Treatment
Because of the potential for a rapid onset of clinical signs, decontamination is best attempted under veterinary supervision.
Emesis is contraindicated in symptomatic animals. Activated charcoal with a cathartic is recommended; however, repeated doses
of activated charcoal have not been proved to be beneficial. Avoid magnesium-based cathartics, as they may compound central
nervous system depression.4 Gastric lavage may be considered in cases of large ingestions, but take care to ensure that anesthesia does not compound
central nervous system depression. Using short-acting induction agents such as propofol or thiopental sodium followed by inhalant
anesthesia is preferred, and the airway must be protected.
Because of baclofen's low protein-binding and urinary excretion, its elimination may be enhanced through fluid diuresis.4 Fluid therapy will also help maintain blood pressure, protect the kidneys from myoglobinuria (secondary to tremors or seizures),
and may aid in reducing cardiac arrhythmias.4 Cardiac monitoring with electrocardiography is recommended, and refractory arrhythmias should be treated as needed. Hypothermia
is common in comatose or recumbent patients, so thermoregulation is important.
Ventilatory support is a prime concern, and endotracheal intubation and positive pressure mechanical ventilatory support may
be needed for an extended time in severe cases. Monitor for aspiration in comatose animals. The use of central nervous system
respiratory stimulants is of questionable value.4 Flumazenil and physostigmine have been used in people with baclofen toxicosis, with varying results.6 Experimental studies of baclofen toxicosis in rats have failed to consistently produce positive outcomes when flumazenil
was used, and the drug can cause serious adverse effects (seizures).6 Phaclofen is a baclofen reversal agent that has been used experimentally, but it is not commercially available.6
Diazepam (0.5 to 1 mg/kg slowly intravenously, to effect) is the drug of choice for baclofen-induced seizures.4 Propofol or isoflurane may be considered in cases that are refractory to diazepam. Take care when administering long-acting
barbiturates or other agents that produce profound or prolonged central nervous system depression in animals experiencing
seizures. Cyproheptadine hydrochloride (1.1 mg/kg orally or rectally, as needed) has been used with some success to reduce
the vocalization or disorientation seen in some animals (ASPCA APCC Database: Unpublished data, 1994-2004).
Hypoglycemia, hypokalemia, and elevated serum creatine phosphokinase, L-lactate dehydrogenase, and aspartate transaminase
activities have occasionally been reported in people with baclofen toxicosis, so obtain baseline serum chemistry profile,
acid-base balance, and electrolyte values.6 Continue to monitor these values and correct any abnormalities until signs have resolved. Baclofen concentrations can be
determined in urine and serum, although they are considered of minimal benefit in managing clinical cases of toxicosis.4
Prognosis
Resolution of clinical signs may take several days in severe cases, but if adequate ventilatory support is available, the
prognosis is generally good. Animals experiencing seizures have a more guarded prognosis. After a patient has recovered from
baclofen toxicosis, no residual central nervous system effects are expected. No specific gross or histopathologic lesions
would be expected in animals that die of skeletal muscle relaxant toxicosis.
"Toxicology Brief" was contributed by Tina Wismer, DVM, DABVT, DABT, ASPCA Animal Poison Control Center, 1717 S. Philo Road,
Suite 36, Urbana, IL 61802. The department editor is Petra A. Volmer, DVM, MS, DABVT, DABT, College of Veterinary Medicine,
University of Illinois, Urbana, IL 61802.
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