Gabriela Francisco Bittar , Gleice Laine de Souza , Gabriela Haro de Melo , Dayane Aparecida Francisco da Silva , José Sérgio Costa Júnior , Rogério Giuffrida & Rosa Maria Barilli Nogueira
Acta Scientiae Veterinariae, 2018. 46: 1587.
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ABSTRACT
Background: Anticonvulsants are widely used in the treatment of small animals for the remission of isolated seizures and
recurrent seizures in epilepsy, including tonic-clonic seizures and in status epileticus. Phenobarbital is the drug of choice
for the management of epileptic seizures, it is considered very effective, safe, low cost and with few side effects. Several
routes of administration may be used, with the oral, intravenous and intramuscular routes being the most common, with
rectal and nasal routes being the least common.
Materials, Methods & Results: Twenty mongrel dogs were used in the present study (aged 1 to 6-year-old, males and
females, weighing 6.0 to 17.0 kg). The patients were previously evaluated via physical examination, temperature, respiratory
and heart rate, laboratory tests (erythrogram and leukogram), and serum biochemistry by analyzing the serum
levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (FA), and gammaglutamyltransferase
(GGT). Four experimental groups were established with five animals in each group: animals receiving
intramuscular injections of phenobarbital (VIM), animals receiving nasal administration of phenobarbital (VN), animals
receiving rectal administration of phenobarbital (VR), and animals receiving oral administration of phenobarbital (VO).
Phenobarbital was administered every 12 h for 15 days. To determine the serum level of phenobarbital, 5 mL of jugular
vein blood was collected in vacuum tubes for evaluation via hemogram. The serum level was determined after 15 days of
continuous administration of phenobarbital, as stable phenobarbital serum levels can only be achieved from 10 to 15 days
after the first administration. For the serum biochemistry evaluation, 10 mL of blood from the jugular vein was collected
using vacuum syringes for assessing ALT, AST, GGT, and FA levels. Statistical analyses were performed with contrasted
variation analysis using the Tukey method and paired t-test for comparison of time points. The level of significance was
determined to be 5%. There was a significant difference (P < 0.05) among drug administration routes, and among the levels
of AST and AF enzymes after the first administration of phenobarbital via the nasal and intramuscular routes. Based on the
results, it was concluded that hepatic alterations secondary to the use of phenobarbital for 15 days may occur with a low
incidence. The phenobarbital serum concentration in dogs varied when administered via nasal, rectal, and intramuscular
routes, but was stable when administered orally.
Discussion: The current results are consistent with those of previous studies, indicating that the chronic use of phenobarbital
causes an increase in the serum levels of ALT and FA enzymes. It was found that phenobarbital serum levels varied
greatly, particularly following nasal, rectal, and intramuscular administration. In the present study, serum phenobarbital
levels were within the normal range when administered via the intramuscular, nasal, rectal, and oral routes. This result is
inconsistent with that of previous studies where the serum levels were below the normal range following oral administration
of phenobarbital. The serum concentration, rather than clinical criteria, should be used as a guide for treatment modification,
as the distribution of this drug varies greatly among animals.
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