Novel approach to zero-order drug delivery via immobilized nonuniform drug distribution in glassy hydrogels

A novel approach to zero-order drug delivery from glassy hydrogel matrices via an immobilized, sigmoidal, initial drug distribution has been developed. The method utilizes a controlled-extraction process on initially dry, drug-loaded hydrogels to generate an inflection-point-containing drug concentration profile followed by a vacuum freeze-drying step to rapidly remove the swelling solvent and immobilize in situ a nonuniform drug distribution. The drug release from such a system generally exhibits typical zero-order characteristics similar to that of a membrane-reservoir device. However, a saturated reservoir of active ingredient as in the membrane-reservoir device is not required because the constant release is achieved via an initially nonuniform concentration distribution instead of the constant activity in a reservoir. The applicability of the present concept and process has been demonstrated experimentally with the release of oxprenolol hydrochloride from hydrogel beads based on 2-hydroxyethyl methacrylate polymerized with a polymeric cross-linking agent.

The efficacy of indapamide in hypertensive patients failing to respond to a beta-blocker alone

A double-blind, placebo-controlled, cross-over study was carried out to evaluate the efficacy and safety of 2.5 mg indapamide in 24 hypertensive patients failing to respond to oxprenolol alone. An additional 6 patients were assessed by ambulatory blood pressure recordings over a 15-hour period with a Remler M2,000 semi-automatic sphygmomanometer. On average, indapamide reduced supine blood pressure by 18.5/10 mmHg and standing blood pressure by 19.6/8.9 mmHg. The ambulatory recordings carried out in 6 patients detected a fall in diastolic pressure not observed using clinic readings in these 6 patients, suggesting that this is a more sensitive method of detecting antihypertensive effect. These responses were not associated with significant changes in heart rate or body weight and there was no significant postural fall in blood pressure. No serious side-effects were reported. Changes in serum potassium, chloride and urate similar to those seen with diuretics were observed. These results suggest that indapamide is a useful and safe adjunct to beta-adrenoceptor blocking therapy for uncontrolled hypertension.

[Abnormal ECG and adrenaline-induced arrhythmias in restraint and water immersion stressed mice and effects of oxprenolol]

Male ddY mice were loaded with restraint and water immersion stress (RWIS) for 1 hr, and their ECG was measured by lead II. A considerable decrease of heart rate and remarkable prolongations of PQ, QT and QRS intervals were observed in the ECG of RWIS mice. Then experimental arrhythmias were induced by methacholine or adrenaline (Adr) on RWIS mice, and their frequencies of appearance were examined. The appearances of methacholine-induced ventricular extrasystole, atrio-ventricular (A-V) block, sino-atrial (S-A) block and sinus standstill were higher in RWIS mice than in normal mice, and the appearances of sinus arrhythmia and supraventricular extrasystole were similar to normal mice. The appearance of Adr-induced arrhythmia of any type was significantly higher in RWIS mice than in normal mice. Then protective effects of 3 beta-blockers, oxprenolol, propranolol and carteolol, on the worsening of Adr-induced arrhythmias on RWIS mice were studied. A single administration of 5 or 10 mg/kg of oxprenolol or 5 mg/kg of propranolol inhibited the appearance of extrasystole and A-V block. The effectiveness of three-times administrations of 1 approximately 10 mg/kg of oxprenolol was similar to that of the single administration. These results suggest that oxprenolol shows a strong antiarrhythmic effect by continuous administrations on chronic syndromes in SART mice, and it shows an immediate effect by a single administration on acute syndromes in RWIS mice.

Effects of prolonged administration of oxprenolol on severity of ischaemic arrhythmias, enzyme leakage, infarct size, and intracellular cardiac muscle action potentials

We examined the effects of prolonged oral administration of oxprenolol (twice daily for 6 weeks) to male Sprague-Dawley rats. At two times (1 or 16-18 h) after the last oral dose, the rats were anaesthetised and subjected to acute coronary artery ligation, and the severity of the resulting arrhythmias was assessed. Ischaemic damage was measured histochemically (using frozen section analysis by toluidine blue dye in nitrobluetetrazolium ) and by myocardial enzyme release. Cardiac muscle (atria and papillary muscle) was also removed and the transmembrane action potentials recorded using conventional microelectrode techniques. When coronary artery ligation was performed 1 h after the last oral dose (at which time there was evidence of substantial myocardial beta 1-adrenoceptor blockade), there was significant reduction in the severity of early arrhythmias, but no evidence that the severity of ischaemic damage was reduced or that the intracellular cardiac action potentials were modified. No protection was observed when coronary artery ligation was carried out 16 h after the last oral dose of oxprenolol. These results support our previous studies with acutely administered beta-adrenoceptor blocking drugs that myocardial beta-adrenoceptor blockade is the main factor involved in the protection afforded by such drugs against early ischaemic arrhythmias and that other possible effects, such as membrane stabilisation and action potential prolongation, are relatively unimportant in this model.

European Infarction Study (E.I.S.). A secondary prevention study with slow release oxprenolol after myocardial infarction: morbidity and mortality

A multicentre, double-blind, randomized study was carried out to compare the effect on survival, cardiac mortality and non-fatal cardiac events of oxprenolol slow release 160 mg b.i.d. compared with placebo in 1741 patients 35 to 69 years of age who had survived acute myocardial infarction. The patients were entered 14-36 days after infarction and were followed for one year. Recruitment was discontinued before the scheduled 4000 patients had been entered. There were 57 deaths (6.6%) in patients randomized with respect to oxprenolol as compared with 45 deaths (5.1%) in patients randomized with respect to placebo. The difference in cumulative mortality rates (30.4%) is not statistically significant. 275 patients from each treatment group discontinued trial medication. The proportion of deaths was noted to be higher in patients who discontinued trial medication (oxprenolol 13.1%; placebo 7.6%) and in patients 65-69 years (oxprenolol 16.7%; placebo 5.6%). In the 1472 patients less than 65 years of age there was a tendency to a lower mortality in 478 'high risk' patients on beta-blockade [oxprenolol 16 patients (6.9%); placebo 25 patients (10.2%)] as compared with a somewhat higher mortality in the corresponding low risk group (oxprenolol 20 patients [4.0%]; placebo 12 patients [2.4%]). In the 1010 patients under 65 years of age who continued on trial medication, 15 patients (3%) in the oxprenolol group and 22 patients (4.3%) in the placebo group died. The overall results in our trial failed to confirm apparently positive effects in other secondary prevention trials. Debate especially concerns patients older than 65 years of age, patients at relatively low risk, and patients who discontinued oxprenolol treatment.

[Continuous 24-hour registration of intra-arterial pressure in basal states and during therapy with a fixed slow-release oxprenolol-chlorthalidone combination, administered once a day]

Intra-arterial 24 hour blood pressure (BP) recording (OXFORD MEDILOG) was carried out in 10 patients with essential hypertension, 6 males and 4 females, aged between 41 and 58 years, 3 at WHO stage 1 and 7 at stage 2, in basal conditions and after 6 weeks of treatment with a fixed combination of 160 mg of slow-release oxprenolol and 20 mg of chlorthalidone per tablet (tb). The fixed combination was given once daily, in the morning, at the dosage of 1 tb, which was increased to 2 tbs o.d. after the first 2 weeks in 6 patients. Computer calculated mean BP and heart rate (HR) values from each consecutive hour of the day were obtained in all patients. Hourly trend of BP and HR were plotted and circadian variations were thus determined. Treatment with fixed combination o.d. significantly reduced systolic and diastolic BP, compared to pretreatment values, throughout of the 24 hours (p less than 0.01; p less than 0.001), without altering the circadian rhythm. Before and after 6 weeks of treatment, a bicycle exercise test was performed in 8 patients, who reached 85% of the maximal predicted HR. Pretreatment resting mean BP (+/- SD) was 190 +/- 31/108 +/- 10 mmHg (HR: 68 +/- 9 b/min) and those during the last minute of exercise 242 +/- 29/125 +/- 5 mmHg (HR: 147 +/- 13 b/min); posttreatment resting BP was 161 +/- 20/88 +/- 7 mmHg (HR: 58 +/- 7 b/min) and at peak exercise, 212 +/- 16/106 +/- 7 mmHg (p less than 0.025 for the systolic pressure; p less than 0.001 for the diastolic pressure).(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of a delayed-action beta blocker by 24-hour ambulatory recording of the arterial pressure]

Twelve students aged 21 to 39 years (mean age 26) with borderline hypertension underwent three 24 hours ambulatory recordings of blood pressure using an Avionics Pressurometer II device: the first recording under basic conditions, the second after taking placebo and the third after being treated for 3 days with a betablocker of long acting effect (oxprenolol R 160 mg) in a randomized study. The blood pressure mean profile showed a double peak during daily activity with a progressive lowering of the blood pressure during sleep. The effect on the blood pressure of long acting oxprenolol begins four hours later, remains for about ten hours and may be still present next day. The shape of the circadian blood pressure profile is not modified. No significant difference between the pressure profiles on the basic conditions and placebo is noticed.

Oxprenolol: clinical pharmacology, pharmacokinetics, and pharmacodynamics

Oxprenolol is clinically a well-established beta blocker that shares with other members of this group the ability to control a variety of disorders, in particular, hypertension and angina. Pharmacologically it is a nonselective beta blocker that possesses partial agonist activity (intrinsic sympathomimetic activity). Pharmacokinetically, oxprenolol behaves as a moderately lipophilic agent. This means that it is well absorbed, but then undergoes considerable first-pass loss. It penetrates well into most tissues, including the central nervous system. About 80% of oxprenolol is bound to protein in the blood, and when acute-phase proteins increase, as, for example, in patients with inflammatory disease, total plasma concentrations of oxprenolol also increase. Apart from this, the plasma concentration:time profile produced after the oral administration of oxprenolol is remarkably consistent and reproducible. Intrasubject and intersubject variability is small, and the administration of the drug after food or with many other drugs has very little effect. The beta-blocking effects of oxprenolol correlate well with the plasma concentrations, but as with other beta blockers, it has not been possible to correlate plasma concentrations directly with its therapeutic actions such as lowering blood pressure or controlling arrhythmias.

United States experience with oxprenolol in hypertension

Double-blind, randomized, parallel-group studies have confirmed that oxprenolol, either alone or in combination with a thiazide, is effective in reducing elevated blood pressure. In 2 of 3 comparisons with placebo, the blood pressure reduction was significantly more effective with oxprenolol; in 1 study, even though the placebo response was pronounced, oxprenolol was still more effective than placebo. In 2 studies propranolol reduced blood pressure by about 2 mm Hg more than oxprenolol. In the larger, longer-term study this difference was significant at the end of the dose-titration period, but there were no significant differences between the 2 treatment groups at study end. Moreover, oxprenolol reduced heart rate less and was associated with fewer side effects. Oxprenolol effectively lowered blood pressure when given once daily and was well tolerated, even in large doses. Blood pressure was reduced less with oxprenolol than with hydrochlorothiazide, -14/-11 versus -20/-13 mm Hg. The mean reduction with oxprenolol was less for black patients than for white. In a 1-year safety study, 86% of the patients continued to have a diastolic pressure of less than 90 mm Hg at study end.

Clinical responses to oxprenolol in the elderly

Data from 6 controlled clinical trials of oxprenolol carried out in the United States were reviewed to determine the efficacy and tolerability of oxprenolol in patients aged greater than or equal to 55 years. All study designs but 1 called for dosage to be increased to a maximum of 480 mg/day. In a 10-week trial of oxprenolol versus placebo given twice daily, oxprenolol reduced diastolic pressure by 8 mm Hg, while placebo reduced it by 3 mm Hg. A comparison of once-daily with twice-daily dosing showed similar results for both groups: -12/-6 mm Hg for once-daily and -9/-8 mm Hg for twice-daily. There were 2 short-term studies comparing oxprenolol and placebo, both given in addition to hydrochlorothiazide. In the first, the change in blood pressure with oxprenolol was -18/-14 mm Hg and with placebo was +6/-3 mm Hg; only 3 of 14 patients receiving oxprenolol received a maximal dosage. In the follow-up study, most of the dosages were titrated to maximum; reductions were -9/-9 mm Hg with oxprenolol treatment and 0/-12 mm Hg with placebo. Two long-term studies compared oxprenolol and propranolol, also as combination therapy with hydrochlorothiazide. In the 14-week study, the reduction in blood pressure was slightly better with oxprenolol: -15/-15 versus -12/-11 mm Hg. In the 27-week study, almost half of the patients in the oxprenolol group received the maximal dosage. Blood pressure was reduced 2 or 3 mm Hg less with oxprenolol than with propranolol. Oxprenolol was well tolerated in the elderly; it produced a low incidence of typical beta-blocker side effects even when given in a once-daily regimen.

Pharmacokinetics of oxprenolol in the elderly

This paper is a brief review of the problems associated with drug therapy in the elderly. Although the elderly are more prone to suffer adverse reactions to drugs and to respond abnormally, impaired drug handling should not be blamed for these problems until other factors have been evaluated. Renal function deteriorates as people grow older, but the absorption, metabolism and distribution of most drugs may not be adversely affected by advancing age. Evidence to the contrary is sometimes based on studies of convalescent patients in whom an effect of disease or drug therapy cannot be excluded. For an assessment of the effects of aging on the pharmacokinetics of oxprenolol, 2 groups of 8 healthy females, mean age 21 and 68 years, respectively, were studied. Oxprenolol, 80 mg, was given orally in a single dose on day 1 and day 8 of a course of treatment; on the intervening days, oxprenolol, 80 mg, was given twice daily. The mean plasma concentration:time curves for both day 1 and day 8 for the 2 age groups were comparable. Thus, age alone does not affect the pharmacokinetics of oxprenolol.

Prazosin and oxprenolol therapy in pregnancy hypertension

Prazosin (Minipress; Pfizer), the first purely alpha-blocking antihypertensive agent, was used to treat 22 pregnant patients with moderately severe hypertension (diastolic blood pressure persistently above 95 mmHg at gestational ages ranging from 18 to 33 weeks). Prazosin was used because it is a postsynaptic alpha-blocking agent producing no direct tachycardia or renin stimulation and because its action in producing visceral vasodilation might improve uteroplacental perfusion. Oxprenolol (Trasicor; Ciba), a beta-blocking agent with intrinsic sympathomimetic activity, was added to the prazosin regimen in 12 cases. In this group pregnancy was prolonged for an average of 32 days and 10 infants survived the neonatal period. Fetal loss, mainly due to abortion, was high in the patients who had significant proteinuria, and it was not possible to prolong the pregnancy in these cases. There were no significant maternal, fetal or neonatal side-effects attributable to this combined alpha- and beta-blocking therapy, which may have both theoretical and practical advantages over other current therapies.

A double-blind study of oxprenolol once and twice daily in hypertensive patients

In a randomized double-blind study of 175 patients with mild-to-moderate hypertension, oxprenolol hydrochloride (160-480 mg) given once daily was compared with the same drug given twice daily for efficacy, safety, and tolerability. Of these patients, 123 (58 receiving the once daily regimen and 65 receiving the twice daily regimen) were included in the analysis of efficacy. Both groups showed similar significant (p less than 0.01) reductions in mean blood pressure during the 6-week titration period and for the remainder of the trial. A comparison of mean standing diastolic blood pressure and supine systolic and diastolic blood presses showed no significant difference between groups during the fixed dosage period. The number of patients reporting adverse experiences was not significantly different for the two regimens. Plasma triglycerides increased in both groups, but there were no other laboratory abnormalities related to treatment. This study shows that oxprenolol given once daily is effective, safe, and well tolerated in the treatment of mild-to-moderate hypertension.

Monitoring of the plasma concentration of a beta blocker with retarded effect (Slow Trasicor, 160 mg) in humans

The plasma oxprenolol concentrations were measured in nine cases for 3 days following the application of 1 dragee (160 mg) daily of Slow Trasicor (CIBA). Blood sampling was carried out at the 1st, 6th, 12th, and 24th h during the 1st day, and at the 12th and 24th h during the 2nd and 3rd days, respectively. Oxprenolol reached a considerable plasma level already after the 1st h: 140 ng/ml on the average during the 1st day. The average concentrations were 284 and 202 at the 6th and 12th h, respectively. It decreased to 43 ng/ml by the 24th h. During the 2nd and 3rd days 124 and 122 ng/ml values were found at the 12th h, and 42 and 50 ng/ml at the 24th h. The results of these studies prove the good absorption of Slow Trasicor, as well as its prolonged presence in the plasma. The corresponding clinical improvements in the patients indicate the therapeutic effect of the plasma levels.

Effect of the chronic administration of oxprenolol on the aortic wall of the normotensive and hypertensive rats

4 groups of male Wistar rats were studied: - normotensive control rats (4 animals) treated with s.c. water - normotensive rats (6 animals) treated with s.c. 5 mg/Kg Oxprenolol - hypertensive control rats (renal artery stenosis) (6 animals) treated with s.c. water - hypertensive rats (renal artery stenosis) (9 animals) treated with s.c. 5 mg/Kg Oxprenolol. The animals were treated and/or operated at six weeks of age and sacrificed at 12 weeks of age. Blood Pressure (BP), Heart Rate (HR), Ventricular Mass (VM) and Thickness of the Aortic Media (A Th) were determined. Oxprenolol did reduce HR but not BP in both normotensive and hypertensive rats: these animals showed a reduced A Th but not a reduced VM compared with untreated control rats. These results suggest a direct effect of Oxprenolol on A Th independently from BP values, but not on VM.

Slow-release oxprenolol compared with oxprenolol in hypertensive patients: a multicenter clinical trial

Oxprenolol (OX) is a nonselective, beta-adrenergic blocking agent with intrinsic sympathomimetic activity. We studied 178 patients in five centers to determine whether a polymer-matrix-based, slow-release preparation of oxprenolol (SR-OX) given once daily was as effective as the standard preparation given twice daily for the treatment of patients with mild to moderate hypertension. After a placebo washout phase, patients were treated with OX until blood pressure was controlled. They were then randomized in a double-blind fashion to continue the same dose, given as either OX bid or SR-OX qd with a placebo as the second dose. All patients took hydrochlorothiazide 50-100 mg/d throughout the study. Blood pressure was reduced 23/15 mm Hg (p less than 0.001) and pulse 8 beats/min in the SR-OX group (n = 67) and 24/17 mm Hg (p less than 0.001) and 8 beats/min in the OX group (n = 72) by titrating standard OX. After randomization to SR-OX or OX, there were no further changes over six weeks. Home-determined blood pressures showed no loss of control in the evening. There were no unexpected adverse effects. We conclude that SR-OX given once daily is as effective as OX given twice daily for the treatment of hypertension.

Oxprenolol in schizophrenic patients with tardive dyskinesia: a double-blind placebo-controlled, crossover study

Tardive dyskinesia is a syndrome of involuntary movements that develops during or following long-term neuroleptic treatment. Current treatment of tardive dyskinesia is unsatisfactory. Neuroleptics can reduce the syndrome, but the underlying pathogenetic process is probably aggravated during treatment. The use of these drugs is necessary, however, when the patient simultaneously exhibits intense psychotic and dyskinetic symptoms. In this controlled study, 8 patients were treated with a beta-blocker drug, oxprenolol, as a slow-release preparation that was administered in increasing doses up to 640 mg per day for one month. We conclude that this drug can ameliorate both the psychotic features of schizophrenics and their tardive dyskinetic movements without producing significant side-effects.

A long-term prevention study with oxprenolol in coronary heart disease

We carried out a randomized double-blind controlled secondary-prevention trial of oxprenolol over seven years. Forty milligrams of oxprenolol or placebo was given twice daily to 1103 men 35 to 65 years old who had an acute myocardial infarction between 1 and 90 months previously. Overall, there was no difference in mortality or cardiac events between the placebo and oxprenolol groups. The major influence on prognosis was the time at which treatment was started after infarction. In 417 patients in whom treatment was started within four months of infarction oxprenolol increased the six-year cumulative survival rate from 77 to 95 per cent (P less than 0.001). In 274 patients with treatment starting between 5 and 12 months of infarction the survival rate was similar in the two groups, but in 412 patients entered between 1 and 7 1/2 years after their first infarction oxprenolol reduced the six-year survival rate from 92 to 79 per cent (P = 0.002). The increased mortality in this latter group mainly occurred late after withdrawal from active treatment. The value of low-dose oxprenolol in secondary prevention appears to be confined to patients treated relatively soon after myocardial infarction.

Intravenous beta-blockade in coronary heart disease: is cardioselectivity or intrinsic sympathomimetic activity hemodynamically useful?

Beta-blocking drugs are increasingly prescribed in coronary heart disease, but controversy surrounds the hemodynamic relevance of their ancillary pharmacologic properties--cardioselectivity and intrinsic sympathomimetic activity. We therefore compared the effects of four intravenous beta-adrenoreceptor antagonists with different ancillary properties on left ventricular function in 24 patients with coronary heart disease. All four drugs depressed the relation between left ventricular filling pressure and cardiac output at rest and during exercise. However, practolol and oxprenolol, which have intrinsic sympathomimetic activity, induced significantly less depression of left ventricular function than either propranolol or metoprolol, which do not have this activity. Cardioselectivity, a property of both practolol and metoprolol, had no discernible hemodynamic advantage. Beta-blocking drugs that have intrinsic sympathomimetic activity appear to be more effective in maintaining cardiac function than drugs without this property, when given intravenously to patients with coronary heart disease.

Pregnancy-associated hypertension: interrelationships of volume and blood pressure changes

In normal human pregnancy there is considerable expansion of both plasma volume and total extracellular fluid volume, together with marked diminution of vascular reactivity in response to intravenous infusion of vasopressor agents. Pregnancy-associated hypertension (pre-eclampsia) is characterised by increased vascular reactivity, vasoconstriction and a fall in plasma volume associated with a shift of fluid from intravascular to interstitial fluid space. Direct expansion of plasma volume in patients with pregnancy-associated hypertension leads to partial correction of the abnormalities of volume homeostasis together with a significant fall in blood pressure. Certain forms of antihypertensive therapy also lead to reversal of volume contraction and improvement in cardiac function. This is associated with lowered vascular resistance and improved placental function, leading to improved pregnancy outcome. Although these observations do not elucidate the ultimate cause/causes of pregnancy-associated hypertension, they help to unravel the pathologic mechanisms by which the syndrome causes its effects and to suggest rational paths by which therapeutic endeavours may be expected to benefit mother and fetus.

Comparison of the beta-adrenoceptor blocking activity of oxprenolol, slow release oxprenolol and a combined oxprenolol diuretic preparation

1 Observations were made in five healthy subjects who exercised before and 2, 3, 6, 8 and 24 h after the oral administration on separate occasions of 160 mg oxprenolol, 160 mg slow release oxprenolol, 160 mg slow release oxprenolol with 0.25 mg cyclopenthiazide and placebo. Blood samples were obtained before and at 1, 2, 3, 6, 8, 12 and 24 h after drug administration and assayed for oxprenolol concentration. 2 The three formulations produced maximum reductions of 29% in the exercise tachycardia 3 to 6 h after drug administration. At 24 h the effects of the three preparations were not significantly different from placebo. 3 There were no significant differences in the plasma concentrations produced by the three formulations during the 24 h period. 4 These observations suggest that the slow release formulations of oxprenolol should be given twice daily to maintain cardiac beta-adrenoceptor blockade throughout a period of 24 h.