📘 ❞ Enrofloxacin serum bioactivity in bottlenose dolphins, Tursiops truncatus, following oral administration of 5 mg per kg in whole fish ❝ كتاب

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INTRODUCTION
Enrofloxacin is a fluoroquinolone antimicrobial agent structu-
rally related to nalidixic acid and norfloxacin and is licensed for
veterinary use only. The fluoroquinolones have a bactericidal
spectrum encompassing gram-negative, gram-positive aerobic
bacteria and mycoplasmas (Reeves
et al
., 1984; Scheer, 1987a).
Enrofloxacin is an important antimicrobial agent that is proving
to be very useful in treatment of infectious diseases in many
domestic animal species (Scheer, 1987a; Jenkins & Friedlander,
1988; Prescott & Yielding, 1990; Van Landuyt
et al
., 1990).
The primary mechanism of action of the fluoroquinolones
appears to be interference wit ht he bacterial enzyme DNA gyrase
(Vancutsem
et al
., 1990; Hooper & Wolfson, 1991). This unique
mechanism of action differs from that of
b
±lactams, tetracy-
clines, aminoglycosides, macrolides, chloramphenicol and folic
acid antagonists and could explain the lack of cross-resistance
between these other antimicrobial agents and the fluoroquino-
lones (Scheer, 1987a).
Enrofloxacin has close to 100% oral bioavailability and attains
excellent body tissue and fluid compartment concentrations in
canines and felines (Scheer, 1987b). These characteristics make
this antimicrobial, when given orally, particularly promising in
use with marine mammals. Although there have been infre-
quent reports of neurological, haematological, gastrointestinal
and cartilaginous toxicities associated wit henrofloxacin, t he
drug has been very well tolerated in a variety of domestic animal
species (Altreuther, 1987; Jenkins & Friedlander, 1988).
In this study we investigated the serum antimicrobial activity
concentrations (SAAC) attained when enrofloxacin tablets were
given to bottlenose dolphins in their morning ration of fish. This
protocol would determine if this method of dosing enrofloxacin is
feasible and would assist veterinarians involved in marine mammal
practice to expand their antimicrobial treatment armamentarium.
MATERIALS AND METHODS
Study design
Following approval from the Animal Care Committee at our
facility, eight healthy adult bottlenose dolphins,
Tursiops
truncatus
(six male, two female) were selected for this study.
They ranged in weight from 154 to 331 kg and were on no other
medical treatments. Eac hanimal received a single oral dose of
enrofloxacin at a dosage of 5 mg/kg body weight. The dose was
rounded to the nearest half tablet or 34 mg increment (68 mg
tablets) and placed intact (not crushed) into a whole fish and
administered wit ht he morning fis hration. Experimental drug
received from Bayer Corporation for our study consisted of the
original `purple tablet' oral preparation of enrofloxacin, which
dissolves rapidly in water. The new chewable tablets now
available do not disintegrate as easily as the former purple tablets
and therefore may cause a greater lag between administration
and absorption. This method of drug delivery with these animals
is standard practice which is convenient and eliminates drug loss
#
1999 Blackwell Science Ltd
170
J. vet. Pharmacol. Therap.
22,
170±173, 1999.
PHARMACOKINETICS
Enrofloxacin serum bioactivity in bottlenose dolphins,
Tursiops truncatus
,
following oral administration of 5 mg/kg in whole fish
Linnehan, R. M., Ulrich, R. W., Ridgway, S. Enrofloxacin serum bioactivity in
bottlenose dolphins,
Tursiops truncatus
, following oral administration of 5 mg/kg
in whole fish.
J. vet. Pharmacol. Therap.
22,
170±173.
Eight adult bottlenose dolphins
Tursiops truncatus
(six male, two female) were
employed in a single-dose study of orally administered enrofloxacin dosed at 5
mg/kg body weight. Blood samples were obtained from all animals at 0, 2, 4, 8,
12 and 24 h following administration of the dose in the animals morning ration
of fish. Serum antimicrobial activity concentrations (SAAC) were determined
using bioassay.
The mean elimination half-life (
t
‰
) of enrofloxacin and its major metabolites
was 6.4
+
2.0 h with a range of 3±9.4 h. The time of maximal serum
concentration (
t
max
) occurred at approximately 4 hwit ha range of 2±8 h
following a single oral dose of 5 mg/kg. This variation in
t
max
most likely
resulted from individual differences in absorption because of variations in the
storage and digestion of the fish ration containing the drug dose within the
compartmentalized cetacean stomach.
(Paper received 18 December 1997; accepted for publication 5 Marc h1999)
Robert W. Ulrich, University of Southern California, School of Pharmacy, 1985
Zonal Ave., Los Angeles, CA 90033, USA