The pharmacological basis of coronary and systemic vasodilator actions of diazepam (Valium)

Brain temperature effects of intravenous heroin: State dependency, environmental modulation, and the effects of dose

Here we examined how intravenous heroin at a dose that maintains self-administration (0.1 mg/kg) affects brain temperature homeostasis in freely moving rats under conditions that seek to mimic some aspects of human drug use. When administered under standard laboratory conditions (quiet rest at 22 °C ambient temperature), heroin induced moderate temperature increases (1.0-1.5 °C) in the nucleus accumbens (NAc), a critical structure of the brain motivation-reinforcement circuit. By simultaneously recording temperatures in the temporal muscle and skin, we demonstrate that the hyperthermic effects of heroin results primarily from inhibition of heat loss due to strong and prolonged skin vasoconstriction. Heroin-induced brain temperature increases were enhanced during behavioral activation (i.e., social interaction) and in a moderately warm environment (29 °C). By calculating the "net" effects of the drug in these two conditions, we found that this enhancement results from the summation of the hyperthermic effects of heroin with similar effects induced by either social interaction or a warmer environment. When the dose of heroin was increased (to 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg/kg), brain temperature showed a biphasic down-up response. The initial temperature decrease was dose-dependent and resulted from a transient inhibition of intra-brain heat production coupled with increased heat loss via skin surfaces-the effects typically induced by general anesthetics. These initial inhibitory effects induced by large-dose heroin injections could be related to profound CNS depression-the most serious health complications typical of heroin overdose in humans.

The on- and off-target effects of morphine in acute coronary syndrome: A narrative review

With potent analgesic properties, perceived hemodynamic benefits and limited alternatives, morphine is the analgesic mainstay for patients with nitrate resistant chest pain due to acute Myocardial Infarction (MI). However, observational data suggest that morphine administration during MI may have negative consequences. While vomiting, hypotension and respiratory depression are established side effects, recent reports have demonstrated attenuated and delayed oral anti-platelet agent absorption, as well as suboptimal reperfusion after MI, all of which may translate into adverse cardiovascular outcomes. These data have resulted in reduced support for morphine in recent European and U.S. clinical practice guidelines for MI; despite the absence of any prospective randomized outcomes trials addressing this question. As such, randomized trials are now necessary to confirm whether or not morphine, which is administered in up to 30% of MI cases, causes adverse clinical outcomes in these patients. However, given that placebo-controlled randomized trial designs evaluating morphine in MI are limited by an ethical requirement for appropriate analgesia, alternative investigational approaches may be necessary. In this article we review the updated evidence for morphine in MI and outline novel strategies that may facilitate future investigation of this clinical dilemma.

The use of benzodiazepines in the treatment of chest pain: a review of the literature

Benzodiazepines, although not listed in the American Heart Association's guidelines for the treatment of chest pain, are often used to provide symptomatic relief to patients who experience chest pain. To investigate the utility of benzodiazepines in the treatment of chest pain, the pharmacologic actions and cardiovascular effects of benzodiazepines were reviewed. In addition, a literature search regarding the use of benzodiazepines to treat patients with chest pain was conducted. The results indicated that benzodiazepines reduce anxiety, pain, and cardiovascular activation. Benzodiazepines amplify gamma-aminobutyric acid (GABA) throughout the central nervous system, and act more peripherally to reduce catecholamines. In addition, preliminary evidence indicates that benzodiazepines may cause coronary vasodilatation, prevent dysrhythmias, and block platelet aggregation, though further study is needed. Both non-cardiac chest pain (associated with musculoskeletal, esophageal, neurologic, and psychiatric conditions) and cardiac chest pain (associated with acute and chronic myocardial ischemia) seem to be effectively treated with benzodiazepines. Benzodiazepines are safe and well tolerated when administered alone or in combination with other medications. Moreover, the risk of dependence is minimal when benzodiazepines are prescribed on a short-term basis. Further study of benzodiazepines in the treatment of acute chest pain is needed to confirm these favorable actions and better define their use in the acute medical setting.

Influence of anesthetics on the incidence of reperfusion-induced arrhythmias and sudden death in rats

PURPOSE

We compared the influence of pentobarbital (P, 60 mg/kg), urethane (U, 1.8 g/kg), and a contribution of diazepam with ketamine hydrochloride (D+K, 10 + 100 mg/kg) anesthesia on the incidence of ischemia/ reperfusion-induced arrhythmias in rats. In anesthetized rats, myocardial ischemia was produced by a 6-min ligation of the left main coronary artery, followed by 5 min of reperfusion. The incidence of reperfusion-induced ventricular fibrillation (VF) and ventricular tachycardia (VT) was markedly decreased in the D+K-anesthetized animals compared with the P-anesthetized group (VF, 46 vs. 89%; VT, 64 vs. 94%). The mean blood pressure (MBP) before coronary ligation was significantly lower in U-anesthetized animals (72 +/- 3.5 vs. 102 +/- 4.1 and 108 +/- 5.9 mm Hg in P and D+K, respectively). The MBP recovery was the best in the D+K-anesthetized group. In experimental work, pentobarbitone anesthesia may be recommended for studying arrhythmias, while the combination of diazepam and ketamine may be useful for hemodynamic investigations.

Effects of diazepam on the carotid sinus baroreflex control of circulation in rabbits

To examine the effects of diazepam on the carotid sinus baroreflex control of circulation, bilateral carotid occlusion was performed on 14 conscious rabbits with aortic denervation. The responses of mean arterial pressure, heart rate, cardiac output and total peripheral resistance were obtained. The haemodynamic responses to carotid occlusion were evaluated at cumulative doses of 0.5 and 1.0 mg kg-1 of diazepam. The administration of diazepam decreased cardiac output and increased total peripheral resistance significantly, but did not affect the arterial pressure and heart rate. The response of total peripheral resistance to carotid occlusion was significantly increased from 0.118 +/- 0.018 (mean +/- SE) to 0.154 +/- 0.026 mmHg min ml-1 at 1.0 mg kg-1 of diazepam. The heart rate response was attenuated significantly from 41 +/- 5 to 24 +/- 4 beats min-1 at 1.0 mg kg-1 of diazepam. Diazepam did not alter the response of arterial pressure to carotid occlusion. We suggest that the dissociated effects of diazepam on the reflex control of circulation reflect the dissociated influences of diazepam on the central sympathetic and vagal-mediated pathways.

An in vivo method for studies of traumatic vasospasm

A study was undertaken to develop a model for investigations of traumatically induced vasospasm. The left ear of the rabbit was denervated under short anesthesia. With the animal under light sedation, spasm of the central ear artery was repeatedly induced with a clip applying forceps. To evaluate the vasospasm, the vessel was transilluminated with cold light, and the internal diameter was continuously measured. The spasm was assessed in terms of its duration, intensity (reduction of initial diameter) and severity (integrated change in diameter over time). Repetitive application of the forceps on the same vessel segment shortened the spasm duration. With prolonged pinch duration, the spasm duration was lengthened. The preparation was stable for at least 3 hours. This model was effective for manipulating small vessels and producing spasm and is of potential value for studying the treatment of vasospasm by topical local intra-arterial and systemic methods.

Atropine, diazepam, and physostigmine: thermoregulatory effects in the heat-stressed rat

We have previously reported that administration of atropine (A) to unrestrained, sedentary, heat-stressed rats resulted in a dose-dependent increase in heating rate (rate of rise of core temperature, degree C/min). Additionally, we have demonstrated that the decrements in treadmill endurance and increments in heating rate of physostigmine (PH)-treated running rats can both be restored to control levels by pretreating the animals with A and diazepam (D). Our objective in the present work was to determine if the administration of D + PH to A-treated unrestrained, sedentary, heat-stressed rats (N = 16/group, 510-530 g) could improve their thermal tolerance. The following drugs were administered singly (at 10 min intervals) via lateral tail vein: vehicle-control (C), A (200 micrograms/kg), D (500 micrograms/kg), and PH (200 micrograms/kg). After drug administration, the rats were heat-stressed (Tamb = 41.5 degrees C) until a core temperature of 42.6 degrees C was attained when they were removed to a 26 degrees C chamber. The heating rates (degrees C/min) and tolerance times (min) of the respective groups were: C- 0.02, 235; A- 0.08, 58; A D- 0.06, 94; and A + D + PH- 0.04, 143. Administration of D with A significantly decreased heating rate, and D + PH more than doubled the thermal tolerance of A-treated rats. Thus, the combination of A + D + PH not only restores PH-induced performance and thermoregulatory decrements of rats exercised in a moderate environment, but also reduces A-induced heat intolerance.

The effect of RO15-1788 on cardiovascular depression caused by fentanyl and diazepam

Cardiovascular depression occurring when diazepam is combined with fentanyl has been investigated using the benzodiazepine antagonist RO15-1788 in the dog. After the initial administration of fentanyl (40 mcg/kg), the mean arterial pressure (MAP) decreased to 89% of its control value. Following the administration of diazepam (1.2 mg/kg), the MAP and the total peripheral resistance (TPR) decreased significantly, to 75% and 83% of their control values respectively. After the administration of RO15-1788 (0.4 mg/kg), the MAP increased significantly to 90% and the TPR to 102% of their control values and, lastly, the administration of naloxone (40 mcg/kg) increased the MAP to 108% of its control value. No relationship was found between the changes in the catecholamines and the changes in the MAP after the administration of fentanyl, diazepam, and RO15-1788. The mechanism of circulatory depression when diazepam was used with fentanyl is interpreted as being a peripheral vasodilatory effect of diazepam acting by way of the benzodiazepine receptors since RO15-1788 was found to antagonize this effect.

Clonazepam and diltiazem both inhibit sodium-calcium exchange of mitochondria, but only diltiazem inhibits the slow action potentials of cardiac muscles

Clonazepam, up to concentrations of 5 x 10(-5) M produced only 15% inhibition of contraction without effecting isoproterenol-induced slow action potentials (APs) of guinea pig papillary muscles. On the other hand, 10(-6) M diltiazem completely inhibited both slow APs and contractions. Both clonazepam and diltiazem inhibited Na+-induced Ca2+ release from isolated mitochondria. The half-maximum effect of clonazepam and diltiazem occurred at 7 and 8 x 10(-6) M respectively. The results suggest that clonazepam more specifically inhibits the Na+-induced Ca2+ release process of mitochondria.

Inhibition of sympathetic neurotransmission in the rat anococcygeus muscle by diazepam

In the rat anococcygeus muscle, diazepam (1.8 X 10(-6) - 2.8 X 10(-5) M), dipyridamole (2 X 10(-6) - 3.2 X 10(-5) M) and ATP (2 X 10(-4) - 6.4 X 10(-3) M) concentration-dependently inhibited the motor response to field stimulation. Glycine (up to 7.5 X 10(-3) M) and GABA (up to 10(-4) M) had no effect on field stimulation. Concentrations of diazepam and dipyridamole which reduced motor response to field stimulation did not relax the tonically contracted rat anococcygeus muscle. However, at these concentrations, diazepam and dipyridamole potentiated the inhibitory responses of the tonically contracted rat anococcygeus muscle to ATP and field stimulation. It is suggested that diazepam and dipyridamole reduced the motor response to field stimulation by potentiating the inhibitory transmitter released during nerve stimulation. Also, since the time-course of the effect of diazepam and dipyridamole on the inhibitory responses to ATP and field stimulation are closely similar, the results would tend to provide additional support for the concept of purinergic transmission in the rat anococcygeus muscle.

The haemodynamic effects of flunitrazepam in anaesthetized patients with valvular or coronary artery lesions

The Haemodynamic effects of flunitrazepam (FLU) 1.25 mg X m-2 administered intravenously were studied in 18 anaesthetized cardiac patients suffering from isolated mitral (MIT, n = 6), aortic (AOR, n = 6) or coronary (COR, n = 6) lesions. A placebo group of 18 clinically similar patients was used to assess the stability of the cardiovascular parameters under the conditions of the study. Heart rate, systemic arterial pressure, cardiac output and central venous pressure changes were measured 2, 5, 8 and 12 min after FLU or saline injection and compared with reference values collected before the start of the haemodynamic test. In the FLU group, the cardiovascular state of all the patients developed following the same pattern and the greatest differences were observed at 12 min post-injection. These differences, expressed as a percentage of the initial values were (* P less than 0.05; ** P less than 0.001; ns = non-significant): mean systemic arterial pressure: COR, -18% (**);MIT, -13% (*); AOR, -23% (**); heart rate: COR, 0% (ns); MIT, -10% (*); AOR, -12% (*); cardiac output: COR, -15% (**); MIT, -13% (*); AOR, -16% (**); stroke volume: COR, -12%(*);MIT, 0% (ns);AOR,-3%(ns). This shows some differences concerning the SV and heart rate changes in the valvular and COR patients. As compared to the data from the literature, most of the haemodynamic effects of FLU seem relatively independent of the initial level of consciousness.

Potentiation of the effects of adenosine on isolated cardiac and smooth muscle by diazepam

1. Adenosine (10(-7) to 3 x 10(-4) M) or 2-chloroadenosine (10(-8) to 10(-5) M) produced concentration-dependent inhibition of the responses of the rat isolated vas deferens to electrical field stimulation. In electrically driven (2 Hz) guinea-pig isolated left atria, adenosine (10(-6) to 10(-3) M) or 2-chloroadenosine (10(-8) to 10(-7) M) produced concentration-dependent decreases in isometric tension. 2. Diazepam (10(-6) and 10(-5) M) had no direct effect per se, but significantly potentiated the inhibitory action of adenosine on both tissues without altering the inhibitory effect of 2-chloroadenosine. 3. The adenosine uptake inhibitors, hydroxynitrobenzylthioguanosine (HNBTG, 10(-5) M) and dipyridamole (10(-5) M) also potentiated the inhibitory actions of adenosine in rat vas deferens, but not hose of 2-chloroadenosine. 4. Following adenosine uptake inhibition in rat vas deferens by HNBTG (10(-5) M), diazepam (10(-5) M) failed to produce any significant further potentiation of the inhibitory action of adenosine. 5. It is concluded that the potentiation of adenosine by diazepam is possibly due to an inhibition of adenosine uptake.

Aortocoronary vein graft flow in response to peripheral venous administration of sodium nitroprusside or diazepam

Vein graft flow (VGF) in response to peripheral venous administration of sodium nitroprusside (SNP) or diazepam was studied in 13 anesthetized patients following cardiopulmonary bypass for aortocoronary vein bypass graft operations. SNP (0.5 microgram/kg/min) significantly reduced mean arterial pressure (p less than 0.05). VGF paralleled the decreased blood pressure, but the reduction was not significant (p greater than 0.05). Diazepam (0.1 mg/kg) did not significantly alter blood pressure or VGF. We conclude that peripheral venous administration of SNP or diazepam is not a pharmacologically reliable method by which to increase VGF in the period immediately following a graft operation.

Systemic vasodilatation following diazepam after combined sympathetic and parasympathetic blockade in patients with coronary heart disease

Clinical and hemodynamic benefits have been documented after giving diazepam to patients with coronary heart disease. The mechanisms by which this agent produces its hemodynamics effects are poorly understood. Partial autonomic blockade was induced in 10 patients by the intravenous administration of 5 mg propranolol and 0.8 mg atropine. Coronary and systemic hemodynamics were normal before and unchanged (p greater than 0.05) after propranolol and atropine administration. However, myocardial extraction of lactate improved in 9 out of 10 patients (from 11% to 24%, p less than 0.05). The patients then received 0.1 mg/kg diazepam intravenously. Diazepam had no effect on the coronary sinus blood flow and resistance while myocardial extraction of lactate further improved in all but one patient (from 24% to 35% at 5 min and 34% at 15 min, p less than 0.05). Heart rate increased by a mean of 4 beats at 5 min (p less than 0.01). Cardiac output was unchanged. Systolic arterial pressure (SAP) decreased significantly (p less than 0.001) at 5 and 15 min (6-10%) and left ventricular end-diastolic pressure (LVEDP) also diminished significantly (p less than 0.001) at 5 and 15 min (18-19%). These changes occurred despite autonomic blockade. These findings suggest, in the absence of change of myocardial blood flow and contractility, a direct peripheral action of the drug on arteries and/or veins.

Cardiovascular effects of diazepam and chlordiazepoxide

In open-chest dog preparations i.v. administration of diazepam and chlordiazepoxide caused increases in coronary blood flow and cardiac output while reducing blood pressure, heart rate, and myocardial contractile force. The decrease in force was independent of the alteration in coronary flow. Arterial--coronary sinus oxygen difference narrowed and myocardial oxygen consumption decreased. These data show that both diazepam and chlordiazepoxide exert an oxygen conserving action along with an increase in myocardial oxygen delivery and suggest that these drugs may be of benefit to the patient with coronary insufficiency by a direct effect on the cardiovascular system as well as through CNS-mediated antianxiety effects.

Systemic and coronary hemodynamic effects of diazepam in patients with normal and diseased coronary arteries

In 12 patients with significant coronary artery disease (group I) and in eight patients with normal coronary arteries (group II), 5 to 8.5 mg of diazepam was given intravenously before coronary angiography. Adequate sedation was obtained in 17 patients. Hypoventilation occurred in all patients but was without clinical correlate. Coronary and cardiovascular effects were assessed before as well as 10 and 20 min after diazepam. Heart rate was unchanged and aortic pressure (AP) decreased significantly ( P < 0.01) in most patients. Cardiac index decreased only in patients of group II ( P < 0.01). Of particular interest was a constant fall in left ventricular end-diastolic pressure (LVEDP) in both groups, ( P < 0.01) and ( P < 0.05) at 10 and 20 min respectively in group I and ( P < 0.01) at 10 and 20 min in group II. Tension-time index and myocardial oxygen consumption (MVO 2 ) were also significantly decreased ( P < 0.05) after diazepam in both groups. Since neither coronary blood flow nor coronary vascular resistance were modified by diazepam, the fall in LVEDP could be due to a decrease in AP (afterload) and/or in venous return (preload). The combination of these effects could reduce intra-cavitary volume, myocardial wall tension and left ventricular MVO 2 . Our data therefore suggest that, in addition to its central sedative effects, diazepam also has a nitroglycerin-like action on the coronary and systemic circulation.

Psychopharmacologic management of anxiety in the cardiac patient

Of 253 patients who had suffered acute myocardial infarction ( MI), 88 percent received daytime sedation while hospitalized. Sixty percent of all prescriptions were for phenobarbital, 30 percent for chlordiazepoxide, and 6 percent for meprobamate. In addition, 79 percent of patients received night time hypnotic medication. Sixty-six percent of such prescriptions were for short-acting barbiturates, 21 percent for chloral hydrate, and 7 percent for diphenhydramine. Multiple drug use was common.

The barbiturates, while inexpensive sedative agents, are of questionable efficacy in reducing anxiety and probably produce only general CNS depression. A narrow margin of safety, liability to produce habituation, and antagonism of warfarin-type anticoagulants are other disadvantages. The benzodiazepine tranquilizers, whose antianxiety efficacy is more clearly established, do not produce general CNS depression, have a wide margin of safety, and do not interact with oral anticoagulants.

Antidepressant agents, phenothiazine tranquilizers, and propranolol were used infrequently or not at all. The risks associated with the use of these agents in patients with acute myocardial infarction are considerable and should be weighed carefully before they are administered.