Antibiotics Compatible with Stimulan (Antibiotic-Loaded Bone Cement)
Only aminoglycosides (gentamicin, tobramycin), glycopeptides (vancomycin), and clindamycin are reliably compatible with PMMA bone cement like Stimulan, while beta-lactam antibiotics including ceftazidime-avibactam and aztreonam should NOT be mixed into bone cement due to thermal instability and rapid degradation.
Thermally Stable Antibiotics for PMMA Cement
The key limiting factor for antibiotic incorporation into PMMA bone cement is thermal stability, as the exothermic polymerization process can exceed 100°C 1:
- Aminoglycosides (gentamicin, tobramycin): Excellent long-term stability at both polymerization temperatures and body temperature (37°C) 1
- Glycopeptides (vancomycin): Excellent thermal stability and sustained release properties 1
- Fluoroquinolones: Excellent long-term stability 1
- Clindamycin: Commonly used in commercial formulations 1
Antibiotics That CANNOT Be Mixed with Bone Cement
Beta-lactam antibiotics degrade rapidly at 37°C and are unsuitable for PMMA incorporation 1:
- Ceftazidime-avibactam
- Aztreonam
- Other cephalosporins
- Penicillins
- Carbapenems
This thermal instability means these antibiotics lose antimicrobial activity both during the high-temperature polymerization process and during sustained release at body temperature 1.
Clinical Application for Orthopedic Infections
For fracture-related infections requiring local antibiotic delivery 1:
- Standard approach: Use gentamicin or tobramycin-loaded PMMA cement (commercially available formulations) 1, 2
- MRSA coverage: Add vancomycin to PMMA cement (requires hand-mixing for high-dose formulations >1g per batch) 2, 3
- High-dose formulations: Hand-mix cement to achieve >1g antibiotic per batch for treatment (vs ≤1g for prophylaxis) 2
Alternative Strategy for Beta-Lactam Coverage
If ceftazidime-avibactam and aztreonam are needed for multidrug-resistant gram-negative infections 1:
- Systemic administration only: Give these antibiotics intravenously, not in cement 1
- For MBL-producing organisms: The combination of ceftazidime-avibactam plus aztreonam should be administered systemically 1, 4
- Local delivery: Use thermally stable antibiotics (aminoglycosides/vancomycin) in cement while giving beta-lactams systemically 1
Evidence Against Topical Beta-Lactams
Recent guidelines suggest against routine use of topical antibiotics as adjunctive therapy 1:
- Limited data with high risk of bias for antibiotic-loaded cement in diabetic foot osteomyelitis 1
- No demonstrated significant clinical benefit over systemic therapy alone 1
- Safety concerns not clearly established 1
Common Pitfalls to Avoid
- Never mix beta-lactams into PMMA cement - they will degrade and lose activity 1
- Don't rely solely on cement antibiotics - always combine with appropriate systemic therapy for active infections 1
- Avoid low-dose cement for treatment - use >1g antibiotic per batch when treating established infection, not prophylaxis doses 2
- Consider renal toxicity - aminoglycosides can elute systemically and cause acute renal failure 3