Antimicrobial agent parenteral preparations with

Age or body weight can affect the systemic availability of many antimicrobial agents. In the physically smaller animal (sheep and pig) the peak serum concentration of a drug is usually higher and is followed by a rapid decline compared with a lower peak and a slower decline of the antibiotic in seruon of the larger animal (cow and horse). The limited experimental data appear to indicate that the extent of systemic availability of IM-administored antibiotics can vary as widely between different sites as between IM and SC sites. A corollary to this observation is that the location of the extra-vascular injection site should be well-defined when determining the systemic availability of parenteral preparations (9). 

Mastitis may be observed at any stage of lactation and has also been seen in non-lactating, nul-liparous mares and in fillies. Mastitis occurs most commonly in the summer months and is often associated with Strep, equi subsp. zooepidemicus infection. The treatment of mastitis usually includes the parenteral administration of appropriate antimicrobial agents (see Ch. 2). The udder may also be treated using frequent milking, hydrotherapy and infusion of commercially available intramammary preparations for cattle. A NSAID may be administered to treat both the fever and the discomfort associated with mastitis. 

The variability associated with drug absorption from the gastrointestinal tract can be overcome by using a parenteral preparation (dosage form). It should preferably be administered either by intravenous infusion or slow intravenous injection to avoid circulatory overload. Intraosseous administration is a useful alternative to intravenous injection of some antimicrobial agents (e.g. sodium ampicillin or amoxycillin, cefotaxime, ceftriaxone, gentamicin or amikacin sulphate) in neonatal foals (Fig. 7.1) (Golenz et al, 1994) and puppies (Lavy et al, 1995). This particularly applies when the neonate is in a state of septic shock and/or dehydration. Total plasma protein concentration is an inaccurate index of hydration status unless monitored (repeatedly measured) and interpreted in conjunction with packed cell volume (PCV). 

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