Comparison of metoprolol as hydrochlorothiazide and antihypertensive agents

Risk of acute myocardial infarction after discontinuation of antihypertensive agents: a case-control study

We performed a nested case-control study in a cohort of antihypertensive drug users to assess the association between discontinuation of different antihypertensive agents and the risk of acute myocardial infarction (AMI). Cases and controls were drawn from the Utrecht Cardiovascular Pharmacogenetics database. Patients who were hospitalised for their first AMI were considered cases and controls were not hospitalised for AMI. Antihypertensive users were defined as current users if the index date (date of AMI) fell within the prescribed duration or as discontinuers if this date fell outside the prescribed duration. According to the recency of discontinuation, discontinuers were divided into the following: recent discontinuers (⩽90 days), intermediate-term discontinuers (91-180 days) and long-term discontinuers (>180 days). We found that the risk of AMI was significantly increased in discontinuers, regardless of time since discontinuation, of beta-blockers (adjusted odds ratio (OR) 1.54; 95% confidence interval (CI; 1.25-1.91), P-value<0.0005), calcium channel blockers (CCBs; adjusted OR 2.25; 95% CI (1.53-3.30), P-value<0.0005) and diuretics (adjusted OR 1.76; 95% CI (1.24-2.48), P-value=0.002) compared to current users of these drugs. Moreover, the risk of AMI was significantly increased in long-term discontinuers (beta-blockers, CCBs, angiotensin-converting enzyme inhibitors and diuretics) and intermediate-term discontinuers (beta-blockers and CCBs) versus current users of these drugs. There was no difference in AMI risk between recent discontinuers of antihypertensive drugs versus current users of these drugs. In conclusion, discontinuation of antihypertensive drugs increases the risk of AMI after >90 days of discontinuation. This further underlines the importance of persistence to antihypertensive drug therapy to reduce the risk of AMI in patients with hypertension.

Peripheral vasoconstriction induced by β-adrenoceptor blockers: a systematic review and a network meta-analysis

AIM

Peripheral vasoconstriction has long been described as a vascular adverse effect of β-adrenoceptor blockers. Whether β-adrenoceptor blockers should be avoided in patients with peripheral vascular disease depends on pharmacological properties (e.g. preferential binding to β1 -adrenoreceptors or intrinsic sympathomimetic activity). However, this has not been confirmed in experimental studies. We performed a network meta-analysis in order to assess the comparative risk of peripheral vasoconstriction of different β-adrenoceptor blockers.

METHOD

We searched for randomized controlled trials (RCTs) including β-adrenoceptor blockers that were published in core clinical journals in the Pubmed database. All RCTs reporting peripheral vasoconstriction as an adverse effect of β-adrenoceptor blockers and controls were included. Sensitivity analyses were conducted including possibly confounding covariates (latitude, properties of the β-adrenoceptor blockers, e.g. intrinsic sympathomimetic activity, vasodilation, drug indication, drug doses). The protocol and the detailed search strategy are available online (PROSPERO registry CRD42014014374).

RESULTS

Among 2238 records screened, 38 studies including 57 026 patients were selected. Overall, peripheral vasoconstriction was reported in 7% of patients with β-adrenoceptor blockers and 4.6% in the control groups (P < 0.001), with heterogeneity among drugs. Atenolol and propranolol had a significantly higher risk than placebo, whereas pindolol, acebutolol and oxprenolol had not.

CONCLUSION

Our results suggest that β-adrenoceptor blockers have variable propensity to enhance peripheral vasoconstriction and that it is not related to preferential binding to β1 -adrenoceptors. These findings challenge FDA and European recommendations regarding precautions and contra-indications of use of β-adrenoceptor blockers and suggest that β-adrenoceptor blockers with intrinsic sympathomimetic activity could be safely used in patients with peripheral vascular disease.

Safety and tolerability of metoprolol OROS in hypertension treatment

One hundred twenty-six patients with mild to moderate hypertension responsive to beta-adrenergic blocking agents--alone or in combination with other antihypertensive drugs--entered this open-label, multicenter study designed to evaluate the safety and tolerability of metoprolol OROS (metoprolol fumarate). Metoprolol OROS was given once daily for 14 weeks in doses ranging from 100 to 600 mg. Satisfactory blood pressure control was achieved by 85% of the patients at doses between 100 and 400 mg. Mean diastolic blood pressure was maintained at or below 90 mm Hg. Adverse reactions were experienced by 29% of the patients; most of these reactions were mild or moderate, and none was unexpected for treatment with a beta-blocker. Only three patients withdrew because of adverse reactions. The results of this study indicate that metoprolol OROS given once daily is safe and well tolerated.

The case for low dose diuretics in hypertension: comparison of low and conventional doses of cyclopenthiazide

In a double blind placebo controlled randomised parallel study the antihypertensive activity and adverse biochemical effects of three doses of cyclopenthiazide were evaluated in patients with mild essential hypertension that had been recently diagnosed or was being treated with a single drug. After a four week placebo washout period 53 patients with diastolic blood pressures between 90-110 mm Hg were randomly assigned to 50, 125, or 500 micrograms cyclopenthiazide or matching placebo for an eight week period of treatment. Blood pressure was measured in the patients' homes by the same observer every two weeks. Serum urea, electrolytes, urate, and creatinine concentrations and 24 hour urinary sodium excretion were monitored every four weeks and serum magnesium concentration and plasma renin activity at the end of the washout and treatment periods. After eight weeks of treatment systolic and diastolic blood pressures were significantly reduced in patients taking 125 and 500 micrograms cyclopenthiazide when compared with those taking placebo. The decrement in serum potassium concentration (0.6 mmol/l) and increase in serum urate concentration 0.06 mmol/l) were greatest with the 500 micrograms dose, the increase in serum urate concentration alone being significant. No change in serum magnesium concentration or 24 hour urinary sodium excretion was noted with any dose of cyclopenthiazide. Only the 500 micrograms dose of cyclopenthiazide significantly increased the mean plasma renin activity (1.8 (95% confidence interval 0.2 to 3.4)-5.4 (3.9 to 6.8) nmol angiotensin I/l/h); the other doses like the placebo had no effect. Cyclopenthiazide 125 micrograms, a dose lower than is currently marketed, produced a similar hypotensive response to 500 micrograms of the drug without upsetting the biochemical profile.

Dose response to hydrochlorothiazide in hypertensives receiving a calcium channel blocker

Seven hypertensive patients receiving the dihydropyridine calcium channel blocking agent nicardipine were given placebo, 6.25, 12.5, 25 and 50 mg hydrochlorothiazide (HCTZ) in a randomized crossover design. Blood pressure (BP) decreased by about 7/3 mmHg irregardless of dose. In contrast, potassium, glucose and uric acid increased in a dose-dependent fashion. The hypokalemic and hyperglycemic responses at 50 mg were larger than usually seen with HCTZ. Low doses of HCTZ provided a modest antihypertensive effect, but 25 and 50 mg of HCTZ were no more effective in lowering BP and gave unusually large metabolic side effects when combined with a calcium channel blocker.

Clinical consequences of abrupt drug withdrawal

Syndromes due to the abrupt withdrawal of drug treatment occur mainly with adrenal corticosteroids and agents with an action on either the cardiovascular system or central nervous system. The abrupt withdrawal of antihypertensive therapy typically results in symptoms of overactivity in the sympathetic nervous system. Clonidine and beta-adrenoceptor antagonists are clinically the most important of these agents, but numerous other drugs have been implicated. Overall, the problem is small when viewed in the context of the huge scale of prescribing of antihypertensive medicines. A more serious problem is the occurrence of crescendo angina following the abrupt withdrawal of beta-adrenoceptor antagonists. Although other factors may be involved, adaptive up-regulation of beta-adrenoceptor density is the most likely cause of crescendo angina, and renders the patient more susceptible to sympathetic nervous stimulation following withdrawal of treatment. Besides leading to a recrudescence of the disease being treated, the withdrawal of corticosteroids can cause a variety of syndromes. In particular, problems can arise as a result of treatment-induced suppression of the hypothalamic-pituitary-adrenal (HPA) axis. Another steroid withdrawal syndrome of unknown aetiology, without significant abnormalities of the HPA axis occurring, has been described. Benign intracranial hypertension may rarely follow steroid withdrawal in children. The syndromes associated with withdrawal of drugs which have an action on the CNS are poorly understood. Withdrawal of neuroleptic drugs can be followed by symptoms that resemble those described following withdrawal of anticholinergic drugs, and those agents with the greatest muscarinic-receptor-blocking properties are those which are most frequently implicated. However, the less common withdrawal dyskinesias are thought to reflect up-regulation of dopaminergic receptors during long term treatment. Gastrointestinal symptoms predominate following the abrupt withdrawal of antidepressants but hypomania and an 'akathisia-like' syndrome have been reported. Barbiturates are no longer recommended as hypnotics because of severe effects of withdrawal and the existence of safer alternatives. Short acting barbiturates can be withdrawn by replacement with either phenobarbitone (phenobarbitol) or diazepam and subsequent gradual reduction in dose. The recognition of dependency on benzodiazepines has been slow because of the similarity of mild withdrawal symptoms to the original problem which led to treatment being offered.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in blood pressure, heart rate and thyroid hormones after sudden withdrawal of pindolol and atenolol in hypertensive patients

In a double-blind study 19 patients with mild and uncomplicated arterial hypertension were randomized to treatment with either pindolol 10 mg or atenolol 100 mg once daily for 4 weeks. After abrupt withdrawal a minor overshoot of free-T3 was seen in both groups. This was, however, statistically significant in the pindolol group only. The only overall haemodynamic changes which was observed after the withdrawal was an overshoot in heart rate in the standing position in the atenolol group. Great inter-individual differences in the haemodynamic parameters were found, however, and changes suggestive for withdrawal syndrome were found in 14 patients (pindolol = 7). The time for this overshoot varied considerably from 48-132 h post-drug in both groups. No correlation between the alterations in free-T3 and the cardiovascular parameters was found.

Is low-dose hydrochlorothiazide effective?

In a double-blind crossover study, 13 patients with pretreatment diastolic blood pressure between 95 and 109 mm Hg received nadolol, 80 mg/day, plus placebo of hydrochlorothiazide and nadolol, plus three different doses of active hydrochlorothiazide. Patients remained on each active regimen for 3 weeks, with an intervening placebo period of 2 to 4 weeks. With 12.5 mg of hydrochlorothiazide daily plus nadolol, there was no greater reduction of blood pressure than with nadolol alone. A dose of 25 mg of hydrochlorothiazide was associated with a significantly greater decrease in systolic but not diastolic pressure, as compared with nadolol alone. A significantly greater reduction in both systolic and diastolic blood pressure was obtained only with the 50 mg/day dose of hydrochlorothiazide. Extension to 6 weeks of treatment with 12.5 mg/day failed to lower the blood pressure more than the level seen at 3 weeks. These results suggest that in combination with nadolol, 12.5 mg of hydrochlorothiazide per day has no significant antihypertensive effect. There was no evidence of a flat dose-response curve in the daily dose range of 12.5 to 50 mg. For most patients, a dose of 50 mg of hydrochlorothiazide was required to lower both systolic and diastolic blood pressure significantly below the level obtained with nadolol alone.

Abrupt withdrawal of beta-blockade therapy in patients with myocardial infarction: effects on infarct size, left ventricular function, and hospital course

The effects of abrupt withdrawal or continuation of beta-blockade therapy during acute myocardial infarction were evaluated in 326 patients participating in the Multicenter Investigation of the Limitation of Infarct Size (MILIS). Thirty-nine patients previously receiving a beta-blocker and randomly selected for withdrawal of beta-blockers and placebo treatment during infarction (group 1) were compared with 272 patients previously untreated with beta-blockers who were also randomly assigned to placebo therapy (group 2). There were no significant differences between the two groups in MB creatine kinase isoenzyme (15.8 +/- 10.9 vs 18.2 +/- 14.4 g-eq/m2, respectively) estimates of infarct size, radionuclide-determined left ventricular ejection fractions within 18 hr of infarction (0.44 +/- 0.15 vs 0.47 +/- 0.16) or 10 days later (0.42 +/- 0.14 vs 0.47 +/- 0.16), creatine kinase-determined incidence of infarct extension (13% vs 6%), congestive heart failure (43% vs 37%), nonfatal ventricular fibrillation (5% vs 7%), or in-hospital mortality (13% vs 9%). Patients in group 1 had more recurrent ischemic chest pain (p = .002) within the first 24 hr after infarction, but not thereafter. However, this did not appear to be related to a rebound increase in systolic blood pressure, heart rate, or double product. In a separate analysis, 20 propranolol-eligible group 1 patients randomly selected for withdrawal of beta-blockade (group 3) were compared with 15 patients randomly selected for continuation of prior beta-blockade therapy (group 4). This comparison yielded similar results. These data indicate that the beta-blockade withdrawal phenomenon is not a major clinical problem in patients with acute myocardial infarction. beta-Blockade therapy can be discontinued abruptly during acute myocardial infarction if clinically indicated.

Alternative pharmacologic approaches to the initial management of hypertension

Recent clinical trials in hypertension report more deaths due to coronary heart disease in mild hypertensives who received aggressive antihypertensive drug therapy and achieved better blood pressure control. Subset analyses of these trials suggest that diuretic therapy may have contributed to this outcome, possibly through a reduction in serum potassium or an elevation in serum lipids. Because of this, patients with an abnormal pretreatment electrocardiogram, history of myocardial infarction, unstable coronary heart disease, or diuretic-induced hyperlipidemia or hypokalemia unresponsive to management are candidates for alternative antihypertensive agents. A review of the literature suggests that most of the currently available beta-blockers, the alpha 1-antagonist prazosin, the angiotensin-converting enzyme inhibitor captopril, and the vasodilator hydralazine are effective alternatives to thiazide therapy in the initial management of hypertension and are recommended for particular subgroups of patients. Monotherapy with the centrally and peripherally acting sympatholytic agents is not recommended because of the frequent side effects encountered and the inferior hypotensive efficacy reported. Calcium channel blocking agents also appear to be suitable alternatives to thiazides in hypertension, but more experience with these is needed. Alternative pharmacologic agents may be selected on the basis of age, and, to a lesser extent, race.

Abrupt withdrawal of atenolol in patients with severe angina. Comparison with the effects of treatment

The effects of abrupt withdrawal of atenolol, a long acting cardioselective beta blocker, were studied in 20 patients with severe stable angina pectoris admitted to hospital for coronary arteriography. During the 144 hour postwithdrawal period no serious coronary events occurred. Mean and maximal daily heart rates rose steadily for at least 120 hours. No important arrhythmias were noted on ambulatory electrocardiographic monitoring. Treadmill exercise testing at 120 hours showed little reduction in the times to angina, ST depression, and maximal exercise when compared with those recorded at 24 hours. This deterioration was small when contrasted with the improvements in these indices produced by atenolol treatment in a similar group of patients not admitted to hospital. No change in catecholamine concentrations or acceleration of the heart rate response to exercise occurred after atenolol withdrawal, suggesting that rebound adrenergic stimulation or hypersensitivity was absent or insignificant. Catastrophic coronary events after beta blockade withdrawal (the beta blockade withdrawal syndrome) have occurred almost exclusively in patients taking propranolol, many of whom had unstable angina at the time of withdrawal. This study showed that in patients with stable angina, even when severe, the abrupt withdrawal of atenolol can be expected to result in only minor clinical consequences. The risk to any patient of so called rebound events after withdrawal of beta blockade seems to be related to both the clinical setting and the agent being used.

Comparison of hydrochlorothiazide and atenolol as initial treatment in uncomplicated hypertension

After screening a local population in the northern part of The Netherlands for hypertension, 119 patients with a diastolic pressure (DP) between 95 and 120 mmHg were randomised and treated either with 50 mg hydrochlorothiazide (n = 59) or 100 mg atenolol (n = 60). After 1 month of treatment 6 patients in the hydrochlorothiazide group and 24 patients in the atenolol group had reached a DP less than or equal to 90 mmHg (p less than 0.001). 43 of the 50 non-responders to hydrochlorothiazide were switched to atenolol and 30 of the 35 non-responders to atenolol were changed to hydrochlorothiazide. One month after the switch 19 patients in the atenolol group and 2 patients in the hydrochlorothiazide group had reached a DP less than or equal to 90 mmHg (p less than 0.001). After 6 months of treatment 32 of the 43 atenolol responders and 7 of the 8 hydrochlorothiazide responders were still receiving the same medication, as their DP was still less than or equal to 90 mmHg. Non-responders to either medication were given the combination (n = 46). 21 patients now became normotensive as did a further 10 after increasing the dose of atenolol to 200 mg. Thus, in all 70 patients had a blood pressure less than or equal to 90 mmHg after treatment for 4 months. Both drugs induced a significant reduction in the total of number of complaints after 1 month of treatment. They did not differ from each other. The reduction was seen both in responders and non-responders and persisted during treatment for 6 months. It is concluded that in terms of short-term efficacy the cardioselective, hydrophilic beta adrenoceptor-blocking drug atenolol is preferable to hydrochlorothiazide in the treatment of uncomplicated hypertension.

Antihypertensive drug withdrawal syndrome

After discontinuation of antihypertensive medications, patients may experience symptoms associated with catecholamine excess, with or without a rapid rise in blood pressure; this is referred to as antihypertensive drug withdrawal syndrome. Though most often associated with the discontinuation of clonidine, this syndrome has been reported to follow the withdrawal of many other antihypertensives. Proposed mechanisms for the syndrome, depending on the drug involved, include enhanced activity of (1) the sympathoadrenal system, (2) the renin-angiotensin-aldosterone system, and (3) the thyroid hormones. The typical patient at risk is a younger person with severe hypertension, who has been on multiple drugs in high doses for a long period. Guidelines are provided for minimizing the occurrence of the syndrome and for treating the reaction, should it occur.

Comparison of withdrawal phenomena after propranolol, metoprolol, and pindolol

Three groups of hypertensive patients were studied after they had received one of the three pharmacologically different beta blockers for at least 1 month: pindolol, 10 mg twice a day (n = 7), propranolol median dose, 80 mg three times a day (n = 9), or metoprolol, 150 mg (twice a day (n = 8). After abrupt withdrawal of drug and replacement with placebo, we measured the following on day 0 and approximately every 2 days up to 3 weeks; beta-adrenergic sensitivity (BAS) by the chronotropic dose of isoproterenol to increase heart rate by 25 bpm (CD25), resting heart rate and blood pressure, and symptoms. All values are medians. On day 0, beta blockade was evident by increased CD25 values of 618 micrograms for pindolol, 57 micrograms for propranolol, and 10 micrograms for metoprolol as compared to 2.8, 2.4, and 3.0 microgram, respectively, at days 14 to 21, which were considered the ultimate baseline. After pindolol on day 0, the CD25 slowly decreased to, but never below, baseline by days 8 to 21. In contrast, after propranolol on day 0, the CD25 decreased significantly two- to fivefold below baseline from days 4 to 14 (BAS) and after metoprolol two- to threefold below baseline from days 2 to 8. After pindolol, heart rate and blood pressure gradually returned to, but not above, ultimate baseline. In contrast, during the period of BAS there was a significant overshoot of heart rate in eight patients after metoprolol (day 0 = 61, peak = 88, baseline = 74) but not after propranolol, while a significant overshoot of blood pressure occurred in six of nine patients after propranolol (day 0 = 140/87, peak = 157/95, baseline = 140/89) but not after metoprolol. Withdrawal symptoms of headache, palpitations, and tremor occurred in one of seven patients after pindolol, six of nine after propranolol, and three of eight after metoprolol. The degree and duration of beta blockade appeared related to drug potency. Withdrawal phenomena occurred after propranolol and metoprolol but not after pindolol.

Prevention of propranolol withdrawal mechanism by prolonged small dose propranolol schedule

Abrupt withdrawal of propranolol may be followed by a "propranolol withdrawal syndrome "due, at least in part, to enhanced beta adrenergic sensitivity. Tapering propranolol dosage is frequently used in the hope of preventing adverse withdrawal events but the success of such a maneuver has not been shown. The rationale for the dose tapering schedule in this study was based on earlier observations after abrupt withdrawal of propranolol. Nine hypertensive patients were gradually withdrawn from long-term propranolol therapy, either by serial dose reduction for 6 to 9 days (n = 3) or by reduction to a prolonged small dose (30 mg daily) for 2 weeks before complete withdrawal (n = 6). During dose reduction of propranolol and for 2 additional weeks of placebo therapy, serial measurements were made of cardiac sensitivity to isoproterenol, heart rate at rest, blood pressure, plasma catecholamines, serum thyroxine (T4) and triiodothyronine (T3) and symptoms. Serial dose reduction decreased but did not prevent cardiac hypersensitivity in two of three patients. The prolonged small dose therapy largely prevented cardiac hypersensitivity and overshoot in heart rate, blood pressure and plasma catecholamines and symptoms. Serum T4 decreased significantly and T3 tended to increase during and after prolonged small dose treatment. These results indicate that prolonged administration of small dose propranolol before complete withdrawal in hypertensive patients prevents enhanced cardiac beta adrenergic sensitivity and other adverse events.

Antihypertensive activity of once daily metoprolol alone and with chlorthalidone and comparison with a twice daily regimen

In a multicentre, double-blind (DB), within-patient study, the antihypertensive effectiveness and tolerability of two oral administration schedules of metoprolol (M) 100 mg b.i.d. versus 200 mg once daily (o.d.), were investigated in 103 outpatients with mild to moderate essential hypertension. The study lasted 14 weeks and was divided into 3 periods: a) a weeks of single-blind (SB) placebo wash-out; b) 4 weeks of SB administration of M 100 mg b.i.d.; at the end of the second week of this period, chlorthalidone (C) 25 mg was added in patients with a recumbent diastolic blood pressure (BP) still greater than 95 mmHg and was continued throughout the following period; and c) DB cross-over administration of M 200 mg/d for 4 weeks on a b.i.d. schedule and 4 weeks on a once daily schedule. In comparison with pretreatment values, heart rate and systolic and diastolic BP were reduced (p less than 0.001) by both M administration schedules; there was no differences between the once and twice daily treatment regimens. During M once daily, betablockade was still maintained over 24 hours or longer, as the heart rate remained significantly lower than the basal value. In 57 patients, C was added at the end of the second week of SB M administration, and a further decrease in BP was observed; again, there was no significant change during once and twice daily M administration. Unwanted effects during M treatment were of minor severity, and the majority occurred when C, too, was added.

Comparison of withdrawal phenomena after propranolol, metoprolol and pindolol

1 After abrupt propranolol withdrawal a rebound increase in cardiac sensitivity to isoprenaline occurred in 9/9 patients and persisted up to 14 days. A mild brief rebound in resting heart rate occurred in 4/9 patients and a rebound in blood pressure occurred in 6/9 patients. These withdrawal phenomena were prevented by gradual withdrawal on a prolonged small dose of propranolol. 2 After abrupt metoprolol withdrawal a rebound increase in cardiac sensitivity to isoprenaline occurred in 8/8 patients but had resolved by 8 days. A marked persistent rebound in resting heart rate occurred in 8/8 patients while a small brief rebound in blood pressure occurred in only one patient. These withdrawal phenomena were largely prevented by gradual withdrawal on a prolonged small dose of metoprolol. 3 After abrupt pindolol withdrawal there was no rebound in isoprenaline sensitivity but a mild brief rebound in resting heart rate occurred in 9/10 patients. There was no rebound in blood pressure. 4 The type, magnitude and frequency of withdrawal phenomena after various beta-adrenergic receptor blockers probably reflects substantial differences in their basic pharmacological characteristics. 5 Caution must be exercised when withdrawing any patient from any beta-adrenoceptor blocker since an adverse cardiac event is unpredictable.

Lack of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy with oxprenolol

The possibility of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy (8-18 months) with the slow-release (SR) formulation of oxprenolol (160-320 mg/day) was assessed in six patients with uncomplicated essential hypertension. The chronotropic dose 25 of isoproterenol (the dose that increases the resting heart rate by 25 beats/min), plasma concentration of catecholamines, triiodothyronin and thyroxin, plasma renin activity and aldosterone, hemoglobin, hematocrit and oxyhemoglobin dissociation were measured on the last day of oxprenolol SR intake and 1, 2, 3, 6 and 13 days after abrupt replacement by identical placebo tablets. The chronotropic dose 25 of isoproterenol (microgram/m2), which was greater than 25.6 in all patients on the last day of oxprenolol SR, fell to 4.83 +/- 2.03 on the second day and to 3.50 on the third day after its abrupt withdrawal and reached a minimal value on the thirteenth day (2.78 +/- 0.30). Throughout the study, plasma concentrations of catecholamines, triiodothyronin and thyroxin and oxyhemoglobin dissociation remained unchanged. Plasma renin activity and plasma aldosterone, which were suppressed during oxprenolol administration, rose significantly during placebo, coinciding with a significant fall in hematocrit and hemoglobin. No major subjective symptoms were reported by the patients. Thus, hypersensitivity of beta-adrenoreceptor-mediated responses was not demonstrated after sudden withdrawal of oxprenolol SR.

Penbutolol or hydrochlorothiazide once a day in hypertension. A controlled study with home measurements

1 The hypotensive effect of single daily dosing with 80 mg penbutolol was compared to 100 mg hydrochlorothiazide and placebo in a double-blind cross-over controlled trial with daily home measurements in ten hypertensive patients. 2 Penbutolol, 80 mg once a day, reduced significantly the supine and standing blood pressure. 3 This hypotensive effect was more potent than hydrochlorothiazide 100 mg particularly in the evening. 4 The hypotensive effect remained for 24 h as shown by the evening (14 h after dose) and morning (24 h after dose) blood pressure readings. 5 No relevant subjective or physical side effects were recorded. There was no significant change nor individual noticeable variation in biochemical data during penbutolol treatment. However, during hydrochlorothiazide treatment, the expected electrolyte changes were observed (symptom-free hypokalemia and hyperuricemia). 6 Penbutolol serum concentration showed no cumulation after one month of treatment. 7 Sudden withdrawal of penbutolol after 1 month of therapy resulted in a slow return to baseline blood pressures over a 2-week period without rebound.

Adverse effects of sudden withdrawal of antihypertensive medication

The withdrawal syndrome following abrupt discontinuation of antihypertensive medication may consist of symptoms of sympathetic overactivity alone or in association with a rapid increase in blood pressure. The phenomenon may occur after discontinuation of any of a variety of drugs. Although the exact incidence of the syndrome is not known, it appears to be rare, at least in patients receiving standard doses of antihypertensive medications. The best treatment is prevention. However, if the syndrome does occur, reinstitution of the previously discontinued medication usually is successful in controlling the withdrawal events.

Time course of blood pressure, pulse rate, plasma renin and metoprolol during treatment of hypertensive patients

Eleven patients were treated for essential hypertension with metoprolol (Selokén) for more than three months. The time course of changes in blood pressure, pulse rate and plasma renin activity was studied during treatment with an oral maintenance dose of 100 mg twice daily. Significant decreases in pulse rate, diastolic blood pressure and plasma renin activity were observed even after the first dose. The plasma concentration of metoprolol reached equilibrium after the second dose. After the third dose there was no further significant change in blood pressure. There was a significant correlation (p < 0.001) between the initial (after three doses) and final (after > 90 days) effect of metoprolol on blood pressure (r = 0.86 and 0.91 for systolic and diastolic blood pressure change, respectively).

The abrupt discontinuation of antihypertensive treatment

Although deleterious events following abrupt withdrawal of antihypertensive treatment are relatively uncommon, considerable attention has recently been focused on this problem. A withdrawal syndrome may occur after termination of almost all types of antihypertensive drugs, but most experience has been with the centrally acting agents and with beta-adrenoreceptor blockers. Abrupt discontinuation of high doses of centrally acting drugs such as alpha-methyldopa, clonidine, and guanabenz can produce a syndrome of sympathetic overactivity that includes agitation, headache, sweating, and nausea and less commonly can provoke rapid upswings in blood pressure. If beta blockers are suddenly stopped, a similar pattern can occur that may be related to excessive activity of thyroid hormones as well as sympathetic factors. Additionally, patients with ischemic heart disease may be susceptible to an acute exacerbation of their cardiac disease when beta-blocker treatment is stopped. It seems likely that discontinuation events can be particularly severe when combinations of different types of antihypertensive medications are sud-disease when betablocker treatment is denly stopped. This problem can be dealt with by educating patients to avoid sudden drug cessation and when elective discontinuation is planned, by gradual dose reduction.

Mechanism of propranolol withdrawal phenomena

Nine patients on chronic treatment with propranolol for essential hypertension for 3 months or longer were studied after abrupt discontinuation of the drug. Each patient demonstrated transient supersensitivity to the chronotropic effects of isoproterenol, beginning 2--6 days (median 4 days) after propranolol withdrawal, lasting for 3--13 days (median 6 days), with the maximum sensitivity on day 6. A significantly lower dose of isoproterenol was necessary to increase heart rate 25 beats/min on day 6 (median dose 1.2 microgram, range 0.3--3.4 microgram) compared with after day 14, when sensitivity had stabilized (median dose 2.3 microgram, range 1.4--7.6 microgram). Six patients had transient symptoms (headache, chest pain, palpitations and sweating) after abrupt propranolol withdrawal, coinciding with supersensitivity to isoproterenol in five. Transient increases in plasma catecholamines and blood pressures and sustained increases in heart rate occurred during the period of isoproterenol supersensitivity in most patients, and may have contributed to symptoms noted. The delayed onset and potentially long duration of beta-adrenergic supersensitivity after abrupt propranolol withdrawal have important clinical implications.

Abrupt withdrawal of beta-blocking agents in patients with arterial hypertension. Effect on blood pressure, heart rate and plasma catecholamines and prolactin

Chronic treatment with beta-blockers was interrupted abruptly in six patients with arterial hypertension. Three patients, who had experienced symptoms during a previous withdrawal, again complained of transient palpitations, tremor, sweating, headache and general malaise. A significant increase in standing blood pressure (BP) and heart rate (HR) was noted after 24 h. The standing HR reached a maximum after 48 h and had decreased significantly on the 7th day (p less than 0.005). There was a strong tendency to greater increase in standing BP and HR in the patients who experienced symptoms than in those who did not. Plasma concentrations of noradrenaline, adrenaline and prolactin did not change significantly. Thus, beta-blocker withdrawal symptoms are reproducible and are indicative of a transient sympathetic hyperresponse. The increased activity is not likely to be caused by increased production of circulating catecholamines, but rather by increased sensitivity of the beta-receptor.

Propranolol withdrawal in angina pectoris: a prospective study

In a prospective study, 100 consecutive patients (mean age 51.3 years) with angina pectoris had propranolol abruptly discontinued 24 to 144 hours (mean 39.0 hours) prior to elective coronary arteriography. The mean duration of therapy was 8.2 months and the mean daily propranolol dose was 216.1 mg. New York Heart Association Class II, III and IV symptoms were present in 30, 41, and 29 patients and one, two, or three coronary arteries were more than 50 per cent narrowed in 37, 29, and 34 cases, respectively. Three patients experienced minor increases in chest pain and two suffered non-transmural myocardial infarctions prior to the time of scheduled cessation of therapy. The same number of minor and major complications occurred in the post-withdrawal period. All four patients who developed non-transmural myocardial infarction in this study had pre-existing Class IV symptoms. The course of the remaining 90 patients was uneventful. These findings do not support the concept of a rebound propranolol withdrawal reaction.

Double-blind comparison of metoprolol, alprenolol, and oxprenolol in hypertension

A double-blind comparison of the beta-blockers metoprolol, alprenolol and oxprenolol was carried out to evaluate their antihypertensive effect and tolerability. 105 patients with previously untreated hypertension entered the trial and 72 completed it. Side-effects were infrequent and were never the reason for drop-out. All three drugs caused a statistically significant reduction in blood-pressure at the lower of the two doses used during a dose-finding period. At the higher dose employed in this period, metoprolol caused a significantly greater reduction in diastolic blood-pressure than did alprenolol or oxprenolol. All three drugs caused a significant reduction in heart rate. During the following period, the beta-blockers were supplemented if necessary with hydrochlorothiazide. This was required less frequently in the metoprolol group than in the other two groups.

Antihypertensive effect and tolerability of metoprolol during long-term treatment: a multicentre study

One hundred and forty-seven patients with essential hypertension participated in this multicentre study. The results indicate that metoprolol in a dosage of 150-450 mg daily is an effective and well tolerated therapy both in patients previously untreated and in patients unsatisfactorily treated with other antihypertensive agents.