| Hypoglycaemic agents: Tachycardia associated with hypoglycaemia may be modified by propranolol. Use of propranolol alongside hypoglycaemic therapy in diabetic patients should be with caution since it may prolong the hypoglycaemic response to insulin.Clonidine: Caution should be exercised when transferring patients from clonidine to beta-adrenoceptor blocking drugs. If propranolol and clonidine are given concurrently, clonidine should not be discontinued until several days after the withdrawal of the beta blocker. If replacing clonidine by beta-adrenoceptor blocking drug therapy, the introduction of the beta-adrenoceptor blocking drugs should be delayed for several days after clonidine administration has stopped. Anti-arrhythmics: Care should be taken when prescribing a beta-adrenergic blocking drug with Class 1 anti-arrhythmic agents such as disopyramide. Flecainaide may have additive cardiac depressant effects.Calcium Channel Blockers: Combined use of beta-adrenoceptor blocking drugs and calcium channel blockers with negative inotropic effects (eg, verapamil, diltiazem) can lead to an exaggeration of these effects particularly in patients with impaired ventricular function and/or SA or AV conduction abnormalities. This may result in severe hypotension, bradycardia and cardiac failure. Neither drug should be administered intravenously within 48 hours of discontinuing the other.Concomitant therapy with dihydropyridine calcium channel blockers eg, nifedipine, may increase the risk of hypotension, and cardiac failure may occur in patients with latent cardiac insufficiency.Drugs with hypotensive effects: Dynamic interactions between propranolol and other drugs with hypotensive effects are to be expected. Reactions are sometimes severe and careful monitoring is advised in co-administration of propranolol with other drugs including ACE inhibitors, diuretics, angiotensin II receptor antagonists, vasodilator antihypertensives, diazoxide, adrenergic neurone blockers, alpha blockers, moxisylyte, moxonidine, nitrates and methyldopa.Anaesthesia: Caution must be exercised when using anaesthetic agents with propranolol. The anaesthetist should be informed and the choice of anaesthetic should be the agent with as little negative inotropic activity as possible. Use of beta-adrenoceptor blocking drugs with anaesthetic drugs may result in attenuation of the reflex tachycardia and increase the risk of hypotension. Anaesthetic agents causing myocardial depression are best avoided.Neostigmine and other anticholinesterases: Propranolol reduces the efficacy of these compounds in treatment of myasthenia gravis.Sympathomimetic Agents and Parenteral Adrenaline: Concomitant use of sympathomimetic agents e.g. adrenaline, may counteract the effect of beta-adrenoceptor blocking drugs. Caution should be taken in the parenteral administration of preparations containing adrenaline to people taking beta-adrenoceptor blocking drugs as, in rare cases, vasoconstriction, hypertension and bradycardia may result.Muscle relaxants (e.g. balcofen): Concomitant use may result in a fall in blood pressure. Tizanidine may also result in bradycardia.Antidepressants, anxiolytics and hypnotics: Plasma levels of propranolol can be increased by fluvoxamine. Anxiolytics, hypnotics and MAOIs when given with propranolol may have an enhanced hypotensive effect. Propranolol may increase plasma concentration of imipramine. Barbiturates may reduce the plasma concentration of propranolol.Corticosteroids: Can antagonise the effects of beta-blockers.Dihydropyridines: Concomitant therapy with dihydropyridines e.g. nifedipine, may increase the risk of hypotension, and cardiac failure may occur in patients with latent cardiac insufficiency.Digitalis Glycosides: These preparations in association with beta-adrenoceptor blocking drugs, may increase atrio-ventricular conduction time.Lignocaine: Administration of propranolol during infusion of lignocaine may increase the plasma concentration of lignocaine by approximately 30%. Patients already receiving propranolol tend to have higher lignocaine levels than controls. The combination should be avoided.Ergotamine: Caution should be exercised if ergotamine, dihydroergotamine or related compounds are given in combination with propranolol since vasospastic reactions have been reported in a few patients.Prostaglandin Synthetase Inhibiting Drugs: Concomitant use of these e.g. ibuprofen or indomethacin, may decrease the hypotensive effects of propranolol.Chlorpromazine: Concomitant administration with propranolol may result in an increase in plasma levels of both drugs. This may lead to an enhanced antipsychotic effect for chlorpromazine and an increased antihypertensive effect for propranolol.Mefolquine: May lead to an increased risk of bradycardia.Cimetidine, hydralazine, alcohol: Concomitant use of cimetidine and hydralazine will increase, whereas concomitant use of alcohol will decrease, the plasma level of propranolol.Dopaminergics (e.g. Levodopa), Aldesleukin, Prostaglandins (alprostadil): May have an enhanced hypotensive effect when used concomitantly with propranolol.Oestrogens: May antagonise the hypotensive effect of propranolol.5HT1 agonists: Propranolol may increase plasma concentrations of rizatriptan.Pharmacokinetic studies have shown that the following agents may interact with propranolol due to effects on enzyme systems in the liver which metabolise propranolol and these agents: quinidine, propafenone, rifampicin, theophylline, warfarin, thioridazine and dihydropyridine calcium channel blockers such as nifedipine, nisoldipine, nicardipine, isradipine and lacidipine. Owing to the fact that blood concentrations of either agent may be affected, dosage adjustments may be needed according to clinical judgement. (See also the interaction above concerning the concomitant therapy with dihydropyridine calcium channel blockers). | |