What Is Daptomycin?

Daptomycin is a cyclic lipopeptide antibiotic used to treat serious infections caused by gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). It was originally marketed under the brand name Cubicin by Merck & Co., though generic versions are now available from multiple manufacturers.

Daptomycin is FDA-approved for:

• Complicated skin and skin structure infections (cSSSI) in adults and children
• Staphylococcus aureus bacteremia (bloodstream infections) in adults and children
• Right-sided infective endocarditis caused by S. aureus in adults

It is also used off-label for conditions such as osteomyelitis, prosthetic joint infections, VRE infections, and diabetic foot infections. Daptomycin is administered intravenously only and is typically given in hospital or home infusion settings.

How does Daptomycin work?

Daptomycin works by binding to bacterial cell membranes in a calcium-dependent process. Once bound, it causes rapid depolarization of the membrane potential, which disrupts the bacteria's ability to produce DNA, RNA, and proteins — all essential for survival. This unique mechanism leads to rapid bacterial cell death.

Additionally, Daptomycin forms a complex with lipid II and phosphatidylglycerol in the bacterial membrane, which inhibits cell wall synthesis. Because of this distinct mechanism of action, Daptomycin remains effective against many bacteria that have developed resistance to other antibiotics, including Vancomycin-resistant strains.

Important: Daptomycin should not be used to treat pneumonia, as it is inactivated by pulmonary surfactant in the lungs.

What doses are available for Daptomycin?

• 350 mg vial — Lyophilized powder for injection (single-dose vial)
• 500 mg vial — Lyophilized powder for injection (single-dose vial)
• 350 mg/50 mL — Premixed IV solution in 0.9% sodium chloride
• 500 mg/50 mL — Premixed IV solution in 0.9% sodium chloride
• 700 mg/100 mL — Premixed IV solution in 0.9% sodium chloride

Your doctor will determine the appropriate dose based on your weight and the type of infection being treated. Typical dosing is 4 mg/kg IV once daily for skin infections or 6 mg/kg IV once daily for bloodstream infections.

How hard is it to find Daptomycin in stock?

Daptomycin scores a 45 out of 100 on the Medfinder findability scale, meaning it can be difficult to locate in stock. As an IV-only antibiotic used primarily for serious MRSA and gram-positive infections, Daptomycin is dispensed through hospital pharmacies and specialty/home infusion pharmacies rather than traditional retail pharmacies. Supply disruptions from generic manufacturers have led to intermittent shortages, and some formulations may have limited availability depending on your region. If your provider has prescribed Daptomycin, Medfinder can help you locate a pharmacy that has it in stock near you.

Who Can Prescribe Daptomycin?

Daptomycin is most commonly prescribed by:

• Infectious Disease Specialists — The most frequent prescribers, particularly for MRSA bacteremia and complex infections
• Hospitalists — Often initiate Daptomycin therapy during hospital stays
• Internal Medicine Physicians — May manage ongoing treatment courses
• Surgeons — Orthopedic and cardiac surgeons for post-surgical infections and prosthetic joint infections
• Emergency Medicine Physicians — May initiate therapy in acute settings
• Nephrologists — For dialysis-related infections
• Dermatologists — For complicated skin and soft tissue infections

Because Daptomycin requires IV administration, it is typically started in a hospital setting. Patients who continue treatment at home will need coordination with a home infusion pharmacy and nursing service.

Is Daptomycin a controlled substance?

No, Daptomycin is not a controlled substance. It is not classified under any DEA schedule. However, it is a prescription-only medication that requires a doctor's order and is administered intravenously in a healthcare setting or through a home infusion service. It cannot be purchased over the counter.

Common Side Effects of Daptomycin

Like all medications, Daptomycin can cause side effects. Common side effects include:

• Diarrhea
• Headache
• Nausea and vomiting
• Constipation
• Injection site reactions
• Insomnia
• Rash
• Elevated creatine phosphokinase (CPK) levels
• Limb pain

Serious side effects to watch for include:

• Myopathy and rhabdomyolysis — Muscle pain, weakness, or elevated CPK levels. Your doctor should monitor CPK levels weekly.
• Eosinophilic pneumonia — Cough, fever, and difficulty breathing. Seek immediate medical attention.
• Peripheral neuropathy — Numbness or tingling in hands or feet.
• Clostridioides difficile-associated diarrhea — Severe, persistent diarrhea during or after treatment.

Contact your healthcare provider immediately if you experience any serious side effects.

Alternative Medications to Daptomycin

If you cannot find Daptomycin in stock or your doctor is considering other options, these alternatives may be appropriate depending on your condition:

• Vancomycin — A glycopeptide antibiotic and first-line treatment for many MRSA infections. Given IV with therapeutic drug monitoring required. Risk of nephrotoxicity and ototoxicity.
• Linezolid — An oxazolidinone antibiotic available in both IV and oral forms. Used for MRSA and VRE infections. Risk of myelosuppression and serotonin syndrome with prolonged use.
• Telavancin — A lipoglycopeptide antibiotic given IV for complicated skin infections and hospital-acquired pneumonia caused by gram-positive organisms.
• Oritavancin — A lipoglycopeptide antibiotic that can be given as a single-dose IV infusion for acute bacterial skin infections, which may simplify treatment.

Always discuss alternatives with your infectious disease specialist or prescribing physician before making any changes to your treatment plan.

Drug Interactions with Daptomycin

Daptomycin has several important drug interactions to be aware of:

• Statins (HMG-CoA reductase inhibitors) — Taking statins with Daptomycin significantly increases the risk of myopathy and rhabdomyolysis. Your doctor may temporarily stop your statin medication during Daptomycin therapy.
• Tobramycin — May increase Daptomycin levels in the blood, raising the risk of side effects.
• Warfarin — INR should be monitored closely during concurrent use.
• Nephrotoxic agents — Other medications that can harm the kidneys may increase the risk of renal impairment when combined with Daptomycin.

Always inform your healthcare team about all medications, supplements, and over-the-counter drugs you are taking before starting Daptomycin therapy.

Final Thoughts on Daptomycin

Daptomycin is a critically important antibiotic for treating serious gram-positive infections, particularly MRSA bacteremia and complicated skin infections. While generic versions have made it more affordable than the original brand Cubicin, intermittent supply disruptions can make it challenging to find — earning it a findability score of just 45 out of 100.

If you or your healthcare provider are having trouble locating Daptomycin in stock, Medfinder can help you search pharmacies in your area to find availability quickly. For patients facing financial barriers, the Merck Patient Assistance Program at merckhelps.com may provide the medication at no cost to qualifying individuals.

Always work closely with your infectious disease specialist to ensure you receive the right antibiotic therapy for your condition.