Vetdrugs 2.0Cloxacillin is a penicillinase-resistant isoxazolyl penicillin directed mainly against susceptible gram-positive bacteria, especially penicillinase-producing staphylococci. Its principal veterinary application is intramammary treatment and control of bovine mastitis. Sodium and benzathine formulations have different persistence characteristics and are used in products intended for different stages of the lactation cycle.
Group
Penicillinase-resistant penicillin
Mechanism of Action
Cloxacillin binds bacterial penicillin-binding proteins and inhibits the transpeptidase reactions responsible for peptidoglycan cross-linking. This disrupts cell-wall integrity and produces bactericidal activity against growing susceptible organisms. Its side chain provides resistance to many staphylococcal penicillinases, supporting activity against penicillinase-producing isolates that retain susceptible penicillin-binding proteins. Antibacterial effect is time dependent.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible staphylococcal infection | 20–40 mg/kg | PO | Every 8 h | |
| Susceptible staphylococcal infection | 10–15 mg/kg | PO | Every 6 h | Up to 84 days; Historical course 14–84 days for site-specific pyoderma, diskospondylitis or joint infection; duration must follow diagnosis and response. |
| Systemic infection | 10–40 mg/kg | PO | Every 6–8 h | Up to 14 days; Historical course 7–14 days; assess whether oral absorption is adequate for severity. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible staphylococcal infection | 20–40 mg/kg | PO | Every 8 h | |
| Susceptible staphylococcal infection | 10–15 mg/kg | PO | Every 6 h | Up to 84 days; Historical course 14–84 days for site-specific pyoderma, diskospondylitis or joint infection; duration must follow diagnosis and response. |
| Systemic infection | 10–40 mg/kg | PO | Every 6–8 h | Up to 14 days; Historical course 7–14 days; assess whether oral absorption is adequate for severity. |
| Historical injectable treatment | Reference only | IM | 20–40 mg/kg IM every 6–8 hours is described for cloxacillin sodium; no compatible injectable preparation is established here. |
Indications
- Intramammary treatment of mastitis caused by susceptible staphylococci and streptococci in lactating dairy cattle, using a lactation product.
- Treatment of existing susceptible intramammary infections at drying off and prevention of new infections during the dry period, where included in the dry-cow product indication.
- Treatment of selected susceptible staphylococcal skin or soft-tissue infections in companion animals where an appropriate systemic formulation is used.
Contraindications
- Penicillin hypersensitivity.
Interactions
- Do not mix with other drugs without compatibility data.
Adverse effects
- Allergy, including anaphylaxis
- Diarrhea after oral use
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Cloxacillin 250 mg capsule | Capsule | 250 mg / capsule | PO |
| Cloxacillin 500 mg capsule | Capsule | 500 mg / capsule | PO |
| Cloxacillin 25 mg/mL oral liquid | Oral Liquid | 25 mg / mL | PO |
Monitoring and Administration
Use susceptibility testing; oxacillin susceptibility can guide interpretation. Methicillin-resistant staphylococci are resistant.
Oral absorption is poor; administer on an empty stomach where feasible.
The described intramammary treatment is 200 mg per affected quarter every 12 hours for three treatments, using a specific 20 mg/mL product. Intramammary administration is outside the calculator route set. Dry-cow and lactating-cow products must not be interchanged.
Lactating-cow intramammary products are repeated every 12 hours for three doses after milking and teat disinfection. Dry-cow benzathine products are infused after the final milking; their duration and withdrawal instructions are not interchangeable with sodium lactating-cow products.