6847203
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
about 8 years ago
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| Question | Answer |
| Give eg's of & indications for beta-blockers. | eg's: bisoprolol, atenolol, propranolol, metoprolol. Indications: • IHD: as a first-line option to improve Sx & prognosis associated with angina & ACS • CHF • AF - to ↓ ventricular rate &,in paroxysmal fibrillation, to maintain sinus rhythm • SVT - 1st line option in those without circulatory compromise • HT - may be used when other medicines (eg calcium channel blockers, ACE inhibitors, thiazide diuretics) are insufficient/inapproriate |
| MOA of beta-blockers. | Beta1-adrenoreceptors are located mainly in the heart, whereas β2-adrenoreceptors are found mostly in smooth muscle of BD vessels & the airways. Via the β1-receptor, β-blockers reduce force of contraction & speed of conduction in the HT. This relieves myocardial ischaemia by reducing cardiac work & O2 demand, & ^myocardial perfusion. They improve prognosis in HF by ‘protecting’ the HT from the effects of chronic sympathetic stimulation. They slow the ventricular rate in AF mainly by prolonging the refractory period of the AV node. SVT often involves a self-perpetuating (‘re-entry’) circuit that takes in the AV node; β-blockers may break this & restore sinus rhythm. In HT, β-blockers lower BP through a variety of means, one of which is by reducing renin secretion from the kidney, since this is mediated by β1-receptors. |
| SE's of beta-blockers. | • Fatigue • Cold extremities • Headache • GI disturbance • Sleep disturbance & nightmares • Impotence |
| CI's, cautions, & important interactions of beta-blockers. | CI's: • Asthma • HT block Cautions: • COPD - β1-selective (eg atenolol, bisoprolol, metoprolol) should be used rather than non-selective (eg propanolol) • HF - start at low doses as they may initially impair cardiac function • Haemodynamic instability • Hepatic failure Important interactions: Beta-blockers must not be used with non-dihydropyridine calcium channel blockers (e.g. verapamil, diltiazem). This combination can cause HF, bradycardia, & even asystole. |
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