Injectable: Ampicillin sodium 250 mg, 500 mg powders for reconstitution (human licensed product only); 150 mg/ml suspension, 100 mg/ml long-acting preparation.
Oral: 500 mg tablets; 250 mg capsule.
Action: 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 bactericidal fashion.
Use: 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. The difficult Gram-negative organisms such as Pseudomonas aeruginosa and Klebsiella are usually resistant. Ampicillin is excreted well in bile and urine. Maintaining levels above the MIC is critical for efficacy and thereby prolonged dosage interval or missed doses can compromise therapeutic response. Dose and dosing interval is determined by infection site, severity and organism. Oral bioavailability is reduced in the presence of food. Used to treat bacterial disease in fish.