Symptoms
Poisoning due to an overdosage of beta-blocker may lead to pronounced hypotension, bradycardia, hypoglycaemia, heart failure, cardiogenic shock, conduction abnormalities (first or second degree block, complete heart block, asystole), or even cardiac arrest. In addition, dyspnoea, bronchospasm, vomiting, impairment of consciousness, and also generalised convulsions may occur. Rhabdomyolysis with myoglobinuria has been reported as a complication of severe overdosage with oxprenolol.
The manifestations of poisoning with beta-blocker are dependent on the pharmacological properties of the ingested drug. Although the onset of action is rapid, effects of massive overdose may persist for several days despite declining plasma levels. Watch carefully for cardiovascular or respiratory deterioration in an intensive care setting, particularly in the early hours. Observe mild overdose cases for at least 4 hours for the development of signs of poisoning.
Management
Patients who are seen soon after potentially life-threatening overdosage (within 4 hours) should be treated by gastric lavage and activated charcoal.
Treatment of symptoms is based on modern methods of intensive care, with continuous monitoring of cardiac function, blood gases, and electrolytes, and if necessary intravenous fluid and electrolytes replacement, and emergency measures such as artificial respiration, resuscitation or cardiac pacemaker.
Significant bradycardia should be treated initially with atropine. Large doses of isoprenaline may be necessary for control of heart rate and hypotension. Glucagon has positive chronotropic and inotropic effects on the heart that are independent of interactions with beta-adrenergic receptors and it represents a useful alternative treatment for hypotension and heart failure.
For seizures, diazepam has been effective and is the drug of choice.
For bronchospasm, aminophylline, salbutamol or terbutaline (beta2-agonist) are effective bronchodilator drugs. Monitor the patient for dysrhythmias during and after administration.
Patients who recover should be observed for signs of beta-blocker withdrawal phenomenon.
- Hypersensitivity to oxprenolol and related derivatives, cross-sensitivity to other beta-blockers or to any of the excipients listed in section 6.1.
- Cardiogenic shock.
- Second or third degree atrioventricular block.
- Uncontrolled heart failure.
- History of cor pulmonale.
- Sick-sinus syndrome.
- Bradycardia (< 45-50bpm).
- Hypotension.
- Untreated phaeochromocytoma.
- Severe peripheral arterial circulatory disturbances.
- History of bronchospasm and bronchial asthma. (A warning stating “Do not take this medicine if you have a history of wheezing or asthma†will appear on the label)
- Chronic obstructive pulmonary disease.
- Prinzmetal's angina (variant angina pectoris).
- Use of anaesthetics which are known to have a negative inotropic effect.
- Metabolic acidosis.
- Prolonged fasting.
- Severe renal failure.
Owing to the danger of cardiac arrest, a calcium antagonist of the verapamil type must not be administered intravenously to the patient already receiving treatment with a beta-blocker.
Not applicable.
Side-Effects: Frequency estimate: very common (>1/10), common (>1/100 to <1/10), uncommon (>1/1,000 to <1/100), rare (>1/10,000 to <1/1,000), very rare (<1/10,000), not known (cannot be estimated from the available data).
Blood and lymphatic system disorders
Very rare: Thrombocytopenia sometimes with purpura.
Not known: Agranulocytosis.
Metabolism and nutrition disorders
Not known: Diabetes mellitus, hypoglycaemia, hyperglycaemia.
Psychiatric disorders
Common: Depression, libido disorder.
Uncommon: Sleep disorder, nightmares.
Rare: Hallucinations.
Not known: Psychosis, confusional state.
Nervous system disorders
Common: Headache, dizziness.
Eye disorders
Uncommon: Visual impairment (vision blurred, vision abnormal).
Rare: Dry eyes, keratoconjunctivitis.
Cardiac disorders
Common: Cardiac failure.
Uncommon: Bradycardia, cardiac conduction disorders.
Not known: Complete atrioventricular block, cardiac arrhythmia.
Vascular disorders
Common: Hypotension, peripheral vascular disorders (e.g. peripheral coldness, paraesthesia).
Rare: Raynaud's phenomenon.
Not known: Necrotising vasculitis, intermittent claudication.
Respiratory, thoracic and mediastinal disorders
Common: Dyspnoea, bronchospasm.
Gastrointestinal disorders
Very common: Dry mouth, constipation.
Common: Nausea.
Uncommon: Diarrhoea, vomiting, flatulence.
Not known: Abdominal discomfort, retroperitoneal fibrosis, dyspepsia.
Musculoskeletal and connective tissue disorders
Not known: Myalgia, arthralgia, muscle cramps, myasthenia gravis.
Skin and subcutaneous tissue disorders
Uncommon: Dermatitis allergic.
Rare: Worsening of psoriasis.
Not known: Rash, toxic epidermal necrolysis, cutaneous lupus erythematosus like lesions,reactivation of cutaneous lupus erythematosus, pruritus, hyperhidrosis.
Reproductive system and breast disorders
Common: Erectile dysfunction.
Renal and urinary disorders
Not known: Glycosuria.
General disorders and administration site conditions
Common: Fatigue.
Rare: Exertional tiredness.
Not known: Hyperpyrexia.
Investigations
Not known: An increase in ANA (anti-nuclear antibodies) has been seen; its clinical relevance is not clear.
Chronic treatment with oxprenolol increases very low density lipoprotein and decreases high density lipoprotein, which may have an adverse effect on the risk of cardiovascular events.
Beta-blockers may mask the symptoms of thyrotoxicosis or hypoglycaemia.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme, website: www.mhra.gov.uk/yellowcard.
None stated.
Slow Corbeton Tablets are indicated in adults for the treatment of:
Hypertension: As monotherapy or for use in combination with other antihypertensives, e.g. with a diuretic, peripheral vasodilator, calcium channel blocker or ACE inhibitor.
Angina Pectoris: For long-term prophylactic use (if necessary nitrates should be employed for alleviating acute attacks).
| Pharmacotherapeutic group: | Beta blocking agent, non selective |
| ATC code: | C07AA |
Oxprenolol, the active substance of Slow Corbeton Tablets, is a non-selective, lipophilic beta-blocker exerting a sympatholytic effect and displaying mild to modest partial agonistic activity (PAA), also known as intrinsic sympathomimetic activity (ISA).
Drugs like oxprenolol with PAA cause comparatively less slowing of the resting heart rate and a less marked negative-inotropic effect than those without PAA. The risk of substantial bradycardia at rest and heart failure is lessened.
The antiarrhythmic effect of oxprenolol is primarily due to suppression of the arrhythmogenic sympathetic influence of catecholamines. Evidence that increased sympathetic stimulation predisposes to many arrhythmias is strong. This is supported by the increased incidence of arrhythmias in man in situations associated with high sympathetic drive or myocardial sensitisation to catecholamines e.g. exercise, emotional stress, phaeochromocytoma, trauma, myocardial ischaemia, anaesthesia, hyperthyroidism.
Oxprenolol decreases cardiac impulse formation in the sinus node with resultant slowing of the sinus rate; it slightly prolongs the sino-atrial conduction time; both the atrio-ventricular (AV) conduction time and the AV node refractory periods are lengthened.
Some beta-blockers such as oxprenolol possess a membrane stabilising activity (MSA) on the cardiac action potential, also known as “quinidine-like†or “local anaesthetic†action, a property that tends to result in greater cardiac depression than is seen with beta-blockers which do not have this pharmacological characteristic. However, at normal therapeutic doses, this property is probably clinically irrelevant and it only becomes manifest after overdose.
In coronary artery disease, oxprenolol is beneficial in increasing exercise tolerance and decreasing the frequency and severity of anginal attacks.
Emotional stress and anxiety states, the symptoms of which are largely caused by increased sympathetic drive, are alleviated by the sympatholytic effect of oxprenolol. The exact way in which beta-blockers exert their antihypertensive action is still not fully understood. Various modes of action have been postulated. During chronic therapy the antihypertensive effect of beta-blockers is associated with a decline in peripheral resistance.
Oxprenolol is effective in lowering elevated supine, standing and exercise blood pressure; postural hypotension is unlikely to occur.
Absorption:
In the gastrointestinal tract, oxprenolol is rapidly and completely absorbed from the sustained release tablets, regardless of whether or not they are taken together with food. Peak plasma concentrations are attained after an average of approximately 3 hours.
During treatment with the sustained release forms, prolongation of the absorption phase enables therapeutically active plasma concentrations to be maintained over a longer period than when the same doses are given in conventional dosage forms and avoids high peak drug concentrations in the plasma.
Biotransformation:
Oxprenolol is subject to first-pass metabolism. Its systemic bioavailability is 20 - 70%.
Distribution:
Oxprenolol has a plasma-protein binding rate of approx. 80% and a calculated distribution volume of 1.2 l/kg.
Oxprenolol crosses the placental barrier. The concentration in the breast milk is equivalent to approx. 30% of that in the plasma.
Oxprenolol is moderately lipid-soluble and crosses the blood-brain barrier.
Elimination:
Oxprenolol has an elimination half-life of 1 - 2 hours. Oxprenolol is extensively metabolised, direct O-glucuronidation being the major metabolic pathway and oxidative reactions minor ones. Oxprenolol is excreted chiefly in the urine (almost exclusively in the form of inactive metabolites). The drug is not likely to accumulate.
Characteristics in patients:
Age has no effect on the pharmacokinetics of oxprenolol.
In patients with acute or chronic inflammatory diseases an increase in the plasma levels of oxprenolol has been observed. The plasma levels may also increase in the presence of severe hepatic insufficiency associated with a reduced metabolism.
Impaired renal function generally leads to an increase in the blood levels of oxprenolol, but the concentrations measured remain within - although at the upper limit of - the concentration range recorded in subjects with healthy kidneys. In addition, in patients with renal failure the apparent elimination half-life for unchanged, i.e. active, oxprenolol is comparable with the corresponding half-life values determined in subjects with no renal disease. Hence, there is no need to readjust the dosage in the presence of impaired renal function.
As beta-blockers increase the AV conduction time, beta-blockers should only be given with caution to patients with first degree AV block.
Beta-blockers should not be used in patients with untreated congestive heart failure.
This condition should first be stabilised.
As with all beta-blockers, oxprenolol should be used with caution in patients with a recent myocardial infarction.
Beta-blockers may unmask myasthenia gravis.
Caution is advised in patients with psoriasis, as oxprenolol can worsen this condition.
If the patient develops increasing bradycardia less than 50-55 beats per minute at rest and the patient experiences symptoms related to bradycardia, the dosage should be reduced or gradually withdrawn.
Beta-blockers are liable to affect carbohydrate metabolism. Diabetic patients, especially those dependent on insulin, should be warned that beta-blockers can mask symptoms of hypoglycaemia (e.g. tachycardia). Hypoglycaemia, producing loss of consciousness in some cases, may occur in non-diabetic individuals who are taking beta-blockers, particularly those who undergo prolonged fasting or severe exercise. The concurrent use of beta-blockers and anti-diabetic medication should always be monitored to confirm that diabetic control is well maintained.
Beta-blockers may mask certain clinical signs (e.g. tachycardia) of hyperthyroidism and the patient should be carefully monitored.
Beta-blockers may reduce liver function and thus affect the metabolism of other drugs.
Like many beta-blockers oxprenolol undergoes substantial first-pass hepatic metabolism. In the presence of liver cirrhosis the bioavailability of oxprenolol may be increased leading to higher plasma concentrations.
In patients with renal impairment, the elimination half-life for unchanged oxprenolol is not expected to be significantly different from the subjects with normal renal function. Creatinine clearance, urea and electrolytes should be monitored in patients with renal impairment since they might be more susceptible to the effects of antihypertensive drugs due to haemodynamic effects particularly patients with severe renal failure.
In patients with peripheral circulatory disorders (e.g. Raynaud's disease or syndrome, intermittent claudication), beta-blockers should be used with great caution as aggravation of these disorders may occur.
As with all antihypertensive agents, a cautious dosage schedule is indicated in patients with severe coronary or cerebral arteriosclerosis.
In patients with phaeochromocytoma a beta-blocker should only be given together with an alpha-blocker,.
Owing to the danger of cardiac arrest, a calcium antagonist of the verapamil type must not be administered intravenously to the patient already receiving treatment with a beta-blocker.).
Anaphylactic reactions precipitated by other agents may be particularly severe in patients taking beta-blockers, especially non-selective drugs, and may require higher than normal doses of adrenaline for treatment. Whenever possible, beta-blockers should be discontinued in patients who are at increased risk for anaphylaxis.
Especially in patients with ischaemic heart disease, treatment should not be discontinued suddenly. The dosage should gradually be reduced, i.e. over 1-3 weeks, if necessary, at the same time initiating alternative therapy, to prevent exacerbation of angina pectoris.
If a patient receiving oxprenolol requires anaesthesia, the anaesthetist should be informed of the use of the medication prior to the use of general anaesthetic to permit him to take the necessary precautions. The anaesthetic selected should be one exhibiting as little inotropic activity as possible, e.g. halothane/nitrous oxide. During treatment with oxprenolol, patients should not undergo anaesthesia with agents causing myocardial depression (e.g.cyclopropane, trichloroethylene, ether, chloroform). If on the other hand, inhibition of sympathetic tone during the operation is regarded as undesirable, the betablocker should be withdrawn gradually at least 48 hours prior to surgery.
The full development of the “oculomucocutaneous syndromeâ€, as previously described with practolol has not been reported with oxprenolol. However some features of this syndrome have been noted such as dry eyes alone or occasionally associated with skin rash. In most cases the symptoms cleared after withdrawal of the treatment.
Discontinuation of oxprenolol should be considered, and a switch to another antihypertensive drug might be advisable, see advice on discontinuation above.
Interference with laboratory tests:
Oxprenolol use may give falsely high fluorometric readings in urine cortisol determinations.
Slow Corbeton Tablets contain lactose
Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Slow Trascor Tablets contain glycerol
May cause headache, stomach upset and diarrhoea.
Patients receiving oxprenolol should be warned that dizziness, fatigue or visual disturbances may occur, in which case they should not drive, operate machinery or do anything else requiring alertness, particularly if they also consume alcohol.
Posology
The dosage should be individualised. Before raising the dosage, the heart rate at rest should always be checked. If it is 50-55 beats/min, the dosage should not be increased, see contraindications.
If the maximum recommended dose is insufficient to produce the desired response appropriate combined therapy should be considered.
When discontinuing prolonged treatment with a beta-blocker, the medication should not be interrupted abruptly, but withdrawn gradually.
The sustained-release formulation provides a longer pharmacological action from a given dose, thus allowing once daily administration. When the dose is raised to more than one Slow Corbeton tablet, it is usual for this to continue to be given once daily.
Oxprenolol is only gradually released from the sustained-release tablet, extending the duration of effect. The occurrence of high peak concentrations in the plasma is thus avoided.
Elderly
No special dosage regime is necessary but concurrent hepatic insufficiency should be taken into account.
Paediatric population
No adequate experience has been acquired on the use of Slow Corbeton Tablets in children.
Adults
Hypertension: 160 mg once daily. If necessary, the dosage can be raised to 320 mg.
Angina pectoris: 160 mg once daily. If necessary, the dosage can be raised to 320 mg.
Method of administration
Slow Corbeton Tablets should be swallowed whole with liquid.
None.
