Product Identity
Ampicillin sodium (CAS 69-52-3) is the sodium salt of ampicillin, a broad-spectrum semisynthetic penicillin. It is a white to off-white crystalline powder, freely soluble in water, and it is supplied to the veterinary pharmaceutical industry as a sterile or non-sterile API for injection powders, oral powders and intramammary or intramuscular preparations. Its sodium form is chosen for formulation because it dissolves quickly and gives a solution of near-neutral pH, which is easier on tissue than the acidic free acid.
| Parameter | Value |
|---|---|
| Chemical name | ampicillin sodium |
| CAS number | 69-52-3 |
| Molecular formula | C16H18N3NaO4S |
| Molar mass | 371.39 g/mol |
| Appearance | white to off-white crystalline powder |
| Solubility | freely soluble in water |
| Typical forms | sterile powder for injection, oral powder |
Mechanism of Action
Ampicillin belongs to the beta-lactam family and acts by inhibiting the transpeptidase enzymes that cross-link the peptidoglycan layer of the bacterial cell wall. Without those cross-links the wall cannot withstand internal osmotic pressure, and the cell lyses. The effect is bactericidal and depends on the drug reaching the growing cell wall during bacterial division, which is why adequate and repeated dosing matters. Ampicillin is not stable against beta-lactamase enzymes, so organisms that produce them, including many staphylococcal strains, are resistant even though the drug binds well to their target proteins.
Clinical Indications in Animals
In veterinary practice, ampicillin sodium is used for respiratory infections such as bronchopneumonia in cattle and pigs, for urinary tract infections, for skin and soft tissue infections including wounds and abscesses, for infections of the reproductive tract, and for systemic infections and septicaemia. Its spectrum covers a number of Gram-positive organisms such as streptococci and susceptible staphylococci, and Gram-negative organisms including Escherichia coli, Salmonella species, Pasteurella and Actinobacillus, which is a wider Gram-negative range than benzylpenicillin provides. It is inactive against Mycoplasma, fungi and viruses, so a diagnosis is important before treatment.
Dosing, Administration and Stewardship
Dose rates are set by the registered product label for each species and by the prescribing veterinarian, and they differ substantially between cattle, pigs, sheep, poultry and companion animals. Injectable preparations are given intramuscularly or subcutaneously, and oral powders are administered in feed or water, where stability in the drinking line and palatability affect the dose actually received. Responsible use means treating only confirmed or strongly suspected bacterial infections, using the shortest effective course, and rotating drug classes where resistance is a concern. Sensitivity testing of isolates from the herd or flock is the most reliable guide, particularly for enteric infections where resistance is common.
Residues, Withdrawal Periods and Compliance
Because treated animals enter the food chain, maximum residue limits for ampicillin in tissues and milk are laid down in the European Union in Commission Regulation (EU) No 37/2010, and comparable limits exist in other jurisdictions and under Codex. Products carry a withdrawal period that must be observed before milk or meat is sold, and farmers are required to record treatments. For finished dosage forms, pharmacopoeial monographs define identity, assay and related substances, and the API is normally released against a certificate of analysis covering those tests together with sterility where the grade is sterile. Bulk material should be stored in sealed containers, protected from moisture and light, and used within the retest period stated by the supplier.
Frequently Asked Questions
Q: What is ampicillin sodium used for in veterinary medicine?
A: It treats bacterial infections of the respiratory tract, urinary tract, skin and soft tissues, reproductive tract and systemic infections in a range of food-producing and companion animals, including cattle, pigs, sheep, poultry and dogs.
Q: How does ampicillin differ from penicillin G?
A: Ampicillin has a broader spectrum, especially against Gram-negative organisms such as E. coli and Salmonella, but like other penicillins it is destroyed by beta-lactamase enzymes produced by resistant bacteria.
Q: Are there withdrawal periods to observe?
A: Yes. Residue limits for ampicillin in tissues and milk are set in Commission Regulation (EU) No 37/2010, and every registered product carries a withdrawal period for meat and milk that must be respected before slaughter or sale.
Q: How should the API be stored?
A: In sealed containers in a dry place, protected from light and moisture, within the retest period stated by the supplier; reconstituted solutions are much less stable and should be used promptly.
Q: Why does sensitivity testing matter?
A: Resistance among enteric bacteria is common, so testing isolates from the farm or clinic shows whether ampicillin will work and helps avoid unnecessary use of a critically important antibiotic class.
Q: What tests accompany the raw material?
A: A certificate of analysis covering identity, assay, related substances, water content and, for sterile grades, sterility and bacterial endotoxins, in line with the applicable pharmacopoeial monograph.