Inter- and intraindividual variability in the concentration-effect (sedation) relationship of flunitrazepam

Comparative study of the effects of zopiclone (7.5 mg), zolpidem, flunitrazepam and a placebo on nocturnal cognitive performance in healthy subjects, in relation to pharmacokinetics

The effect of zopiclone (7.5 mg) on attention, vigilance and memory components was evaluated during a nocturnal period in comparison to a placebo, to zolpidem (10 mg) and to flunitrazepam (1 mg) in a double blind, randomized study, after administration of a single dose in 16 young healthy volunteers. It appears that there is a clear effect on attention and vigilance; this effect is apparent during the kinetic phase of the absorption of the medication. The effect on memory is transient and is absent four hours after the ingestion of the drug. The objective results are not strictly consistent with the chronology of the subjective parameters (Leeds scale — Visual Analogue Scale). The three hypnotics under comparison do not fundamentally differ except in their kinetic/pharmacodynamic effect relationship. One important fact, taking the parameters as a whole, is that there is no objective “residual” effect.

Probing the combined effect of flunitrazepam and lidocaine on the stability and organization of bilayer lipid membranes. A differential scanning calorimetry and dynamic light scattering study

Combined effects of flunitrazepam (FNZ) and lidocaine (LDC) were studied on the thermotropic equilibrium of dipalmitoyl phosphatidylcholine (dpPC) bilayers. This adds a thermodynamic dimension to previously reported geometric analysis in the erythrocyte model. LDC decreased the enthalpy and temperature for dpPC pre- and main-transitions (ΔHp, ΔHm, Tp, Tm) and decreased the cooperativity of the main-transition (ΔT(1/2,m)). FNZ decreased ΔHm and, at least up to 59 μM, also decreased ΔHp. In conjunction with LDC, FNZ induced a recovery of ∆T(1/2,m) control values and increased ΔHm even above the control level. The deconvolution of the main-transition peak at high LDC concentrations revealed three components possibly represented by: a self-segregated fraction of pure dpPC, a dpPC-LDC mixture and a phase with a lipid structure of intermediate stability associated with LDC self-aggregation within the lipid phase. Some LDC effects on thermodynamic parameters were reverted at proper LDC/FNZ molar ratios, suggesting that FNZ restricts the maximal availability of the LDC partitioned into the lipid phase. Thus, beyond its complexity, the lipid-LDC mixture can be rationalized as an equilibrium of coexisting phases which gains homogeneity in the presence of FNZ. This work stresses the relevance of nonspecific drug-membrane binding on LDC-FNZ pharmacological interactions and would have pharmaceutical applications in liposomal multidrug-delivery.

Intrathecal fentanyl added to intrathecal bupivacaine for day case surgery: a randomized study

BACKGROUND AND OBJECTIVE

The implication of intrathecal lidocaine in neurological toxicity has made intrathecal bupivacaine the commonly used drug for local anaesthesia in ambulatory surgery. However, in high doses intrathecal bupivacaine may produce a high level of sensory and motor block, and arterial hypotension; discharge from hospital may be delayed. Intrathecal opioids added to low-dose local anaesthetics produce a synergistic effect without increasing the sympathetic block or delaying discharge. The aim of our study was to identify the minimum effective dose of intrathecal fentanyl that in combination with low-dose intrathecal bupivacaine would provide adequate surgical conditions without prolonging recovery.

METHODS

A prospective, single, blind, randomized study was conducted in 45 adult males scheduled for minor urological procedures using intrathecal anaesthesia on a day care basis. Patients were randomly assigned to one of three groups (n = 15 each). They received bupivacaine 0.17% 5 mg--with either fentanyl 7.5 microg (fenta-7.5), 10 microg (fenta-10) or 12.5 microg (fenta-12.5) intrathecally in a total volume of 3 mL. The quality of anaesthesia, haemodynamic stability, time to two-segment and S2 regression, time to micturition, and time to discharge were assessed.

RESULTS

The time to two-segment regression and S2 regression with fenta-12.5 was significantly longer than with fenta-7.5 and fenta-10 (P < 0.01). Fenta-7.5 had a significantly higher number of failed blocks (four patients) compared with fenta-12.5 (P < 0.05). The time out of bed, time to micturition and time to discharge were significantly longer with fenta-10 and fenta-12.5 compared with fenta-7.5, and also with fenta-12.5 compared with fenta-10 (P < 0.01). Haemodynamic stability did not differ for all the drug combinations.

CONCLUSIONS

Fentanyl 12.5 microg added to low-dose bupivacaine (5 mg) intrathecally provides better surgical anaesthesia and increased reliability of block than intrathecal fentanyl 7.5 or 10 microg. Haemodynamic stability was the same for all dose combinations used.

Important physical principles in anaesthesiology

The aim of this Review is to introduce anaesthesiologists to the basic physical principles that are important for their work. A better understanding of the underlying processes during anaesthesia is required for greater safety and efficiency. Relevant physical quantities are presented along with the area of anaesthesiology where they are used. This approach provides better targeting to the needs of practising anaesthesiologists. This text has been a part of a specialist course in anaesthesiology at the University of Ljubljana for some years. Current results show that both the students and the specialist anaesthesiologists now show a better understanding of the underlying physical principles required for their work and are more successful in fulfilling the needs of their practical work.

High-dose midazolam and the attenuation of the contractile response to vasoconstrictors in coronary artery segments

BACKGROUND AND OBJECTIVE

Benzodiazepines may cause hypotension and are reported to interfere with smooth vascular muscle activity. The aim was to elucidate the influence of three different benzodiazepines on the vascular reactivity of coronary arteries.

METHODS

Using the model of isolated vessels, we studied the impact of midazolam (0.15, 1.5, 15 microg mL(-1)), diazepam (0.1, 1.0, 10 microg mL(-1)) and flunitrazepam (0.01, 0.1, 1.0 microg mL(-1)) on the contractile responses to histamine (2 x 10(-5) mol L(-1)) and serotonin (3 x 10(-5) mol L(-1)) in isolated intact and denuded coronary arteries.

RESULTS

Midazolam significantly attenuated the contractile response when administered in high concentrations (15 microg mL(-1)). This effect was more pronounced in intact than in denuded preparations (histamine: -22.7 versus -7.3%, P = 0.0079; serotonin: -47.1 versus -15.9%, P < 0.0001). Diazepam and flunitrazepam exerted no significant effects on the vascular tone of coronary arteries.

CONCLUSIONS

Midazolam, but not diazepam or flunitrazepam, attenuates the contractile responses to vasoconstrictors in concentrations beyond those used in clinical practice. This effect is in part mediated by endothelial factors.

Anaesthesia for day case surgery: a survey of adult clinical practice in the UK

BACKGROUND AND OBJECTIVE

In October 2000, we conducted a national postal survey of consultant day case anaesthetists in the UK to explore the range and variation in the practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). The survey was carried out as part of a larger study that comprised a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery). We report the findings of this national survey of adult urology and orthopaedic day case anaesthetic practice in the UK.

METHODS

The survey used a structured postal questionnaire and collected data on the duration of the surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flows used for anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

RESULTS

The overall response rate for the survey was 74% (63% for urology, 67% for orthopaedics). The survey indicated the following practice in adult urology and adult orthopaedic day case surgery: 6 and 12% used premedication; propofol was the preferred induction agent (96 and 97%) and isoflurane the preferred maintenance agent (56 and 58%); 32 and 41% used prophylactic antiemetics; 86 and 93% used a laryngeal mask.

CONCLUSIONS

This survey identifies the variation in current clinical practice in adult day surgery anaesthesia in the UK and discusses this variation in the context of current published evidence.

Effect of dexamethasone on motor brachial plexus block with bupivacaine and with bupivacaine-loaded microspheres in a sheep model

BACKGROUND AND OBJECTIVE

It has been suggested that dexamethasone potentiates the sensory block produced by bupivacaine when both drugs are loaded in microspheres. The aim of the study was to evaluate the effect of dexamethasone on the brachial plexus block obtained with plain bupivacaine and bupivacaine-loaded microspheres.

METHODS

Dexamethasone alone (Group 5) or added to plain bupivacaine (75 mg) with (Groups 3 and 4) and without pH correction (Group 2) was compared with plain bupivacaine (75 mg; Group 1). The effect of a small dose of dexamethasone (0.42 mg) was then evaluated on the brachial plexus block obtained with bupivacaine (750 mg) as bupivacaine-loaded microspheres (Group 6). Dexamethasone was added either in the suspending medium (Group 7) or incorporated with bupivacaine into microspheres (Group 8). The motor block was evaluated in a plexus brachial sheep model.

RESULTS

Dexamethasone alone did not produce any motor block. When added to plain bupivacaine without pH correction, complete motor block could not be obtained. When the pH was corrected, addition of dexamethasone to plain bupivacaine seemed to delay the onset of motor block and did not prolong its duration, and it had no effect on the pharmacokinetics of bupivacaine. With bupivacaine-loaded microspheres, the duration of complete motor block was reduced when a small dose of dexamethasone was added in the suspending medium. However, the duration of motor block was significantly prolonged when dexamethasone was incorporated with bupivacaine into microspheres.

CONCLUSIONS

Despite the delayed onset of motor block, the incorporation of dexamethasone in bupivacaine-loaded microspheres dramatically increases the duration of action (700 +/- 485-5160 +/- 2136 min), which could be clinically relevant when such a drug-delivery system will be available.

Haemodynamic response to a small intravenous bolus injection of epinephrine in cardiac surgical patients

BACKGROUND AND OBJECTIVE

The aim was to study the rapid changes in cardiac output and systemic vascular resistance produced by intravenous epinephrine (5 microg) on a beat-by-beat basis.

METHODS

Ten patients were studied during cardiac surgery. Radial or brachial arterial pressure was recorded continuously during intravenous administration of epinephrine (5 microg). Cardiac output and systemic vascular resistance were derived for each beat using arterial pulse contour analysis calibrated by lithium indicator dilution. In each patient a further dose of epinephrine (5 microg) was administered during cardiopulmonary bypass with the blood flow kept constant so that changes in arterial pressure corresponded to changes in systemic vascular resistance.

RESULTS

When the patients were not on cardiopulmonary bypass, the epinephrine produced an initial increase in systemic vascular resistance to 129 +/- 15% (mean +/- SD) of control, followed by a more prolonged reduction to 57 +/- 13% of control. Cardiac output showed a small initial reduction coincident with the increase in systemic vascular resistance, followed by an increase to 152 +/- 24% of control. During cardiopulmonary bypass, the changes produced by epinephrine on systemic vascular resistance were qualitatively similar but smaller in amplitude, probably because of a greater volume of dilution in the bypass circuit.

CONCLUSIONS

Small bolus doses of epinephrine produce an initial increase in systemic vascular resistance followed by a much greater reduction that may cause hypotension.

Anaesthesia for day case surgery: a survey of paediatric clinical practice in the UK

BACKGROUND AND OBJECTIVE

In October 2000, we conducted a national postal survey of day case consultant anaesthetists in the UK to explore the range and variation in practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). This paper reports the findings of this national survey of paediatric day case anaesthetic practice carried out as part of a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery).

METHODS

The survey used a structured postal questionnaire and collected data on the duration of surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flow rates used for general anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

RESULTS

The overall response rate for the survey was 74 and 63% for the paediatric section of the survey. Respondents indicated that 19% used premedication, 63% used propofol for induction, 54% used isoflurane for maintenance, 24% used prophylactic antiemetics and 85%, used a laryngeal mask. The findings of this national survey are discussed and compared with published evidence.

CONCLUSIONS

This survey identifies the variation in clinical practice in paediatric day surgery anaesthesia in the UK.

Recollection of dreams after short general anaesthesia: influence on patient anxiety and satisfaction

BACKGROUND AND OBJECTIVE

We ascertained whether dreams during short general anaesthesia influence subsequent patient satisfaction and anxiety.

METHODS

Fifty female patients were randomized into two groups to test for a difference between intravenous and inhalational anaesthesias. In Group Propo, anaesthesia was induced and maintained with propofol; in Group Metho-Iso, anaesthesia was induced with methohexital and maintained with isoflurane. Satisfaction and anxiety with anaesthesia were evaluated using a visual analogue scale from 0 to 100. Dream incidence rate, satisfaction and anxiety were assessed from immediately after waking until 3 months later.

RESULTS

Seventeen patients (34%) dreamed during anaesthesia. There were no significant differences in satisfaction or anxiety after anaesthesia between the dreaming and non-dreaming patients (satisfaction, 92.3 +/- 21.6 versus 92.1 +/- 21.6; anxiety, 21.1 +/- 21.1 versus 30.3 +/- 32.1), or between Group Propo and Group Metho-Iso (satisfaction, 94.4 +/- 19.3 versus 90.0 +/- 23.4; anxiety, 26.0 +/- 27.6 versus 28.4 +/- 30.7). There was no significant difference in the incidence rate of dreaming with the type of anaesthesia used (Group Propo, 11 patients; Group Metho-Iso, 6 patients).

CONCLUSIONS

Dreaming during general anaesthesia is common but does not influence satisfaction or anxiety after anaesthesia.

In vitro drug-drug interactions with perospirone and concomitantly administered drugs in human liver microsomes

In vitro metabolism studies were conducted to assess drug-drug interactions between perospirone, an antipsychotic agent, and concomitantly administered drugs--biperiden, flunitrazepam, haloperidol, and diazepam--using human liver microsomes. The metabolism of perospirone in the presence of 100 microg/ml drugs was decreased to 45-73% of that in their absence, whereas no effects were observed with any of the drugs at 1 microg/ml or lower. The effects of perospirone on the metabolism of concomitantly administered drugs were also assessed, and no inhibitory effect was observed. Thus, the metabolism of perospirone and concomitantly administered drugs did not demonstrate any marked mutual inhibition in the human liver microsomes. On the other hand, the perospirone metabolism was markedly reduced by ketoconazole indicating a major role for CYP 3A4. Based on the inhibition constant (Ki) for perospirone metabolism and the plasma unbound concentration of ketoconazole, in vivo perospirone clearance was estimated to be reduced to 64-90% of the control level. Thus careful attention should be paid to the possibility of increase in unchanged perospirone concentration when perospirone is co-administered with drugs that are known as CYP3A4 inhibitors, including macrolide antibiotics and other imidazole antifungals.

Modulation of rate of onset and intensity of drug effects reduces abuse potential in healthy males

Low, medium, and high doses of flunitrazepam were tested in three independent randomized, double-blind, balanced cross-over, placebo-controlled trials to study the influence of rate of onset of effects and dose administered on its acute effects. Three groups of 12 healthy male volunteers received six oral doses of placebo or flunitrazepam in slow and fast onset conditions as follows: six capsules of 0.16 mg (slow) and a single capsule of 0.8 mg (fast) in the low dose trial; six 0.25 mg (slow) and a single 1.25 mg (fast) capsules for medium dose; and six 0.4 mg (slow) and a single 2 mg (fast) capsule for high dose. At each dose level, slow or fast increasing flunitrazepam plasma concentrations lead to similar peak levels, but induced differential subjective and behavioral effects. In addition to objective and subjective sedation, flunitrazepam induced some pleasurable feelings, which were more intense in the fast than in the slow conditions. At the highest dose, unpleasant sedative effects surmounted positive effects, while at the lowest dose pleasurable effects were of low intensity. At the medium dose, the balance between pleasurable and unpleasant feelings resulted in euphorigenic effects, which were evident in the fast condition but were blunted in the slow condition.

Human variability and noncancer risk assessment- An analysis of the default uncertainty factor

A 10-fold uncertainty factor is used for noncancer risk assessments to allow for possible interindividual differences between humans in the fate of the chemical in the body (kinetics) and target organ sensitivity (dynamics). Analysis of a database on the variability in each of these aspects is consistent with an even subdivision of the 10-fold factor into 10(0.5) (3.16) for kinetics and 10(0.5) (3.16) for dynamics. Analysis of the number of subjects in a normally and log-normally distributed population which would not be covered by factors of 3.16 supports this subdivision and also the use of a 10-fold factor to allow for both aspects. Analysis of kinetic data for subgroups of the population indicates that the standard default value of 3.16 for kinetics will not be adequate for all routes of elimination and all groups of the population. A scheme is proposed which would allow the selection of appropriate default uncertainty factors based on knowledge of the biological fate and effects of the chemical under review. Copyright 1998 Academic Press.

Flunitrazepam versus placebo premedication for anxiety control in general dental practice

Our objective was to examine the performance of sublingual administration of the short- to intermediate-acting benzodiazepine flunitrazepam on patients with dental anxiety. The study was designed as a randomized double-blind, placebo-controlled crossover trial with nearly identical dental interventions performed on two separate occasions in 24 adult patients. Flunitrazepam (1 mg) significantly reduced anxiety and was well tolerated. With few exceptions, both the patients and the dentist clearly favored the session with flunitrazepam. Most patients also preferred the remaining part of the day when they had been premedicated with flunitrazepam. They were apparently not particularly troubled by being somewhat drowsy. Dizziness was not reported as a problem. Flunitrazepam appears to be an effective, safe, and recommendable alternative for premedication of anxious dental patients.

Abuse liability of flunitrazepam

Flunitrazepam is among the most frequently prescribed hypnotics in many countries. Although it was never marketed in the United States, flunitrazepam, in recent years, has been smuggled into the country, and reports of abuse--including alleged use of the drug to facilitate "date rape"--have attracted a great deal of scrutiny. It has been suggested that flunitrazepam may have greater liability for abuse than other benzodiazepines; such suggestions are supported by surveys of opioid abusers, many of whom report a distinct preference for flunitrazepam over other benzodiazepines. Experimental studies of animals and normal human subjects indicate that, although flunitrazepam has high efficacy and is very potent, it is pharmacologically similar to most other benzodiazepines. Although the studies are limited in number and scope, the data show no apparent differences between flunitrazepam and other benzodiazepines in ability to produce drug-taking or drug-seeking behavior, in capacity to produce physiologic dependence, nor in the characteristics of withdrawal after administration of an antagonist or discontinuation of treatment. Similar to other benzodiazepines, flunitrazepam produces dose-dependent effects on psychomotor performance and recall. Flunitrazepam does not seem to be involved in medical emergencies more often than other benzodiazepines, and there is no indication that flunitrazepam is more toxic than other benzodiazepines when taken in overdose by drug abusers or other individuals. Survey research among typical patient populations suggests that flunitrazepam is characteristic of benzodiazepines in that it is used appropriately and conservatively, with low liability for abuse. Thus the reported preference for flunitrazepam among opioid abusers seems to be the only way in which flunitrazepam is distinguished from other benzodiazepines; it is unclear what characteristics of the drug may be responsible for this reported preference. The evidence considered in this review indicates that abuse of flunitrazepam in this special population is not associated with any distinctive threats to the health of the general public.

A comparison of the acute behavioral effects of flunitrazepam and triazolam in healthy volunteers

Flunitrazepam is an hypnotic benzodiazepine marketed in different European countries. Epidemiological studies have shown that it is frequently abused by opioid addicts. In a survey, "liking" scores for flunitrazepam in methadone maintenance patients were higher than ratings for other benzodiazepines. A double-blind, placebo controlled, crossover clinical trial was conducted to assess the acute behavioral effects of flunitrazepam (0.50 and 2 mg) and triazolam (0.25 and 0.50 mg) in healthy male volunteers. Drug effects on physiological measures, psychomotor performance, and subjective rating scales, including specific questionnaires to evaluate abuse liability (e.g., ARCI or "liking" scores), were assessed before and 6 h after drug administration. Flunitrazepam 2 mg produced the most intense disruptive effects on all the performance tasks, triazolam 0.50 impaired performance except balance. All study drugs at all doses produced sedation symptoms in all or part of the subjective effects questionnaires. Only flunitrazepam 2 mg induced significative increases in some of the scales ("liking", "good effects", "high") that could be related to a possible abuse potential. The results seem to indicate that flunitrazepam, when administered to healthy subjects, produces some pleasurable subjective feelings, that could indicate a higher abuse liability of this drug as compared with other benzodiazepines.

Pharmacokinetic-pharmacodynamic relationships for benzodiazepines

This article reviews the literature on the plasma concentration-effect relationships for benzodiazepines, in humans and in experimental animals. Only literature that explicitly links pharmacokinetics to pharmacodynamics is included. The following questions are evaluated. Can concentration-effect relationships be demonstrated? If so, are these relations stable? Are the influences of specific factors such as age and disease on these relationships established? It is clear that, when studies are conducted and interpreted appropriately, relations can be found for a wide range of benzodiazepine effects. These include objective measures such as electroencephalography, semisubjective measures such as psychomotor performance, and subjective measures such as mood/sedation scales. A generally applicable model of the relationship which will allow prediction of effect is, however, not yet established. The relationship appears to be dependent on route and rate of administration, because of factors such as distributional delay, formation of active metabolites and, probably, acute tolerance. Furthermore, intra- and interindividual variability is considerable, probably due to varying experimental conditions and intrinsic interindividual differences. The limited data available on factors influencing the plasma concentration-effect relationships for benzodiazepines demonstrate clear changes in the pharmacodynamics after multiple doses, suggesting the development of tolerance, and a subsensitivity in patients with panic disorder. The influence of factors such as age, disease and drug interactions on the pharmacokinetic-pharmacodynamic relationship remains less clear.

Flunitrazepam consumption among heroin addicts admitted for in-patient detoxification

The use of benzodiazepines among 973 heroin addicts admitted for inpatient detoxification over a 10-year period was assessed in a cross-sectional study. A total of 780 (80.2%) patients had a history of benzodiazepine use; 666 (68.5%) were consuming benzodiazepines at the time of admission and 419 (43.1%) on an almost daily basis. Seventy-five (7.7%) patients fulfilled criteria for sedative-hypnotic abuse or dependence. Consumption of benzodiazepines began after subjects had become addicted to heroin. Flunitrazepam was ranked first by 68.4% of patients, followed by clorazepate (13%), and diazepam (12.4%). The prevalence of benzodiazepine use, in particular flunitrazepam, among heroin addicts is very high. Specific abuse liability studies are needed to determine whether pharmacologic reasons exist to explain heroin addicts' preference for this compound.

Data-derived safety factors for the evaluation of food additives and environmental contaminants

A safety factor of 100-fold is commonly applied to animal data to derive the acceptable daily intake (ADI) of food additives; other factors have been used in some cases and higher values are used more frequently for determining the tolerable daily intake (TDI) of environmental chemicals. The 100-fold factor is considered to represent the product of a 10-fold factor to allow for species differences between the test animal and humans and a 10-fold factor to allow for inter-individual differences. A scheme is proposed whereby data relevant to the safety assessment of a compound, e.g. species differences in toxicokinetics, can contribute quantitatively to the safety factor and therefore to the ADI or TDI. For this to be possible, it is necessary to subdivide each of the 10-fold factors into two separate factors to allow for differences in toxicokinetics and toxicodynamics. For any compound, data on one particular aspect may be used to derive a specific data-derived factor for that aspect. The overall safety factor will then be calculated as the product of the known data-derived factor(s) and default values for the remaining unknown factors. In this way the derivation of the safety factor would be clearly defined and the potential impact of additional data on other aspects identified. Additional safety factors (over and above the 100-fold or overall data-derived factor) are also proposed to allow for the nature or severity of the toxicity and the adequacy of the database. These factors are consistent with previous evaluations and will allow the logical derivation of factors greater than either 100 or the appropriate data-derived factor. These additional factors will be of greatest value in the derivation of safety factors for the calculation of the TDIs of environmental contaminants but may also be applied if necessary to the safety assessment of food additives. In such cases the rationale and logic for a safety factor in excess of 100 will be clearly defined.