Adverse Effects and Contraindications

ADVERSE EFFECTS AND CONTRAINDICATIONS

·        Propranolol can accentuate myocardial insufficiency and can precipitate CHF/edema by blocking sympathetic support to the heart, especially during cardiovascular stress. However, when compensation has been restored, careful addition of a β₁ blocker is now established therapy to prolong survival.

·        Bradycardia: resting HR may be reduced to 60/min or less. Patients of sick sinus are more prone to severe bradycardia.

·        Propranolol worsens chronic obstructive lung disease, can precipitate lifethreatening attack of bronchial asthma: contraindicated in asthmatics.

·        Propranolol exacerbates variant (Prinzmetal’s) angina due to unopposed α mediated coronary constriction. In some patients, even classical

·        angina may be worsened if ventricular dilatation and asynergy of contraction occurs—specially with high doses.

·        Carbohydrate tolerance may be impaired in prediabetics.

·        Plasma lipid profile is altered on long term use: total triglycerides and LDLcholesterol tend to increase while HDLcholesterol falls. This may enhance risk of coronary artery disease. Cardioselective β blockers and those with intrinsic sympathomimetic activity have little/no deleterious effect on blood lipids.

·        Withdrawal of propranolol after chronic use should be gradual, otherwise rebound hypertension, worsening of angina and even sudden death can occur. This is due to supersensitivity of β receptors occurring as a result of longterm reduction in agonist stimulation.

·        Propranolol is contraindicated in partial and complete heart block: arrest may occur.

·        Tiredness and reduced exercise capacity: due to blunting of β₂ mediated increase in blood flow to the exercising muscles as well as attenuation of glycogenolysis and lipolysis.

·        Cold hands and feet, worsening of peripheral vascular disease are noticed due to blockade of vasodilator β₂ receptors.

·        Side effects not overtly due to β blockade are— g.i.t. upset, lack of drive, nightmares, forgetfulness, rarely hallucinations. Male patients more frequently complain of sexual distress.