Antimicrobials · Penicillins
The facts most likely to be tested
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Amoxicillin-clavulanate is the first-line antibiotic for acute bacterial rhinosinusitis when treatment is indicated.
Clavulanate acts as a beta-lactamase inhibitor to expand the spectrum of amoxicillin against beta-lactamase-producing organisms.
This agent is the drug of choice for human and animal bite wounds due to its coverage of *Eikenella corrodens* and *Pasteurella multocida*.
Amoxicillin-clavulanate is the preferred empiric therapy for acute otitis media in patients who have received recent amoxicillin or have concurrent purulent conjunctivitis.
The most common adverse effect of this medication is gastrointestinal distress, specifically diarrhea, due to the clavulanate component.
This drug provides broad-spectrum coverage including Gram-positive cocci, Gram-negative rods, and anaerobes.
Amoxicillin-clavulanate is associated with an increased risk of idiosyncratic drug-induced liver injury, specifically cholestatic hepatitis.
Vignette unlocked
A 34-year-old male presents to the urgent care clinic with a laceration on his right hand sustained during a fistfight yesterday. Physical examination reveals a 2-cm puncture wound over the third metacarpophalangeal joint with surrounding erythema and edema. The patient has no known drug allergies. He is afebrile and neurovascularly intact.
What is the most appropriate empiric antibiotic therapy for this patient?
Amoxicillin-clavulanate
This vignette tests the high-yield indication for amoxicillin-clavulanate in bite wounds, which require coverage for oral flora including *Eikenella corrodens*.
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High yield triage
Classification
Extended-spectrum penicillin combined with a beta-lactamase inhibitor.
Indications
Acute otitis media, rhinosinusitis, human/animal bites, and community-acquired pneumonia.
Mechanism of Action
Inhibits bacterial cell wall synthesis; clavulanate prevents beta-lactamase degradation.
Side Effects
Diarrhea is common; anaphylaxis and cholestatic jaundice are critical.
Contraindications / Monitoring
History of penicillin allergy; monitor renal function and liver enzymes.
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Mechanism of Action
Amoxicillin binds to penicillin-binding proteins (PBPs) to inhibit peptidoglycan cross-linking. Clavulanate acts as a suicide inhibitor of beta-lactamase enzymes produced by resistant organisms. This combination expands the spectrum to include Staphylococcus aureus and Haemophilus influenzae.
Unique Properties
The addition of clavulanate provides coverage against beta-lactamase-producing bacteria that render standard amoxicillin ineffective. It is the preferred agent for polymicrobial infections involving both aerobic and anaerobic flora.
Indications
First-line for acute otitis media when initial therapy fails or high-dose amoxicillin is insufficient. It is the drug of choice for human and animal bites (e.g., Pasteurella multocida) and is used for sinusitis and aspiration pneumonia.
Pharmacokinetics
Renally excreted; dosage adjustments are required for patients with severe renal impairment (CrCl <30 mL/min). It is well-absorbed orally, though the clavulanate component is primarily responsible for gastrointestinal side effects.
Side Effects & Adverse Events
Diarrhea and nausea are the most frequent complaints. Cholestatic jaundice is a rare but classic board-tested adverse effect associated with the clavulanate component. Type I hypersensitivity reactions, including anaphylaxis, require immediate cessation.
Contraindications
History of penicillin-induced cholestatic jaundice or hepatic dysfunction. Severe hypersensitivity reactions (e.g., Stevens-Johnson syndrome, anaphylaxis) to any beta-lactam are absolute contraindications.
Monitoring
Monitor liver function tests (LFTs) if therapy is prolonged, as transient elevations may occur. Assess renal function (BUN/Creatinine) to ensure appropriate dosing in elderly or comorbid patients.
Clinical Pearls
Always choose this for animal bites to cover Pasteurella. If a patient develops a non-pruritic rash after amoxicillin, consider Epstein-Barr virus infection rather than a true penicillin allergy.