Ampicillin
Ampicillin is used for susceptible bacterial infections. Sodium injection is a soluble preparation; trihydrate injection is a suspension and must never be given intravenously.
Group
Aminopenicillin antibacterial
Mechanism of Action
Inhibition of bacterial penicillin-binding proteins blocks cell-wall peptidoglycan synthesis. Beta-lactamase production commonly confers resistance.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible infection — soluble injection | 10 mg/kg | IV, IM, SC | Every 8 h | Ampicillin sodium solution, dose expressed as ampicillin activity. Do not substitute trihydrate suspension for an IV dose. |
| Susceptible infection — oral | 20 mg/kg | PO | Every 8 h | Oral absorption is lower than amoxicillin; use an appropriate oral preparation. |
| Susceptible infection — trihydrate suspension | 6.6 mg/kg | IM, SC | Every 12 h | Ampicillin trihydrate suspension only. Never administer intravenously. |
Cat
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible infection — soluble injection | 10 mg/kg | IV, IM, SC | Every 8 h | Ampicillin sodium solution, dose expressed as ampicillin activity. Do not substitute trihydrate suspension for an IV dose. |
| Susceptible infection — oral | 20 mg/kg | PO | Every 8 h | Oral absorption is lower than amoxicillin; use an appropriate oral preparation. |
| Susceptible infection — trihydrate suspension | 6.6 mg/kg | IM, SC | Every 12 h | Ampicillin trihydrate suspension only. Never administer intravenously. |
Horse
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible infection — soluble injection | 15–40 mg/kg | IM, IV | Every 6 h | Ampicillin sodium; select the dose using infection severity and susceptibility. More frequent dosing than the older twice-daily regimen maintains beta-lactam exposure. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible infection — trihydrate suspension | 4.4–11 mg/kg | IM | Every 24 h | Up to 7 days; Cattle including calves; product-specific restrictions apply. Polyflex label: maximum seven treatment days; milk 48 hours and meat six days after the final dose. |
Pig
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible infection — trihydrate suspension | 6.6 mg/kg | IM | Every 12–24 h | Trihydrate suspension; withdrawal must be determined for the actual product and regimen. |
Indications
- Susceptible urinary, respiratory, skin and soft-tissue infections.
- Parenteral treatment when oral beta-lactam administration is unsuitable.
Contraindications
- Penicillin hypersensitivity.
- Never inject ampicillin trihydrate suspension intravenously.
- Oral administration is unsuitable in adult horses because of low absorption and dysbiosis risk.
- Oral aminopenicillins can precipitate severe enterotoxemia in rabbits, guinea pigs, chinchillas and hamsters.
- Do not rely on oral absorption in shock or septicemia.
Interactions
- Do not mix with other drugs in the same vial or syringe, particularly aminoglycosides.
Adverse effects
- Allergic reactions and anaphylaxis.
- Diarrhea and dysbiosis.
- CNS excitation or seizures after overly rapid IV injection or excessive exposure.
Toxicity
Consider renal clearance and the sodium load of sodium formulations. Monitor for hypersensitivity, neurologic effects and GI intolerance; administer IV solutions slowly. Assess possible cross-reactivity in animals with serious allergy to other beta-lactams.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Ampicillin sodium 1 g vial, IM reconstitution Strength expressed as ampicillin activity. Add 3.5 mL water to the 1-g vial to obtain 4 mL withdrawable solution. IV reconstitution uses a different dilution. | Injection | 250 mg / mL | IM |
| Polyflex 250 mg/mL reconstituted suspension Ampicillin activity supplied as trihydrate. Suspension: shake well; never administer intravenously. Follow the species-specific reconstitution and route instructions. | Injection | 250 mg / mL | IM, SC |
