May cause additive negative chronotropic and/or inotropic effect w/ amiodarone, disopyramide, quinidine, flecainide and Ca channel blockers. May cause additive hypotensive effect w/ phenothiazines. β-adrenergic stimulating effects of sympathomimetic agents are antagonised. Concomitant admin w/ catecholamine-depleting drugs (e.g. reserpine) may cause additive effects and potentiate depression. Reduced antihypertensive effect w/ aluminium and NSAIDs. Coadministration w/ warfarin increases its bioavailability and prothrombin time. Altered antidiabetic response when used w/ antidiabetic agents and insulin. Potentially Fatal: Increased risk of QT interval prolongation and torsades de pointes w/ thioridazine.
Sinus bradycardia, cardiogenic shock, sick sinus syndrome, Raynaud's syndrome, 2nd and 3rd degree heart block, overt CHF, bronchial asthma, COPD, untreated phaeochromocytoma, Prinzmetal's angina; severe peripheral arterial disease, metabolic acidosis. Concomitant use w/ thioridazine.
Propranolol is a non-cardioselective β-blocker that competitively blocks β1- and β2-receptors resulting in decreased heart rate, myocardial contractility, BP and myocardial oxygen demand. It has membrane-stabilising properties. Onset: 1-2 hr (oral). Absorption: Almost completely absorbed from the GI tract. Bioavailability: Approx 25%. Time to peak plasma concentration: Approx 1-2 hr (oral). Distribution: Widely distributed, enters breast milk, crosses blood brain barrier and placenta. Volume of distribution: 4 L/kg. Plasma protein binding: Approx 90%. Metabolism: Undergoes hepatic metabolism via CYP2D6 isoenzyme, and CYP1A2 to 4-hydroxypropranolol (biologically active). Excretion: Via urine (96-99% as metabolites and <1% as unchanged drug). Elimination half-life: Approx 3-6 hr.
Sinus node dysfunction, DM, history of nonallergic bronchospasm (e.g. chronic bronchitis, emphysema), myasthenia gravis, 1st degree heart block. May mask signs of hyperthyroidism and hypoglycaemia. Renal or hepatic impairment. Abrupt withdrawal may exacerbate angina symptoms or precipitate MI in patients w/ coronary artery disease. Elderly. Pregnancy and lactation. Patient Counselling Avoid cigarette smoking. Monitoring Parameters Monitor ECG, heart rate and BP