Mechanisms involved in the relaxing effect of midazolam on coronary arteries

Vascular effects of midazolam, flumazenil, and a novel imidazobenzodiazepine MP-III-058 on isolated rat aorta

Hypotensive influences of benzodiazepines and other GABAA receptor ligands, recognized in clinical practice, seem to stem from the existence of "vascular" GABAA receptors in peripheral blood vessels, besides any mechanisms in the central and peripheral nervous systems. We aimed to further elucidate the vasodilatatory effects of ligands acting through GABAA receptors. Using immunohistochemistry, the rat aortic smooth muscle layer was found to express GABAA γ2 and α1-5 subunit proteins. To confirm the role of "vascular" GABAA receptors, we investigated the vascular effects of standard benzodiazepines, midazolam, and flumazenil, as well as the novel compound MP-III-058. Using two-electrode voltage clamp electrophysiology and radioligand binding assays, MP-III-058 was found to have modest binding but substantial functional selectivity for α5β3γ2 over other αxβ3γ2 GABAA receptors. Tissue bath assays revealed comparable vasodilatory effects of MP-III-058 and midazolam, both of which at 100 µmol/L concentrations had efficacy similar to prazosin. Flumazenil exhibited weak vasoactivity per se, but significantly prevented the relaxant effects of midazolam and MP-III-058. These studies indicate the existence of functional GABAA receptors in the rat aorta, where ligands exert vasodilatory effects by positive modulation of the benzodiazepine binding site, suggesting the potential for further quest for leads with optimized pharmacokinetic properties as prospective adjuvant vasodilators.

Benzodiazepines Reduce Blood Pressure in Short Term: A Systematic Review and Meta-analysis

PURPOSE OF REVIEW

Benzodiazepines, due to their anxiolytic properties, are prescribed to reduce anxiety and insomnia. They might have hypotensive effect via potentiation of the inhibitory effect of gamma-amino butyric acid (GABA) in the central nervous system and vasodilatory properties. However, studies comparing the effect of benzodiazepines in lowering blood pressure (BP) are equivocal. This systematic review and meta-analysis was planned to assess the efficacy of benzodiazepines in reducing blood pressure in short term among hypertensive patients.

RECENT FINDINGS

Various trials and retrospective analysis conducted previously have reported that benzodiazepines cause short- as well as long-term BP reduction in patients with increased anxiety with hypertension. On the other hand, several studies investigating the efficacy of benzodiazepines in patients with hypertension have reported inconclusive results. The primary question about the effect of benzodiazepines in lowering BP remains unanswered. In this meta-analysis of seven studies, benzodiazepines were found comparable to standard drugs in reducing systolic and diastolic BP in patients having hypertension. Although, the mean difference in systolic BP with benzodiazepines and placebo was statistically not significant, the difference can be considered as clinically meaningful. The current review offers preliminary evidence that benzodiazepines may have antihypertensive properties and may be used as add-on antihypertensive in a subset of patients in short term. The existing data are encouraging, but more clinical trials and mechanistic research are required to ascertain the long-term benefits.

Effect of Preoperative Antianxiety Medications on Blood Pressure and Blood Loss in Total Knee Arthroplasty: A Case-Control Study

Background

The increasing number of canceled operations in patients undergoing total knee arthroplasty (TKA) due to high blood pressure readings has put a considerable burden on surgeons. In this study, we aim to assess the effect of giving antianxiety drugs preoperatively on maintaining blood pressure (BP) and blood loss for patients undergoing TKA surgery.

Methods

This retrospective case-control study included patients who underwent total knee arthroplasty and divided them into two main groups: those who had taken a 3 mg bromazepam oral tablet at the night preoperatively and the control group. The blood pressure of patients was then measured preoperatively (baseline), in the morning of surgery, in the operating room before anesthesia, and during the surgery. The percentage of measured BP was calculated by dividing the measured BP by the baseline, then multiplying by 100.

Results

301 patients were included in our study: 137 received bromazepam and 164 as a control group. The ratio of systolic BP (SBP) in the morning of surgery to the baseline (percentage of morning SBP) decreased significantly in the bromazepam group compared with the controls. The ratio of SBP, in the operating room before anesthesia (percentage of preanesthesia SBP) also decreased significantly in the bromazepam group. However, the percentage of SBP in the middle of surgery did not change significantly. In addition, there was a significant difference change from the baseline in diastolic BP and mean arterial BP between the two groups in the morning of surgery, inside the theatre, and in the middle of the operation. The bromazepam group also showed a significant decrease in blood loss.

Conclusion

Preoperative oral antianxiety drugs (bromazepam) helps in controlling hemodynamic changes associated with anxiety, including maintaining BP in well-controlled hypertensive and healthy patients undergoing TKA, and it plays a role in decreasing the total blood loss.

Midazolam's Effects on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-lymphocytes

Midazolam (MDZ) could affect lymphocyte immune functions. However, the influence of MDZ on cell’s K⁺ currents has never been investigated. Thus, in the present study, the effects of MDZ on Jurkat T lymphocytes were studied using the patch-clamp technique. Results showed that MDZ suppressed the amplitude of delayed-rectifier K⁺ current (I_K(DR)) in concentration-, time-, and state-dependent manners. The IC₅₀ for MDZ-mediated reduction of I_K(DR) density was 5.87 μM. Increasing MDZ concentration raised the rate of current-density inactivation and its inhibitory action on I_K(DR) density was estimated with a dissociation constant of 5.14 μM. In addition, the inactivation curve of I_K(DR) associated with MDZ was shifted to a hyperpolarized potential with no change on the slope factor. MDZ-induced inhibition of I_K(DR) was not reversed by flumazenil. In addition, the activity of intermediate-conductance Ca²⁺-activated K⁺ (IK_Ca) channels was suppressed by MDZ. Furthermore, inhibition by MDZ on both I_K(DR) and IK_Ca-channel activity appeared to be independent from GABAA receptors and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes. In conclusion, MDZ suppressed current density of I_K(DR) in concentration-, time-, and state-dependent manners in Jurkat T-lymphocytes and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes.

Vasodilatory effects of a variety of positive allosteric modulators of GABAA receptors on rat thoracic aorta

Different subtypes of GABAA (gamma-aminobutyric acid A) receptors, through their specific regional and cellular localization, are involved in the manifestation of various functions, both at the central and peripheral levels. We hypothesized that various non-neuronal GABAA receptors are expressed on blood vessels, through which positive allosteric modulators of GABAA receptors exhibit vasodilatory effects. This study involved two parts: one to determine the presence of α1-6 subunit GABAA receptor mRNAs in the rat thoracic aorta, and the other to determine the vasoactivity of the various selective and non-selective positive GABAA receptor modulators: zolpidem (α1-selective), XHe-III-074 (α4-selective), MP-III-022 (α5-selective), DK-I-56-1 (α6-selective), SH-I-048A and diazepam (non-selective). Reverse transcription-polymerase chain reaction (RT-PCR) analysis data demonstrated for the first time the expression of α1, α2, α3, α4 and α5 subunits in the rat thoracic aorta tissue. Tissue bath assays on isolated rat aortic rings revealed significant vasodilatory effects of diazepam, SH-I-048A, XHe-III-074, MP-III-022 and DK-I-56-1, all in terms of achieved relaxations (over 50% of relative tension decrease), as well as in terms of preventive effects on phenylephrine (PE) contraction. Diazepam was the most efficient ligand in the present study, while zolpidem showed the weakest vascular effects. In addition, diazepam-induced relaxations in the presence of antagonists PK11195 or bicuculline were significantly reduced (P < 0.001 and P < 0.05, respectively) at lower concentrations of diazepam (10-7 M and 3 × 10-7 M). The present work suggests that the observed vasoactivity is due to modulation of "vascular" GABAA receptors, which after further detailed research may provide a therapeutic target.

Vasorelaxant effects of benzodiazepines, non-benzodiazepine sedative-hypnotics, and tandospirone on isolated rat arteries

Benzodiazepines (BDZs) and non-BDZ sedative-hypnotics are effective for the management of chronic insomnia; however, they are associated with adverse effects such as headache, dizziness, and palpitations. Furthermore, long-term use of these medications is associated with decreased blood pressure (BP) or depressed baroreflex function. Therefore, here, we assessed whether BDZs and non-BDZs cause vasorelaxation directly. Vasorelaxation in response to 22 BDZs, 2 non-BDZs, and tandospirone was determined by myograph methods using isolated Wistar rat thoracic aortas. All the drugs relaxed phenylephrine-contracted rat aortas in a concentration-dependent manner. Zolpidem and tandospirone caused over 80% relaxation at a concentration of 10 μM; diazepam, estazolam, etizolam, and tofisopam caused 60-70% relaxation; whereas 18 other BDZs (alprazolam, bromazepam, brotizolam, chlordiazepoxide, clobazam, clonazepam, clorazepate, ethyl loflazepate, flunitrazepam, flurazepam, lorazepam, lormetazepam, midazolam, nimetazepam, nitrazepam, oxazepam, temazepam, and triazolam) and zaleplon caused less than 50% relaxation. The relaxation was partially but significantly inhibited to the same extent by a nitric oxide (NO) synthase antagonist and after endothelium removal. Binding assay of gamma-aminobutyric acid type A receptors was performed using [3H]flunitrazepam. No correlation was observed between vasorelaxation at a concentration of 10 μM and the binding affinities for 23 drugs. The study demonstrated that zaleplon, zolpidem, tandospirone, and many BDZs cause vasorelaxation to different extents via endothelial NO-dependent and endothelium-independent pathways. In conclusion, the direct vasodilatory effects of these drugs may be involved in the mechanisms underlying their adverse effects. Additionally, the decreased BP observed in persons who take BDZs or non-BDZs may be partly due to direct vasodilation.

Substance abuse and conscious sedation: theoretical and practical considerations

Substance abuse is an issue that has been widely recognised both in the medical and dental professions. Many different recreational drugs exist and their use can have important consequences in relation to conscious sedation. As the use of illicit drugs is growing, it is important to have an understanding of the impact of substance abuse on determining if a patient is a suitable candidate for conscious sedation. It is important to appreciate that while human studies in this area are limited, animal studies and observation of the reactions of substance abusers to sedative agents demonstrate a potential link between illicit drug use and conscious sedation through drug interaction. This paper aims to discuss the importance of understanding substance abuse, the potential effects such substances can have in relation to conscious sedation and appropriate management techniques for substance abusers in order to provide optimum safe care when undergoing conscious sedation techniques.

Moderate procedural sedation and opioid analgesia during transradial coronary interventions to prevent spasm: a prospective randomized study

OBJECTIVES

The aim of this study was to test the hypothesis that moderate procedural sedation can reduce the incidence of radial artery spasm.

BACKGROUND

Transradial access for left heart catheterization and percutaneous coronary intervention is increasingly used for emergent and elective procedures, in lieu of the femoral approach. However, increased rates of access site crossover have been reported, with radial artery spasm being a major contributor to this effect.

METHODS

Patients undergoing elective transradial percutaneous coronary intervention were prospectively randomized to receive fentanyl and midazolam during the procedure or no treatment (control subjects). The primary endpoint was angiographically confirmed radial artery spasm. Patient discomfort was quantified with a visual analogue scale.

RESULTS

Two thousand thirteen patients (age 64.5 ± 8.4 years) were randomized. Spasm occurred in 2.6% of the treatment group versus 8.3% of control subjects (p < 0.001; odds ratio [OR]: 0.29). The number needed to treat to avoid 1 case of spasm was 18 (95% confidence interval [CI]: 12.9 to 26.6). The access site crossover rate was 34% lower in the treatment group: 9.9% versus 15.0% (OR: 0.62; 95% CI: 0.48 to 0.82). Patient discomfort visual analogue scale score was 18.8 ± 12.5 in the treatment group versus 27.4 ± 17.4 in control subjects (p < 0.001). No significant differences were observed in the 30-day rate of death or repeat hospital stay for any cause: 4.6% versus 4.5% (OR: 1.02; 95% CI: 0.67 to 1.56).

CONCLUSIONS

Routine administration of relatively low doses of an opioid/benzodiazepine combination during transradial interventional procedures is associated with a substantial reduction in the rate of spasm, the need for access site crossover, and the procedure-related level of patient discomfort.

Anxiolytic therapy with alprazolam increases muscle sympathetic activity in patients with panic disorders

Anxiolytic therapy with the benzodiazepine alprazolam is an established therapy in patients with panic disorder. Normally, panic-like anxiety and its concomitant physical symptoms quickly disappear under such treatment. Therefore we investigated whether there is a difference in sympathetic nervous system in patients with panic disorder compared to healthy controls. Three groups of subjects were included: ten patients with panic disorder, who received alprazolam and 20 healthy control subjects who were given either alprazolam (n=10) or matching placebo (n=10). Muscle sympathetic nerve activity (MSNA) and heart rate did not differ at baseline but significantly increased both in patients and healthy controls after intake of alprazolam (1 mg). However, in both groups both MSNA and heart rate were significantly elevated when compared to both baseline and the placebo control group. This study demonstrates (1) that anxiolytic therapy with alprazolam increases muscle sympathetic nerve activity and heart rate not only in patients with panic disorder but also in healthy controls and (2) that a significant difference in sympathetic nervous system activity between patients and controls, at baseline and during the therapy with alprazolam could not be demonstrated.