectively, p=0.034).

Diazepam-induced prospective memory impairment and its relation to retrospective memory, attention, and arousal

The amnestic effects of benzodiazepines are well documented on a variety of memory tasks. However, prospective memory (PM), or remembering to execute an action at a future time, has not been studied previously. This study examined the effect of diazepam on word list recall, PM, sustained attention, and subjective ratings of arousal. Forty-eight healthy participants, aged 19-35, received an average of 0.19 mg/kg oral diazepam or placebo in a double-blind manner. Retrospective memory and PM were assessed by free recall of unrelated word lists and by instructing participants to request a hidden belonging at the end of the session, respectively. Sustained attention was measured by multiple trials of a digit cancellation task, and subjective arousal was assessed by self-ratings of drowsiness. Diazepam impaired performance on all measures, including PM. Reduced PM performance was associated with decreased subjective arousal in the diazepam group but was unrelated to sustained attention. This is the first report of the effects of benzodiazepines on prospective remembering, and further supports the view that the arousal/attentional system is composed of partially independent subsystems that have differential relationships to memory.

Kinetic disposition of lorazepam with focus on the glucuronidation capacity, transplacental transfer in parturients and racemization in biological samples

The present study investigates the kinetic disposition with focus on the racemization, glucuronidation capacity and the transplacental transfer of lorazepam in term parturients during labor. The study was conducted on 10 healthy parturients aged 18-37 years with a gestational age of 36-40.1 weeks, treated with a single oral dose of 2 mg racemic lorazepam 2-9 h before delivery. Maternal venous blood and urine samples were obtained over a 0-48 h interval and the umbilical cord sample was obtained immediately after clamping. Lorazepam enantiomers were determined in plasma and urine samples by LC-MS/MS using a Chiralcel OD-R column. In vitro racemization of lorazepam required the calculation of the pharmacokinetic parameters as isomeric mixtures. The data were fitted to two-compartment model and the pharmacokinetic parameters are reported as means (95% CI): t(1/2a) 3.2h (2.6-3.7 h), K(a) 0.23 h(-1) (0.19-0.28 h(-1)), t(1/2) 10.4h (9.4-11.3h), beta 0.068 h(-1) (0.061-0.075h(-1)), AUC(0-infinity) 175.3(ngh)/ml (145.7-204.8(ngh)/ml), Cl/F 2.6 ml/(minkg) (2.3-2.9 ml/(minkg)), Vd/F178.8l (146.5-211.1l), Fel 0.3% (0.1-0.5%), and Cl(R) 0.010 ml/(minkg) (0.005-0.015 ml/(minkg)). Placental transfer of lorazepam evaluated as the ratio of vein umbilical/maternal vein plasma concentrations, obtained as an isomeric mixture, was 0.73 (0.52-0.94). Pregnancy changes the pharmacokinetics of lorazepam, with an increase in the apparent distribution volume, an increase in apparent oral clearance, and a reduction of elimination half-life. The increase in oral clearance may indicate an increase in glucuronidation capacity, with a possible reduction in the plasma concentrations of drugs depending on glucuronidation capacity as the major metabolic pathway.

Quantitative assay of lorazepam and its metabolite glucuronide by reverse-phase liquid chromatography-tandem mass spectrometry in human plasma and urine samples

A LC/MS/MS method for the quantitative determination of lorazepam in human plasma and urine samples was developed and validated. The enantioselective assay allowed to separate the enantiomers and to verify the stereochemical instability of lorazepam. The linearity assessed for lorazepam unchanged was 0.2-20 ng of each enantiomer/ml plasma and 0.2-15 ng of each enantiomer/ml urine. The linearity assessed for total lorazepam (after enzymatic hydrolysis) was 1-30 ng of each enantiomer/ml plasma and 10-150 ng of each enantiomer/ml urine. The coefficients of variation obtained for the intra- and interassay precision were less than 15%. The method was applied to the investigation of the kinetic disposition and metabolism of racemic lorazepam administered as a single oral dose of 2 mg to a parturient. The occurrence of racemization required the calculation of the pharmacokinetic parameters as enantiomeric mixtures of lorazepam (t(1/2a) 3.5h; K(a) 0.198 ngh(-1); t(1/2) 11.5h; beta 0.060 h(-1); AUC(0-infinity) 192.1ngh/ml; CLt/f 2.41ml/minkg; Vd/f 173.5l; Fel 0.41%, and Cl(R) 0.0099 ml/minkg) and its metabolite lorazepam-glucuronide (t(1/2f) 1.2h; K(f) 0.578 h(-1); t(1/2) 16.6h; beta 0.042 h(-1); AUC(0-infinity) 207.6 ngh/ml; Fel 51.80%, and Cl(R) 98.32 ml/minkg). However, the determined confidence limits make the method suitable for application to clinical pharmacokinetic studies, even if the quantification of both the enantiomers is required.

Acute effects of lorazepam on laboratory measures of aggressive and escape responses of adult male parolees

Acute benzodiazepine administrations typically decrease aggressive responding, but increases in aggression have been reported in some studies. The benzodiazepine lorazepam has been studied less frequently than other benzodiazepines in aggression research, although it is often used to suppress violent aggression in patients. The present study was designed to investigate the effects of acute administrations of lorazepam on aggressive responding in adult humans on a laboratory aggression task. Eight adult males participated in experimental sessions on the Point Subtraction Aggression Paradigm (PSAP), which provided subjects with aggressive, escape and monetary-reinforced response options. Acute oral doses (1, 2 and 4 mg) of lorazepam decreased both aggressive responding and monetary-reinforced responding in seven of eight subjects. In one subject, lorazepam produced dose-dependent increases in aggressive responding. The effects of lorazepam on escape responding were the same as the effects on aggressive responding. The results are consistent with prior research using the PSAP and clinical data showing that benzodiazepines generally decrease aggression, and contrast with other studies that have shown that benzodiazepines can increase aggression. Since lorazepam affected both aggressive and escape responding, it is suggested that while lorazepam often produces sedation, it also modifies human aggressive responding, in part, by suppressing reactions to aversive stimuli.

Specific effects of an amnesic drug: effect of lorazepam on study time allocation and on judgment of learning

We investigated the effects of lorazepam, a benzodiazepine, on the allocation of study time, memory, and judgment of learning, in a cognitive task where the repetition of word presentation was manipulated. The aim was to assess whether lorazepam would affect the learning processes and/or whether the participants would be aware of the amnesic difficulty. A total of 30 healthy volunteers participated in the study, 15 of whom received a capsule containing the lorazepam drug (0.038 mg/kg) and 15 a placebo capsule. First, the accuracy of delayed judgments of learning (JOL) was measured in both groups. For the JOL ratings, results showed that all the participants benefited from word repetition. Although the overall performance was lower in the lorazepam than in the placebo group, the accuracy of the JOL ratings was preserved by the drug. Second, all the participants benefited from the repetition of learning, although the performances of the lorazepam-treated subjects remained lower than those of the placebo participants. The repetition of learning had an effect on JOL in both groups. Finally, the time spent learning each (allocation study time) pair of words was measured. For the placebo group, results revealed that study time decreased significantly with the frequency of presentation. For the lorazepam group, no effect of presentation frequency was found. Overall, our findings suggest that the lorazepam drug has a differential effect on the monitoring and the control processes involved in a learning task. The implications of these findings are discussed within the theoretical framework of metacognition.

Effects of word frequency on recall memory following lorazepam, alcohol, and lorazepam alcohol interaction in healthy volunteers

Free recall of words has been extensively used in psychopharmacology to assess the effects of CNS-active drugs on memory functions. However, there is a relative lack of information on the impact of word frequency on the subsequent recall of words following the administration of psychoactive drugs. The present double-blind, placebo-controlled, repeated-measures experiment used lorazepam and alcohol to test the effects of word frequency on immediate and delayed word recall in 24 healthy volunteers. One half of the words contained in the lists had a high frequency (HF) of occurrence and the remainder were of low frequency (LF). The results showed that LF words were more sensitive to memory impairment than HF words. However, the more accurate recall of HF words (with respect to LF words) was eliminated when a combination of lorazepam with alcohol was administered. These findings indicate that word frequency has a significant impact on memory and, as such, is a factor to be taken into account when using memory recall tasks to assess the effects of psychoactive drugs on memory.

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.

Facilitation of visuo-motor learning by transcranial direct current stimulation of the motor and extrastriate visual areas in humans

Performance of visuo-motor tasks requires the transfer of visual data to motor performance and depends highly on visual perception and cognitive processing, mainly during the learning phase. The primary aim of this study was to determine if the human middle temporal (MT)+/V5, an extrastriate visual area that is known to mediate motion processing, and the primary motor cortex are involved in learning of visuo-motor coordination tasks. To pursue this, we increased or decreased MT+/V5, primary contralateral motor (M1) and primary visual cortex excitability by 10 min of anodal or cathodal transcranial direct current stimulation in healthy human subjects during the learning phase of a visually guided tracking task. The percentage of correct tracking movements increased significantly in the early learning phase during anodal stimulation, but only when the left V5 or M1 was stimulated. Cathodal stimulation had no significant effect. Also, stimulation of the primary visual cortex was not effective for this kind of task. Our data suggest that the areas V5 and M1 are involved in the early phase of learning of visuo-motor coordination.

THEINTEGRATION OFPHARMACOKINETICS ANDPHARMACODYNAMICS: Understanding Dose-Response

Pharmacokinetic (PK) and pharmacodynamic (PD) studies have proven to be powerful and instructive tools, particularly in elucidating important aspects of human pharmacology. Nevertheless, they remain imperfect tools in that they only allow researchers to indirectly extrapolate, through computational modeling, the dynamic processes of drug action. Furthermore, neither tool alone provides a complete nor necessarily relevant picture of drug action. This review explores the utility and applications of PK and PD in the study of drugs, provides examples of lessons learned from their application to studies of human pharmacology, points out some of their limitations, and advances the thesis that these tools ideally should be employed together in an integrated approach. As we continue to apply these tools across the continuum of age and disease, they provide a powerful means to enhance our understanding of drug action, drug interactions, and intrinsic host factors that influence pharmacologic response.

GABAergic mechanisms gate tactile discrimination learning

In contrast to mechanisms mediating synaptic plasticity, the pharmacological basis of perceptual learning remains to be clarified. Here we report that a specific form of perceptual learning is influenced by GABAergic mechanisms. We induced perceptual learning by Hebbian co-activation of the skin of the tip of the right index fingers in human subjects. Under placebo conditions, tactile 2-point discrimination was improved on the co-activated, but not on the left, index finger. This augmentation was completely eliminated by lorazepam, a GABAA receptor agonist. No drug effects were found on the left index finger indicating that the drugs had no effect per se on performance. The results demonstrate that perceptual learning is subject to pharmacological gating by basic mechanisms known to mediate and modulate synaptic plasticity.

Facilitation of implicit motor learning by weak transcranial direct current stimulation of the primary motor cortex in the human

Transcranially applied weak direct currents are capable of modulating motor cortical excitability in the human. Anodal stimulation enhances excitability, cathodal stimulation diminishes it. Cortical excitability changes accompany motor learning. Here we show that weak direct currents are capable of improving implicit motor learning in the human. During performance of a serial reaction time task, the primary motor cortex, premotor, or prefrontal cortices were stimulated contralaterally to the performing hand. Anodal stimulation of the primary motor cortex resulted in increased performance, whereas stimulation of the remaining cortices had no effect. We conclude that the primary motor cortex is involved in the acquisition and early consolidation phase of implicit motor learning.

Relationship between cerebral pharmacokinetics and anxiolytic activity of diazepam and its active metabolites after a single intra-peritoneal administration of diazepam in mice

The relationship between the cerebral pharmacokinetics of diazepam and its active metabolites (desmethyldiazepam, oxazepam) and the anxiolytic effect evaluated by the four-plates test and the light/dark test were investigated after a single intra-peritoneal injection of diazepam (1 mg/kg or 1.5 mg/kg). For up to 30 min after administration, the sedative effect interfered with the anxiolytic effect, thus the results of the anxiolytic effect were not interpretable. From 30 min to 60 min after administration, this interference disappeared, the cerebral level of benzodiazepines was stable (the brain elimination of diazepam was compensated for by the appearance of desmethyldiazepam followed by oxazepam) but the anxiolytic effect decreased dramatically in all the tests with diazepam 1 mg/kg or 1.5 mg/kg. The acute tolerance to benzodiazepines and the difference of affinity for subtypes of GABA(A) receptors between diazepam, desmethyldiazepam, oxazepam could explain this result.