Comparison of the relationship between structure and CNS effects for lorazepam, clonazepam and alprazolam

Conversion factors for assessment of driving impairment after exposure to multiple benzodiazepines/z-hypnotics or opioids

AIMS

Norway has introduced legal concentration limits in blood for 28 non-alcohol drugs in driving under the influence cases. As of 2016 this legislation also regulates the assessment of combined effects of multiple benzodiazepines and opioids. We herein describe the employed methodology for the equivalence tables for concentrations of benzodiazepines/z-hypnotics and opioids implemented in the Norwegian Road Traffic Act.

METHODS

Legislative limits corresponding to impairment at blood alcohol concentrations (BAC) of 0.02%, 0.05% and 0.12% were established for 15 different benzodiazepines and opioids. This was based on a concept of a linear relationship between blood drug concentration and impairment in drug naïve users. Concentration ratios between these drugs were used to establish conversion factors and calculate net impairment using diazepam and morphine equivalents.

RESULTS

Conversion factors were established for 14 benzodiazepines/z-hypnotics (alprazolam, bromazepam, clobazam, clonazepam, etizolam, flunitrazepam, lorazepam, nitrazepam, nordiazepam, oxazepam, phenazepam, temazepam, zolpidem and zopiclone) and two opioids (methadone and oxycodone).

CONCLUSIONS

Conversion factors to calculate diazepam and morphine equivalents for benzodiazepines/z-hypnotics and selected opioids, respectively, have been operative in the Norwegian Road Traffic Act as of February 2016. Calculated equivalents can be applied by the courts to meter out sanctions.

Clinical pharmacology, clinical efficacy, and behavioral toxicity of alprazolam: a review of the literature

Alprazolam is a benzodiazepine derivative that is currently used in the treatment of generalized anxiety, panic attacks with or without agoraphobia, and depression. Alprazolam has a fast onset of symptom relief (within the first week); it is unlikely to produce dependency or abuse. No tolerance to its therapeutic effect has been reported. At discontinuation of alprazolam treatment, withdrawal and rebound symptoms are common. Hence, alprazolam discontinuation must be tapered. An exhaustive review of the literature showed that alprazolam is significantly superior to placebo, and is at least equally effective in the relief of symptoms as tricyclic antidepressants (TCAs), such as imipramine. However, although alprazolam and imipramine are significantly more effective than placebo in the treatment of panic attacks, Selective Serotonin Reuptake Inhibitors (SSRIs) appear to be superior to either of the two drugs. Therefore, alprazolam is recommended as a second line treatment option, when SSRIs are not effective or well tolerated. In addition to its therapeutic effects, alprazolam produces adverse effects, such as drowsiness and sedation. Since alprazolam is widely used, many clinical studies investigated its cognitive and psychomotor effects. It is evident from these studies that alprazolam may impair performance in a variety of skills in healthy volunteers as well as in patients. Since the majority of alprazolam users are outpatients, this behavioral impairment limits the safe use of alprazolam in patients routinely engaged in potentially dangerous daily activities, such as driving a car.

Alprazolam 0.125 mg twice a day improves aspects of psychometric performance in healthy volunteers

The effects of alprazolam (0.125 mg) taken twice a day on several cognitive and performance tasks (Pictures test, Digit-Symbol Substitution Test, Choice Reaction Time [CRT], Critical Flicker Fusion [CFF]) were investigated in healthy students. A double-blind, independent group design was used to compare placebo with alprazolam (32 volunteers in each group). After random assignment, all subjects received placebo for 3 days (D) followed by 14 days of treatment with either alprazolam or placebo. Subjects completed a battery of tests at D0, D3, D7, D10, and D14. D3 performance was poorer in the alprazolam group except for CFF values (ascending values and total values), and the only significant improvement was in total reaction time on the CRT test. However, a significant improvement in performance (except in recognition reaction time) was shown at D7, D10, and D14 in the alprazolam group compared with the control group results. This study shows that repeated low doses of alprazolam produce small improvements in some aspects of psychomotor and cognitive functions. Training effect, tolerance effect, anxiolytic effect, and changes in receptor function and/or number are discussed to explain the performance improvement.

Effects of alcohol and hypnosedative drugs on digit-symbol substitution: comparison of two different computerized tests

Computerized symbol-digit substitution tests (SDSTs) and 'yes/no' digit-symbol substitution tests (YNDSTs), together with a digit-digit copying test (DDCT) were compared in a double-blind crossover study for hypnosedative and alcohol effects in 12 young healthy subjects. The tests were carried out before and 1, 3.5 and 5 h after intake of 15 mg diazepam, 30 mg oxazepam, 7.5 mg zopiclone, 15 mg zolpidem or 0.65+0.35 g/kg ethanol, these impaired performance by varying extents. The drug-induced decrements were similar in the YNDSTs and SDSTs; the errors were subject-related and increased with alcohol intake in the YNDSTs but not in the SDSTs. Pooled baseline values in YNDSTs correlated well (Pearson) with those in the SDSTs. The SDSTs also correlated well with the DDCTs. The same correlations were seen when comparing absolute performances after ethanol and hypnosedatives. When using the delta-values (changes from baseline), the correlation between YNDSTs and SDSTs was high after placebo but low after alcohol and hypnosedatives. When using ANCOVA to measure the responses to drugs (delta-drug-delta-placebo), the correlation between YNDSTs and SDSTs was fairly significant after most but not all active drugs. Subjective visual analogue variables did not correlate with objective performances. By comparing absolute performances with hypnosedatives we conclude that YNDSTs and SDSTs are similar, with the delta-values indicating differences between them.

Alcohol pharmacodynamics in young-elderly adults contrasted with young and middle-aged subjects

Effects of aging on ethyl alcohol (EtOH) pharmacodynamics were examined over progressive dosing schedules (0.4, 0.6, 0.8, 1.0 g/kg) in groups of young (25.0 +/- 2.9 years), middle-aged (41.1 +/- 6.6 years), and young-elderly adults (60.9 +/- 2.6 years) using three computerized cognitive-neuromotor tasks: digit-symbol substitution (DSS), keypad reaction time (KRT), and subcritical tracking (SCT). Hysteresis curves of performance impairment (adjusted for pre-drug baseline) as a function of blood alcohol concentration (BAC) were examined for time-course effects, and regression analyses were performed to assess the contribution of age beyond that accounted for by BAC. Results reflected differences in the patterning but not magnitude of impairment for elderly subjects, with earlier decrements and more rapid acute tolerance observed for DSS, in conjunction with less pharmacodynamic sensitivity for SCT. Regression analyses furthermore indicated that age and impairment were negatively related, arguing against synergistic intoxication effects as a function of aging. Analyses specifically comparing performance at baseline versus legally intoxicating BACs (> 1.0 mg/ml) likewise reflected a lack of interactive effects involving the elderly. Elderly subjects nevertheless exhibited significantly lower baseline performance for DSS and KRT than young subjects and achieved higher BACs with equivalent doses. These latter findings support the exercise of caution by elderly individuals consuming EtOH prior to engaging in neuromotor pursuits such as driving.

Lorazepam 0.25 mg twice a day improves aspects of psychometric performance in healthy volunteers

The effects of lorazepam (0.25 mg) twice a day on several cognitive and performance tasks, pictures test, digit-symbol substitution test (DSST), choice reaction time (CRT) and critical flicker fusion (CFF), were investigated in healthy students. A double-blind independent group design was used to compare placebo and lorazepam (30 volunteers in each group). After randomisation, all subjects received placebo for 3 days (D), followed by 14 days of treatment, with either lorazepam or placebo. Subjects completed a battery of tests at Do, then D(3), D(7) , D(10) and D(14). D(3) performance was poorer in the lorazepam group except for CFF (ascending values and total values), yet the only significant improvement was in total reaction time on the CRT test. However, a significant improvement of performance was shown at D(7), D(10) and D(14) in the lorazepam group compared with the control group (except in recognition reaction time). The current study shows that low repeated doses of lorazepam are able to produce small improvements in some aspects of psychomotor and cognitive functions in healthy volunteers. Different points are discussed to explain the performance improvement: training effect, tolerance effect, partial inverse agonist effect and the possible release of cholecystokinin.

Effects of psychotropic drugs on digit substitution: comparison of the computerized symbol-digit substitution and traditional digit-symbol substitution tests

The digit-symbol substitution test (DSST), performed with paper and pencil or computerized, is widely used to reveal decrements in human attention and cognition. We programmed sets of adjustable tasks (digit-symbol, digit-digit, symbol-digit, symbol-symbol) into a microcomputer and compared the symbol-digit substitution (SDST) and the digit copying test (DDCT) with the traditional DSST in two placebo-controlled double-blind studies of psychotropic drugs with pre-trained young healthy subjects. Performances were measured before drug intake and several times after it; matched, different codes were used at consecutive tests. DSST and SDST substitutions remained at the baseline level after placebo, while the simple DDCT performance improved during the placebo session. The prolonged (3 min) test was not exhaustive because interim counts at 90 s predicted the final performance well. In Trial I, 15 mg diazepam orally reduced DSST and SDST functions in a similar way, but it also impaired simple copying in the DDCT, though to a lesser extent. Ebastine, an H(1)-antihistamine, proved inert alone and failed to increase the effects of diazepam on these variables. In Trial II, 7.5 mg zopiclone, 0.4 mg suriclone and 50 mg chlorpromazine, alone and in combinations, impaired the DSST performance in the manner expected. The drug effects were similar in the SDST, and somewhat less in the DDCT, while the substitution errors were subject related and not altered significantly by any treatment. The simple correlation matrices (Pearson, Spearman), confirmed by analysis of covariance, showed that the results of DSST correlated fairly well with those of SDST after zopiclone, chlorpromazine and their combination, but not after suriclone or its combination with chlorpromazine. The DDCT results correlated with those of the substitution tests when analysing pooled baseline values, but not when analysing the performances after drug intake. Subjective visual analogue variables correlated poorly or not at all with objective performances. Our results suggest that manual dexterity in these computerized tests might contribute significantly to the total impairment of performance in response to different drugs. The DSST and SDST matched each other fairly well in their sensitivity to drug effects, yet this similarity may depend on the drug used.