CVS drugs Flashcards
What effect does digoxin have on the contraction and rate of the heart?
Positively inotropic (contractility)
Negatively chronotropic (heart rate)
How does digoxin work?
Inhibits Na+K+ATPase membrane pump, causing an increase in intracellular sodium, therefore an increase in intracellular calcium, increasing the end of diastole and therefore increasing diastolic volume
What are some symptoms and signs of digoxin toxicity?
Confusion
Loss of appetite
Nausea
Vomiting
Diarrhoea
Evidence of cardiotoxicity (palps, arrhythmias, conduction disturbances, eosinophilia, rash, blurred or yellow vision
How to test for digoxin toxicity?
Measure plasma digoxin concentration, or do digoxin specific antibody fragments
What are the contraindications and cautions for digoxin?
Caution:
Sick sinus syndrome
Hypokalaemia
Hypomagnesaemia
Hypercalcaemia
Thyroid disease
Severe resp disease
Patients who have recently had an MI
Avoid:
Heart block
WPW syndrome
VT or VF
Myocarditis
Constrictive pericarditis
What are the interactions for digoxin?
Amiodarone (increased plasma digoxin conc. - halve digoxin)
Calcium channel blockers (increased plasma digoxin)
Drugs which cause hypokalaemia (e.g. diuretics)
Dosage of digoxin
0.75-1.5mg for rapid control of AF or flutter
125-250micrograms OD for maintenance of AF or flutter
62.5-125micrograms OD for heart failure (in patients with sinus rhythm).
Dosage of bendroflumethiazide
5-10mg for management of oedema
2.5mg for hypertension
Dosage of indapamide
2.5mg for hypertension
Mechanism of action for indapamide
Thiazide diuretic
What are the contraindications for bendroflumethiazide?
Addisons
Symptomatic hyperuricaemia
Refractory hyponatraemia, hypokalaemia or hypercalcamia
What are the interactions for bendroflumethiazide?
Other antihypertensives
Antidiabetic drugs (reduced hypoglycaemic effect)
Lithium (increased lithium conc)
NSAIDs (impaired diuresis and increased risk of nephrotoxicity)
Other drugs causing hyponatraemia.
