Heart Failure Agents
High-yield Verified · Oct 2026Each drug pushes on a heart-failure pathway the older drugs leave alone — the natriuretic peptides (sacubitril/valsartan), the sinoatrial pacemaker current (ivabradine) or the NO–sGC–cGMP signal (vericiguat) — and each mechanism predicts its catch: angioedema and a misleading BNP, bradycardia and phosphenes, or hypotension.
Nursing view → administration, monitoring and patient teaching
Drugs
Mechanism
Sacubitril/valsartan: sacubitril’s active metabolite LBQ657 inhibits neprilysin (neutral endopeptidase), raising natriuretic peptides, while valsartan blocks the angiotensin II AT1 receptor and angiotensin II-dependent aldosterone release. Ivabradine blocks the HCN channel carrying the sinoatrial pacemaker If current, lowering heart rate without negative inotropy. Vericiguat stimulates soluble guanylate cyclase independently of and synergistically with nitric oxide, raising cGMP and causing smooth-muscle relaxation and vasodilation.
Natriuretic peptides and neprilysin
Stretched heart muscle releases natriuretic peptides: ANP mainly from the atria and BNP mainly from the ventricles in heart failure. They act by raising cGMP in target tissues, causing vasodilation and diuresis and inhibiting the RAAS and sympathetic activity; in the kidney ANP dilates afferent and constricts efferent arterioles, raising GFR, and inhibits sodium and water reabsorption. Neprilysin degrades ANP and BNP.
Sacubitril is a prodrug converted by esterases to LBQ657, the neprilysin inhibitor. Neprilysin also breaks down angiotensin II and bradykinin. Blocking it alone would let angiotensin II accumulate, so it is combined with the ARB valsartan; and because bradykinin also accumulates, adding an ACE inhibitor (which blocks bradykinin breakdown too — see the ACE-inhibitor page) raises the risk of angioedema; hence the 36-hour gap when switching.
ProBNP is cleaved by corin into equal amounts of active BNP and inactive NT-proBNP. Only BNP is a neprilysin substrate, so on sacubitril/valsartan BNP rises while NT-proBNP falls — NT-proBNP is the marker to follow.
Ivabradine: the If current and the sinus node
Sinoatrial pacemaker cells have no resting phase: after each action potential they depolarize spontaneously, and autonomic input sets how fast — parasympathetic input slows the rate and sympathetic input speeds it. The If ("funny") current, carried by HCN4 channels, drives that pacemaker activity.
Ivabradine selectively inhibits If, lowering the spontaneous firing rate of the sinus node and lengthening diastole, with no effect on ventricular repolarization or myocardial contractility. The reduction is larger when the baseline heart rate is higher. It is indicated only for patients in sinus rhythm, and a rhythm maintained exclusively by a pacemaker (pacemaker dependence) is a contraindication.
A related current, Ih, curtails retinal responses to bright light; partial Ih block under sudden changes in luminosity probably explains the phosphenes.
Vericiguat: soluble guanylate cyclase without enough nitric oxide
Guanylate cyclase comes in two forms: a membrane receptor for natriuretic peptides and a soluble form (sGC) that is the receptor for nitric oxide. Both make cGMP, which activates protein kinase G. The nitrate page traces the NO–cGMP route that nitrates feed; here the point is what happens when NO falls short.
In heart failure, NO synthesis is impaired and sGC activity is reduced — reactive oxygen species lower NO and can strip sGC of its heme. Vericiguat stimulates sGC directly, independently of NO, and sensitizes it to the NO that is present, restoring cGMP under low-NO conditions; unlike NO-donating vasodilators it does not cause tolerance.
cGMP is made by guanylate cyclases and hydrolyzed by phosphodiesterases; PDE-5 inhibitors therefore add to vericiguat’s effect, and the label does not recommend the combination because of hypotension. Another sGC stimulator is contraindicated.
Comparing the drugs
Target, effect and catch
| Drug | Target | Main effect | Signature catch |
|---|---|---|---|
| Sacubitril/valsartan | Neprilysin (via LBQ657) + AT1 receptor | ↑ Natriuretic peptides, ↓ angiotensin II effects | Angioedema (no ACE inhibitor, 36-h gap); BNP unreliable |
| Ivabradine | HCN channel (If) in the SA node | ↓ Heart rate, no negative inotropy | Bradycardia, atrial fibrillation, phosphenes |
| Vericiguat | Soluble guanylate cyclase | ↑ cGMP → vasodilation | Hypotension, anemia; embryo-fetal toxicity |
Pharmacokinetics at a glance
| Drug | Absorption | Elimination | Half-life |
|---|---|---|---|
| Sacubitril/valsartan | Sacubitril bioavailability ≥ 60%; food no clinically significant effect | LBQ657 mainly urine; valsartan mainly feces; highly protein-bound | Sacubitril 1.4 h · LBQ657 11.5 h · valsartan 9.9 h |
| Ivabradine | About 40% (gut and liver first pass); food raises exposure | CYP3A4 oxidation; equipotent N-desmethyl metabolite | Effective about 6 h |
| Vericiguat | 93% with food | Glucuronidation (UGT1A9, UGT1A1) to an inactive metabolite; CYP < 5% | About 30 h |
Pharmacokinetics
- Sacubitril is a prodrug; LBQ657 accumulates — sacubitril/valsartan
- Esterases convert sacubitril to LBQ657, which is not further metabolized to a significant extent. Steady state is reached in 3 days; LBQ657 accumulates 1.6-fold while sacubitril and valsartan do not. All three are 94–97% protein-bound, so the drug is unlikely to be removed by hemodialysis.
- Sacubitril/valsartan elimination — sacubitril/valsartan
- 52–68% of sacubitril (mainly as LBQ657) is excreted in urine; about 86% of valsartan and its metabolites leaves in feces. LBQ657 crosses the blood–brain barrier only to a limited extent (0.28%).
- Ivabradine: first pass and CYP3A4 — ivabradine
- Absolute bioavailability is about 40% because of first-pass elimination in gut and liver; food delays absorption by about 1 hour and raises exposure by 20–40%. CYP3A4 oxidation produces the N-desmethyl metabolite, equipotent and circulating at about 40% of the parent, also cleared by CYP3A4 — so CYP3A4 inhibitors and inducers move both.
- Ivabradine half-life and clearance — ivabradine
- Distribution half-life 2 hours, effective half-life about 6 hours; only about 4% is excreted unchanged in urine, with metabolites cleared in feces and urine to a similar extent.
- Vericiguat: once daily, glucuronidated — vericiguat
- Half-life is 30 hours in heart failure, with steady state after about 6 days. It is glucuronidated mainly by UGT1A9 to an inactive N-glucuronide (CYP metabolism < 5%); about 53% of a dose appears in urine (mostly metabolite) and 45% in feces (mostly unchanged). A meal raises AUC by 44% and reduces variability.
Uses & drug choice
- Sacubitril/valsartan to reduce cardiovascular death and heart-failure hospitalization in adults with chronic heart failure (benefit clearest when LVEF is below normal)
- Sacubitril/valsartan for symptomatic heart failure with systemic left ventricular systolic dysfunction in children aged 1 year and older
- Ivabradine to reduce hospitalization for worsening heart failure in stable symptomatic chronic heart failure with LVEF ≤ 35% (sinus rhythm, resting heart rate ≥ 70 bpm, on a maximally tolerated beta-blocker or unable to take one)
- Vericiguat to reduce cardiovascular death and heart-failure hospitalization after a heart-failure hospitalization or outpatient IV diuretics, in adults with symptomatic chronic heart failure and ejection fraction below 45%
Adverse effects
- Angioedema (sacubitril/valsartan)
- Neprilysin breaks down bradykinin, so its inhibition lets bradykinin build up; ACE inhibitors also block bradykinin breakdown, which is why the two are never combined and a 36-hour gap separates them.
- Hypotension, hyperkalemia and renal impairment (sacubitril/valsartan)
- Valsartan blocks angiotensin II and angiotensin II-dependent aldosterone release, while the extra natriuretic peptides vasodilate; kidneys that depend on the RAAS lose filtration pressure and potassium excretion falls.
- Bradycardia and heart block (ivabradine)
- If block slows sinus-node firing, and AH and PR intervals can lengthen; the effect is additive with other negative chronotropes and with CYP3A4 inhibitors that raise ivabradine levels. Slowing the rate can lengthen the uncorrected QT and favor torsade de pointes in susceptible patients.
- Phosphenes (ivabradine)
- Partial block of the retinal Ih current, which normally curtails responses to bright light, lets sudden changes in luminosity produce transient brightness, halos or multiple images.
- Hypotension (vericiguat)
- More cGMP relaxes vascular smooth muscle; PDE-5 inhibitors, which slow cGMP breakdown, deepen the effect.
- Fetal toxicity (all three)
- RAS blockade (valsartan) reduces fetal renal function in the second and third trimesters; ivabradine and vericiguat caused heart and great-vessel malformations in animal studies.
Toxicity & antidote
Ivabradine overdose causes severe, prolonged sinus bradycardia and pauses that can be refractory to atropine, sometimes with QT prolongation and torsade de pointes. There is no antidote: give fluids and atropine, consider isoproterenol, and pace temporarily when the bradycardia is poorly tolerated.
Sacubitril/valsartan and vericiguat overdoses most likely cause hypotension, treated symptomatically; neither is likely to be removed by hemodialysis because both are highly protein-bound.
Interactions
Contraindications
- Sacubitril/valsartan with an ACE inhibitor, or within 36 hours of switching from or to one — Neprilysin inhibition plus ACE inhibition raises bradykinin and the risk of angioedema (labeled contraindication).
- Sacubitril/valsartan with a history of angioedema from a previous ACE inhibitor or ARB — Labeled contraindication — prior angioedema raises the risk of angioedema with sacubitril/valsartan.
- Sacubitril/valsartan with aliskiren in a patient with diabetes — Labeled contraindication — the same dual-RAS rule as on the ACE-inhibitor and ARB pages (hypotension, hyperkalemia, renal impairment).
- Ivabradine with acute decompensated heart failure, clinically significant hypotension or bradycardia, or sick sinus syndrome, sinoatrial block or third-degree AV block without a functioning demand pacemaker — Labeled contraindications — ivabradine slows the sinus node and can cause bradycardia, sinus arrest and heart block.
- Ivabradine with severe hepatic impairment, pacemaker dependence, or a strong CYP3A4 inhibitor — Labeled contraindications — strong CYP3A4 inhibitors raise ivabradine levels and worsen bradycardia; a pacemaker-dependent rhythm cannot be slowed.
- Ivabradine with second-degree AV block, or a demand pacemaker set at 60 beats per minute or more use caution — Not recommended (avoid second-degree block unless a functioning demand pacemaker is present); a pacemaker set at 60 or more prevents the heart-rate target.
- Vericiguat in pregnancy, or with another soluble guanylate cyclase stimulator — Labeled contraindications — vericiguat may cause fetal harm (boxed warning).
High-yield
- Natriuretic peptides — the benefit: more vasodilation and natriuresis
- Angiotensin II — the reason valsartan comes in the same tablet
- Bradykinin — the reason for no ACE inhibitor and the 36-hour gap
BNP is chewed too — so it rises on the drug; NT-proBNP is not.
- Beat — If block in the SA node lowers heart rate (sinus rhythm only)
- Not the squeeze — no negative inotropy, no change in ventricular repolarization
Its side effects follow the same channels: bradycardia from If, phosphenes from retinal Ih.
Practice questions
Q1A 63-year-old man with HFrEF has taken lisinopril for years. His cardiologist switches him to sacubitril/valsartan and he takes his first dose the same evening as his last lisinopril tablet. Within hours his lips and tongue swell.
What mechanism best explains this reaction?
- A.Unblocked angiotensin II acting on AT1 receptors
- B.Accumulation of bradykinin from combined neprilysin and ACE inhibition
- C.IgE-mediated allergy to valsartan
- D.Sacubitril acting directly on bradykinin receptors
- E.Higher natriuretic peptides causing salt and water retention
Show answer
B. Accumulation of bradykinin from combined neprilysin and ACE inhibition — Neprilysin and ACE both break down bradykinin. Starting sacubitril/valsartan before the ACE inhibitor has cleared lets bradykinin accumulate and causes angioedema — which is why the combination is contraindicated and a 36-hour gap is required. Valsartan blocks the AT1 receptor, so angiotensin II is not left acting there; sacubitril is a prodrug whose esterase product, LBQ657, works by inhibiting neprilysin; and natriuretic peptides cause diuresis and inhibit sodium and water reabsorption rather than retaining salt.
Q2A 70-year-old woman began sacubitril/valsartan 3 months ago. She now has more dyspnea and edema. Her BNP is higher than before she started, but her NT-proBNP has fallen.
How should these results be interpreted?
- A.Both markers confirm worsening heart failure
- B.The NT-proBNP assay is falsely low because of valsartan
- C.BNP is a neprilysin substrate, so it rises on the drug; NT-proBNP is the reliable marker
- D.Renal failure has raised BNP but not NT-proBNP
- E.Sacubitril cleaves NT-proBNP into BNP
Show answer
C. BNP is a neprilysin substrate, so it rises on the drug; NT-proBNP is the reliable marker — ProBNP is split into BNP and NT-proBNP. Neprilysin degrades BNP but not NT-proBNP, so neprilysin inhibition raises BNP independently of heart-failure status, while NT-proBNP reflects the disease — her symptoms need clinical assessment, but the BNP rise is expected.
Q3A 58-year-old man with HFrEF in sinus rhythm, heart rate 78 bpm on maximally tolerated carvedilol, starts ivabradine. Two weeks later he reports brief bright spots in his vision when he walks from a dark room into sunlight.
What explains his visual symptom?
- A.Retinal ischemia from hypotension
- B.Digoxin-like xanthopsia
- C.Partial inhibition of the retinal Ih current
- D.Optic neuritis from CYP3A4 metabolites
- E.Carvedilol-induced cataracts
Show answer
C. Partial inhibition of the retinal Ih current — Ivabradine blocks the cardiac If current and partly blocks the related retinal Ih current, which normally curtails responses to bright light. Sudden changes in luminosity then produce phosphenes — usually in the first 2 months, mild, and mostly resolving. The label ties them to ivabradine’s effects on retinal photoreceptors and to sudden variations in light intensity, and in dogs its retinal changes reversed within a week without damage to ocular structures — a reversible current effect, not ischemic, inflammatory or lens damage. He takes carvedilol, not digoxin.
Q4A 66-year-old man was recently hospitalized for worsening HFrEF (ejection fraction 30%) and is started on vericiguat. He also takes sildenafil for erectile dysfunction.
Why should the sildenafil be stopped?
- A.Sildenafil induces UGT1A9, lowering vericiguat levels
- B.Both raise cGMP signaling, adding to hypotension
- C.Sildenafil blocks the If current
- D.Vericiguat inhibits CYP3A4, raising sildenafil levels
- E.Sildenafil is a nitric oxide donor
Show answer
B. Both raise cGMP signaling, adding to hypotension — Vericiguat stimulates sGC to make more cGMP, and PDE-5 inhibitors prevent cGMP breakdown. Together they deepen vasodilation, so the label does not recommend the combination; another sGC stimulator is contraindicated. Sildenafil enhances cGMP signaling by inhibiting cGMP-specific phosphodiesterases — it does not donate nitric oxide or block If, ivabradine’s target. The problem is pharmacodynamic: sildenafil does not change vericiguat’s pharmacokinetics, vericiguat does not change sildenafil’s, and vericiguat does not inhibit CYP3A4.
Sources
- Entresto (sacubitril/valsartan) — FDA label: boxed fetal toxicity, angioedema, ACE-inhibitor washout — FDA / DailyMed
- Ivabradine tablets (Novadoz) — FDA label: contraindications, bradycardia, atrial fibrillation, phosphenes — FDA / DailyMed
- Verquvo (vericiguat) — FDA label: boxed embryo-fetal toxicity, sGC mechanism — FDA / DailyMed
- Sacubitril-Valsartan — neprilysin, bradykinin, BNP vs NT-proBNP — StatPearls (NCBI)
- Ivabradine — the If (funny) current, monitoring — StatPearls (NCBI)
- The use of stems in the selection of INN (stems -sartan, -tril, -bradine, -ciguat) — World Health Organization
- Atrial Natriuretic Peptide — cGMP actions, renal effects, neprilysin — StatPearls (NCBI)
- Natriuretic Peptide B Type Test — ventricular release, corin cleavage to BNP and NT-proBNP — StatPearls (NCBI)
- Physiology, Sinoatrial Node — pacemaker potential, autonomic control — StatPearls (NCBI)
- Vericiguat — two guanylate cyclases, NO-independent sGC stimulation — StatPearls (NCBI)
- Lisinopril — ACE also degrades bradykinin; aldosterone and potassium excretion — StatPearls (NCBI)
- Biochemistry, Cyclic GMP — synthesis by guanylate cyclases, hydrolysis by phosphodiesterases — StatPearls (NCBI)
By LearnDrugs
Educational summary for medical students. Always verify against current prescribing information and guidelines. Not medical advice.