Amoxicillin

Amoxicillin: Uses, Dosage and Side Effects

Overview

Amoxicillin Binds to penicillin-binding proteins involved in bacterial cell wall synthesis, thereby decreasing cell wall strength and rigidity, affecting cell division, growth and septum formation. Acts in a time-dependent fashion.

Uses of Amoxicillin

• effective against a variety of Gram-positive and Gram-negative aerobic organisms as well as many obligate anaerobes.

Dose of Amoxicillin in Dogs and Cats

Dogs and Cats:

• Parenteral: 7 mg/kg i.m. q24h; 15 mg/kg i.m. q48h for depot preparations.
• Oral:

10 mg/kg p.o. q8–12h.

11–15 mg/kg p.o. q8h for bacterial cystitis. Evidence of a need for clavulanic acid is lacking even in infections with beta-lactamase-producing bacteria.

Side Effects of Amoxicillin in Dogs and Cats

• Nausea
• diarrhoea
• skin rashes (type 1 (Ig-E mediated) reaction)

Contraindications of Amoxicillin in Dogs and Cats

• Avoid oral antibiotics in critically ill patients, as absorption from the GI tract may be unreliable.

Some Notes:

• Resistance is possible due to bacterial production of penicillinases (beta-lactamases), e.g. some Escherichia coli, Staphylococcus aureus. Gram-negative organisms (Pseudomonas, Proteus, Klebsiella) are usually resistant.
• Amoxicillin is excreted well in bile and urine achieving high concentrations in urine.
• Oral amoxicillin may be given with or without food.
• It is important to maintain levels above the MIC for a high percentage of the time by ensuring regular dosing; missing doses can seriously compromise efficacy.
• Refrigerate oral suspension after reconstitution; discard if solution becomes dark or after 7 days.
• Avoid concurrent use with bacteriostatic antibiotics (e.g. tetracycline, erythromycin, chloramphenicol); clinical signficance of antagonstic activity is unknown.
• Do not mix in the same syringe as aminoglycosides. A synergistic effect is seen when beta-lactam and aminoglycoside antimicrobials are used concurrently.