Ampicillin

Ampicillin: Uses, Dosage, and Side Effects

Overview

• It 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. It acts in a time-dependent fashion.

Uses of Ampicillin

• Active against many Gram-positive and Gram-negative aerobic organisms and obligate anaerobes, but not against those that produce penicillinases (beta-lactamases), e.g. Escherichia coli, Staphylococcus aureus.

Dose of Ampicillin in Dogs and Cats

Dogs:

• Routine infections: 10–20 mg/kg i.v., i.m., s.c., p.o. q6–8h.

• CNS or serious bacterial infections: up to 40 mg/kg i.v. q6h has been recommended.

Cats:

10–20 mg/kg i.v., i.m., s.c., p.o. q6–8h.

Side Effects of Ampicillin in Dogs and Cats

• Nausea, diarrhea, and skin rashes are the commonest adverse effects.

Contraindications of Ampicillin in Dogs and Cats

• Avoid oral antibiotic agents in critically ill patients, as absorption from the GI tract may be unreliable.
• Do not use in animals with hypersensitivity to penicillins.

Some Notes:

• Maintaining levels above the MIC is critical for efficacy; thereby, prolonged dosage intervals or missed doses can compromise therapeutic response.
• The difficult Gram-negative organisms such as Pseudomonas aeruginosa and Klebsiella are usually resistant.
• Ampicillin is excreted well in bile and urine.
• Oral bioavailability is reduced in the presence of food.
• After reconstitution, the sodium salt will retain adequate potency for up to 8 hours if refrigerated but use within 2 hours if kept at room temperature.