heart drugs Flashcards
what consitutes to congestive heart failure?
cardiac output is below normal range due to biochemical defect or related underlying cause such as hypertension
what are symptoms of congestive heart failure
decrease exercise tolerance, tachycardia, oedema, shortness of breath, cardiomegaly and failure to pass urine
what type of drugs are used to treat congestive heart failure? and what is main drug used and what is brief mechanism of action of the others
inotropes: increase intracellular calcium
cardiac glycosides
beta 1 agonists
type 3 phosphodiesterase inhibitors; increase cAMP in heart, thus increasing strength of contraction
dopamine: D1 receptors cause renal arterial vasodilation, reducing blood pressure, presynaptic D2 receptors inhibit noradrenaline release
diuretics: reduce pre load (venous pressure) causing more efficient contractions
main drug: cardiac glycosides
what is the effect of cardiac glycosides
increase cardiac output, decrease heart rate, decrease cardiac area, decrease body weight, urine output increases, increase of atrioventricular conduction time
give an example of 2 cardiac glycosides and what is their mechanism of action
ouabain: leads to greater increase in intracellular sodium concentration in response to membrane potential, thus causing greater contraction
digoxin: inhibits sodium/potassium ATPase pump, causing increase in intracellular calcium:
in heart there is sodium/calcium pump which pumps calcium out and sodium in, due to inhibition of ATPase pump there is increase of sodium concentration and so less calcium concentration is pumped out, increasing intracellular calcium
how does body potassium effect digoxin?
hypokalaemia increases digoxins actions, hyperkalaemia decreases it
what are unwanted effects of cardiac glycosides?
atrioventricular block, ectopic beats, anorexia, nausea, vomiting
has low therapeutic index
what are symptoms of angina pectoris and why is it caused?
ischaemic chest pain
cause: imbalance between oxygen supply and output, can be brought on by exercise
what is the treatment for angina pectoris?
reduce metabolic demand, improve myocardial perfusion
drugs: organic nitrates/ites, calcium channel antagonists, beta adrenoceptor antagonists (to reduce metabolic demand)
surgery: bypass stents
name some organic nitrates/ites used for treatment and what is their action on body
nitrites: amyl nitrite
nitrates: glyceryl trinitrate (nitroglycerin), isosobide dinitrate
action: relaxation of smooth muscle, causing dilation of large veins, reduce preload
redistribution of coronary flow to ischaemic areas
what is action of beta adrenoceptor antagonists in treatment of angina pectoris, and how does it affect exercise tolerance
reduction in heart rate, blood pressure and contractility of cardiac muscle (reduces oxygen demand)
increases exercise tolerance in angina patients, decreases tolerance in normals
increased time in diastole, causing increase in myocardial perfusion as well as increase in left ventricular left diastolic volume
are co-administered with nitrates
what are side affects of organic nitrates/nitrites
reflex tachycardia due to lowered blood pressure
what is mechanism for calcium channel antagonists in angina, give examples and their difference
inhibitors of L type voltage gated calcium channels in heart
inhibit calcium entry and so reduce coronary after load
verapamil; selective for cardiac muscle, nifedipine; selective for smooth muscle (reduces after load)
what are unwanted effects of calcium channel blockers
supress cardiac contractility, and slow conduction
bradycardia
high degree of AV block
what drugs are used in treatment of coronary heart disease and what is their mechanism
drugs have prognostic benefit
aspirin: anti-platelet agent, alters balance between thromboxane A2 and PGI2, low doses of aspiring has prophylactic effect against thrombosis
statins: inhibit enzyme HMG-CoA reductase, the rate limiting step in cholesterol synthesis , aimed at treating underlying atheromatous disease
