Why Skin and Lung Infections Need Careful Choices

Common Infections With Different Severity

Skin infections range from small boils to spreading cellulitis and deep abscesses. Pneumonia acquired in the community ranges from mild illness treated at home to life-threatening disease needing hospital care. Each requires a different level of antibiotic choice.

MRSA and Oral Options

MRSA is a common cause of serious skin infection, and many oral antibiotics have lost reliability against it. Clinicians have looked for options that work by mouth as well as by IV, which is one reason oral delafloxacin was developed.

Why Fluoroquinolones Need Restraint

Fluoroquinolones are effective, but their serious side effects have led the FDA to restrict them to infections where other treatments are not appropriate. Understanding both the benefit and the risk is essential for patients considering these drugs.

Key Takeaways

• Baxdela (delafloxacin) received FDA approval on June 19, 2017, for adults with ABSSSI caused by designated susceptible bacteria, including MRSA.
• The FDA added community-acquired bacterial pneumonia as an indication in October 2019.
• Baxdela is available as oral tablets and as an IV injection.
• Two phase 3 ABSSSI trials enrolling about 1,042 adults found it noninferior to vancomycin plus aztreonam for early clinical response.
• The boxed warning covers tendinitis and tendon rupture, peripheral neuropathy, central nervous system effects, and myasthenia gravis exacerbation. These can be serious, disabling, and may persist.
• Fluoroquinolones should be reserved for infections where other antibiotics are not appropriate, and Baxdela is contraindicated in people with known fluoroquinolone hypersensitivity.

What Is Baxdela

Brand and Generic Names

Baxdela is the brand name for delafloxacin. The drug was developed by Rib-X Pharmaceuticals, which later became part of Melinta Therapeutics, the company that marketed it in the United States.

Dosage Forms

Baxdela is available as tablets for oral use and as an injection for intravenous infusion. Both forms allow treatment in hospital and outpatient settings, depending on the infection and patient.

Drug Class

Delafloxacin is a fluoroquinolone, the same class as ciprofloxacin and levofloxacin. It is an anionic fluoroquinolone, meaning its chemical structure carries a negative charge that changes how it behaves in the body and in acidic environments.

FDA Approvals: 2017 and 2019

The 2017 Decision

The FDA approved Baxdela on June 19, 2017, for adults with ABSSSI caused by designated susceptible bacteria. The approval recognized the drug's activity against MRSA and some gram-negative organisms, as well as its availability in oral and IV forms.

Expedited Review

Delafloxacin was designated a Qualified Infectious Disease Product, which entitled it to expedited review.

The 2019 Pneumonia Approval

In October 2019, the FDA approved Baxdela for adults with community-acquired bacterial pneumonia caused by designated susceptible organisms. This extended the label beyond skin infections.

Stewardship Language

The FDA emphasized that clinicians should order delafloxacin only when an infection is proven or strongly suspected to be bacterial, to limit the development of drug-resistant bacteria.

The Fluoroquinolone Class

A Long History

Fluoroquinolones were introduced in the 1980s and became widely used for many infections, including urinary, respiratory, and skin infections. Their broad activity and oral bioavailability made them popular.

Growing Concern

Over time, serious side effects were recognized, including tendon rupture, nerve damage, and central nervous system effects. Resistance also increased, leading to FDA safety communications that restricted use for certain uncomplicated infections.

Where Baxdela Fits

Baxdela carries the same class warnings as other fluoroquinolones. Its place in treatment is for specific serious infections where its profile is appropriate, not for routine use.

How Delafloxacin Works

DNA Enzyme Targets

Delafloxacin inhibits two bacterial enzymes, DNA gyrase and topoisomerase IV, which are needed for DNA replication, transcription, repair, and recombination. Blocking these enzymes leads to bacterial death.

Concentration-Dependent Killing

The drug is bactericidal and shows concentration-dependent activity. Its potency is preserved in acidic environments, which may help against some infections where pH is lower.

Oral and IV Equivalence

The oral and IV forms are designed to achieve similar drug exposure, allowing a switch between them as the patient improves.

Why Delafloxacin Is Different: The Anionic Structure

What Anionic Means

Most fluoroquinolones carry a positive charge or are zwitterionic. Delafloxacin is anionic, meaning it carries a negative charge. This structure is the basis for its distinct activity profile.

Activity Against Resistant Strains

Laboratory studies reported that delafloxacin retained activity against many staphylococci that were resistant to other fluoroquinolones. Clinical relevance depends on the organism and susceptibility testing.

Limits of the Distinction

A different chemical structure does not remove the class warnings. Delafloxacin still carries the same boxed warning as other fluoroquinolones.

Which Bacteria It Targets

Skin Infection Organisms

The ABSSSI indication covers gram-positive organisms including Staphylococcus aureus (MRSA and methicillin-susceptible strains), Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus anginosus group organisms. Some gram-negative organisms are also included in the labeled spectrum.

Pneumonia Organisms

The CABP label covers designated susceptible organisms such as Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Legionella pneumophila, and Mycoplasma pneumoniae. Confirm the complete list in the current prescribing information.

Culture Matters

Susceptibility testing confirms whether a particular isolate is susceptible, and it helps avoid fluoroquinolone use when another drug is more appropriate.

Approved Uses and Labeling Limits

Who Is Eligible

The labeled populations are adults with ABSSSI or CABP caused by designated susceptible bacteria. The label is not for children.

Restrictions for Uncomplicated Infections

The FDA advises that fluoroquinolones should not be used for uncomplicated infections such as acute sinusitis, acute bronchitis, or uncomplicated urinary tract infections when other options exist, because the risks may outweigh the benefits.

Not Approved For

Baxdela is not approved for bacteremia, endocarditis, or other conditions outside the labeled indications. Use outside the label is a clinical decision.

The ABSSSI Trials

Design

Two phase 3 trials compared delafloxacin with vancomycin plus aztreonam in adults with ABSSSI. The trials were randomized and designed to test whether delafloxacin was as effective as the comparator for early clinical response.

Population

Together, the two trials enrolled about 1,042 adults. The population included cellulitis, abscesses, and wound infections of defined size.

Primary Endpoint

The primary endpoint was early clinical response, defined as a reduction in lesion size of at least 20 percent within 48 to 72 hours after treatment began.

The 2019 Pneumonia Approval

What Changed

In October 2019, the FDA approved delafloxacin for CABP. The approval extended the drug's use to adults with community-acquired pneumonia caused by designated susceptible organisms.

Why Pneumonia Requires Caution

Pneumonia can be serious, and fluoroquinolones are among the options clinicians consider. The boxed warning applies to this use as well, so the benefit must be weighed carefully against risks.

Alternatives

Many patients with CABP can be treated with other antibiotics, such as amoxicillin or macrolides, depending on severity and local resistance. The choice depends on the clinical picture.

Trial Results Explained

Noninferiority

The two ABSSSI trials showed that delafloxacin was noninferior to vancomycin plus aztreonam for early clinical response. Noninferiority means it was not meaningfully worse within a prespecified margin.

Oral and IV Data

The trials included both oral and IV dosing options as part of the treatment strategy, reflecting how skin infections are managed in practice.

Reading the Numbers

Noninferiority does not show superiority. Trial populations are selected, and clinicians interpret results alongside the patient's condition and culture data.

The Boxed Warning Explained

What a Boxed Warning Means

A boxed warning is the strongest safety message the FDA requires on a prescription label. It signals serious or life-threatening risks that clinicians and patients must consider before use.

Categories in the Baxdela Warning

The boxed warning covers tendinitis and tendon rupture, peripheral neuropathy, central nervous system effects, and exacerbation of myasthenia gravis. These effects can occur together and may be disabling.

Why It Applies to Every Fluoroquinolone

The same class-wide concerns apply to other fluoroquinolones, which is why the FDA restricted their use for infections where alternatives exist.

Tendon Warning

What Can Happen

Tendinitis or tendon rupture can occur, most often in the Achilles tendon. Risk is higher in older adults, people taking corticosteroids, and those who have had organ transplants.

Warning Signs

Stop taking the drug and contact your clinician right away if you have pain, swelling, or inflammation in a tendon, or if you hear a snap or feel weakness in a limb.

Rest and Activity

Avoid strenuous exercise during treatment if your team advises it, and report any tendon pain early.

Nerve and Neuropathy Warning

What Peripheral Neuropathy Means

Peripheral neuropathy is damage to nerves outside the brain and spinal cord. It can cause numbness, tingling, burning pain, or weakness, usually in the hands and feet.

Persistence

Fluoroquinolone-related neuropathy may persist after stopping the drug. Report any new symptoms promptly.

What to Report

Tell your care team about numbness, tingling, burning, or weakness, especially if it begins during treatment.

Central Nervous System Effects

Possible Effects

Fluoroquinolones can cause dizziness, insomnia, confusion, anxiety, or seizures. Mental status changes and psychiatric symptoms have been reported.

Who Is at Higher Risk

Older adults, people with seizure disorders, and those with kidney problems may have higher risk.

What to Do

Report confusion, unusual behavior, hallucinations, or seizures immediately. Do not drive or operate machinery if you feel dizzy or drowsy.

Myasthenia Gravis Warning

What It Is

Myasthenia gravis is a neuromuscular condition causing muscle weakness and fatigue. Fluoroquinolones can worsen the weakness.

Who Should Be Cautious

People with myasthenia gravis should discuss alternatives with their neurologist. The boxed warning specifically highlights this risk.

Warning Signs

Report new muscle weakness, double vision, drooping eyelids, or trouble breathing or swallowing right away.

Other Warnings: Blood Sugar, Aorta, and More

Blood Sugar Changes

Fluoroquinolones can cause high or low blood sugar, which matters for people with diabetes. Symptoms of low blood sugar include shakiness, sweating, and confusion.

Aortic Problems

Fluoroquinolones have been associated with aortic aneurysm or dissection in some patients. Report sudden chest, back, or abdominal pain.

Other Reactions

Severe diarrhea, hypersensitivity, photosensitivity, and C. difficile infection have been reported. Report any unusual or severe symptoms promptly.

Dosing and Administration

Labeled Regimens

Baxdela is given as oral tablets or IV infusion. Dosing and duration depend on the infection and route. Confirm the current regimen in the prescribing information on DailyMed.

Switching Routes

Patients may switch from IV to oral dosing as they improve, according to the care team's plan.

Missed Doses

Take a missed oral dose as soon as you remember unless it is close to the next dose. Do not double up.

Food, Antacids, and Absorption

Antacids and Minerals

Antacids, calcium, iron, zinc, and magnesium products can reduce absorption of fluoroquinolones. Separate them from your dose as your pharmacist directs.

Food

Some fluoroquinolones are affected by food, particularly dairy products. Ask your pharmacist for specific timing instructions for your prescription.

Hydration

Drink fluids as your team advises during treatment, unless you have a condition that limits fluid intake.

Kidney Function and Dosing

Why It Matters

Kidney function influences how fluoroquinolones are cleared. Reduced kidney function may require dose adjustment and closer monitoring.

Monitoring

Your team may check kidney function before and during treatment, especially in older adults and people with existing kidney disease.

Dialysis

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

Common Side Effects

Gastrointestinal Effects

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

Headache and Dizziness

Headache and dizziness are commonly reported. Report severe or persistent symptoms.

Infusion-Site Reactions

For IV use, pain, redness, or swelling at the site can occur. Nurses monitor the line and report problems.

Who Should Not Receive Baxdela

Fluoroquinolone Hypersensitivity

People with known hypersensitivity to fluoroquinolones should not take Baxdela. This is a labeled contraindication.

Other Considerations

People with a history of tendon disorders, myasthenia gravis, seizure disorders, or significant kidney disease need careful evaluation. Pregnant or breastfeeding patients need individualized decisions.

Children

The labeled populations are adults. Fluoroquinolones are generally avoided in children unless specialist evaluation supports use.

Drug Interactions

Corticosteroids

Corticosteroids increase the risk of tendon rupture when combined with fluoroquinolones. Your team will weigh this risk.

Blood Sugar Medicines

Diabetes medicines, including insulin and oral agents, can interact with fluoroquinolone-related blood sugar changes. Monitor glucose and report symptoms.

Antacids, Minerals, and Other Drugs

Antacids and mineral supplements can reduce absorption. Give your care team a full list of medications, including over-the-counter products and supplements.

How Baxdela Compares With Other Options

Vancomycin

Vancomycin is an IV option for serious MRSA infections and was part of the comparator in the ABSSSI trials. It requires drug-level monitoring but does not carry the fluoroquinolone boxed warning.

Linezolid and Tedizolid

Oxazolidinones are oral and IV options for skin infections. They have different warnings, including blood count effects and serotonin syndrome risk.

Doxycycline and Trimethoprim-Sulfamethoxazole

Some oral antibiotics are used for skin infections. Each has its own spectrum, resistance patterns, and warnings, so clinicians choose based on culture and local data.

Antibiotic Stewardship and Fluoroquinolone Restrictions

Why Restrictions Exist

The FDA has restricted fluoroquinolones for uncomplicated infections because serious side effects can outweigh benefits when safer options exist.

Culture First

Susceptibility testing should guide whether Baxdela is appropriate and whether a fluoroquinolone is needed at all.

Protecting the Drug

Overuse of fluoroquinolones increases resistance. Responsible use preserves their value for infections that truly need them.

Availability and Cost

Availability

Baxdela is available through pharmacies for oral tablets and through hospitals and infusion centers for IV use. Availability depends on the setting, so your care team can confirm stock.

Cost

Baxdela is a branded antibiotic and typically costs more than generic fluoroquinolones. Ask your pharmacist or insurer for current figures.

Coverage

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

Pregnancy, Breastfeeding, and Children

Pregnancy

Fluoroquinolones have raised concern in pregnancy, and decisions require a careful risk-benefit discussion with the obstetric and infectious disease teams.

Breastfeeding

Fluoroquinolones pass into breast milk. Discuss breastfeeding with your care team before starting treatment.

Children

The labeled populations are adults. Use in children is outside the labeled indications and requires specialist judgment.

Questions to Ask Your Care Team

• Is a fluoroquinolone the right choice for my infection, or is there a safer option?
• Do I have any history of tendon problems, nerve disease, myasthenia gravis, or seizures?
• Am I taking corticosteroids or medicines that interact with fluoroquinolones?
• When should I stop the drug and call you right away?
• How long will the course last, and will I switch from IV to oral?

Frequently Asked Questions

Q: What is Baxdela used for?

A: It is approved for adults with acute bacterial skin and skin structure infections and, since 2019, community-acquired bacterial pneumonia, caused by designated susceptible bacteria.

Q: When was it approved?

A: The FDA approved it for ABSSSI on June 19, 2017, and for CABP in October 2019.

Q: What is the boxed warning?

A: It warns of serious and potentially disabling effects, including tendon rupture, peripheral neuropathy, CNS effects, and worsening of myasthenia gravis.

Q: Does it cover MRSA?

A: Yes, for skin infections caused by susceptible MRSA. Testing confirms activity for each isolate.

Q: Is it a pill?

A: It is available as both tablets and an IV injection.

Q: Can I take it if I'm allergic to other fluoroquinolones?

A: No. Known hypersensitivity to fluoroquinolones is a contraindication.

Q: What should I do if I feel tendon pain?

A: Stop the drug and contact your clinician right away. Tendon pain or swelling during treatment needs prompt evaluation.

Medical Disclaimer

This article is for general education only and does not provide medical advice, diagnosis, or treatment. Skin infections and pneumonia 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 chest pain, trouble breathing, confusion, seizures, sudden tendon pain, or severe weakness, seek emergency care immediately.

Sources and Further Reading

• U.S. FDA approval of Baxdela (delafloxacin) for ABSSSI, June 19, 2017
• U.S. FDA approval of Baxdela for CABP, October 2019
• Medscape coverage of the 2017 FDA approval, June 19, 2017
• Melinta Therapeutics announcements of FDA approvals for ABSSSI and CABP
• Delafloxacin meglumine review in Drugs of Today, 2018
• FDA Drug Safety Communications on restricting fluoroquinolone use for uncomplicated infections
• Baxdela U.S. Prescribing Information, including the boxed warning, contraindications, and dosing

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 MyOnlineMedShop, visit our blog or contact us.