By Rania Gollakner, BS, DVM, MPH

What is cloxacillin?

Cloxacillin (brand names: Cloxapen®, Orbenin®, Tegopen®) is a penicillin antibiotic used to treat certain bacterial infections, usually staphylococcal infections.

Its use in cats and dogs to treat certain bacterial infections is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How is cloxacillin given?

Cloxacillin is given by mouth in the form of a capsule or liquid solution. Shake the liquid form before measuring unless otherwise directed. Measure the liquid form carefully. If possible, give this medication on an empty stomach. If vomiting occurs after dosing on an empty stomach, give future doses with a meal or a treat.

This medication will take effect quickly, in about 1 to 2 hours, but it may take a few days for effects to be recognized.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effect is gastrointestinal upset such as vomiting and diarrhea. Serious side effects include signs of an allergic reaction, such as severe vomiting, severe diarrhea, difficulty breathing, swelling of the face, hives, or sudden skin rash.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Cloxacillin should not be used in pets that are allergic to it, other penicillins, or cephalosporins. It should be used cautiously in pets that are pregnant or lactating as the effects are unknown. It should be used cautiously in pets that have liver, kidney, or blood dysfunction.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with cloxacillin: antacids, aminoglycosides, aspirin, chloramphenicol, erythromycin, indomethacin, neomycin, phenylbutazone, or tetracycline.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working.

How do I store cloxacillin?

Store capsules at room temperature between 59°F and 77°F (15°C and 25°C) and protect from light and moisture. For the liquid form, refrigerate for up to 14 days between 35°F and 46°F (2°C and 8°C) unless otherwise directed on the label.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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