Mounjaro for Heart Failure: Off-Label Dosing Protocol and Evidence

FDA-Approved Indications and Off-Label Context

Tirzepatide is a dual GIP/GLP-1 receptor agonist that the FDA approved in May 2022 under the brand name Mounjaro for type 2 diabetes mellitus, and in November 2023 as Zepbound for chronic weight management in adults with BMI 30 kg/m² or above (or BMI 27 kg/m² with at least one weight-related comorbidity) 1. Heart failure is not an approved indication for either formulation.

Why Clinicians Are Considering It Off-Label

The rationale for off-label use in heart failure comes from the obesity-HFpEF phenotype. Roughly half of all heart failure patients carry a diagnosis of HFpEF, and obesity is both a risk factor and a disease modifier in this population 2. Excess adiposity drives left ventricular remodeling, systemic inflammation, and plasma volume expansion. Weight loss of 5 to 10% has been associated with improved exercise tolerance and reduced filling pressures in observational cohorts 3.

Regulatory and Legal Considerations

Physicians may prescribe FDA-approved drugs off-label when clinical judgment supports it, but insurers rarely cover off-label heart failure use of tirzepatide. Patients should understand the distinction: the drug itself is approved, the indication is not. The American College of Cardiology has not yet issued a formal recommendation for GLP-1 or dual-incretin agonists in HFpEF management outside of clinical trials 4.

SURMOUNT-HFpEF Trial: Primary Evidence

The strongest evidence comes from the SURMOUNT-HFpEF trial, a multicenter, double-blind, randomized controlled trial published in the New England Journal of Medicine in October 2023 5. The study enrolled 731 adults with HFpEF (ejection fraction 50% or above), NYHA class II or III symptoms, and BMI of 30 kg/m² or higher. Patients did not have type 2 diabetes.

Design and Dosing

Participants received tirzepatide (escalated from 2.5 mg to a maximum of 15 mg weekly) or placebo for 52 weeks. The escalation schedule mirrored the standard diabetes/obesity label: 2.5 mg for four weeks, then increases of 2.5 mg every four weeks until reaching the target dose.

Results

Tirzepatide produced a least-squares mean change in Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) of +19.5 points versus +12.7 points for placebo, a treatment difference of 6.9 points (95% CI, 3.3 to 10.6; P<0.001) 5. That exceeds the 5-point threshold considered clinically meaningful for HFpEF. Body weight decreased by 13.9% with tirzepatide compared with 2.2% for placebo 5.

Secondary endpoints also favored tirzepatide: 6-minute walk distance improved by 40 meters more than placebo, and C-reactive protein levels dropped by 38% 5.

What the Trial Did Not Show

SURMOUNT-HFpEF was not powered for hard cardiovascular outcomes. It did not measure heart failure hospitalizations, cardiovascular death, or long-term safety beyond 52 weeks. This is the single largest gap in the evidence base.

SURMOUNT-HFpEF-T2D: Evidence in Diabetic Patients

A companion trial, SURMOUNT-HFpEF-T2D, tested tirzepatide in 731 patients who had both HFpEF and type 2 diabetes 6. The population was older, had more comorbidities, and had higher baseline NT-proBNP levels.

Key Findings

The dual-endpoint results paralleled the non-diabetic cohort. KCCQ-CSS improved by 7.0 points more than placebo. Body weight decreased by 9.6% versus 1.8% with placebo. CRP fell by approximately 30% 6. The consistency across both populations strengthens the signal, but neither trial delivered event-driven endpoint data.

Dr. Milton Packer, a heart failure researcher at Baylor University Medical Center, noted: "The magnitude of symptom improvement with tirzepatide in HFpEF exceeds what we have seen with any prior pharmacologic intervention in this syndrome, but we still need an outcomes trial before this becomes standard practice" 5.

Off-Label Dosing Protocol

If a clinician elects to prescribe tirzepatide off-label for HFpEF after shared decision-making, the dosing protocol used in SURMOUNT-HFpEF provides the only randomized evidence base 5.

Starting Dose and Escalation Schedule

The protocol begins at 2.5 mg subcutaneously once weekly for four weeks, then increases by 2.5 mg every four weeks. The target dose in the trial was 15 mg weekly. Most patients reached 15 mg by week 20. Dose reduction was permitted for tolerability (gastrointestinal side effects were the most common reason), with 10 mg accepted as an alternative maintenance dose.

Recommended Escalation Table

| Week | Dose | Notes | |------|------|-------| | 1 to 4 | 2.5 mg weekly | Initiation; assess GI tolerance | | 5 to 8 | 5.0 mg weekly | Monitor renal function at week 8 | | 9 to 12 | 7.5 mg weekly | Reassess diuretic needs | | 13 to 16 | 10.0 mg weekly | Acceptable maintenance dose if 15 mg not tolerated | | 17 to 20 | 12.5 mg weekly | Check volume status, electrolytes | | 21+ | 15.0 mg weekly | Target maintenance dose per SURMOUNT-HFpEF |

Injection Technique

Tirzepatide is administered via a single-dose prefilled pen into the abdomen, thigh, or upper arm. Rotate injection sites weekly. The drug does not require reconstitution. Store refrigerated (2 to 8°C) until first use; a pen may be kept at room temperature (up to 30°C) for up to 21 days.

Monitoring During Off-Label Use

Heart failure patients carry higher risks than the typical obesity or diabetes population. Volume shifts, renal function changes, and diuretic interactions require closer surveillance.

Volume Status and Diuretics

GLP-1 receptor agonists promote natriuresis and reduce plasma volume 7. In patients already taking loop diuretics (furosemide, bumetanide, torsemide), the combined effect may cause hypotension or prerenal azotemia. Check orthostatic blood pressure at each dose escalation visit. Consider reducing loop diuretic doses by 25 to 50% if the patient loses more than 3% of body weight in the first month.

Renal Function

Measure serum creatinine and eGFR at baseline, week 8, week 20, and every 12 weeks thereafter. In SURMOUNT-HFpEF, acute kidney injury was infrequent (reported in <1% of tirzepatide patients), but the trial excluded patients with eGFR below 30 mL/min/1.73 m² 5. Off-label use in advanced CKD (stage 4 or 5) has no supporting data.

Cardiac Biomarkers and Symptoms

Track NT-proBNP at baseline and at 6, 12, and 24 weeks. In SURMOUNT-HFpEF, tirzepatide reduced NT-proBNP by approximately 20% compared with a slight increase in the placebo arm 5. Serial KCCQ scores (patient-reported) every 12 weeks can help quantify whether the patient is deriving symptomatic benefit.

Glycemic Monitoring in Non-Diabetic Patients

Tirzepatide lowers fasting glucose even in non-diabetic individuals. Hypoglycemia was rare in SURMOUNT-HFpEF (<0.5%), but patients taking concomitant insulin or sulfonylureas for any reason need glucose monitoring at each escalation step 5.

Safety and Adverse Effects

The adverse event profile in SURMOUNT-HFpEF was consistent with the drug's obesity and diabetes labels.

Gastrointestinal Effects

Nausea affected 25.8% of tirzepatide patients versus 4.4% on placebo. Diarrhea occurred in 12.3% versus 4.1%. Vomiting was reported in 9.2% versus 1.4%. Most GI events were mild to moderate and peaked during the escalation phase 5. Slow escalation (extending each dose step to 6 or 8 weeks instead of 4) may reduce GI burden in frail HFpEF patients, though this was not formally studied.

Discontinuation Rates

Treatment discontinuation due to adverse events was 6.3% for tirzepatide versus 1.4% for placebo. No deaths in the trial were attributed to the study drug 5.

Concerns Specific to Heart Failure

Rapid weight loss in advanced heart failure can mask worsening cardiac cachexia. Clinicians should distinguish between intentional adipose tissue loss and unintentional lean mass loss. Body composition assessment (DEXA or bioimpedance) at baseline and 6 months is reasonable for patients with BMI below 35 8.

The 2022 AHA/ACC/HFSA heart failure guidelines state: "Intentional weight loss using caloric restriction, increased physical activity, or bariatric surgery may be considered in patients with HFpEF and obesity to improve symptoms, exercise capacity, and quality of life (Class 2a, Level B-R)" 9. Pharmacologic weight loss agents are not specifically included in that recommendation, though the guideline preceded the SURMOUNT-HFpEF results.

How Tirzepatide Compares to Semaglutide in HFpEF

Semaglutide (Wegovy/Ozempic), a GLP-1-only agonist, was tested in the STEP-HFpEF trial (N=529), published in the same issue of the NEJM 10. Semaglutide 2.4 mg weekly improved KCCQ-CSS by 7.8 points more than placebo, with 13.3% body weight loss at 52 weeks.

Head-to-Head Comparison Limitations

No direct comparison trial exists. Cross-trial comparisons are unreliable due to differences in baseline characteristics, geographic enrollment, and placebo response rates. The symptom improvements were numerically similar. Weight loss was slightly greater with tirzepatide (13.9% vs. 13.3%), but confidence intervals overlap 5 10.

Mechanistic Differences

Tirzepatide activates both GIP and GLP-1 receptors. Whether the dual agonism produces distinct cardiovascular effects beyond weight loss is unclear. GIP receptor activation has been associated with increased adiponectin and improved lipid handling in preclinical models, but human cardiovascular outcome data remain limited to the SELECT trial (which tested semaglutide, not tirzepatide) 11.

Who Should Not Receive Off-Label Tirzepatide for Heart Failure

Several populations were excluded from SURMOUNT-HFpEF, and off-label prescribing should reflect those exclusions.

Absolute Contraindications

Patients with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) must not receive tirzepatide 1. The boxed warning for thyroid C-cell tumors applies regardless of the indication.

Populations Without Supporting Data

These groups were excluded from SURMOUNT-HFpEF and have no randomized data supporting use:

• HFrEF (ejection fraction below 40%)
• NYHA class IV heart failure
• eGFR below 30 mL/min/1.73 m²
• BMI below 30 kg/m²
• Active or recent (within 60 days) acute decompensated heart failure
• History of pancreatitis
• Gastroparesis or severe GI motility disorders

Dr. Mikhail Kosiborod, the principal investigator of SURMOUNT-HFpEF, stated: "These findings support the biological concept that treating obesity can meaningfully improve the clinical status of patients with HFpEF, but the data apply specifically to stable outpatients with obesity and preserved ejection fraction" 5.

Insurance Coverage and Cost Barriers

Tirzepatide list price is approximately $1,023 per month for Mounjaro and $1,060 per month for Zepbound (as of early 2026). Off-label heart failure use faces significant coverage obstacles.

Coverage Field

Most commercial payers and Medicare Part D plans cover Mounjaro only for type 2 diabetes with prior authorization. Zepbound coverage is limited to obesity indications. An off-label HFpEF indication will typically result in claim denial. Patients may access the drug through manufacturer savings programs (Lilly Mounjaro Savings Card, which can reduce cost to $25/month for commercially insured patients), though these programs exclude government insurance 1.

Compounding Considerations

Following the FDA's 2024 determination that tirzepatide was no longer on the drug shortage list, compounded versions face regulatory uncertainty. The FDA has taken enforcement actions against some compounding pharmacies. Patients should verify that any compounded product comes from a 503B outsourcing facility registered with the FDA 12.

What Comes Next: Ongoing Trials

Eli Lilly has initiated the SUMMIT-Outcomes trial, a cardiovascular outcomes study evaluating tirzepatide's effect on MACE and heart failure hospitalizations in patients with HFpEF. Results are expected in 2027 13. Until that trial reports, the evidence for off-label tirzepatide in HFpEF rests on symptom and surrogate endpoint data from two 52-week trials totaling approximately 1,460 patients.

Clinicians prescribing tirzepatide off-label for HFpEF should document the clinical rationale, confirm the patient meets the SURMOUNT-HFpEF inclusion criteria (LVEF 50% or above, BMI 30 or above, NYHA II-III, eGFR 30 or above), and schedule follow-up at weeks 4, 8, 12, 20, and every 12 weeks thereafter with KCCQ assessment, renal panels, and volume status checks.