Central actions of beta-adrenoceptor blocking drugs in man

Pharmacological Hypotension as a Cause of Delirious Mania in a Patient with Bipolar Disorder

Delirious mania is a severe but often underrecognized syndrome characterized by rapid onset of delirium, mania, and psychosis, not associated with a prior toxicity, physical illness, or mental disorder. We discuss the case of a delirious mania potentially triggered and maintained by a systemic hypotension induced by antihypertensive drugs. Symptoms recovered completely after the discontinuation of antihypertensive medications and the normalization of blood pressure levels.

Drug-induced cognitive impairment: Effect of cardiovascular agents

INTRODUCTION

Cardiovascular agents can be associated with a negative effect on cognition, especially in older adults, critically ill people, and those with baseline cognitive impairment. Negative effect on cognition is commonly reported as uncomplicated acute confusion and delirium and, less commonly, chronic cognitive changes due to drug-induced depression and/or dementia.

METHODS

A literature review of case reports, case series, prospective cohort studies, clinical trials, and literature reviews were included in this study. Articles were located using online databases PubMed and Medline using the following keywords: antiarrhythmic agents, anticholinergic burden, antihypertensive agents, beta-blockers, cardiovascular agents, cognitive impairment, delirium, cognition, dementia, depression, digoxin, diuretics, and drug-induced cognitive impairment.

RESULTS

In general, use of all antihypertensives, especially in the case of polypharmacy or inappropriate dosing, can lead to hypotension and/or bradycardia, and thus lead to mental/cognitive status change due to decreased cerebral perfusion. Use of diuretics can be associated with fluid/electrolyte and/or acid-base imbalance, resulting in the onset of confusion and delirium. In addition, cardiovascular agents with central bioavailability, such digoxin and select antiarrhythmics, and antihypertensives may carry a risk for cognitive impairment due to various mechanisms proposed, such as antagonism of central muscarinic acetylcholine receptors, neurotransmission imbalance in the brain, and disruption of physiologic function of sodium/potassium ATPase in the neuronal cells.

DISCUSSION

When dealing with an individual who presents with acute, subacute, and chronic changes in cognitive function, one should perform a thorough medication history as the first step in order to aid in the identification of drug-induced cognitive impairment.

Atenolol offers better protection than clonidine against cardiac injury in kainic acid-induced status epilepticus

BACKGROUND AND PURPOSE

Status epilepticus is increasingly associated with cardiac injury in both clinical and animal studies. The current study examined ECG activity for up to 48 h following kainic acid (KA) seizure induction and compared the potential of atenolol and clonidine to attenuate this cardiac pathology.

EXPERIMENTAL APPROACH

Sprague-Dawley rats (male, 300-350 g) were implanted with ECG and electrocorticogram electrodes to allow simultaneous telemetric recordings of cardiac and cortical responses during and after KA-induced seizures. Animals were randomized into saline controls, and saline vehicle-, clonidine- or atenolol-pretreated KA groups.

KEY RESULTS

KA administration in the saline-pretreated group produced an immediate bradycardic response (maximal decrease of 28 ± 6%), coinciding with low-level seizure activity. As high-level seizure behaviours and EEG spiking increased, tachycardia also developed, with a maximum heart rate increase of 38 ± 7% coinciding with QTc prolongation and T wave elevation. Both clonidine and atenolol pretreatment attenuated seizure activity and reduced KA-induced changes in heart rate, QTc interval and T wave amplitude observed during both bradycardic and tachycardic phases in saline-pretreated KA animals. Clonidine, however, failed to reduce the power of EEG frequencies. Atenolol and to a lesser extent clonidine attenuated the cardiac hypercontraction band necrosis, inflammatory infiltration, and oedema at 48 h after KA, relative to the saline-KA group.

CONCLUSIONS AND IMPLICATIONS

Severe seizure activity in this model was clearly associated with altered ECG activity and cardiac pathology. We suggest that modulation of sympathetic activity by atenolol provides a promising cardioprotective approach in status epilepticus.

No effect of 5-day treatment with acetylsalicylic acid (aspirin) or the beta-blocker propranolol (Inderal) on free cortisol responses to acute psychosocial stress: a randomized double-blind, placebo-controlled study

BACKGROUND

The characterization of an individual's hypothalamic-pituitary-adrenal axis stress response is a main research topic in neuropsychobiology since alterations have been causally linked to several disease states. Over the last years, several studies focused on the identification of sources of inter- and intraindividual variability, but there is still a paucity of experimental data on the effect of different pharmaceuticals on cortisol responses to acute psychological stress. Therefore, in this randomized double-blind placebo-controlled study, we investigated the effect of treatment with two popular and clinically used pharmaceuticals on stress-related cortisol responses, namely acetylsalicylic acid (aspirin), a known prostaglandin synthesis inhibitor, and the beta-blocker propranolol (Inderal), a nonselective beta-receptor antagonist.

METHODS

For 5 days, 73 healthy subjects (50 men, 23 women; mean age 47.3 +/- 7.7 years) received either a daily oral dose of 100 mg aspirin, 80 mg propranolol (Inderal), aspirin + propranolol, or placebo. After treatment, subjects were confronted with the Trier Social Stress Test, a widely-used standardized psychosocial stress protocol. Cortisol responses were measured by six saliva samples taken before and after the stress exposure.

RESULTS

Subjects showed a significant cortisol increase after stress (p < 0.0001). The four treatment groups did not differ in their cortisol responses (group effect p > 0.44; interaction p > 0.97). Additionally, controlling for gender, age, smoking status, body mass index, mean arterial blood pressure or pre-stress cortisol levels yielded similar results in the total sample as well as in the male or female subgroups, respectively.

CONCLUSION

Neither short-term treatment with aspirin nor propranolol altered the acute free cortisol response to psychological stress in healthy adults.

Separate mechanisms for behavioral, cardiovascular, and hormonal responses to dextroamphetamine in man

The neurochemical specificity of physiological, biochemical, and psychological responses to dextroamphetamine was tested by pretreating volunteers with haloperidol (0.014 mg/kg IM), propranolol (0.1 mg/kg IV), thymoxamine (0.1 mg/kg IV), or placebo prior to 0.3 mg/kg IV amphetamine. Healthy volunteers (N = 12) participated in the studies, but not all volunteers received each drug combination. Haloperidol prevented dextroamphetamine-induced behavioral excitation, but did not significantly affect plasma norepinephrine or pressor responses, whereas propranolol inhibited norepinephrine and pressor responses without influencing excitation or other behavioral responses. Thymoxamine did not affect any of the responses measured. None of the agents significantly affected plasma cortisol or growth hormone responses. The prolactin rise following dextroamphetamine was potentiated by haloperidol. The results are consistent with the hypothesis that behavioral excitation after dextroamphetamine occurs through a dopaminergic mechanism, and pressor responses through a noradrenergic mechanism.

Psychomotor performance and antihypertensive treatment

1. The aim of treatment of hypertension is prevention of cardiovascular complications without adverse drug reactions. Psychomotor performance can be measured objectively yet there remains uncertainty concerning the psychomotor effects of antihypertensive drugs during chronic treatment. This uncertainty is partly due to the confounding adverse effects of cerebrovascular disease and hypertension itself. There are as yet insufficient good quality data on psychomotor effects with which to differentiate between the commonly used agents. However, in general, the beneficial effect of lowering blood pressure tends to more than offset any adverse effects of the agent used.

Effects of (-)-pindolol and SDZ 216-525 on social and agonistic behavior in mice

In view of conflicting results reported for 5-HT1A receptor involvement in murine social conflict, this study examined the effect of two compounds, SDZ 216-525 and (-)-pindolol, on agonistic and social behavior in male mice. In a resident-intruder paradigm, (-)-pindolol (1.0-20.0 mg/kg), a beta-adrenergic 5-HT1A/1B antagonist, significantly attenuated all agonistic behaviors across the dose range employed. Social behaviors showed significant decreases, while nonsocial cage exploration showed significant increases at all doses. Defensive evade was significantly attenuated at 20.0 mg/kg. SDZ 216-525 (0.025-1.0 mg/kg), a selective 5-HT1A antagonist, significantly attenuated offensive posturing and bite-attacks at 1.0 mg/kg, and all offensive behaviors nonsignificantly at the smaller doses tested. Rearing was significantly attenuated at 1.0 mg/kg, while cage exploration increased at this dose. Defensive and social behaviors remained largely unchanged. These results show that both compounds tested produced significant reductions in offensive behavior, with concomitant changes in defensive, social, and nonsocial behaviors. Results are discussed in relation to SDZ 216-525 and (-)-pindolol potential for the control of anxiety and agonistic behavior.

Receptor occupancy in lumbar CSF as a measure of the antagonist activity of atenolol, metoprolol and propranolol in the CNS

1. The antagonist activity of atenolol, metoprolol and propranolol in the CNS was estimated by determining the extent to which the drugs occupy animal beta 1- and beta 2-receptors in CSF ex vivo at the time of lumbar puncture. 2. Five CSF and plasma samples were obtained 4 h after drug intake from subjects treated for hypertension with atenolol, 100 mg once daily and five from subjects treated with metoprolol, 50 mg three times daily. Twenty-four samples were obtained 1, 2, 4 or 12 h after drug intake from subjects receiving a single 40 mg dose of propranolol. 3. The receptor occupancy in the samples was determined by adding beta 1-receptors of rabbit lung and beta 2-receptors of rat reticulocytes into the samples and labeling the receptors with a nonselective beta-adrenoceptor antagonist, (-)-[3H]-CGP-12177. 4. Atenolol and metoprolol occupied, as expected, larger fractions of beta 1- than beta 2-receptors in CSF and plasma samples. The receptor fraction occupied by atenolol in CSF was significantly (P < 0.05) lower than that occupied by metoprolol. The differences in occupancy between the drugs in plasma, however, were not statistically significant. 5. Propranolol occupied larger fractions of beta 2- than beta 1-receptors in the samples. Although propranolol concentrations in CSF were only 1/20-1/40 of those in plasma, the receptor occupancy of propranolol in CSF was similar to that in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of a β2-adrenoceptor antagonist (ICI 118,551), diazepam and placebo in the treatment of acute anxiety

The effect of β( 2)-adrenoceptor antagonism in acute anxiety neurosis was investigated by comparing the effects of ICI 118,551, a specific β(2)-adrenoceptor antagonist, diazepam and placebo in a double-blind, parallel group study. Sixty-three patients, who fulfilled criteria for Anxiety Disorder (DSM III) and were psychotropic drug- free (apart from six using hypnotics), were entered. Anxiety symptoms were rated using the Hamilton Anxiety Scale (HAS) and Spielberger State Anxiety Scale. Assessments were made at entry and following a 7-day single-blind placebo treatment phase, at the end of which only 51 wished to continue and had sufficient symptoms (HAS score >16 or reduction <25% on placebo) for entry to the next phase. Following a double- blind, random allocation they then received ICI 118,551 (50 mg), diazepam (2 mg) or placebo thrice daily for 4 weeks. Symptoms were assessed after 2 and 4 weeks in this active treatment phase (i.e. at weeks 3 and 5 of the study). Thirty-five patients completed the study. A statistically significant improvement in HAS score was seen for all patients but there were no significant differences between treatments. Treatments did not differ in their effects on blood pressure or heart rate. β(2)-Adrenoceptor antagonism does not seem to have important effects on anxiety symptoms in anxiety neurosis.

Subjective symptoms and pharmacokinetics/dynamics of metoprolol CR in elderly subjects--a comparison with atenolol

In a double-blind, randomised, cross-over study, the pharmacokinetic/dynamic effects and subjective symptoms of a new controlled-release (CR) formulation of metoprolol (50 and 100 mg) have been compared with atenolol (50 mg) and placebo in 20 elderly healthy subjects. The metoprolol CR formulation displayed an even plasma concentration-time profile over the dosage interval while atenolol produced a peak at 2-4 h. All three active treatments produced significant beta 1-blockade at 24 h compared to placebo. Four hours after dose intake, the degree of beta 1-blockade was significantly greater with conventional atenolol 50 mg than with either dose of metoprolol CR. Subjective well-being was examined with a self-administered questionnaire (MSE-profile), including three dimensions: Contentment, Vitality and Sleep. No significant differences were detected between placebo and either dose of metoprolol CR. At 2 h, following atenolol, a deterioration in Vitality was observed compared to placebo and metoprolol CR 100 mg. At the end of the dosage interval there was no longer any significant difference between the treatments. Perceived leg fatigue during exercise, evaluated 4 h after dosing, was more pronounced during treatment with atenolol than metoprolol CR 50 mg. The results suggest that the metoprolol CR formulation was not associated with significant effects on subjective well-being, whereas atenolol caused a deterioration at the time of the peak plasma concentration of the drug.

Propranolol, clonidine, urapidil and trazodone infusion in essential tremor: a double-blind crossover trial

Accelerometric tremorgrams were recorded from 25 subjects affected by essential tremor and analysed by a Berg-Fourier frequency analyser before and during venous infusion of the following drugs: propranolol (beta-blocker), clonidine (alpha-presynaptic adrenergic agonist), urapidil (alpha-postsynaptic blocker), trazodone (adrenolytic agent) and placebo. The washout interval between infusions was 3 days. Recordings and data analyses were performed in a double-blind crossover trial. Tremor was classified as: at rest; postural (arms hyperextended); and intention (finger-nose test). Analysis of the results showed that propranolol and clonidine reduced significantly (P = 0.01 and P = 0.009, respectively) the power spectrum of postural tremor, but left at rest and intention tremors unchanged. No significant effects on the tremor power spectrum were observed after placebo, urapidil or trazodone administration. None of the drugs had any effect on tremor frequency.

The effects of beta-antagonists and anxiolytics on conflict behavior in the rat

The present studies were designed to evaluate the effects of beta-adrenoceptor antagonists and traditional anxiolytics (phenobarbital and diazepam), alone and in combination, on behavior in the Conditioned Suppressioned of Drinking (CSD) conflict paradigm, an "animal model" for the study of anxiety and antianxiety agents. In daily 10-minute sessions, water-deprived rats were trained to drink from a tube which was occasionally electrified (0.5 mA), electrification being signalled by the presence of a tone. Within 2-3 weeks, control responding had stabilized (10-15 shocks/session and 10-15 ml water/session); drug tests were then conducted at weekly intervals. As expected, diazepam (0.6-10 mg/kg) and phenobarbital (10-40 mg/kg) administration resulted in a marked and dose-dependent increase in punished responding at doses which did not markedly alter background responding (water intake). Neither propranolol (0.5-8 mg/kg) nor the beta-1-selective antagonist atenolol (1-16 mg/kg) significantly affected punished responding in the CSD. Both propranolol and atenolol produced significant beta-1-adrenoceptor blockade, as evidenced by the production of significant bradycardic effects in conscious rats at the doses employed. Pretreatment with 2.0 mg/kg propranolol did not alter the anticonflict effects of diazepam (0.6-10 mg/kg) or phenobarbital (10-40 mg/kg). Further, reduction of the shock intensity to 0.125 mA (i.e., decreased suppression) failed to alter the behavioral response to propranolol (1.5-5 mg/kg) or the interaction of 2.0 mg/kg propranolol with diazepam. Finally, chronic administration of propranolol (2.0 mg/kg, twice daily) did not affect punished responding over the course of 5 weeks of treatment. These data suggest that the CSD paradigm, although an effective "animal model" for the study of benzodiazepine and barbiturate anticonflict effects, cannot serve as an "animal model" for the study of the situation-specific (i.e., phobic) anxiety for which propranolol and related agents are presently used.

Central nervous system considerations in the use of beta-blockers, angiotensin-converting enzyme inhibitors, and thiazide diuretics in managing essential hypertension

The most common mild side effects occurring with use of beta-blockers, thiazide diuretics, and angiotensin-converting enzyme inhibitors for blood pressure control are central nervous system symptoms, specifically lethargy, sedation, and fatigue. These symptoms affect 5% to 10% of patients taking these drugs. The mechanism by which beta-blockers may induce central nervous system effects is uncertain. Relative lipophilicity as a factor affecting penetrance of the blood-brain barrier has not proved to be a reliable predictor of whether the drug will cause such disturbances. Comparisons of atenolol (hydrophilic) and metoprolol (lipophilic) have shown no differences between these drugs with respect to side effects of the central nervous system. The incidence of central nervous system effects with angiotensin-converting enzyme inhibitors is similar to that for most beta-blockers. The precise role of the angiotensin-converting enzyme in the central nervous system is not well defined. Most thiazide diuretics are not associated with major complications of the central nervous system, although electrolyte imbalance may occasionally lead to complaints of neurologic symptoms. Because the incidence of central nervous system effects with these three classes of drugs is so low, concern for the side effects of the central nervous system is not a prime consideration in the choice of an initial antihypertensive agent.

Is there a central nervous withdrawal syndrome associated with discontinuing long-term treatment with propranolol?

Thirty healthy volunteers were treated with beta-adrenoceptor blocking doses of long-acting propranolol for at least 28 days before being randomized to continue propranolol treatment, receive identical placebo under double-blind conditions, or discontinue all treatment. No evidence of a central nervous withdrawal syndrome occurred during the next 28 days as assessed by changes in psychomotor tests, rating scales, visual analogue scales, tremor recordings and melatonin excretion. Three subjects in the placebo withdrawal group but none in the propranolol group complained of insomnia for up to 14 days of the withdrawal period.

Bevantolol. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in hypertension and angina pectoris

Bevantolol is a new beta-adrenoceptor antagonist which possesses a relatively high degree of selectivity for beta 1-adrenoceptors. It is devoid of intrinsic sympathomimetic activity and possesses only weak local anaesthetic properties. Interestingly, bevantolol has been shown to cause a lowering effect on peripheral vascular resistance. Available clinical data indicate that bevantolol, given once or twice daily, is an effective agent in the management of mild to moderate hypertension and stable angina pectoris. In hypertension bevantolol has been shown to be of comparable therapeutic efficacy to both atenolol and propranolol, while in patients with angina pectoris the drug compared favourably with atenolol. During short and long term administration bevantolol has been well tolerated and few patients have withdrawn from treatment because of adverse effects. However, although the properties of bevantolol may offer theoretical advantages in some patients, only a few comparative studies have been reported, and thus it is presently unclear what advantages bevantolol may offer over existing treatments for hypertension or angina pectoris.

Disturbances of sleep and wakefulness associated with the use of antihypertensive agents

Sleep disturbances are frequently associated with the use of antihypertensive drugs. They are observed mainly during the administration of drugs that affect central adrenergic mechanisms. Beta-adrenoceptor antagonists which readily penetrate into the brain (propranolol, pindolol) increase wakefulness and/or decrease REM sleep. Alpha 2-adrenoceptor agonists (clonidine, guanfacine) markedly reduce the duration of REM sleep. The catecholamine depleting agent reserpine increases REM sleep during single or repeated-dose administration, while the MAOI phenelzine shows opposite effects. The 5-HT2 antagonist ritanserin, which is chemically related to the antihypertensive agent ketanserin, increases slow wave sleep while REM sleep is decreased. Sleep disturbances have not been reported during the administration of calcium entry antagonists. However, they seem to modify the effects of hypnotics and CNS stimulants. There are no formal studies on the effects of angiotensin converting enzyme inhibitors and vasodilators on sleep in man.

Lipophilicity, hydrophilicity, and the central nervous system side effects of beta blockers

One of the attributes of beta-adrenergic blocking agents that has distinguished these drugs from each other is degree of lipophilicity. While this feature may play a role in facilitating passage across the blood-brain barrier, it is essential to realize that crossing the barrier is not necessarily synonymous with the ability to cause central nervous system (CNS) effects. Several studies have found some degree of CNS side effects, particularly tiredness and fatigue, with atenolol, a hydrophilic beta blocker. Pindolol, a moderately lipophilic beta blocker, has been reported to cause greater disturbances on electroencephalogram (EEG) than propranolol, the most highly lipophilic beta blocker. The investigational agent bevantolol exhibits a moderate degree of lipophilicity and a low frequency of CNS side effects. Drug-induced increases in plasma catecholamine levels, the possible saturation of CNS receptor sites at relatively low drug levels, and the specific structural details of beta-blocker molecules have been suggested as possible contributory factors in determining the degree of CNS effects.

Quantifying side-effects of beta-blockers: the role of visual analogue scales

Beta-blockers are often prescribed for patients who are asymptomatic and for whom the benefits of therapy are likely to be small. Side-effects are therefore of great importance. Symptoms such as muscle fatigue and peripheral coldness are commonly associated with treatment with beta-blockers but these subjective phenomena are difficult to detect and quantify so that their prevalence and severity are uncertain. Conventional symptom questionnaires may be relatively insensitive and visual analogue scales (VAS), which permit interval quantification of subjective phenomena, may have some advantages. They appear to be able to detect the presence of tiredness of the legs and peripheral coldness among hypertensive patients taking beta-blockers and are more sensitive than descriptive or 'category' questionnaires. However, some patients find VAS hard to understand and a minority of patients score erratically for all symptoms. A most detailed explanation is of paramount importance. Scores derived from VAS surveys are not normally distributed and should be examined using non-parametric statistical methods; normalising transformations do not improve the sensitivity of the method.

Central nervous system effects of beta-adrenergic-blocking drugs: the role of ancillary properties

Among the side effects commonly reported with the use of beta-blockers are symptoms related to the central nervous system (CNS). In this study we compared the effects of four beta-blockers with different ancillary properties (atenolol, metoprolol, propranolol, and pindolol) and placebo on objective and subjective measures of CNS function in 30 healthy male subjects. All subjects were randomly assigned to a double-blind, placebo controlled, Latin-square design study in which five 1 week periods of drug or placebo administration were separated by 2 week washout periods. Laboratory evaluations were conducted at the end of each treatment period, and included multistage exercise stress testing; questionnaire assessments of mood state, sexual function, and sleep habits; tests of psychomotor function; and overnight polysomnographic measures of sleep. Significant effects on sleep continuity were observed for each of the lipophilic drugs, as reflected in the number of awakenings (pindolol = 6.4 +/- 5.0; propranolol = 6.3 +/- 3.2; metoprolol = 7.2 +/- 4.7; atenolol = 3.6 +/- 2.9; placebo = 3.9 +/- 2.7) and time of wakefulness (pindolol = 20.6 +/- 27.0 min; propranolol = 15.5 +/- 23.0 min; metoprolol = 19.5 +/- 24.3 min; atenolol = 10.2 +/- 11.6 min; placebo = 9.2 +/- 74.5 min). Only pindolol significantly affected rapid eye movement (REM) sleep time (pindolol = 54.5 +/- 21.9 min; placebo = 74.5 +/- 74.5 min) and REM latency (pindolol = 175.0 +/- 60.7 min; placebo = 95.4 +/- 43.8 min). Subjective reports of sleep similarly indicated increased wakefulness and greater restlessness with lipophilic beta-blockers.(ABSTRACT TRUNCATED AT 250 WORDS)

Is pindolol a mixed agonist-antagonist at central serotonin (5-HT) receptors?

The effects of the non-selective beta-adrenergic blocking agent pindolol upon central monoaminergic neurotransmission in rats were studied by means of in vivo biochemical methods. It was found that (-)-pindolol elicited a clearcut, selective, dose-dependent and stereospecific reduction of brain 5-HT synthesis rate. The synthesis reduction was not accompanied by any change in the tissue tryptophan levels and could not be prevented by depleting the monoamine stores by means of reserpine. Furthermore, in non-pretreated animals, (-)- but not (+)-pindolol (nor the beta 1- and beta 2-selective adrenoceptor antagonists metoprolol, betaxolol and ICI 118,551) decreased the 5-HIAA level and the 5-HIAA/5-HT ratio while neither enantiomer altered the concentrations of 5-HT or NA, or DA and its metabolites. It is suggested that these effects of (-)-pindolol may be due to direct stimulation of 5-HT receptors in the CNS. The action of the compound is discussed within the context of literature data indicating its ability to act as an antagonist of certain other aspects of 5-HT receptor activation. The possibility is considered that, in addition to its beta-adrenergic properties, (-)-pindolol is a mixed agonist-antagonist at central 5-HT receptors.

Adverse reactions and interactions with beta-adrenoceptor blocking drugs

beta-Blocking drugs are widely used throughout the world and serious adverse reactions are relatively uncommon. Most of those which do occur are pharmacologically predictable and may be avoided by ensuring that patients who are to be given beta-blockers do not have a predisposition to the development of bronchospasm, cardiac failure or peripheral ischaemia. In some situations, the use of a beta 1-selective blocking drug may reduce the risk of a severe adverse reaction, but there is little evidence that other ancillary properties such as partial agonist activity are of relevance in this context. Long term experience with many of the beta-blockers in current use suggests that unpredictable major adverse reactions such as the practolol oculomucocutaneous syndrome are unlikely to be repeated, although some of these drugs may be associated with immunological disturbances and some have been implicated in the development of retroperitoneal fibrosis. beta-Blocking drugs appear to be associated with a number of subjective side effects including muscle fatigue, peripheral coldness and some neurological symptoms. These side effects are highly subjective and are therefore difficult to quantify and it is not known whether they are of major importance in terms of their effect upon patients' overall well-being. It cannot be assumed that simply because such side effects can be elicited that they do, in fact, matter. However, because beta-blockers are often prescribed for patients who have no symptoms and for whom the benefits of therapy are generally small, such side effects would be of considerable importance if they had an overall effect upon quality of life. There are theoretical reasons to suppose that the incidence and severity of such side effects may be related to the ancillary properties of the individual drugs, but there is little evidence that parameters such as beta 1-selectivity, or partial agonist activity are clinically important determinants of the severity of these side effects. Lipophilicity, however, may be associated with an increased incidence of neurological symptoms. beta-Blocking drugs may cause a variety of metabolic disturbances including an increase in serum VLDL-cholesterol concentrations. However, long term studies have not shown that such disturbances are associated with an increased risk of cardiovascular disease, indicating that such metabolic changes may not be of major importance in practice. beta-Blocking drugs may be involved in a number of interactions with other drugs, but few of these have been shown to be of clinical significance.(ABSTRACT TRUNCATED AT 400 WORDS)

The antianxiety effect of beta-blockers on punished responding

Clinically effective anxiolytic drugs generally increase responding that is suppressed by punishment. Although beta-adrenergic antagonists have been reported to reduce anxiety in humans, such effects have not been reported reliably in animal punishment procedures. In the present study, three pigeons were trained to key peck under a multiple schedule. In the presence of a white light every thirtieth response produced grain. In the presence of a red light every thirtieth response produced grain and electric shock which suppressed responding to approximately 10 percent of that occurring in the alternate component. Propranolol (1.0-5.6 mg/kg) and, less reliably, atenolol significantly increased punished responding in a dose-related manner; propranolol effects were approximately twice as large as those of atenolol. Both drugs no more than weakly increased unpunished response rates at doses that increased punished responding. These results suggest that beta-blockers have an antianxiety effect on punished behavior, and that peripheral beta-blockade, the predominant action of beta-blockers regardless of whether they readily penetrate the brain, is likely to be involved in this effect.

Differential effects of atenolol and enalapril on memory during treatment for essential hypertension

A randomized single-blind study was designed to compare the performance on memory tests requiring recall of information relevant to everyday life of two groups of hypertensive patients. One group of 13 patients were taking a beta-adrenoceptor blocker (atenolol) and the other group of 12 patients received the angiotensin-converting enzyme inhibitor (enalapril). The results suggested that when compared with placebo the group of patients treated with enalapril showed no changes in memory function, whilst there was a mild, but consistent deficit in the group taking atenolol.

Acebutolol: ten years of experience

During 10 years of clinical use involving almost 3 million patient-years, acebutolol has become established as a remarkably safe and well-tolerated beta-blocking agent, effective in treating essential hypertension and cardiac arrhythmias. The existence of a long-lived active metabolite (diacetolol) confers a 24-hour duration of action, which permits effective use of a once-daily regimen, particularly for hypertension. Acebutolol has low lipid solubility and low protein binding; the former property reduces the risk of central side effects, and the latter means that displacement interactions with other drugs are unlikely. Because acebutolol and its metabolite normally have both renal and hepatic excretion pathways, an alternative pathway is available should either be compromised through disease. Acebutolol is cardioselective, and clinical use has borne out the low incidence of bronchospasm in patients with impaired lung function. The possession of intrinsic sympathomimetic activity (ISA) leads to only modest reductions in cardiac output, which in turn reduces the chance of excessive bradycardia and the likelihood of precipitating heart failure. A combination of selectivity and ISA may be responsible for the low incidence of tiredness and cold extremities observed with acebutolol compared with other beta blockers. The unique pharmacologic and pharmacokinetic profile of acebutolol confers several therapeutic advantages and may be responsible for the generally low level of side effects experienced in clinical use.

Effect of beta-blockers on psychomotor performance in normal volunteers

The effects of beta-adrenergic receptor antagonists on psychometric tests including vehicle handling, choice reaction time, and kinetic visual acuity (KVA), are reviewed. The beta-blockers had little effect on the performance tests, with the unexplained but reproducible effect of enhanced KVA performance with atenolol. Although the beta-blockers had little effect on performance tests they were shown to have psychotropic effects in normal volunteers. The reasons for the conflicting evidence concerning the effect of these drugs on performance tests is discussed in relation to the present experiments and to variables that may influence response. It is concluded that one should use tests that are as independent as possible from potentially confounding variables. The use of evoked potentials in the electroencephalogram is one such test. A preliminary study is described in which the effects of beta-blockers were detected using visual evoked responses on the electroencephalogram.

CNS-related (side-)effects of beta-blockers with special reference to mechanisms of action

beta-Adrenoreceptor antagonists are liable to produce behavioural side-effects such as drowsiness, fatigue, lethargy, sleep disorders, nightmares, depressive moods, and hallucinations. These undesirable actions indicate that beta-blockers affect not only peripheral autonomic activity but also some central nervous mechanisms. In experimental animals beta-blockers have been found to reduce spontaneous motor activity, to counteract isolation-, lesion-, stimulation- and amphetamine-induced hyperactivity, and to produce slow-wave and paradoxical sleep disturbances. Furthermore, central effects such as tranquilizing influences are used for the treatment of conditions such as anxiety. Several different mechanisms of action could be responsible for these CNS effects: Centrally mediated specific actions on centrally located beta-adrenergic receptors, known to exist downstream from, and at the terminals of, 'vigilance-enhancing' central noradrenergic pathways. Centrally mediated specific actions on centrally located receptors of the non-adrenergic type; an affinity of some beta-blockers towards 5-HT-receptors is well documented. Centrally mediated non-specific actions on centrally located neurones, owing to the membrane-stabilizing effects of beta-blockers. Peripherally mediated actions whereby beta-blockers induce changes in the autonomic activity in the periphery, which are relayed to the CNS to induce changes in activity of a variety of central systems. It can be assumed that with any one of the beta-blockers all these mechanisms come into play, yet with varying degrees depending on characteristics of the drugs such as lipophilicity and hydrophilicity, the ratio of antagonist versus (partial) agonist properties, affinity to 'alien' receptor sites, strength of membrane-stabilizing activity, stereospecific affinity, and potency.

Acute effects of metoprolol on muscle sympathetic activity in hypertensive humans

Recordings of multiunit sympathetic activity were made from muscle branches of the peroneal nerve in eight previously untreated subjects with essential hypertension during intravenous administration of the cardioselective beta-adrenoceptor antagonist, metoprolol. Intraarterial blood pressure and central venous pressure were monitored simultaneously. After metoprolol, heart rate fell and central venous pressure increased in all subjects. Blood pressure increased in some subjects and decreased in others whereas the rate of rise of the systolic pulse wave regularly decreased. Sympathetic activity, discharged in pulse synchronous bursts of action potentials, was quantitated by counting the number of bursts and their amplitudes in the mean voltage neurogram. In all subjects, the average diastole was associated with outflow of more sympathetic impulses after metoprolol than before. Total sympathetic activity (expressed as bursts/min multiplied by mean burst strength) also increased after the drug. The mechanism behind the increase of sympathetic activity may be either a direct central nervous effect or a reflex effect elicited from arterial baroreceptors or cardiac receptors.

Importance of membrane stabilizing effect in massive overdose of propranolol: plasma level study in a fatal case

Plasma propranolol levels were measured in a woman who took 3120 mg of propranolol in a suicide attempt. Highest plasma level, measured at the 12th hour, was 1475 ng/ml. Elimination half life was prolonged to 13.8 h. She suffered from coma and profound hypotension, then died on the 20th day. By estimating brain propranolol concentration from the plasma level, and reviewing the clinical pictures of previously reported cases, we propose that central nervous suppression by propranolol, with membrane stabilizing effect as its pharmacological basis, may cause life threatening abnormalities in patients with massive overdose of propranolol.

Beta-adrenoceptor blocking drugs: adverse reactions and drug interactions

Beta adrenoceptor blocking drugs are relatively well tolerated and adverse reactions to them are not common. The ones that do occur are reviewed in this paper under the following headings: Short term adverse reactions, drug interactions, long term adverse reactions, risks in pregnancy and hazards of abrupt withdrawal. Predictable short term effects may be caused either by the actions of these drugs on the beta 1- or beta 2-receptors. The beta 1 adverse effects are hypotension, bradycardia and cardiac failure; these are best avoided by not giving beta-adrenoceptor blocking drugs to susceptible patients with cardiac disease. The beta 2 adverse effects on the bronchi, the peripheral arteries and various metabolic functions may be reduced to some extent by using a relatively cardioselective drug. Unpredictable short term effects such as fatigue, sexual dysfunction and gastrointestinal symptoms may occur but are not common problems with this group of drugs. Similarly, serious drug interactions are infrequent. Under the heading of long term adverse effects the practolol problem and the risk of causing malignant disorders have been considered. There is no evidence that any of the currently available drugs will cause either a practolol syndrome or malignant disease in man. However, the need for careful appraisal by drug regulatory bodies and continued vigilance by all prescribers of beta-adrenoceptor blocking drugs remains. The possible adverse effects of treatment during pregnancy are also considered. It now appears that beta-adrenoceptor drugs can be used safely in pregnancy but since neonatal bradycardia and hypoglycemia may occur, care should be taken to look for these complications. A serious deterioration may occur when beta-adrenoceptor drugs, given to patients with significant ischemic heart disease, are suddenly stopped. This is a rare occurrence but prescribers should be aware of it.

Beta-adrenoceptor blockade and migraine

Except for propranolol, no other Beta-blocker has been studied thoroughly in the prophylaxis of migraine. Of those studied, propranolol, atenolol and timolol were shown to be useful in double-blind clinical trials. The mode, or even the site of action of these drugs in unknown. Possible mechanisms of action are peripheral vascular effects, a central action, 5-HT antagonism, an anxiolytic effect and a multifactorial action. The only common property of the successful drugs is lack of partial agonist activity and their profiles do not fully support any of the above hypotheses. Trials of drugs in the prophylaxis of migraine have in general been unsatisfactory due to the difficulty in controlling many variables. Beta-blockers with differing properties offer an opportunity to define the properties necessary for anti-migraine activity and perhaps shed light on the pathogenesis of migraine.