You are here: Urology Textbook > Drugs in Urology > Amoxicillin/Clavulanic Acid

Amoxicillin/Clavulanic Acid: Mechanism of Action, Side Effects and Dosage

Amoxicillin is an aminopenicillin for oral and parenteral antibiotic therapy, which, in combination with the β-lactamase inhibitor clavulanic acid, has a significantly broader antibiotic spectrum than penicillin.

Mechanism of Action:

Amoxicillin inhibits the peptidoglycan synthesis of the bacterial wall: it binds to so-called penicillin-binding proteins (peptidoglycan synthetases) and inhibits the polymerization of the peptidoglycan and covalent cross-linking of the bacterial wall. Clavulanic acid has no antibiotic activity; it inhibits the β-lactamase of many bacteria and prevents the inactivation of amoxicillin.

Antibiotic Spectrum of Amoxicillin/Clavulanic Acid:

Streptococci, meningococci, pneumococci, enterococci, staphylococci, Haemophilus influenzae, E. coli, Salmonella, Proteus, Klebsiella, and some anaerobes. Increasing resistance in the gram-negative area is caused by ESBL (extended spectrum β-lactamases), which are not inhibited by clavulanic acid.

Urological Indications for Amoxicillin/Clavulanic Acid:

Complicated urinary tract infections in adults and children, often as oral step-down treatment after initial parenteral therapy and known antibiogram. Treatment of prostatitis or epididymitis. For uncomplicated UTIs, amoxicillin/clavulanic acid is a second-choice antibiotic; it has a broad spectrum, causing side effects and developing resistance. Combined with clavulanic acid, intravenous perioperative antibiotic prophylaxis is possible for endourological procedures. Amoxicillin without clavulanic acid is suitable for endocarditis prophylaxis.

Pharmacokinetics of Amoxicillin/Clavulanic Acid:

• 70–90% bioavailability with oral administration, half-life 1 h. Amoxicillin is only slightly hepatically metabolized, 60–70% are excreted unchanged renally.
• Clavulanic acid is more strongly metabolized hepatically, 30–50% are excreted unchanged renally.

Side Effects of Amoxicillin/Clavulanic Acid:

• Common (over 1%) are gastrointestinal side effects (diarrhea, nausea), exanthema, and moderate increase in liver enzymes.
• Rare but potentially serious side effects are pseudomembranous enterocolitis, severe cutaneous skin reactions, anaphylaxis, cholestatic jaundice, hemolytic anemia, and thrombocytopenia.

Drug Interactions:

Probenicid inhibits renal tubular excretion and increases the serum concentration of amoxicillin/clavulanic acid.

Contraindications:

Penicillin allergy. Increased risk for exanthema with given to patients with infectious mononucleosis or CLL.

Dosage of Amoxicillin/Clavulanic Acid:

• Oral dosage: adults 625 mg (500 mg amoxicillin and 125 mg clavulanic acid) or 1000 mg (875 mg amoxicillin and 125 mg clavulanic acid) 1-1-1 p.\,o. Children receive 25–40/3.6–6.4 mg/kgBW amoxicillin/clavulanic acid as a daily dose, divided into three single doses.
• The intravenous dosage is 1.2 g (1000 mg amoxicillin and 200 mg clavulanic acid) or 2.2 g (2000 mg amoxicillin and 200 mg clavulanic acid) 1-1-1. Children receive 25/5 mg/kgBW amoxicillin/clavulanic acid 1-1-1. A dose reduction is necessary in case of renal insufficiency below 30 ml/min.

References

Simon und Stille 1997 SIMON, C. ; STILLE, W.: Antibiotika-Therapie in Klinik und Praxis.
9. Auflage.
Stuttgart New York : Schattauer, 1997

  Deutsche Version: Pharmakologie und Nebenwirkungen von Amoxicillin/Clavulansäure