The effect of a non-selective lipophilic beta-blocker on the blood pressure and noradrenaline, vasopressin, cortisol and renin release during alcohol withdrawal

Ocular Intracameral Pharmacokinetics for a Cocktail of Timolol, Betaxolol, and Atenolol in Rabbits

The mechanisms of drug clearance from the aqueous humor are poorly defined. In this study, a cocktail approach was used to simultaneously determine the pharmacokinetics of three β-blocker agents after intracameral (ic) injection into the rabbit eyes. Aqueous humor samples were collected and analyzed using LC-MS/MS to determine drug concentrations. Pharmacokinetic parameters were obtained using a compartmental fitting approach, and the estimated clearance, volume of distribution, and half-life values were the following: atenolol (6.44 μL/min, 687 μL, and 73.87 min), timolol (19.30 μL/min, 937 μL, and 33.64 min), and betaxolol (32.20 μL/min, 1421 μL, and 30.58 min). Increased compound lipophilicity (atenolol < timolol < betaxolol) resulted in higher clearance and volume of distributions in the aqueous humor. Clearance of timolol and betaxolol is about 10 times higher than the aqueous humor outflow, demonstrating the importance of other elimination routes (e.g., uptake to iris and ciliary body and subsequent elimination via blood flow).

Rats in acute withdrawal from ethanol exhibit left ventricular systolic dysfunction and cardiac sympathovagal balance shift

There is strong evidence that sympathovagal balance plays an important role in the progression of cardiac dysfunction in non-alcoholics. The purpose of this investigation was to determine whether a pattern of continuous ethanol intake and withdrawal modulates the cardiac sympathovagal balance and left ventricular (LV) systolic function in rats. Male Wistar rats were treated with a continuous ethanol liquid diet for 49 days, and then subjected to 1-day withdrawal and 21-day abstinence. Cardiac sympathovagal balance and LV systolic function were evaluated based on heart rate variability (HRV), Western blotting, and echocardiography. Longitudinal data obtained from the same rats showed that the 49-day continuous ethanol treatment induced LV systolic dysfunction, expressed by decreased fractional shortening and ejection fraction. At the 1-day withdrawal, LV systolic dysfunction was deteriorated, and the low-frequency power/high-frequency power (LF/HF) ratio in HRV was elevated because of the depressed HF and the increased LF. Western blot analysis showed an increased expression of myocardial tyrosine hydroxylase and a decreased expression of myocardial acetylcholine. All anomalies were recovered to baseline values with 21-day abstinence. We concluded that acute withdrawal from a 49-day continuous ethanol regimen is sufficient to promote the shift of cardiac sympathovagal balance toward sympathetic predominance and reduced vagal tone, contributing to the further deterioration of LV systolic function in rats. Those providing medical care for alcoholics should be aware of this enhanced susceptibility to LV systolic dysfunction with abrupt termination of a continuous ethanol regimen.

Reduced baroreflex sensitivity in acute alcohol withdrawal syndrome and in abstained alcoholics

Acute alcohol withdrawal is often associated with increased sympathetic activity, and a decreased baroreflex sensitivity (BRS) can be assumed. Parameters of heart rate variability (HRV), blood pressure variability (BPV), BRS as well as cardiac index (CI), left ventricular work index (LVWI) and total peripheral resistance (TPR) were investigated in 20 patients undergoing acute alcohol withdrawal and matched controls. Measures were obtained during the peak of withdrawal symptomatology prior to treatment as well as 2 and 24h under continuous clomethiazole treatment. Alcohol withdrawal scores were obtained and correlated with autonomic measures. In addition, parameters were assessed in 15 subjects who abstained from alcohol after long-term intake. We found a severe down-regulation of BRS during acute alcohol withdrawal and to a milder extent in abstained alcoholics. Furthermore, HRV and BPV did not unequivocally reveal signs of elevated sympathetic activity. Non-linear parameters of HRV and parameters of BRS correlated with the severity of AWS. The distinct decrease of BRS in AWS and in long-term abstained subjects described here is of importance since similar alterations have been identified as independent prognostic factors for cardiac mortality in other diseases.

Mechanisms of cardiovascular dysregulation during alcohol withdrawal

Alcohol withdrawal (AW) is often accompanied by functional cardiovascular abnormalities which return to normal in few days. However, in some patients, they can predict future alterations in the cardiovascular system, even if they remain in abstinence. These changes are mediated by several central and peripheral mechanisms closely related to AW. The level of activation in the sympathetic nervous system is an important factor regulating the functioning of the cardiovascular system in AW directly and/or indirectly with L-type calcium channels and nitric oxide (NO). Other factors may contribute to cardiovascular alterations in AW including the renin-angiotensin-aldosterone system, vasopressin, cortisol and sodium sensitivity. Monitoring of the cardiovascular system is needed in patients undergoing treatment for AW. The patients with elevated systolic blood pressure (SBP) and diastolic blood pressure (DBP) after resolution of AW may require a fuller work-up of their cardiovascular system.

L-type Ca2+ channels mediate cardiovascular symptoms of alcohol withdrawal in humans

The cardiovascular effects and plasma concentrations after intravenous verapamil injection (5 mg) were compared in seven alcohol dependents during alcohol withdrawal syndrome (AWS) to those after resolution of these symptoms. At the onset of AWS, verapamil caused a bradycardiac response, which was absent after resolution of AWS. At the same period, a hypotensive effect of verapamil was weakened. No differences in verapamil plasma concentrations were observed between different periods. These results suggest that L-type Ca(2+) channels are involved in mediating cardiovascular symptoms of AWS.

Overexcitement and disinhibition. Dynamic neurotransmitter interactions in alcohol withdrawal

In alcohol withdrawal, abnormalities occur in a number of neurotransmitter systems: there is reduced inhibitory function, and increased activity of excitatory systems. The former, indicated by reduced GABA and alpha-2-adrenoceptor activity, acts in conjunction with, and is exacerbated by, the latter, which itself may be due to the potentiation of NMDA activity by depletion of magnesium, and overactivity of catecholaminergic and CRF neurones. These dysfunctions produce immediate effects and may also contribute to the long-term changes in brain excitability by a kindling-like process. It is possible that early and active treatment may oppose this process. Present strategies for treatment of alcohol withdrawal enhance GABA and alpha-2 inhibitory, or reduce excitatory, mechanisms. Future possibilities include the use of CRF and/or NMDA antagonists.

The effects of acute and chronic ingestion of ethanol on the autonomic nervous system

Evidence is reviewed linking clinical effects of ethanol with actions on the sympathetic and parasympathetic nervous systems. The studies reported include a series of investigations by the authors. Acutely, ethanol causes peripheral vasodilation and may also result in changes in heart rate and blood pressure. Ethanol may contribute to acute problems which may present clinically, including micturition syncope, accidental hypothermia and facial flushing. However, increased sympathetic nervous activity plays a role in causing hypertension and other symptoms during ethanol withdrawal in chronic alcoholics. Some chronic alcoholics may have neuropathy involving sympathetic nerves, and this can result in distal sweating loss and occasionally in orthostatic hypotension. Also, hypothalamic lesions associated with Wernicke's encephalopathy may result in hypothermia. Neuropathy involving parasympathetic nerves in not uncommon in alcoholics with other evidence of nervous system damage, but it is generally asymptomatic. Occasionally, vagal neuropathy may cause disorder of gastrointestinal motility, and neuropathy affecting the sacral innervation may be a factor in alcoholic impotence.

Alcohol and hypertension: implications from research for clinical practice

Despite the fact that recent epidemiological and laboratory studies appear to confirm that alcohol has an effect upon blood pressure, its impact has largely been ignored in clinical practice. This study was undertaken in an effort to answer four basic questions Is there an association between blood pressure and ethanol ingestion and if so is it causal or related to common genetic and/or environmental factors?; If an association exists, what is its likely physiological mechanism?; What additional studies are needed in order to further elucidate the relationship between alcohol and blood pressure?; What clinical recommendations, if any, are justified with our present state of knowledge?

Pseudo-phaeochromocytoma due to alcohol withdrawal

Alcohol withdrawal hypertension is a common clinical problem which often goes unrecognized. We report a case in which the symptoms and signs of withdrawal with a marked elevation in blood pressure mimicked the features of a phaeochromocytoma. Despite a positive phentolamine test no further evidence for phaeochromocytoma was found and both blood pressure and symptoms settled as the features of alcohol withdrawal abated.