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PubMed1975

Comparative trial of propranolol and practolol in hyperthyroidism.

The possible role of practolol in the management of hyperthyroidism has been studied by comparing it with propranolol. 2. In a double-blind cross-over trial, propranolol (40 mg), practolol (120 mg) and a placebo four times daily for one week were compared in twenty-one hyperthyroid patients by sequential analysis. 3. Judged by their effect on the symptoms and signs of thyrotoxicosis, both propranolol and practolol were significantly better than the placebo but no clear distinction could be made between the two active compounds. 4. Propranolol and practolol reduced heart rate by 24 and 17% respectively compared with placebo. 5. Patients generally preferred propranolol or practolol to placebo but this preference did not achieve significance with either drug. 6. Only in its effect on heart rate was practolol significantly inferior to propranolol, and it would appear to be a useful alternative to propranolol in the management of the peripheral manifestations of hyperthyroidism.

Clinical Trials as Topic↗
PubMed1983

Changes in heart rate and forearm blood flow following intravenous boluses of isoprenaline in the presence of practolol and propranolol.

1 Increases in heart rate and forearm blood flow following graded intravenous bolus injections of isoprenaline sulphate, were measured in a double-blind randomised study of six subjects who received either placebo, practolol 50 mg, practolol 200 mg, propranolol 10 mg or propranolol 40 mg. 2 Dose related increases in forearm blood flow were produced by the graded boluses of isoprenaline sulphate. 3 Practolol 50 mg attenuated the heart rate response to isoprenaline but did not significantly affect the changes in forearm blood flow. Practolol 200 mg further attenuated the heart rate responses but also decreased the forearm blood flow responses. 4 Propranolol 10 mg and propranolol 40 mg significantly attenuated both the heart rate and forearm blood flow responses. The effect on forearm blood flow tended to be greater than the effect on heart rate. 5 Practolol 200 mg had the same effect on heart rate responses as propranolol 10 mg but a significantly smaller effect on the forearm blood flow responses. 6 The measurement of forearm blood flow following intravenous bolus injections of isoprenaline provides useful information about the beta 2-adrenoceptor antagonism of propranolol and practolol. However, application of the technique may be limited by the magnitude of the heart rate response and by the short-lived nature of the increase in forearm blood flow.

Adult↗
PubMed1983

Heart rate and blood pressure responses to intravenous boluses of isoprenaline in the presence of propranolol, practolol and atropine.

Six healthy subjects were studied on two occasions. Graded bolus injections of isoprenaline sulphate were given intravenously and control dose-response curves were drawn for the changes in heart rate and blood pressure. In a random order each subject received an intravenous infusion of either propranolol or practolol and further dose-response curves were constructed PRE- and POST-atropine (0.04 mg/kg). Exercise tachycardia was reduced 26.1 +/- 2.7% by propranolol and this was not significantly different from the reduction by practolol (21.2 +/- 1.9%). Propranolol attenuated the isoprenaline tachycardia (dose ratio 43.7) and after atropinisation the dose ratio was not significantly altered (41.1). Practolol also attenuated the isoprenaline tachycardia (dose ratio 4.4) but after atropinisation the dose ratio was significantly increased to 8.8, though this remained significantly less than the dose ratio for propranolol. At a heart rate increase of 25 beats/min, the isoprenaline-induced control fall in mean blood pressure was 9-11 mm Hg. After propranolol administration this fall was converted to a small increase of + 2.3 +/- 1.3 mm Hg. Following practolol, however, the mean blood pressure reduction was 19.7 +/- 2.9 mm Hg. Practolol did not significantly block the isoprenaline-induced fall in diastolic pressure. The difference in potency of propranolol and practolol, demonstrated by their effect on isoprenaline induced tachycardia at doses shown to have equal effects on exercise tachycardia, is contributed to but not fully explained by the reflex withdrawal of cardiac vagal tone which occurs with cardioselective but not non-selective antagonists.

Adrenergic beta-Antagonists↗
PubMed1976

Comparison of the actions of acebutolol, practolol and propranolol on calcium transport by heart microsomes and mitochondria.

1 The effects of acebutolol, practolol and propranolol (0,5-3 mM) on calcium uptake, calcium binding and ATPase activities of the rabbit and rat heart microsomal and mitochondrial fractions were investigated. 2 Dose-response and time course experiments revealed that propranolol greatly inhibited microsomal and mitochondrial calcium uptake whereas both acebutolol and practolol showed slight depressant effects. 3 The ATPase activities of microsomal and mitochondrial fractions were decreased by acebutolol, practolol and propranolol; however, the latter agent was more effective than the other two. 4 The inhibitory effects of acebutolol, practolol and propranolol on mitochondria and microsomes were not antagonized by adrenaline. 5 Propranolol decreased calcium binding by the microsomal fraction only, whereas acebutolol and practolol had no effect on microsomal or mitochondrial calcium binding. 6 The sensitivity of the rabbit heart subcellular fractions to the beta-adrenoceptor blocking drugs was similar to that of the rat heart; however, the calcium uptake and ATPase activities of microsomes were more sensitive to propranolol than mitochondria in both species. 7 Perfusion of rat hearts with 0.2-1 mM propranolol decreased contractile force, and microsomal and mitochondrial fractions obtained from these hearts accummulated less calcium in comparison to the control. On the other hand, acebutolol and practolol (0.2-1nM) had no appreciable effects on contractile force or subcellular fractions under similar conditions. 8 The negative inotropic effect of propranolol may partly be due to its inhibitory actions on calcium transport by subcellular organelles of the myocardium; the depressant action of propranolol on calcium transport is unlikely to be due to its beta-adrenoceptor blocking property.

Acebutolol↗
PubMed1975

Improvement in prognosis of myocardial infarction by long-term beta-adrenoreceptor blockade using practolol. A multicentre international study.

In a large-scale double-blind controlled trial of practolol (200 mg twice daily) in the long-term prophylactic treatment of 3038 patients recovering from acute myocardial infarction treatment was started one to four weeks after the acute attack. The trial was originally planned to include 4000 patients treated for at least a year but had to be terminated prematurely because of the serious oculocutaneous and peritoneal reactions reported elsewhere. Nevertheless, important findings, probably applicable to other beta-adrenoreceptor antagonists, have emerged in relation to mortality and morbidity. (1) The practolol-treated group showed a significant reduction in overall mortality and in sudden deaths; (2) there was a highly significant reduction in "all cardiac events"; (3) the reduction in overall mortality was virtually confined to patients whose original pre-entry infarcts were sited anteriorly; (4) the protective effect of practolol was most evident in those patients with pre-entry anterior infarcts whose blood pressures at entry were below the mean for the trial as a whole; (5) there were highly significant group differences in favour of the drug relating to the incidence of angina pectoris and cardiac arrhythmias, and to the numbers of patients who had to be withdrawn from the trial because of these conditions; (6) significantly more patients were withdrawn from the treatment group because of suspected adverse reactions. It is concluded that practolol used in the long-term treatment of patients who have survived the acute phase of myocardial infarction reduces the death rate when the original infarct is sited anteriorly. It is postulated that the favourable results of the trial were due to beta-adrenoreceptor blockade rather than to some other property specific to practolol itself. Since practolol produces severe side effects in long-term use it is recommended that an alternative beta-adrenoreceptor blocking agent should be used.

Adrenergic beta-Antagonists↗
PubMed1986

Practolol: aspects of its metabolism and ocular binding in the hamster.

The metabolism and ocular binding of practolol were investigated after oral administration of 14C-practolol to hamsters treated with three modifiers of mixed-function oxidase activity: piperonyl butoxide, cobalt chloride or phenobarbitone. The major urinary metabolites of practolol were 3-hydroxypractolol and polar metabolites which included glucuronide conjugates. A number of unidentified metabolites constituted a minor portion of urinary radioactivity. Each pretreatment modified both the urinary excretion pattern (0-24 h) of practolol and its metabolites and also the metabolite profile of eye extracts 24 h after an oral dose. None of the modifiers of mixed-function oxidase activity had any significant effect on the ocular binding (both extractable and non-extractable components) of practolol and its metabolites. The results indicated that the non-extractable component was neither practolol nor 3-hydroxypractolol.

Animals↗
PubMed1978

A comparative study of three beta 1-adrenoreceptor blocking drugs with different degree of intrinsic stimulating activity (metoprolol, practolol and H 87/07) in patients with angina pectoris.

Three beta1-selective beta-blocker (metoprolol, practolol and H 87/07) were compared in 29 patients with stable angina pectoris. The main pharmacological difference between the three beta-blockers was their intrinsic stimulating activity (I.S.A.), metoprolol being devoid of I.S.A., practolol having moderate I.S.A. and H 87/07 having high I.S.A. Each drug was given in randomized order and the length of each cross-over period was 2 weeks. Daily activity was measured by an automatic step-counter, and subjective symptoms and nitroglycerin consumption were registered on a diary-card. Objective data, such as ECG changes and exercise capacity, were obtained by bicycle ergometer tests performed at the end of each period. At rest, the heart rate was significantly lower on metoprolol than on practolol or H 87/07. During exercise, the heart rate was significantly higher on H 87/07 than on practolol or metoprolol. No other haemodynamic differences were found between the three beta-blockers. No differences were found between the three test periods with regard to daily activity, expressed as the number of steps walked, while on the beta-blocker with high I.S.A., H 87/07, the attack rate and nitroglycerin consumption were significantly higher than when the patients were on metoprolol and practolol. No difference was found between the three beta-blockers with regard to total work or exercise time until 1 mm of S-T segment depression. Except for one patient who experienced a severe exanthema on practolol, the three beta-blockers were equally well tolerated.

Adrenergic beta-Antagonists↗
PubMed1973

Pharmacodynamic studies of beta adrenergic antagonism induced in man by propranolol and practolol.

The pharmacodynamic activities of two beta adrenergic antagonists, propranolol and practolol, were compared in eight hypertensive patients. The activity of each antagonist was established in relation to its blood concentration at maximal and submaximal adrenergic blockade defined by inhibition of exercise tachycardia. Maximal inhibition of exercise tachycardia was comparable with both drugs and averaged 74+/-7% of the control value during drug treatment. This inhibition was achieved with a blood concentration of 2.5+/-0.4 mug/ml practolol and 0.10+/-0.08 mug/ml propranolol. The antagonist activities of these drugs against adrenergic stimulation with isoproterenol infusion indicated a much greater relative potency of propranolol against this stimulus, and in vivo estimates of PA(2) values differed by more than 600-fold. Relative antagonist activity of practolol during isoproterenol stimulation was equivalent both at cardiac (inotropic and chronotropic) and at vascular adrenergic receptors, whereas greater antagonist activity of propranolol was observed at vascular receptors than at cardiac receptors. Thus, the activity of practolol was not limited to cardiac receptors as previously suggested. Practolol did not reduce cardiac output at any dose level and the effect on resting blood pressure was small. Both practolol and propranolol had much greater hypotensive activity during exercise. These studies have defined the differing pharmacodynamic activities on the cardiovascular system of two effective beta adrenergic receptor antagonists and have established the blood levels of these antagonists necessary to achieve effective adrenergic blockade.

Acetanilides↗
PubMed1977

The effect of practolol and butoxamine on aortic arch malformation in beta adrenoreceptor stimulated chick embryos.

An equimolar dose of the beta-1 adrenoreceptor antagonist practolol administered to embryonic chicks prevents the induction of aortic arch malformations by isoproterenol. Whereas 3.75 X 10(-9) mole isoproterenol in 5 microliter saline solution induced aortic arch anomalies in 39% of embryos injected at Hamburger-Hamilton developmental stage 26, pretreatment with practolol one to two minutes before catecholamine administration reduced the anomaly rate to to 4%. Practolol when injected alone did not influence survival rate nor did it cause cardiovascular malformations. Probably the most significant result of this study involves the prevention by practolol of aortic hypoplasia and interrupted aortic arch complexes, anomalies frequently induced by isoproterenol when administered at this stage of embryonic chick development. Butoxamine, a beta-2 adrenoreceptor antagonist, did not block the overall effect of isoproterenol nearly as effectively as did practolol. Results from the present study suggest that aortic arch anomalies may be induced in embryonic chicks via beta-1 adrenoreceptor stimulation. Beta-2 receptor stimulation does not appear to be as significantly involved.

Abnormalities, Drug-Induced↗
PubMed1975

Comparison of the antihypertensive effect of propranolol and practolol combined with chlorthalidone.

A double blind cross-over trial of fixed doses of propranolol (640 mg/day) and the cardioselective drug practolol (1600 mg/day) was performed in 28 patients with essential hypertension whose blood pressure was not adequately controlled by chlorthalidone (100 mg 3 times weekly) alone. Chlorthalidone alone was given during the first (control) period, and it was continued throughout the propranolol and practolol treatment periods, each of 10 weeks. The systolic and diastolic blood pressures were lowered significantly by both the beta blocking drugs. The changes in blood pressure caused by altering the patient's position were the same after both beta blockers. Propranolol produced slightly lower values than practolol, but the difference was significant only for diastolic blood pressure in the sitting and supine positions. In individual patients the final blood pressure after propranolol was correlated with the final blood pressure after practolol. Only minimal side-effects of either drug were noticed. It is concluded that the doses employed both of propranolol and practolol had a good and approximately equal antihypertensive effect when combined with chlorthalidone treatment. There was no correlation between the final blood pressure and plasma renin activity.

Antihypertensive Agents↗
PubMed1981

A comparison between propranolol, practolol and betaxolol (SL75212) on the circulatory and metabolic responses to insulin-induced hypoglycaemia.

1. Six healthy male volunteers received equivalent intravenous beta-blocking doses of propranolol, practolol and betaxolol (SL75212) or saline at weekly intervals Sixty minutes later 0.1 unit/kg insulin was given intravenously. 2. In all studies, maximum hypoglycaemia (mean 1.2 mmol/l) was reached thirty minutes after insulin. Recovery from hypoglycaemia was delayed with propranolol but practolol and betaxolol had no effect. 3. Propranolol blocked the tachycardia and widening of pulse pressure seen in saline treated subjects. It also blocked the rebound rise in free fatty acids (FFA) and glycerol concentrations that followed the nadir of hypoglycaemia. 4. Neither practolol nor betaxolol had significant effects on pulse rate or blood pressure but betaxolol resembled propranolol in blocking the rebound rise in FFA and glycerol, while practolol blocked the rise in glycerol alone. 5. The magnitude of the rise in growth hormone following hypoglycaemia was similar in all groups, but the peak was earlier after practolol and betaxolol.

Adrenergic beta-Antagonists↗
PubMed1982

Inhibition of gastrointestinal mucosal glycoprotein synthesis by the beta-adrenergic blocking drug, practolol.

The effect of administration of practolol and other beta-blocking agents on gastrointestinal mucosal glycoprotein synthesis was studied in the rat. Practolol, at a dose of 50 mg/kg, inhibited the incorporation of N-acetylglycosamine into gastric mucosal glycoproteins, while acebutolol, atenolol, pronethalol and propranolol had no inhibitory effect, even at a dose of 200 mg/kg. In addition, practolol inhibited the incorporation of N-acetylneuraminic acid, D-fucose and L-serine into gastric mucosal glycoproteins, while the other beta-blocking agents had no effect. Administration of practolol caused no significant change in the rate of incorporation of glycoprotein precursors into intestinal mucosal glycoproteins. These results indicate that of the beta-blocking drugs studied, inhibition of glycoprotein synthesis is associated only with practolol and is independent of its beta-blocking effect.

Adrenergic beta-Antagonists↗
PubMed1988

Metabolites of procainamide and practolol inhibit complement components C3 and C4.

Drug-induced systemic lupus erythematosus arises from toxic side-effects of administration of hydralazine, isoniazid, procainamide and practolol. Hydralazine and isoniazid are nucleophilic drugs and inhibit the covalent binding reaction of complement components, C3 and C4, an effect likely to lead to deposition of immune complexes (a feature of systemic lupus erythematosus). Procainamide and practolol do not themselves inhibit C3 and C4. A range of metabolites and putative metabolites of procainamide and practolol were synthesized, and tested for their ability to inhibit the covalent binding reactions of C3 and C4. The highly nucleophilic hydroxylamine metabolite of procainamide was strongly inhibitory in both tests, as was a putative hydroxylamine metabolite of practolol. These studies indicate a potential role for the hydroxylamine metabolites in mediating the toxic side-effects of procainamide and practolol, and emphasize the need for adequate measurements of hydroxylamine metabolites in human tissue.

Acecainide↗
PubMed1979

Beneficial effect of practolol in preventing adrenaline-induced systemic and myocardial metabolic changes.

The aim of the study was to investigate whether the beta blocking agent, practolol, is able to modify some of the metabolic and hormonal responses and the local myocardial changes evoked by an excess of adrenaline similar to that seen after acute coronary occlusion. Adrenaline (1.2 micrograms/kg/min) and practolol (1 mg/kg) were infused concurrently to anaesthetized intact dogs for 5 h. Blood free fatty acid and triiodothyronine levels were measured initially and after 2, 4 and 5 h of infusion. At the end of the infusion the myocardium was subjected to biochemical, histoenzymatic and electron microscopic examination. The results were compared with those obtained in dogs infused with adrenaline alone and with saline alone. Practolol reduced the adrenaline-induced increase in free fatty acids and a fall in triiodothyronine in the blood. Myocardial acetate accumulation and ATP decrease were both reduced by practolol. Histoenzymatic and electron microscopic changes were less. These effects of practolol upon systemic and myocardial disturbances induced by the excess of adrenaline indicate that it might be effective in modifying any excessive adrenergic response which may occur in acute myocardial infarction.

Adenosine Diphosphate↗
PubMedDate not supplied

The effects of propranolol, practolol and metoprolol on exercise-induced tachycardia in relation to plasma levels in man.

1. The effects of single oral doses of propranolol, practolol and a new cardioselective beta-adrenoceptor blocking drug, metoprolol, on exercise-induced tachycardia in relation to plasma levels were studied in six normal volunteers. 2. Exercise undertaken on treadmill was submaximal which, under control conditions, increased the heart rate from 74-3 (s.e.m. = 6-8) to 153-8 (s.e.m. = 9.8) beats/min. 3. Plasma concentrations of propranolol and practolol were assayed fluorometrically and of metoprolol by electron-capture gas liquid chromatography, the details of which are described. 4. Between 1-5 and 2 h after drug ingestion 80 mg of propranolol associated with plasma level of 50-60 ng/ml (half-life 2-75 h), reduced the exercise-induced tachycardia by 27%, 250 mg of practolol with plasma levels of 1050-1100 ng/ml reduced it by 28% and 100 mg of metoprolol with plasma concentrations of 140-150 ng/ml (half-life 1-7 h), reduced it by 30%. 5. The resting heart rates were reduced significantly by propranolol and metoprolol but not by practolol. 6. Metoprolol is a potent short-acting beta-adrenoceptor antagonist; its advantages as a cardioselective agent over practolol in therapeutic use are discussed.

Adult↗
PubMed1976

Comparison of verapamil and practolol in paroxysmal supraventricular tachycardia.

40 patients with paroxysmal supraventricular tachycardia were allocated to two different treatment groups according to their year of birth. Those patients born on odd years were given 5 mg of practolol intravenously, those born on even years receiving 5 mg of verapamil, and if the tachycardia continued, the same injection was repeated after 5 minutes. If practolol treatment failed, the patient was given 5 mg of verapamil half an hour later, and vice versa. Verapamil restored sinus rhythm in 19 patients out of 20. Practolol proved effective in 8 out of 20. In patients who were switched over to the other treatment verapamil was effective in 9 out of 11 and practolol in 1 patient. Side effects were few. Marked hypotension occurred in 2 patients, in 1 patient after 5 mg of verapamil, and after 5 mg of practolol in the other. It is concluded that verapamil is a very effective agent in the treatment of paroxysmal supraventricular tachycardia. Selection of patients is emphasized to increase the safety of its use.

Adolescent↗
PubMed1998

[Room temperature phosphorimetric determination of practolol with dansyl chloride labeling].

Dansyl Chloride (DNS-Cl) was used as a phosphorescent labeling agent for the determination of practolol. The derivative was formed by refluxing practolol-ethyl acetate solution with the solid DNS-Cl in the presence of potassium carbonate anhydride. Room-temperature phosphorescent (RTP) properties of the derivative were studied by a micelle-stabilized room-temperature phosphorescence (MS-RTP) method. Phosphorescence lifetimes of practolol-DNS and the DNS-Cl were found to be 0.791 and 0.408ms, respectively. By applying the derivative MS-RTP technique, practolol could be quantitatively determined without previous separation process. Detection limit of practolol with the proposed method was 0.19 microg/mL.

Dansyl Compounds↗
PubMed1975

[Comparable ergometric examinations before and after administration of practolol and bunitrolol (author's transl)].

By means of a standardized, single-level ergometric load of 1.5 watt/kg body weight, the effects of a new beta-adrenergic receptor blocking agent bunitrolol (o-(2-hydroxy-3-tertiary butylamino)-propoxy)-benzonitrile) was compared with the well-known cardiovascular properties of practolol during an intraindividual therapeutic crossover trial after intravenous administration. In the absence of any side-effects, bunitrolol shows a higher degree of beta-adrenergic receptor bocking activity than practolol, with a distinct specificity towards myocardial receptors and very low cardiodepressive properties at rest. Bunitrolol caused a marked reduction (33%) in exercise-induced myocardial work effort, whilst practolol achieved a reduction of only 17% under equal conditions. Thus, the same physical work load is performed after bunitrolol more economically by decreasing both heart rate and blood pressure. The circulatory effects of an intravenous dose of 5 mg bunitrolol seems to be twice as effective as 10 mg practolol. This implies that beta-adrenergic receptor blockade by bunitrolol during work performance is four times as effective as practolol. The observed marked effect of bunitrolol on the diastolic blood pressure is discussed.

Adult↗