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

Beta-blockers and depression: the more the murkier?

OBJECTIVE

To review the literature regarding the purported association between oral ingestion of beta-blocker drugs and depressed mood.

DATA SOURCE

MEDLINE was searched for published articles using the key words propranolol, atenolol, metoprolol, nadolol, timolol, beta-blocker, beta-adrenergic antagonist, or beta-adrenergic blocker in combination with the key words depression, depressive symptomatology, major depressive disorder, or depressed mood from January 1966 through December 1996.

DATA SYNTHESIS

Findings regarding the association are equivocal. Plausible explanations include study design, case definition, and confounding disease states. Most of the evidence supporting an association has used case series and case reports. Findings from cross-sectional observational studies and case-control studies are equivocal. Case definition and measurement instruments may partially explain these inconsistencies. Studies using a diagnosis of depression generally do not support the relationship. Trials using depressive symptoms are about evenly split, but they have generally enrolled a small number of patients and have questionable statistical power. Studies defining antidepressant prescriptions dispensed as a marker for depression generally support the association. Evidence exists both for and against the hypothesis that lipophilic beta-blockers cause more depression than do hydrophilic beta-blockers.

CONCLUSIONS

beta-Blockers may have been unjustly associated with depression and their use avoided for that reason. Future studies into the association between depression and beta-blocker use should evaluate whether the association is affected by case definition and study design characteristics, including disease, dose-response, bias, measurement error, or ability to precisely measure the length of the exposure.

A pilot study of nadolol for overt aggression in developmentally delayed individuals

OBJECTIVE

The aim of this preliminary pilot study was to investigate the safety and efficacy of open-label nadolol as an adjunctive pharmacological treatment for aggression and/or inattention/overactivity in a developmentally delayed child, adolescent, and young adult population.

METHOD

Twelve subjects enrolled and completed (mean age 13.8 years, range 9 through 24) a 5-month, open, prospective protocol of nadolol (mean dose 109 mg, range 30 through 220 mg) with systematic baseline and outcome evaluations and weekly clinical assessment.

RESULTS

All subjects were developmentally delayed and most were cognitively delayed. Ten subjects (83%) showed clinical improvement while receiving nadolol. Significant improvements were noted on observer-rated overt categorical aggression, severity of illness, and global impressions of improvement. No significant effects were found for inattention/overactivity. Nadolol was well tolerated, with few side effects.

CONCLUSIONS

Overt categorical aggression presenting in developmentally delayed children, adolescents, and young adults may respond to nadolol treatment.

Systemic side effects of topical beta-adrenergic blockers

Glaucoma, a disease that affects between 1 and 3% of the population above the age of 60, is most commonly treated by topical beta-adrenergic blockers. Although effective in lowering intraocular pressure and helping to preserve sight, beta blockers also may have adverse influences on the cardiac, pulmonary, and central nervous systems, and on endocrine functions. Clinicians' awareness that their patients may be treated with topical beta blockers will help them to elicit this information and the history, prescribe the medicine correctly, and be cognizant of a possible role this medicine may have in any deterioration of a patient's systemic clinical status.

Prediction of sleep disorders induced by beta-adrenergic receptor blocking agents based on receptor occupancy

beta-adrenergic receptor blocking agents (beta-blocking agents) have been widely used clinically for the treatment of various cardiovascular conditions. However, beta-blocking agents are liable to cause sleep disturbance, such as vivid dreams, nightmares, increased waking, and insomnia. The mechanisms of the sleep disorders are not known, but several may conceivably be responsible for these CNS-related side effects. In the present study, we hypothesized that the sleep disorders are induced by the blockade of central or peripheral beta 2 receptors and/or central serotonin (5-HT) receptors. To verify the hypothesis, we retrospectively analyzed the relationships between the extent of the sleep disorders and the beta 1, beta 2, or 5-HT receptor occupancies for four beta-blocking agents (atenolol, metoprolol, pindolol, and propranolol). No significant correlations were observed among pharmacokinetic/physicochemical parameters (therapeutic dose, plasma concentration, plasma unbound concentration, cerebrospinal fluid concentration, and lipid solubility) and pharmacodynamic parameters (the scores of the sleep disorders such as the number of dreams). Furthermore, no significant relationship (correlation coefficient: r < 0.3) was observed between beta 1 receptor occupancies of the drugs and the number of dreams. On the other hand, good relationships (r > 0.95) were observed between central and peripheral beta 2 or central 5-HT receptor occupancies and the number of dreams. These findings suggest that beta 2 and/or 5-HT receptor occupancy is superior to beta 1 receptor occupancy as an index for the sleep disorders.

Changes in depressive status associated with topical beta-blockers

Depression and sexual dysfunction have been related to side effects of topical beta-blockers. We performed a preliminary study in order to determine any difference between a non selective beta-blocker (timolol) and a selective beta-blocker (betaxolol) regarding CNS side effects. Eight glaucomatous patients chronically treated with timolol 0.5%/12h, suffering from depression diagnosed through DMS-III-R criteria, were included in the study. During the six-month follow up, depression was quantified through the Beck and Zung-Conde scales every two months. In a double blind cross-over study with control group, the patients under timolol treatment presented higher depression values measured through the Beck and the Zung-Conde scales (p < 0.001 vs control). These results suggest that betaxolol could be less of a depression-inducer than timolol in predisposed patients.

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.

Side effects of beta-blocker treatments as related to the central nervous system

During the last decade beta-adrenoceptor antagonists have become one of the first-line treatments for hypertension. Generally, they have been shown to be safe with a low frequency of serious side effects. However, minor subjective symptoms, usually considered to be CNS-related, have been reported for all beta-blockers used. Thus, all beta-blockers on the market seem to have a high benefit:risk ratio; independent of their physicochemical properties and pharmacodynamic profile, however, they seem to cause CNS-related side effects to about the same extent. These minor side effects, the mechanisms of which are unclear, consist of subtle effects on general well being, decreased initiative, a depressed frame of mind, and disturbed sleep. Generally, however, beta-blockers in therapeutic dosages do not affect the qualitative functions of the brain. The results so far available have been obtained primarily by using objective methods. Further comparison has now been initiated using documented subjective methods to investigate whether the objectively documented differences are of any clinical relevance to the patient's quality of life. Although it cannot be claimed with certainty, nonselective beta-blockers seem to cause CNS-related side effects to a greater extent than beta 1-selective blockers. Differences in the degree of hydrophilicity of the beta-blocker are apparently of no clinical relevance in this respect. Rather, the plasma concentration of the beta-blocking drug (degree of beta-blockade) seems to be the major determinant of whether or not CNS-related symptoms appear in susceptible patients.

Comparison of CNS-related subjective symptoms in hypertensive patients treated with either a new controlled release (CR/ZOK) formulation of metoprolol or atenolol

The present study evaluated and compared subjective symptoms in hypertensive patients (N = 83) at therapeutically comparable dosages of a new controlled release (CR/ZOK) formulation of metoprolol (100 mg od) and atenolol (50 mg od). The trial was a 4-week randomized double-blind study preceded by a placebo run-in period. Blood pressure (BP) was recorded 24 hours after intake of last dose. In subpopulations, 24-hour ambulatory BP was recorded and exercise tests performed. Subjective symptoms were evaluated with a previously documented questionnaire (MSE-profile) which has been shown to be sensitive in detecting CNS-related symptoms caused by beta blockers. The MSE-profile includes three dimensions: Contentment, Vitality and Sleep. The results showed that there were no significant differences between the groups in BP reduction either at 24 hours or over the entire 24-hour dose interval. Furthermore, the degree of beta 1-blockade (reduction in exercise-induced tachycardia) 24 hours after last dose did not differ between the groups. There were no significant differences regarding subjective symptoms (Contentment, Vitality, Sleep) between the two treatment groups. An a posteriori power analysis showed that the power to detect a true difference was of an acceptable magnitude. In conclusion, there was no difference in CNS-related symptoms between metoprolol and atenolol at therapeutically comparable dosages indicating that the degree of lipophilicity may be of minor importance for the occurrence of such symptoms.

CNS side effects of centrally-active antihypertensive agents: a prospective, placebo-controlled study of sleep, mood state, and cognitive and sexual function in hypertensive males

A prospective, placebo-controlled, comparative evaluation was conducted on two widely prescribed, sympatholytic antihypertensive agents with known CNS effects. In order to separately assess these effects in younger and older male hypertensives, patients were assigned to either of two treatment studies based on age. For study I, 24 males aged 31-59 (mean = 49.8; SD = 7.4) with mild hypertension (mean DBP = 100.2 mm Hg; SD = 8.0) received 3 months of treatment with propranolol (20-80 mg bid), clonidine (0.1-0.3 mg bid), or double-blind placebo in a counterbalanced, crossover design. For study II, 23 elderly hypertensive males (mean DBP = 102.6 mm Hg; SD = 8.2) aged 60-78 years (mean = 65.1; SD = 4.6) were randomized to propranolol (20-40 mg bid) or double-blind placebo therapy. Patients received cognitive testing, mood assessments, and all-night polysomnographic evaluations before and after each treatment period. Multivariate analysis of EEG sleep data was statistically significant for study I, with significant univariate effects on four of the six primary sleep variables: total sleep time was reduced, sleep maintenance decreased, REM latency increased, and percent total REM time was reduced. A similar MANOVA analysis for the effects of treatment on the sleep of older patients (study II) was not significant. However, propranolol administration was found to be associated with a significant decline in cognitive performance in these patients. Significant mood effects were observed with each of the study drugs, and nocturnal penile tumescence (NPT) was significantly decreased in both younger and older patients. Overall, this research suggests that distinct patterns of CNS effects are associated with each of the antihypertensive agents studied.

The importance of lipid solubility and receptor selectivity of beta-adrenoceptor blocking drugs for the occurrence of symptoms and side-effects in out-patients

Short-term studies indicate that the side-effects of adrenergic beta-receptor blockade may be influenced by lipid solubility and receptor selectivity of the blockers. The aim of the present study was to investigate the extent to which lipid solubility and receptor selectivity are related to the occurrence of symptoms during ordinary beta-blocker treatment in out-patients. Two hundred and five patients (mean age 60 years) on beta-blockade were interviewed about their symptoms. Eighty-five per cent of the patients had been on beta-blocker treatment for more than 1 year. The blockers most commonly used were atenolol (51.0%), timolol (20.0%), propranolol (18.5%) and metoprolol (7.8%). beta-Blocker treatment was associated with a significantly increased frequency of central nervous system and peripheral symptoms. The increase in central nervous system symptoms was significantly smaller in those on beta-blockers with low rather than with intermediate (P = 0.015) or high lipid solubility (P = 0.007). The increase in peripheral symptoms was not significantly different with beta 1-selective and non-selective blockers. The results indicate that the liability of beta-blockers to cause side-effects on the central nervous system is determined partly by their lipid solubility, and that receptor selectivity has only a small impact on their tendency to cause peripheral side-effects.

Propranolol does not alter cerebral blood flow and functions in cirrhotic patients without previous hepatic encephalopathy

Since it has been suggested that propranolol could lead to hepatic encephalopathy, we undertook a study to assess the effects of propranolol on cerebral blood flow and cerebral functions. Sixteen patients with alcoholic cirrhosis and large esophageal varices and without major hepatic dysfunction (Child-Pugh score less than 14) or previous hepatic encephalopathy were randomized to receive either propranolol or placebo. The following measurements were performed before and 15 min after single intravenous administration of 15 mg propranolol or placebo and again 1 week after chronic oral administration of propranolol 160 mg per day or placebo: cerebral blood flow by the xenon-133 inhalation technique, quantitative electroencephalogram, psychometric test (number connection test), arterial ammonia, pH and pCO2, resting and exercise heart rates (after single administration, electroencephalogram, number connection test and biochemical measurements were not performed). Cerebral blood flow was not significantly modified by treatment (propranolol group: 80 +/- 23 vs. 76 +/- 11 and 83 +/- 9; placebo group: 73 +/- 10 vs. 75 +/- 11 and 81 +/- 18 ml per 100 gm per min, respectively, before and after single and repeated administration). Likewise, neither of the two treatments significantly altered number connection test, quantitative electroencephalogram index, arterial ammonia, pH and pCO2. We conclude that, in this population of cirrhotic patients, propranolol did not alter cerebral blood flow or neuropsychological functions. As a consequence, hemodynamic alterations cannot be considered as causes of possible cerebral side effects of propranolol in cirrhotic patients without severe hepatic dysfunction and previous hepatic encephalopathy.

Differential enhancement of rapid eye movement sleep signs in the cat: a comparison of microinjection of the cholinergic agonist carbachol and the beta-adrenergic antagonist propranolol on pontogeniculo-occipital wave clusters

The cholinergic agonist carbachol and the beta-adrenergic antagonist propranolol were microinjected at the same pontine sites and their effects on polygraphic rapid eye movement (REM) sleep, especially pontogeniculo-occipital (PGO) waves, were measured. While both propranolol and carbachol enhanced PGO wave activity and polygraphic REM sleep, the carbachol-correlated enhancement was more impressive. The increases in REM sleep signs elicited by carbachol were 5-fold over baseline and lasted throughout the 4-h recording period. Propranolol elicited 2.5-fold increases that were significant in the first 2 h only. Yet, the increase in PGO wave activity evoked by propranolol was equal to that of carbachol during non-REM sleep and wakefulness. The results indicate that while propranolol is less potent in activating the distributed neuronal network responsible for REM sleep generation, it selectively facilities that part of the network responsible for PGO waves.

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.

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)