Why Complicated UTIs Are Harder When Resistance Is Present

More Than a Bladder Infection

Uncomplicated bladder infections usually respond to standard oral antibiotics. Complicated UTIs involve the upper urinary tract, such as pyelonephritis, or occur alongside catheters, obstruction, kidney stones, or recent urologic procedures. They can become severe and may spread to the bloodstream.

Carbapenemases Change the Picture

Some Enterobacteriaceae, including Klebsiella pneumoniae, produce carbapenemase enzymes that destroy carbapenem antibiotics. When carbapenemase-producing organisms cause urinary infections, standard carbapenem therapy can fail. Clinicians then need an agent that keeps the carbapenem active.

Why Protected Carbapenems Matter

Carbapenems are among the most powerful antibiotics available, and they should be preserved for serious infections. A carbapenem paired with a protective inhibitor can extend their usefulness in carefully selected cases.

Key Takeaways

• Vabomere (meropenem/vaborbactam) received FDA approval on August 29, 2017, for adults 18 and older with cUTI, including pyelonephritis, caused by designated susceptible Enterobacteriaceae.
• Meropenem is the carbapenem; vaborbactam is a beta-lactamase inhibitor that protects meropenem from KPC-type carbapenemases.
• In TANGO-1, about 98 percent of patients receiving Vabomere had cure or improvement with a negative urine culture at the end of IV treatment, compared with about 94 percent with piperacillin/tazobactam.
• The labeled regimen is a 3-hour IV infusion every 8 hours, with adjustments for kidney function.
• Vaborbactam does not inhibit metallo-beta-lactamases, so those organisms are generally not covered.
• Warnings include serious hypersensitivity reactions, seizures associated with carbapenems, and C. difficile infection.

What Is Vabomere

Brand and Components

Vabomere is the brand name for a fixed-dose combination of meropenem and vaborbactam. It was developed under the name Carbavance and is associated with Rempex Pharmaceuticals, a unit of The Medicines Company. It is supplied as an injection for intravenous use.

Drug Class

Meropenem is a carbapenem, a beta-lactam antibiotic with very broad activity against gram-negative and gram-positive organisms. Vaborbactam is a cyclic boronic acid beta-lactamase inhibitor with little antibacterial activity on its own.

Dosage Form

Vabomere is not a tablet. It is given by intravenous infusion, usually in a hospital, infusion center, or other setting where staff can monitor the infusion.

FDA Approval: August 29, 2017

The Decision

The FDA approved Vabomere on August 29, 2017, for adults aged 18 and older with cUTI, including pyelonephritis, caused by designated susceptible Enterobacteriaceae. The agency identified E. coli, Klebsiella pneumoniae, and the Enterobacter cloacae complex as the organisms covered by the labeled indication.

Priority Review and Designation

Vabomere was designated a Qualified Infectious Disease Product (QIDP) and received priority review, reflecting the FDA's recognition of unmet need for carbapenemase-producing organisms.

Review Findings

The FDA's review concluded that the TANGO-1 trial provided statistical evidence of effectiveness for cUTI, including acute pyelonephritis, caused by meropenem-susceptible isolates. The review also noted that meropenem alone is not FDA-approved for cUTI.

Meropenem: The Carbapenem Partner

Mechanism

Meropenem binds penicillin-binding proteins in the bacterial cell wall and disrupts cell wall construction, leading to bacterial death. It is bactericidal and has broad activity against many gram-negative organisms.

Limit Without Protection

Meropenem is destroyed by KPC-type carbapenemases. When those enzymes are present, meropenem alone may fail, which is the problem vaborbactam addresses.

Long Track Record

Meropenem has been used for decades in serious infections. Its safety profile is well characterized, including seizure risk in certain patients.

Vaborbactam: Protecting Meropenem

What It Targets

Vaborbactam binds and inhibits KPC-type serine carbapenemases, which are among the most common carbapenemases in Enterobacteriaceae in the United States. By inhibiting these enzymes, it helps meropenem reach its targets.

Limits

Vaborbactam does not inhibit metallo-beta-lactamases such as NDM, VIM, and IMP. Organisms producing these enzymes are generally not covered by the combination.

Acinetobacter

Vaborbactam does not improve meropenem activity against Acinetobacter, so this combination is not a treatment for Acinetobacter infections.

How the Combination Works Together

The Problem

KPC-producing organisms hydrolyze meropenem before it can reach its bacterial targets. Without protection, the carbapenem is inactive against those strains.

The Solution

Vaborbactam occupies and inactivates the KPC enzyme, allowing meropenem to act. The two components are supplied together so that the protective inhibitor is given with the carbapenem in the correct ratio.

Why Susceptibility Matters

Not every carbapenem-resistant organism produces KPC, and not every KPC-producing strain is susceptible to the combination. Laboratory testing determines whether the specific isolate is covered.

Why KPC Matters

A Hospital Concern

KPC-producing Enterobacteriaceae have spread through hospitals and long-term care facilities. They can cause pneumonia, bloodstream infections, and urinary infections, often in patients with prior antibiotic exposure or devices such as catheters.

Limited Options Before Approval

Before Vabomere, clinicians facing KPC infections often relied on older agents with significant toxicity or on combinations with uncertain benefit. A targeted combination gave them a more defined option for some cUTI cases.

Infection Control

Because KPC-producing organisms spread between patients, hospitals use screening, contact precautions, and surveillance. Antibiotics are only one part of managing these infections.

Which Bacteria It Targets

Labeled Organisms

The labeled cUTI indication covers designated susceptible Enterobacteriaceae, including Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae complex. Susceptibility is determined by laboratory testing of each isolate.

Not Covered

The label does not cover Pseudomonas aeruginosa or Acinetobacter infections, and metallo-beta-lactamase producers are generally not covered.

Culture Matters

Urine culture with susceptibility testing identifies the organism and guides whether Vabomere is appropriate. Empiric choices may be made while results are pending and adjusted when the laboratory reports back.

Approved Use and Labeling Limits

Who Is Eligible

The labeled population is adults 18 and older with cUTI, including pyelonephritis, caused by designated susceptible Enterobacteriaceae.

Stewardship Statement

The label directs use only for infections proven or strongly suspected to be caused by susceptible bacteria. This language protects the drug's effectiveness and the broader carbapenem class.

Not Approved For

Vabomere is not approved for uncomplicated UTIs, bloodstream infections as a standalone indication, or children. Decisions outside labeled uses rest with the treating clinician.

The TANGO-1 Trial: Design

Overview

TANGO-1 was a phase 3, randomized, double-blind, double-dummy, multicenter trial. Adults with cUTI or acute pyelonephritis were randomized to meropenem/vaborbactam or piperacillin/tazobactam, a standard comparator for serious gram-negative infections.

Population

The trial enrolled 545 adults. The FDA's modified intention-to-treat analysis included 272 patients receiving meropenem/vaborbactam and 273 receiving piperacillin/tazobactam.

Double-Dummy Design

Double-dummy design means each group received matching active drug and placebo versions of the other arm's drugs. This keeps the regimens looking identical, which reduces bias in how outcomes are assessed.

Outcomes Assessed

The trial measured overall success, a composite of clinical cure or improvement and a negative urine culture, at the end of IV treatment and at a later test-of-cure visit.

The TANGO-1 Trial: Results

End of IV Treatment

At the end of IV treatment, the FDA reported that about 98 percent of patients receiving meropenem/vaborbactam had cure or improvement with a negative urine culture, compared with about 94 percent receiving piperacillin/tazobactam.

Later Follow-Up

At a later test-of-cure visit, reported figures were lower and closer together. Published and press summaries differ in how they report these visit-specific rates, so check the FDA review and published trial report for exact numbers.

Noninferiority

The trial met its noninferiority objective, meaning the new combination was not meaningfully worse than the comparator within a prespecified margin.

Reading the Numbers Carefully

Noninferiority Versus Superiority

Noninferiority does not prove that Vabomere is more effective than piperacillin/tazobactam. It shows the drug performed comparably, while providing coverage for carbapenemase-producing organisms that piperacillin/tazobactam may not treat reliably.

Population Limits

The trial enrolled selected patients who met study criteria. Real-world patients may have more comorbidities or different organisms, which can change outcomes.

Applying Results to One Patient

Trial averages do not predict an individual outcome. Clinicians weigh culture results, severity, and alternatives before choosing Vabomere.

The TANGO-2 Trial and Carbapenem-Resistant Infections

Design

TANGO-2 was a phase 3 trial in patients with suspected carbapenem-resistant Enterobacteriaceae infections. Participants received meropenem/vaborbactam or best available therapy, which often included older agents with more toxicity.

Why It Matters

TANGO-2 helps clinicians understand how the combination performs in more difficult infections. Its findings support the drug's role in carbapenem-resistant settings, though the labeled cUTI indication was defined by TANGO-1.

Interpretation

Trials of heavily pretreated or critically ill patients can be harder to interpret. Results should be read alongside the specific infection and patient.

Resistance and Susceptibility Testing

Why Testing Matters

Resistance mechanisms vary. An isolate that produces KPC may be susceptible to Vabomere, while one that produces metallo-beta-lactamases may not be. Testing the specific isolate is essential.

Monitoring Resistance

Hospitals track carbapenemase patterns through surveillance. Clinicians should review local antibiograms when choosing therapy.

Preventing Resistance

Using Vabomere only when needed, shortening courses appropriately, and following infection-control practices help limit resistance.

Dosing and Administration

Labeled Regimen

The labeled regimen is 4 grams total, meaning 2 grams of meropenem and 2 grams of vaborbactam, given as a 3-hour intravenous infusion every 8 hours. Confirm the current dosing in the prescribing information on DailyMed.

Infusion

Pharmacists prepare the drug, and nurses monitor the infusion. Patients should report discomfort, pain, or redness at the IV site.

Duration

Treatment length depends on the infection, response, and culture results. The care team sets the plan and reviews it as the patient improves.

Missed Doses

Hospital staff manage missed or delayed doses. Patients should not make up doses on their own.

Kidney Function and Dosing

Why Kidney Function Matters

Meropenem and vaborbactam are cleared by the kidneys. Reduced kidney function increases drug exposure and can raise the risk of side effects, so the label includes dose adjustments.

Monitoring

Clinicians check creatinine before starting therapy and monitor kidney function during treatment, especially in older adults and people with dehydration or other nephrotoxic drug exposure.

Dialysis

Patients on dialysis need individualized dosing planned with nephrology and pharmacy teams.

Common Side Effects

Headache

Headache was among the more frequently reported adverse reactions in clinical use. It is usually mild, but it should be reported if it is severe or persistent.

Infusion-Site Reactions

Reactions at the infusion site, including pain, redness, or swelling, are commonly reported. Nurses monitor lines and can move or treat them as needed.

Diarrhea and Gastrointestinal Effects

Diarrhea, nausea, and vomiting can occur. Persistent or bloody diarrhea needs prompt evaluation because C. difficile infection can develop with nearly all antibiotics.

Serious Risks and Warnings

Hypersensitivity and Anaphylaxis

Serious allergic reactions, including anaphylaxis, can occur. The FDA specifically cautioned that Vabomere should not be used in patients with a history of anaphylaxis to beta-lactams. Hives, facial swelling, trouble breathing, or fainting require emergency care.

Seizures

Carbapenems can cause seizures, particularly in patients with kidney impairment or existing seizure disorders. The FDA highlighted seizure risk in its announcement.

C. difficile Infection

C. difficile can cause severe diarrhea and colitis. Any new or worsening diarrhea during or after treatment should be reported promptly.

Seizure and Neurologic Risk

What to Watch For

Confusion, twitching, jerking movements, or loss of consciousness should be reported immediately. These can signal neurologic toxicity.

Who Is at Higher Risk

Risk increases with reduced kidney function, prior seizures or brain conditions, and higher drug exposure. Correct dosing for kidney function is a key protective step.

What Happens Next

If seizures or neurologic changes occur, the care team reviews the dose, checks kidney function, and may change antibiotics. Symptoms often improve after dosing is corrected.

Who Should Not Receive Vabomere

History of Anaphylaxis

People with a history of anaphylaxis to beta-lactam antibiotics should not receive Vabomere. This was the FDA's specific caution.

Known Allergy

People with a known allergy to meropenem, vaborbactam, or other carbapenems should not receive the drug without specialist review.

Seizure History and Kidney Disease

People with seizure disorders or significant kidney disease need careful evaluation and dose planning.

Drug Interactions

Valproic Acid

Carbapenems can lower blood levels of valproic acid, which may reduce seizure control. Patients taking valproic acid should discuss this interaction with their team before treatment.

Medication Review

Give your care team a full list of medications, including prescriptions, over-the-counter products, and supplements. Pharmacists check for interactions before starting therapy.

Probenecid

Some drugs slow kidney clearance of carbapenems and may increase exposure. Your pharmacist will check whether any of your medicines need attention.

How Vabomere Compares With Other Options

Piperacillin/Tazobactam

Piperacillin/tazobactam was the comparator in TANGO-1 and is a standard option for serious infections. Vabomere is designed for infections where carbapenemase-producing organisms are a concern.

Meropenem Alone

Meropenem alone is not FDA-approved for cUTI and can fail against KPC producers. The vaborbactam component is what makes the combination distinct.

Other Newer Agents

Other protected combinations and newer antibiotics exist for resistant urinary infections. Choice depends on the organism, resistance pattern, and local data.

Antibiotic Stewardship

Use Only When Indicated

Carbapenems should be reserved for infections that need them. Using Vabomere when simpler options would work increases resistance pressure.

Culture First

Urine culture with susceptibility results should guide therapy. Clinicians reassess treatment as results return and narrow or switch when appropriate.

Protecting the Drug

Protected carbapenems are valuable only while they remain effective. Responsible use protects that value for future patients.

Availability and Cost

Availability

Vabomere is given in hospital and infusion settings. Availability depends on the facility, so the care team can confirm stock.

Cost

Vabomere is a branded specialty antibiotic and is expensive. Costs are usually bundled into the hospital stay. Ask your insurer or hospital financial counselor for current figures.

Coverage

Coverage for FDA-approved indications is generally more straightforward. Prior authorization may be required.

Pregnancy, Breastfeeding, and Children

Pregnancy

Pregnant patients with urinary infections need careful evaluation. Decisions about Vabomere should involve obstetric and infectious disease teams, weighing benefits against limited data.

Breastfeeding

Discuss breastfeeding with your care team before treatment so they can consider the infant's needs.

Children

The labeled population is adults 18 and older. Use in children is outside the labeled indication and requires specialist judgment.

Questions to Ask Your Care Team

• Did my culture identify an organism susceptible to meropenem/vaborbactam?
• Why was this drug chosen over other options, including piperacillin/tazobactam?
• Do I have any history of severe reactions to penicillins or carbapenems?
• How will my kidney function and seizure risk be monitored?
• What signs of confusion, seizure, or severe diarrhea should the nurses report right away?

Frequently Asked Questions

Q: What is Vabomere used for?

A: Vabomere is approved for adults 18 and older with complicated urinary tract infections, including pyelonephritis, caused by designated susceptible Enterobacteriaceae.

Q: When was it approved?

A: The FDA approved it on August 29, 2017.

Q: Is Vabomere a pill?

A: No. It is given only by IV infusion over about 3 hours.

Q: What does vaborbactam do?

A: It protects meropenem from KPC-type carbapenemases, which otherwise destroy the antibiotic.

Q: Does it work against all carbapenem-resistant bacteria?

A: No. Metallo-beta-lactamase producers and Acinetobacter are generally not covered. Testing is essential.

Q: Is it safe if I'm allergic to penicillin?

A: Discuss any allergy with your care team. The FDA specifically cautioned against use in patients with a history of anaphylaxis to beta-lactams.

Q: Why does it cause seizures in some people?

A: Carbapenems can lower the seizure threshold, especially when kidney function is reduced. Dose correction and monitoring reduce this risk.

Medical Disclaimer

This article is for general education only and does not provide medical advice, diagnosis, or treatment. Complicated urinary tract infections can be serious and require evaluation by a qualified clinician. Do not start, stop, or change any antibiotic without guidance from your care team. For dosing, warnings, and interactions, consult the current U.S. prescribing information on DailyMed. If you have fever with chills, flank pain, confusion, seizures, or difficulty breathing, seek emergency care immediately.

Sources and Further Reading

• U.S. FDA announcement: FDA approves new antibacterial drug Vabomere for complicated urinary tract infections, August 29, 2017
• FDA review memorandum for NDA 209776 (meropenem-vaborbactam), 2017
• Drugs.com Vabomere FDA approval history
• Medscape and Healio coverage of the FDA approval, August 2017
• TANGO-1 phase 3 trial summaries and published report (Kaye et al.)
• TANGO-2 phase 3 trial summaries in carbapenem-resistant Enterobacteriaceae infections
• Vabomere U.S. Prescribing Information, including dosing, warnings, and renal guidance

This article reflects information available as of October 2026. Confirm current prescribing details with your healthcare provider and the latest FDA labeling. For more on antibiotic options, visit MyOnlineMedShop blog or contact us.