Can I give co-amoxiclav (amoxicillin/clavulanic acid) and cloxacillin tablets together?

Co-amoxiclav and Cloxacillin Should Not Be Given Together

Co-amoxiclav (amoxicillin/clavulanic acid) and cloxacillin should not be administered together as this combination provides redundant antimicrobial coverage without additional clinical benefit and increases the risk of adverse effects. 1

Rationale for Not Combining These Antibiotics

• Both medications are beta-lactam antibiotics with overlapping spectrum of activity, particularly against Staphylococcus aureus, making their combination therapeutically redundant 1
• Co-amoxiclav already contains clavulanic acid which protects amoxicillin from beta-lactamase enzymes, providing coverage against beta-lactamase-producing organisms that cloxacillin targets 2
• Combining these antibiotics increases the risk of adverse effects without providing additional clinical benefit 3
• Guidelines recommend using the narrowest spectrum antibiotic effective for the condition rather than combining broad-spectrum agents unnecessarily 4

Appropriate Clinical Use

When to Use Co-amoxiclav:

• First-line for acute bacterial rhinosinusitis in both adults and children 1
• Treatment of respiratory tract infections caused by amoxicillin-resistant Haemophilus influenzae 5
• Alternative treatment for methicillin-susceptible Staphylococcus aureus infections 1
• Empiric therapy for mixed infections where both gram-positive and gram-negative coverage is needed 1

When to Use Cloxacillin:

• Targeted therapy for known methicillin-susceptible Staphylococcus aureus (MSSA) infections 1
• Recent research shows cloxacillin can be as effective as co-amoxiclav in treating uncomplicated pediatric bacterial lymphadenitis, with the advantage of narrower spectrum 6

Alternative Approaches

If broader coverage is needed beyond what either antibiotic provides individually:

• For severe mixed infections, guidelines recommend specific combinations like co-amoxiclav with ciprofloxacin for certain neutropenic patients or complex infections 4
• For severe pneumonia, guidelines recommend a combination of a broad-spectrum beta-lactam (such as co-amoxiclav) with a macrolide (clarithromycin or erythromycin) rather than adding another beta-lactam 1

Potential Risks of Inappropriate Combinations

• Increased risk of adverse effects, particularly gastrointestinal issues 3
• Unnecessary broad-spectrum coverage promotes antimicrobial resistance 4
• Potential for drug interactions affecting metabolism and clearance 1
• Higher cost without additional clinical benefit 3

Special Considerations

• If treatment failure occurs with initial antibiotic therapy, guidelines recommend changing to a different class of antibiotic rather than adding another agent from the same class 1
• For patients with penicillin allergy, neither co-amoxiclav nor cloxacillin should be used, and alternative antibiotic classes should be considered 1
• During pregnancy, both antibiotics are generally considered compatible, but should not be used in combination 1

In conclusion, while both co-amoxiclav and cloxacillin are valuable antibiotics when used appropriately, their combination provides redundant coverage and should be avoided in favor of more targeted antibiotic therapy based on the specific infection being treated.