Cardio drugs Flashcards
Digoxin
- MoA
- Clinical Indications:
- Prescription dose:
- Adverse effects:
- Interactions:
- MoA: Na+K+ATPase inhibitor - causes Na+ to be retained in myocytes –> Ca2+ is also retained –> Phases 4 and 0 of cardiac action potential are prolonged ==> increased end-diastolic volume + increased time between contractions
- Clinical Indications: ventricular rate control, esp for supraventricular arrhythmias (A.fib and A.flutetr), HF
- Prescription dose:
> 0.75-1.5mg divided doses over 24h for RAPID CONTROL of a.fib/a/flutter
> 125 - 250 micrograms for daily maintenance
> 62.5 - 125 micrograms daily for HF
> dose reduced in elderly/renal impairment - Adverse effects: DIGOXIN TOXICITY: nausea, vomiting, visual disturbance, confusion, dizziness –> withdraw drug + correct e- disturbance + give digoxin-specific antibody fragments
- Interactions: amiodarone (HALVE digoxin dose, as amiodarone causes increase in digoxin conc), CCB, hypoK drugs (like diuretics), hypomagnesaemia drugs (like PPIs)
What do intotropic and chronotropic mean? How would you classify different cardio drugs into inotropic and chronotropic?
Inotropic: increases strength of contraction - digoxin, dobutamine, milrinone
Chronotropic: increases heartbeat rate - epinephrine, dopamine
When should you AVOID digoxin?
heartblock, WPW syndrome, ventricular tachycardia, myocarditis, constrictive pericarditis
Thiazide diuretics
- MoA
- Clinical Indications:
- Prescription dose:
- Adverse effects:
- Interactions:
- MoA: Inhibits Na+Cl- symporter in distal convoluted tuble –> Na+ and Cl- are not reabsrobed ==> Na+ and water are expelled, blood volume and pressure go down
- Clinical Indications: HTN, oedema in HF (but loop diuetric is preferred in HF)
- Prescription dose:
> 5-10mg mane [morning] for oedema
> 2.5mg mane for HTN - Adverse effects:
> Hypos: hypoK, hypoNa, hypoMg
> Hypers: HyperCa, hyperuricaema (both can cause gout!), hyperglycaemia (avoid in pts w hx of dm) - Interactions: increases plasma conc. of lithium and NSAIDs, avoid using with other drugs that cause HypoNA (diuretics, antideprssants, carbamazepine)
Name some thiazide diuretics and thiazide-like diuretics
thiazide: bendroflumethiazide, hydrochlorothiazide
thiazide-like: indapamide, chlortalidone, metolazone
Thiazide diuretics should NOT be used to treat ________ HTN
gestational
Thiazide diuetrics are ineffective if eGFR is ________
<30mLs/min
Loop Diuretics (furosemide)
- MoA
- Clinical Indications:
- Prescription dose:
- Adverse effects:
- Interactions:
- MoA: inhibits Na+ resaborption in loop of henle
- Clinical Indications: Chronic HF, pulmonary oedeoma**, resistant HTN
- Prescription dose:
> 20-40mg mane for oedema (can go up to 120mg)
> 40-80mg for HTN - Adverse effects: GI disturbance, postural hypotension, hyperglycaemia, hyperuricaemia, hypocalcaemia, renal and hepatic toxicity, ototoxiity**
- Interactions: lithium, other antihypertensives, NSAIDs (nephrotoxity), aminoglycoside abx and vancomycin (ototoxicity), other diuretics, digoxin (cardiotoxicity)
Main difference b/w thiazide and loop diuretics?
Thiazide causes HyperCa, loop causes HypoCa
STRONG loop diuretic that you only need 1mg of
Bumetanide
Are loop diuetrics first line for anything?
No
What must you establish before giving loop diuretic?
Adequate urine output from pt
Sufficient eGFR - if too low, may need higher dose
Aldosterone-dependent, K-sparing diuretics (Spironolactone)
RMBR: spironolaKtone - k sparing!
- MoA
- Clinical Indications:
- Prescription dose:
- Adverse effects:
- Interactions:
- MoA: competitive antagonist for aldosterone receptor in renal tubules, –> reduces aldosterone-induced proteins ==> K+ retained, NA+ and water lost
- Clinical Indications: oedema in congestive HF, ascites, hyperaldosteronism, nephrotic syndrome
- Prescription dose:
> ascites: 50mg twice a day (can be increased to up to 200mg)
> HF: 25mg once a day - Adverse effects: cross-reacts with intracellular androgen receptorms –> gynaecomastia, hypogonadism, impotence, menstrual irregularities. ACUTE renal failure.
- Interactions: other K-retaining drugs (ACE-I, ARBs), NSAIDs, lithium, antihypertensives
What is the drug monitering regimen for K+ sparing diuretics
- baseline U&Es and LFTs
- re-check after 1 week
- check every 4 weeks for 12 weeks
- check every 3 months for a year
- check every 6 months after that
What pt advice do you give for spironolactone
Take with/after food. Do NOT take NSAIDs OTC.
When to use which diuretic
High BP: thiazide is first-line. Act within 1-2 hours, effects last for up to 24h. Milder effect and less dramatic water loss than loop.
Pulmonary oedema: loop diuretics. Very fast acting and cause rapid water loss. Frequent visits to toilet.
HF oedema: K-sparing. Weaker diuretic, prevents too much K+ loss.