Electroencephalographic effects and serum concentrations after intranasal and intravenous administration of diazepam to healthy volunteers

Strategies to Improve Drug Strength in Nasal Preparations for Brain Delivery of Low Aqueous Solubility Drugs

Intranasal administration is a promising route for brain drug delivery. However, it can be difficult to formulate drugs that have low water solubility into high strength intranasal solutions. Hence, the purpose of this work was to review the strategies that have been used to increase drug strength in intranasal liquid formulations. Three main groups of strategies are: the use of solubilizers (change in pH, complexation and the use cosolvents/surfactants); incorporation of the drugs into a carrier nanosystem; modifications of the molecules themselves (use of salts or hydrophilic prodrugs). The use of high amounts of cosolvents and/or surfactants and pH decrease below 4 usually lead to local adverse effects, such as nasal and upper respiratory tract irritation. Cyclodextrins and (many) different carrier nanosystems, on the other hand, could be safer for intranasal administration at reasonably high concentrations, depending on selected excipients and their dose. While added attributes such as enhanced permeation, sustained delivery, or increased direct brain transport could be achieved, a great effort of optimization will be required. On the other hand, hydrophilic prodrugs, whether co-administered with a converting enzyme or not, can be used at very high concentrations, and have resulted in a fast prodrug to parent drug conversion and led to high brain drug levels. Nevertheless, the choice of which strategy to use will always depend on the characteristics of the drug and must be a case-by-case approach.

Overcoming the challenges of developing an intranasal diazepam rescue therapy for the treatment of seizure clusters

Seizure clusters must be treated quickly and effectively to prevent progression to prolonged seizures and status epilepticus. Rescue therapy for seizure clusters has focused on the use of benzodiazepines. Although intravenous benzodiazepine administration is the primary route in hospitals and emergency departments, seizure clusters typically occur in out‐of‐hospital settings, where a more portable product that can be easily administered by nonmedical caregivers is needed. Thus, other methods of administration have been examined, including rectal, intranasal, intramuscular, and buccal routes. Following US Food and Drug Administration (FDA) approval in 1997, rectal diazepam became the mainstay of out‐of‐hospital treatment for seizure clusters in the United States. However, social acceptability and consistent bioavailability present limitations. Intranasal formulations have potential advantages for rescue therapies, including ease of administration and faster onset of action. A midazolam nasal spray was approved by the FDA in 2019 for patients aged 12 years or older. In early 2020, the FDA approved a diazepam nasal spray for patients aged 6 years or older, which has a different formulation than the midazolam nasal product and enhances aspects of bioavailability. Benzodiazepines, including diazepam, present significant challenges in developing a suitable intranasal formulation. Diazepam nasal spray contains dodecyl maltoside (DDM) as an absorption enhancer and vitamin E to increase solubility in an easy‐to‐use portable device. In a Phase 1 study, absolute bioavailability of the diazepam nasal spray was 97% compared with intravenous diazepam. Subsequently, the nasal spray demonstrated less variability in bioavailability than rectal gel (percentage of geometric coefficient of variation of area under the curve = 42%–66% for diazepam nasal spray compared with 87%–172% for rectal gel). The diazepam nasal spray safety profile is consistent with that expected for rectal diazepam, with low rates of nasal discomfort (≤6%). To further improve the efficacy of rescue therapy, investigation of novel intranasal benzodiazepine formulations is underway.

A Short Review on the Intranasal Delivery of Diazepam for Treating Acute Repetitive Seizures

Benzodiazepines such as diazepam, lorazepam and midazolam remained the mainstay of treatment for acute repetitive seizures (ARS). The immediate care for ARS should often begin at home by a caregiver. This prevents the progression of ARS to prolonged seizures or status epilepticus. For a long time and despite social objections rectal diazepam gel remained only FDA-approved rescue medication. Intranasal administration of benzodiazepines is considered attractive and safe compared with rectal, buccal and sublingual routes. Intranasal delivery offers numerous advantages such as large absorptive surface area, bypass the first-pass metabolism and good patient acceptance as it is needle free and painless. Recent clinical studies have demonstrated that diazepam nasal spray (NRL-1; Valtoco^®, Neurelis Inc.,San Diego, CA, USA) showed less pharmacokinetic variability and reliable bioavailability compared with the diazepam rectal gel. Diazepam nasal spray could be considered as a suitable alternative for treating seizure emergencies outside the hospital. This review summarizes the treatment options for ARS and findings from clinical studies involving intranasal diazepam for treating seizure emergencies.

Human Abuse Potential of an Abuse-Deterrent (AD), Extended-Release (ER) Morphine Product Candidate (Morphine-ADER Injection-Molded Tablets) vs Extended-Release Morphine Administered Intranasally in Nondependent Recreational Opioid Users

Objective. To compare the relative human abuse potential after insufflation of manipulated morphine abuse-deterrent, extended-release injection-molded tablets (morphine-ADER-IMT) with that of marketed morphine ER tablets.

Methods. A randomized, double-blind, double-dummy, active- and placebo-controlled five-way crossover study was performed with adult volunteers who were experienced, nondependent, recreational opioid users. After intranasal (IN) administration of manipulated high-volume (HV) morphine-ADER-IMT (60 mg), participants were randomized (1:1:1:1) to receive IN manipulated low-volume (LV) morphine ER (60 mg), IN manipulated LV morphine-ADER-IMT, intact oral morphine-ADER-IMT (60 mg), and placebo in crossover fashion. Pharmacodynamic and pharmacokinetic assessments included peak effect of drug liking (E_max; primary endpoint) using drug liking visual analog scale (VAS) score, E_max using overall drug liking, and take drug again (TDA) VASs scores, and mean abuse quotient (AQ), a pharmacokinetic parameter associated with drug liking.

Results. Forty-six participants completed the study. After insufflation of HV morphine-ADER-IMT and LV morphine-ADER-IMT, drug liking E_max was significantly lower (P < 0.0001) compared with IN morphine ER. Overall drug liking and TDA E_max values were significantly lower (P < 0.0001) after insufflation of HV morphine-ADER-IMT and LV morphine-ADER-IMT compared with IN morphine ER. Mean AQ was lower after insufflation of HV (9.2) and LV (2.3) morphine-ADER-IMT or ingestion of oral morphine-ADER-IMT (5.5) compared with insufflation of LV morphine ER (37.2).

Conclusions. All drug liking, take drug again, and abuse quotient endpoints support a significantly lower abuse potential with insufflation of manipulated morphine-ADER-IMT compared with manipulated and insufflated non-AD ER morphine.

Determination of minimal steady-state plasma level of diazepam causing seizure threshold elevation in rats

OBJECTIVE

Diazepam, administered by the intravenous, oral, or rectal routes, is widely used for the management of acute seizures. Dosage forms for delivery of diazepam by other routes of administration, including intranasal, intramuscular, and transbuccal, are under investigation. In predicting what dosages are necessary to terminate seizures, the minimal exposure required to confer seizure protection must be known. Here we administered diazepam by continuous intravenous infusion to obtain near-steady-state levels, which allowed an assessment of the minimal levels that elevate seizure threshold.

METHODS

The thresholds for various behavioral seizure signs (myoclonic jerk, clonus, and tonus) were determined with the timed intravenous pentylenetetrazol seizure threshold test in rats. Diazepam was administered to freely moving animals by continuous intravenous infusion via an indwelling jugular vein cannula. Blood samples for assay of plasma levels of diazepam and metabolites were recovered via an indwelling cannula in the contralateral jugular vein.

RESULTS

The pharmacokinetic parameters of diazepam following a single 80-μg/kg intravenous bolus injection were determined using a noncompartmental pharmacokinetic approach. The derived parameters Vd , CL, t1/2α (distribution half-life) and t1/2β (terminal half-life) for diazepam were, respectively, 608 mL, 22.1 mL/min, 13.7 minutes, and 76.8 minutes, respectively. Various doses of diazepam were continuously infused without or with an initial loading dose. At the end of the infusions, the thresholds for various behavioral seizure signs were determined. The minimal plasma diazepam concentration associated with threshold elevations was estimated at approximately 70 ng/mL. The active metabolites nordiazepam, oxazepam, and temazepam achieved levels that are expected to make only minor contributions to the threshold elevations.

SIGNIFICANCE

Diazepam elevates seizure threshold at steady-state plasma concentrations lower than previously recognized. The minimally effective plasma concentration provides a reference that may be considered when estimating the diazepam exposure required for acute seizure treatment.

Effects of alprazolam on cortical activity and tremors in patients with essential tremor

Background

Essential tremor (ET) is characterised by postural and action tremors with a frequency of 4–12 Hz. Previous studies suggest that the tremor activity originates in the cerebello-thalamocortical pathways. Alprazolam is a short-acting benzodiazepine that attenuates tremors in ET. The mechanisms that mediate the therapeutic action of alprazolam are unknown; however, in healthy subjects, benzodiazepines increase cortical beta activity. In this study, we investigated the effect of alprazolam both on beta and tremor-related cortical activity and on alterations in tremor presentation in ET patients. Therefore, we characterised the dynamics of tremor and cortical activity in ET patients after alprazolam intake.

Methods

We recorded hand tremors and contralateral cortical activity in four recordings before and after a single dose of alprazolam. We then computed the changes in tremors, cortico-muscular coherence, and cortical activity at the tremor frequency and in the beta band.

Results

Alprazolam significantly attenuated tremors (EMG: 76.2±22.68%), decreased cortical activity in the tremor frequency range and increased cortical beta activity in all patients (P<0.05). At the same time, the cortico-muscular coherence at the tremor frequency became non-significant (P<0.05). We also found a significant correlation (r = 0.757, P<0.001) between the reduction in tremor severity and the increased ratio of cortical activity in the beta band to the activity observed in the tremor frequency range.

Conclusions

This study provides the first quantitative analysis of tremor reduction following alprazolam intake. We observed that the tremor severity decreased in association with an increased ratio of beta to tremor-related cortical activity. We hypothesise that the increase in cortical beta activity may act as a blocking mechanism and may dampen the pathological oscillatory activity, which in turn attenuates the observed tremor.

A review of the clinical pharmacokinetics of opioids, benzodiazepines, and antimigraine drugs delivered intranasally

BACKGROUND

Interest in the development of drug-delivery devices that might improve treatment compliance is growing. A dosage formulation that is easy to use, such as intranasal application with transmucosal absorption, may offer advantages compared with other routes of drug delivery. The literature concerning intranasal application is diffuse, with a large number of published studies on this topic. Some cerebroactive pharmaceuticals delivered intranasally might follow the pathway from the nose to the systemic circulation to the brain. To determine the suitability of these drugs for intranasal drug delivery, a systematic review was performed.

OBJECTIVE

The aim of this review was to compare the pharmacokinetic properties of intranasal, intravenous, and oral formulations in 3 classes of cerebroactive drugs that might be suitable for intranasal delivery-opioids, benzodiazepines, and antimigraine agents.

METHODS

A search of MEDLINE, PubMed, Cumulative Index of Nursing and Allied Health Literature, EMBASE, and Cochrane Database of Systematic Reviews (dates: 1964-April 2009) was conducted for pharmacokinetic studies of drugs that might be suitable for intranasal delivery. A comparison of pharmacokinetic data was made between these 3 routes of administration.

RESULTS

A total of 45 studies were included in this review. Most of the opioids formulated as an intranasal spray reached a T(max) within 25 minutes. The bioavailability of intranasal opioids was high; in general, >50% compared with opioids administered intravenously. Intranasal benzodiazepines had an overall T(max) that varied from 10 to 25 minutes, and bioavailability was between 38% and 98%. T(max) for most intranasal antimigraine drugs varied from 25 to 90 minutes. Intranasal bioavailability varied from 5% to 40%.

CONCLUSIONS

This review found that intranasal administration of all 3 classes of drugs was suitable for indications of rapid delivery, and that the pharmacokinetic properties differed between the intranasal, oral, and intravenous formulations (intravenous > intranasal > oral).

Pharmacokinetics and tolerability of intranasal diazepam and midazolam in healthy adult volunteers

OBJECTIVE

The purpose of this pilot study was to determine the pharmacokinetics and tolerability of an investigational diazepam (DZP) formulation and a parenteral midazolam (MDZ) formulation following intranasal (i.n.) administration for the efficient treatment of seizure emergencies.

METHODS

Each subject received 5 mg of DZP and MDZ via both i.n. and intravenous routes in a four-way, randomized crossover trial. Blood samples were collected over 48 h. DZP and MDZ concentrations were measured using HPLC. Using analog scales, subjects rated tolerability (0 = no change from normal; 10 = maximum intolerability) and pain (0 = no pain; 4 = extreme pain) prior to and 0, 5, 15, 60 min, and 8 h after administration.

RESULTS

The C(max) and T(max) values for i.n. DZP and MDZ were 179.2 ng/ml and 28.8 min vs 62.8 ng/ml and 21.6 min, respectively. Immediately following i.n. administration, subjects reported tolerability scores of 6.75 and 6.0, and identical pain scores, 3.2, for DZP and MDZ, respectively.

CONCLUSION

Both formulations were rapidly absorbed following i.n. administration with transient discomfort. DZP had a longer half-life, which may result in an extended duration of action. Further studies in large patient populations to evaluate the safety after long term use, efficacy and pharmacokinetics of i.n. DZP are warranted.

Intranasal delivery of antiepileptic medications for treatment of seizures

Acute isolated seizure, repetitive or recurrent seizures, and status epilepticus are all deemed medical emergencies. Mortality and worse neurologic outcome are directly associated with the duration of seizure activity. A number of recent reviews have described consensus statements regarding the pharmacologic treatment protocols for seizures when patients are in pre-hospital, institutional, and home-bound settings. Benzodiazepines, such as lorazepam, diazepam, midazolam, and clonazepam are considered to be medications of first choice. The rapidity by which a medication can be delivered to the systemic circulation and then to the brain plays a significant role in reducing the time needed to treat seizures and reduce opportunity for damage to the CNS. Speed of delivery, particularly outside of the hospital, is enhanced when transmucosal routes of delivery are used in place of an intravenous injection. Intranasal transmucosal delivery of benzodiazepines is useful in reducing time to drug administration and cessation of seizures in the pre-hospital setting, when actively seizing patients arrive in the emergency room, and at home where caregivers treat their dependents. This review summarizes factors to consider when choosing a benzodiazepine for intranasal administration, including formulation and device considerations, pharmacology and pharmacokinetic/pharmacodynamic profiles. A review of the most relevant clinical studies in epilepsy patients will provide context for the relative success of this technique with a number of benzodiazepines and relatively less sophisticated nasal preparations. Neuropeptides delivered intranasally, crossing the blood-brain barrier via the olfactory system, may increase the availability of medications for treatment of epilepsy. Consequently, there remains a significant unmet medical need to serve the pharamcotherapeutic requirements of epilepsy patients through commercial development and marketing of intranasal antiepileptic products.

Can nasal drug delivery bypass the blood-brain barrier?: questioning the direct transport theory

The connection between the nasal cavity and the CNS by the olfactory neurones has been investigated extensively during the last decades with regard to its feasibility to serve as a direct drug transport route to the CSF and brain. This drug transport route has gained much interest as it may circumvent the blood-brain barrier (BBB), which prevents some drugs from entering the brain. Approximately 100 published papers mainly reporting animal experiments were reviewed to evaluate whether the experimental design used and the results generated provided adequate pharmacokinetic information to assess whether the investigated drug was transported directly from the olfactory area to the CNS. In the analysis the large anatomical differences between the olfactory areas of animals and humans and the experimental conditions used were evaluated. The aim of this paper was to establish the actual evidence for the feasibility of this direct transport route in humans. Twelve papers presented a sound experimental design to study direct nose to CNS transport of drugs based on the authors' criteria. Of these, only two studies in rats were able to provide results that can be seen as an indication for direct transport from the nose to the CNS. No pharmacokinetic evidence could be found to support a claim that nasal administration of drugs in humans will result in an enhanced delivery to their target sites in the brain compared with intravenous administration of the same drug under similar dosage conditions.

Volition and the idle cortex: beta oscillatory activity preceding planned and spontaneous movement

Prior to the initiation of spontaneous movement, evoked potentials can be seen to precede awareness of the impending movement by several hundreds of milliseconds, meaning that this recorded neural activity is the result of unconscious processing. This study investigates the neural representations of impending movement with and without awareness. Specifically, the relationship between awareness and 'idling' cortical oscillations in the beta range (18-24Hz) was assessed. It was found that, in situations where there was awareness of the impending movement, pre-movement evoked potentials were associated with a decrease in beta range oscillations. In contrast, when awareness of the impending movement was not present, the onset of the pre-movement potential was associated with tonic levels of beta range oscillations. A model is considered where by distributed neural activity remains outside of conscious awareness through the persistence of tonic slow wave cortical oscillations.

A fuzzy physiologically based pharmacokinetic modeling framework to predict drug disposition in humans

To date, the application of physiologically based pharmacokinetic (PBPK) models in support of drug discovery remains limited, in part due to information deficit and uncertainty regarding model parameters. Fuzzy set theory provides a suitable way to objectively account for parameter uncertainty in models. Here, we present a fuzzy set-based PBPK modeling framework and demonstrate its utility in predicting diazepam pharmacokinetics in human plasma, following intravenous dosing, from available animal in vivo and literature data. For computationally expensive PBPK models, the sparse grid method is proposed as an efficient alternative to commonly used fuzzy arithmetic algorithms for function simulation.

A fuzzy physiologically based pharmacokinetic modeling framework to predict drug disposition in humans

To date, the application of physiologically based pharmacokinetic (PBPK) models in support of drug discovery remains limited, in part due to information deficit and uncertainty regarding model parameters. Fuzzy set theory provides a suitable way to objectively account for parameter uncertainty in models. Here, we present a fuzzy set-based PBPK modeling framework and demonstrate its utility in predicting diazepam pharmacokinetics in human plasma, following intravenous dosing, from available animal in vivo and literature data. For computationally expensive PBPK models, the sparse grid method is proposed as an efficient alternative to commonly used fuzzy arithmetic algorithms for function simulation.

Increased EEG power and slowed dominant frequency in patients with neurogenic pain

To study the mechanisms of chronic neurogenic pain, we compared the power spectra of the resting EEG of patients (n = 15, 38-75 years, median 64 years, 6 women) and healthy controls (n = 15, 41-71 years, median 60 years, 8 women). On an average, the patient group exhibited higher spectral power over the frequency range of 2-25 Hz, and the dominant peak was shifted towards lower frequencies. Maximal differences appeared in the 7-9 Hz band in all electrodes. Frontal electrodes contributed most to this difference in the 13-15 Hz band. Bicoherence analysis suggests an enhanced coupling between theta (4-9 Hz) and beta (12-25 Hz) frequencies in patients. The subgroup of six patients free from centrally acting medication showed higher spectral power in the 2-18 Hz frequency range. On an individual basis, the combination of peak height and peak frequency discriminated between patient and control groups: discriminant analysis classified 87% of all subjects correctly. After a therapeutic lesion in the thalamus (central lateral thalamotomy, CLT) we carried out follow-up for a subgroup of seven patients. Median pain relief was 70 and 95% after 3 and 12 months, respectively. The average EEG power of all seven patients gradually decreased in the theta band and approached normal values only after 12 months. The excess theta EEG power in patients and its decrease after thalamic surgery suggests that both EEG and neurogenic pain are determined by tightly coupled thalamocortical loops. The small therapeutic CLT lesion is thought to initiate a progressive normalization in the affected thalamocortical system, which is reflected in both decrease of EEG power and pain relief.

Effect of diazepam on adenosine 3',5'-cyclic monophosphate (cAMP) plasma levels in anesthetized patients

BACKGROUND

It has been previously demonstrated that diazepam inhibits the cyclic nucleotide phosphodiesterase type 4 isozyme (PDE4). PDE enzymes mediate the hydrolysis of the nucleotide adenosine 3',5'-cyclic monophosphate (cAMP).

OBJECTIVE

The aim of this study was to determine whether IV administration of diazepam affects cAMP plasma levels in anesthetized patients.

METHODS

In this prospective study, patients scheduled to undergo elective myocardial revascularization surgery with anesthetization with etomidate (0.3 mg/kg), fentanyl (total dose 20-25 microg/kg), and cisatracurium (150 microg/kg), supplemented with sevoflurane (2% in an oxygen/air mixture), were randomly assigned to 1 of 3 groups to receive diazepam (0.28 mg/kg IV), diazepam vehicle (alcohol and propylene glycol IV), or saline. Before the start of the surgical procedure, at 5 and 10 minutes after administration of diazepam, vehicle, or saline, blood samples were obtained for determination of the diazepam, cAMP, and catecholamine levels.

RESULTS

Ten patients received diazepam, 10 received vehicle, and 5 received saline. The mean (SEM) arterial serum concentrations of diazepam were 2.1 (0.2) microg/mL and 1.1 (0.4) microg/mL, respectively, at 5 and 10 minutes after administration. cAMP plasma levels increased from mean (SEM) baseline values of 30.0 (1.7) nmol/L to 35.5 (1.5) nmol/L (P < 0.05) and 43.1 (1.7) nmol/L (P < 0.05) at 5 and 10 minutes, respectively, after diazepam administration. No significant changes in cAMP plasma levels were observed compared with the mean (SEM) baseline value of 32.0 (1.7) nmol/L at 5 minutes (31.8 [1.3] nmol/L) and 10 minutes (30.9 [1.4] nmol/L) after vehicle administration. Epinephrine plasma concentration increased from a mean (SEM) baseline value of 0.13 (0.02) ng/mL to 0.22 (0.02) ng/mL (P < 0.05) at 10 minutes after administration of vehicle and 0.21 (0.02) ng/mL (P < 0.05) at 10 minutes after administration of diazepam.

CONCLUSION

In this preliminary study, diazepam increased cAMP plasma levels in anesthetized patients, presumably through inhibition of PDE4 activity.

Is nose-to-brain transport of drugs in man a reality?

The blood-brain barrier that segregates the brain interstitial fluid from the circulating blood provides an efficient barrier for the diffusion of most, especially polar, drugs from the blood to receptors in the central nervous system (CNS). Hence limitations are evident in the treatment of CNS diseases, such as Parkinson's and Alzheimer's diseases, especially exploiting neuropeptides and similar polar and large molecular weight drugs. In recent years interest has been expressed in the use of the nasal route for delivery of drugs to the brain, exploiting the olfactory pathway. A wealth of studies has reported proof of nose-to-brain delivery of a range of different drugs in animal models, such as the rat. Studies in man have mostly compared the pharmacological effects (e.g. brain functions) of nasally applied drugs with parenterally applied drugs and have shown a distinct indication of direct nose-to-brain transport. Recent studies in volunteers involving cerebrospinal fluid sampling, blood sampling and pharmacokinetic analysis after nasal, and in some instances parenteral administration of different drugs, have in my opinion confirmed the likely existence of a direct pathway from nose to brain.

The effects of diazepam on sensory gating in healthy volunteers

Sensory or P50 gating, as measured with the double click paradigm, reflects a slow inhibitory preattentional information process. It protects living organisms from being flooded by environmental stimuli. The effects of a single dose of diazepam (10 mg) on the amplitude of the P50's and P50 gating, as measured from auditory evoked potentials elicited by double clicks (80 dB white noise, interstimulus interval 500 ms) were investigated in a double blind, placebo controlled study in healthy volunteers. P50 gating was found, however diazepam had no effects on the amplitude of the P50, nor on P50 gating. The results contribute to the specificity of psychoactive drugs to control gating and demonstrate that this slow inhibitory process is not effected by this benzodiazepine. Moreover, the results confirm that P50 and P50 gating are indeed preattentive processes that are not controlled by diazepam.

The effect of diazepam on motor cortical oscillations and corticomuscular coherence studied in man

EEG recordings from sensorimotor cortex show oscillations around 10 and 20 Hz. These modulate with task performance, and are strongest during periods of steady contraction. The 20 Hz oscillations are coherent with contralateral EMG. Computer modelling suggests that oscillations arising within the cortex may be especially dependent on inhibitory systems. The benzodiazepine diazepam enhances the size of GABA(A) IPSPs; its effects are reversed by the antagonist flumazenil. We tested the effect of these drugs on spectral measures of EEG and EMG, whilst eight healthy human subjects performed a precision grip task containing both holding and movement phases. Either an auxotonic or isometric load was used. EEG changes following electrical stimulation of the contralateral median nerve were also assessed. The EEG power showed similar changes in all task/stimulation protocols used. Power around 20 Hz doubled at the highest dose of diazepam used (5 mg), and returned to control levels following flumazenil. EEG power at 10 Hz was by contrast little altered. The peak frequency of EEG power in both bands was not changed by diazepam. Corticomuscular coherence at ca 20 Hz was reduced following diazepam injection, but the magnitude of this effect was small (mean coherence during steady holding in the auxotonic task was 0.062 in control recordings, 0.051 after 2.5 mg and 5 mg doses of diazepam). These results imply that 20 Hz oscillations in the sensorimotor cortex are at least partially produced by local cortical circuits reliant on GABA(A)-mediated intracortical inhibition, whereas 10 Hz rhythms arise by a different mechanism. Rhythms generated during different tasks, or following nerve stimulation, are likely to arise from similar mechanisms. By examining the formulae used to calculate coherence, we show that if cortical oscillations are simply transmitted to the periphery, corticomuscular coherence should increase in parallel with the ratio of EEG to EMG power. The relative constancy of coherence even when the amplitude of cortical oscillations is perturbed suggests that corticomuscular coherence itself may have a functional role in motor control.

Intranasal bioavailability of diazepam in sheep correlated to rabbit and man

The purposes of the present study were to estimate the nasal bioavailability of diazepam in sheep and to compare this to earlier results in rabbits and humans. Additional, to compare the absorption during various initial periods in the two animal models and man, due to the importance of early absorption in emergency treatment. In a cross-over design, diazepam was nasally administered (7 mg) and intravenously (3 mg), respectively, to six sheep. Diazepam was solubilised in polyethylene glycol 300 in the nasal formulation. The mean nasal bioavailability, t(max) and C(max) were 15% (S.D.+/-8), 5 min (S.D.+/-3) and 934 ng/ml (S.D.+/-593), respectively. Sheep bioavailability was lower than rabbit 54% (P<0.001) and man 34% (P<0.05). In conclusion, the nasal absorption of diazepam was found to be fast, indicating the potential of nasal delivery in acute treatment. The initial (30 min) nasal bioavailability (30 min) for sheep and rabbit is a factor of 2.3 lower and 1.6 higher than man, respectively. The correlation of bioavailability was not optimal between sheep, man and rabbit with differences both in relation to extend and rate.