ModeratePenicillins with extended spectrum×Tetracyclines
Updated · Methodology
Mechanism
A bacteriostatic agent (doxycycline) suppresses the bactericidal action of a beta-lactam (amoxicillin), which requires active bacterial division. Antibacterial efficacy drops.
Symptoms
Persistent fever, infection symptoms, and inflammation markers 48–72 hours after starting therapy. Resistant strain selection possible.
Management
Avoid the combination — choose a single antibiotic based on pathogen and infection site. For mixed infections (e.g. aspiration pneumonia), prefer switching to amoxicillin-clavulanate (broader spectrum) or a cephalosporin with metronidazole. For Lyme disease, use doxycycline monotherapy; for respiratory infections with confirmed sensitivity, amoxicillin.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Bactrim (sulfamethoxazole and trimethoprim) prescribing information (2013)– ; DailyMed setid f59d0c04-9c66-4d53-a0e1-cb55570deb62