Intravenous administration of calcium antagonists of the verapamil-type should not be given to patients treated with β-blockers.
Generally when treating patients with asthma, concomitant therapy with a β2-agonist (tablet and/or inhalation) should be administered. The dosage of β2-agonists may require adjustment (increase) when treatment with Betaloc ZOK is started. The risk of Betaloc ZOK interfering with β2-receptors is however less than with conventional tablet formulations of β1-selective blockers.
During treatment with Betaloc ZOK, the risk of interfering with carbohydrate metabolism or masking hypoglycaemia is likely to be less than during treatment with conventional tablet formulations of β1-selective blockers and much less than with non-selective β-blockers.
Patients suffering from heart failure should have their decompensation treated both before and during treatment with Betaloc ZOK.
Very rarely, a pre-existing A-V conduction disorder of moderate degree may become aggravated (possibly leading to A-V block).
If the patients develop increasing bradycardia, Betaloc ZOK should be given in lower doses or gradually withdrawn.
Betaloc ZOK may aggravate the symptoms of peripheral arterial circulatory disorders, mainly due to its blood pressure lowering effect.
Where Betaloc ZOK is prescribed for a patient known to be suffering from a phaeochromocytoma, an alpha-blocker should be given concomitantly.
Prior to surgery the anaesthetist should be informed that the patient is receiving Betaloc ZOK. It is not recommended to stop β-blocker treatment in patients undergoing surgery. Acute initiation of high-dose metoprolol to patients undergoing non-cardiac surgery should be avoided, since it has been associated with bradycardia, hypotension and stroke including fatal outcome in patients with cardiovascular risk factors.
Abrupt interruption of the medication is to be avoided. Sudden withdrawal of β-blockade is hazardous, especially in high-risk patients and increase the risk of myocardial infarction and sudden death. Any withdrawal of Betaloc ZOK should therefore, if possible, be made gradually over at least two weeks when the dose is reduced by half in each step, down to the final dose when a 50-mg tablet is reduced to half a tablet. The final dose should be given for at least four days before discontinuation. If symptoms occur, a slower withdrawal rate is recommended.
In patients taking β-blockers anaphylactic shock assumes a more severe form.
Effects on ability to drive and use machines: Patients should know how they react to Betaloc ZOK before they drive or use machines because occasionally dizziness or fatigue may occur.