be administered by intramuscular or subcutaneous injection, because those routes limit the systemic absorption of procaine. Most commonly, procaine penicillin reactions occur when the drug is administered by the correct intramuscular route, but the injection inadvertently results in the intravenous absorption of a small amount of procaine [28]. Less commonly, but more significantly, an inexperienced or inattentive individual may directly inject procaine penicillin intravenously. This is most likely to occur when there is an indwelling intravenous catheter, because of the perceived convenience. Inadvertent intravenous administration of mare’s milk has occurred when the intravenous catheter injection port was confused with the nasogastric feeding tube port, resulting in an acute anaphylactic reaction.
Prevention
In general, further administration of procaine penicillin is discontinued after a procaine reaction occurs. Inadvertent, direct intravenous administration of procaine penicillin can be avoided by emphasizing that opaque medications should not be administered intravenously (notable exceptions of propofol and lipid emulsions in selected circumstances) [26]. Important safeguards to prevent confusion of intravenous and enteral access ports when multiple tubes and catheters are placed in patients are to color‐code enteral administration devices, labeling injections ports and enteral ports, and use of connections that are incompatible between enteral and intravenous ports [27]. Protocols to trace the tubing to the site of entry in the patient before injecting any medication are recommended but may be overlooked by inexperienced or inattentive individuals [27].
Diagnosis
Severity of procaine reactions vary with amount absorbed and individual variation [29]. Clinical signs range from hyper‐reactivity to seizures to death [26, 28, 29]. Inadvertent intravenous administration of milk was associated with acute signs of collapse and respiratory distress, consistent with anaphylaxis. Peripheral pulses were weak and mucous membranes were congested.
Treatment
Personnel should be moved away from the affected horse and the horse should be moved to a safe, quiet place (stall) and sedated, if possible [26]. External stimulation should be minimized by reducing light and sound. If seizure activity occurs, benzodiazepines and phenobarbital may be administered, if safe to do so [26]. The inadvertent administration of milk was treated by immediate removal of the contaminated intravenous catheter and aggressive supportive therapy, including epinephrine, corticosteroids, intravenous fluids, antimicrobial therapy, and inotropic support.
Expected outcome
Horses typically recover from procaine reactions, but fatal reactions can occur. More commonly, self‐trauma may result from the hyper‐excitability and seizures. The foal with inadvertent intravenous administration of milk did recover with aggressive treatment and no long‐term consequences were noted.
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