Texas Equine Veterinary Association

The answer as to when the neonatal body water approximates that of the mature equine has not been completely elucidated in the literature. Studies involving gentamicin have shown that by two weeks of age a return to adult dosing regimens is adequate for susceptible microbes (Burton 2013). This leads one to believe that total body water shifts to more like a mature equine after two weeks of age. Typically, I change aminoglycoside dosing back to adult doses at two weeks of age and continue elevated doses of ceftiofur until one month of age. Antibiotics fix everything, right? Human studies have shown the importance of appropriate antimicrobial interventions early in the course of disease and the profound impact early, effective treatment can have on survival (Corley et al, 2007). Empirical decision-making on antimicrobial selection prior to any culture results being returned makes the practice of early and accurate intervention difficult. When making empirical decisions regarding antimicrobial therapy one must consider likely etiologic agents, disease process, site of probable infection as well as limitations of personnel or owners in delivering the drug of choice effectively. Neonates with bacteremia can have single or multiple bacterial species infections with anywhere from 20 to 30% having mixed bacterial infections (Corley et al, 2007). Bacterial species likely to be cultured from foals with septicemia include: Escherichia coli, Actinobacillus spp, Streptococcus spp, Klebsiella spp, and Enterococcus spp. Corely et. al. found foals with gram-negative bacteremia or Actinobacillus spp, to have more profound changes in consciousness that he suggested may be due to the circulatory changes incited by the toxins produced by these bacteria (2007). When rapid, effective levels of antimicrobials are desired parenteral use is the easiest way to achieve this goal. It is important to keep in mind the effects of differing body water compositions have on depot medications, specifically ceftiofur crystalline-free acid (CCFA). Maximal plasma levels of CCFA were not achieved until anywhere from 10 to 18 hours after the initial administration of 13.2mg/kg subcutaneously (Pusterla 2017). If CCFA is used as the antimicrobial of choice a dose of intravenous ceftiofur should be used simultaneously on the first dose of CCFA to ensure rapid adequate plasma levels of drug. Common Parenteral Antimicrobials used in the Neonate Amikacin 20–30 mg/ kg IV or IM q 24hrs Gentamicin 11–15mg/kg IV or IM q 36hrs Ampicillin sodium 20mg/kg IV or IM q 6-8 hrs Ceftiofur 5–10mg/kg IV,IM or SQ q 6–12 hrs Ceftiofur Crystalline free acid 13.2mg/kg SQ q 48 hrs. Recent research has given practitioners more diversity when choosing oral antibiotics for use in the foal. Cefpodoxime is an oral third generation cephalosporin that is useful for treatment of E.coli and Streptococcal infections. It is imperative to use third and fourth generation cephalosporins judiciously due to salmonella resistance in humans. Minocycline shows great promise treating neonatal hypoxia in addition to susceptible infections. In rodent models Min et. al., found minocycline to suppress early peripheral inflammation and decrease hypoxia induced neonatal brain injury (2017). Minocycline was found to be more bioavailable in foals when compared to adult horses (Giguere 2017). When treating foals with suspected hypoxia I tend to use minocycline as my antimicrobial of choice due to the very interesting research found in human medicine regarding its anti-inflammatory effects. Oral Antimicrobial Dosing in the Neonate Cefpodoxime 10mg/kg PO q 6 hrs for E.coli, q 12 hrs for other infections Chloramphenicol 50mg/kg PO TID - QID Minocycline 4 mg/kg PO BID Metronidazole 15mg/kg PO QID Metronidazole 25mg/kg PO BID Although bacterial elimination is a core tenant of treatment it is essential to also target the severe clinical insults resulting from the systemic response to inflammation (SIRS) triggered by multiple disease processes. Pharmacologic interventions that ameliorate the inflammatory cascade initiated by SIRS include nonsteroidal anti- inflammatories, antioxidants and LPS binding agents. NSAID Advances Doses of COX 2 specific NSAIDs have been investigated in the neonate. Firocoxib was investigated in 36-hour old foals for seven days at a dose of 0.2mg/kg IV daily (Wilson 2017). However, this dosing should be used with caution until safety and clinical efficacy is more completely studied. Meloxicam is an interesting COX 2 specific NSAID that may have less analgesia when compared to flunixin. However, foals from two days of age to six weeks tolerated the drug very well when given for up to three weeks at a dose of 0.6mg/kg PO q 12 hours. (Radial et al, 2013). DMSO. At least it smells like we are doing something. DMSO has long been used in equine medicine. While the fantastical claims of its utility cannot be proven in the literature, I do utilize it frequently. I feel clinically I see the most utility in its use in treatment of neonatal foals. DMSO is a free radical scavenger. It traps the free radical hydroxide and its metabolite DMS traps free radical oxygen. The anti-inflammatory effects seen during use are likely secondary to the radical scavenging effects helping to maintain microcirculation (Brayton). In human medicine the "HAT" method of treating sepsis has been utilized and is being studied extensively due to reported

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