Food Animal Drugs
Due to the restrictions on antimicrobial use, choosing antimicrobials for food and fiber animals is somewhat simpler than in dogs and cats in many regards.
Beginning in 2023, no more over the counter antimicrobials are allowed. This will affect injectable oxytetracycline, injectable tylosin, procaine penicillin G and mastitis tubes.
Currently, I most often use Naxcel (ceftiofur sodium) preoperatively for dairy cattle for Csections and for most abdominal surgeries. Naxcel does not affect the milk supply and the cow’s milk can be sold. I use penicillin or ampicillin for rumenotomies due to the flora involved and ampicillin for most beef and small ruminant surgeries. Excede (ceftiofur acid) is also useful in beef animals. The longer acting formulations (procaine penicillin, ceftiofur acid) are handy for therapeutic use because they last longer in the cow; however, they also last longer in the milk, meaning the milk withholding (how long before it can be safely sold) is prolonged, as well. These are fine for beef cattle whose milk isn’t sold. Fluroquinolones should not be used except as labeled.
Aminoglycosides such as gentamicin are not prohibited but have a tremendously long meat withdrawal; the drugs can be found in the kidneys for over 18 months. Just don’t use them in anything that could be eaten (cattle, sheep, goats, pigs, camelids).
While I tend to assume prophylactic antibiotics are important for my abdominal surgeries, recent research suggests that antibiotics are needed pre/postop for Csections but that antibiotics should not be used for elective abdominal surgery.
- are you likely dealing with gram positive, gram negative or both types of organisms?
- is there a drug labeled for the species and the disease?
- what drugs are legal in the species?
- where is the infection? can the antibiotics reach it? what drugs will be effective in that environment?
- how sick is the animal? can you use a bacteriostatic drug or do you need a bacteriocidal drug?
- does the animal have any other conditions that would increase the risk of certain drugs? e.g. renal disease or liver failure
- what drugs should you avoid using in order to save them for human use?
- is the animal milking or likely to go to market soon? what is your withholding window?
- how valuable is the animal and how expensive is the drug?
- what routes of administration are available to you and how frequently can the drug be administered?
- what are the resistance patterns in your area? can you assume certain drugs will be more effective than others?
Selecting antimicrobials (Dr. Alex Bianco)
|Drug||IV||IM/SQ||PO||Anaerobes||Good penetration||Use in a dairy cow|
|Cephalosporins||EQ/SRC||x||x (on label only)|
Swine Antibiotherapy Handbook: (also has good info for other species)
Gamithromycin SQ (macrolide)is being studied for use in camelids.
Small ruminants (from Dr. Pippa Gibbons)
|Antimicrobial group||Drug examples||Spectrum of activity||Notes|
|Beta lactams- penicillins||PPG, ampicillin||Anaerobic, Gm +, some Gm –||PPG is not effective at label doses|
|Beta lactams, cephalosporins||Naxcel, Excenel, Excede||Gm + and Gm –|
|Tetracyclines||LA200||broad spectrum, rickettsials||Oxytetracycline used at cattle dose|
|Florfenicol||Nuflor, Resflor||broad spectrum||Florfenicol used at cattle dose|
|Macrolides||Draxxin, Micotil, Zactran, Tylan||Gm +, respiratory Gm –||Gamithromycin, tylosin and tulathromycin used at cattle dose
Micotil kills goats, pigs, horses, humans and camelids; use 10mg/kg SQ for sheep
Procaine Pencillin G is labeled for administration at a very low dose. This label dose is NOT effective and should be avoided. Generally doses of 22,000 – 66,000 IU/kg are recommended rather than the label dose of 6600 IU/kg.
This article does a great job of fairly painlessly explaining why and how pharmacodynamics and pharmacokinetics play a role.
Update on withdrawal intervals following extralabel use of procaine penicillin G in cattle and swine. JAVMA | JAN 1, 2022 | VOL 260 | NO. 1
Pharmacology chapter, Dairy Production Medicine ebook
Randomized prospective trials to study effects of reduced antibiotic usage in abdominal surgery in cows. J. Dairy Sci. 101:8217–8223. With careful attention, maybe we can pick which cases get preop antibiotics.
OSU VMC Antimicrobial use guidelines – great place to start when choosing a drug
Wikipedia– often has very good pharmacological information
Pharmacology course notes and the online drug monographs