Biology Reference
In-Depth Information
Giorgi et al.
2009a
,
b
,
c
), goats (de Sousa et al.
2008
), and horses (Giorgi et al.
2007
)
than in humans (Grond and Sablotzki
2004
). The clinical effectiveness of this drug
has been questioned in the animal species in which the drug is mainly metabolized
into inactive substances. The animal species seem to be related to both the bioavail-
ability of tramadol and the metabolic patterns leading to differing amounts of M1
(KuKanich and Papich
2004
; de Sousa et al.
2008
; Giorgi et al.
2007
,
2009a
,
b
,
c
). In
dromedary camels (Elghazali et al.
2008
), a single study reported plasma
concentrations of tramadol, but no data were reported for its active metabolite M1
in plasma. Therefore, the aim of the present study was to test the intravenous (IV)
and intramuscular (IM) administration of tramadol in alpacas (domesticated species
of South American camelid) to assess its pharmacokinetic profile.
17.2 Materials and Methods
Eight healthy male alpacas (
Vicugna pacos
), aged 5-9 years and weighing
41-58 kg, were used. The animals were previously determined to be clinically
healthy based on a physical examination and full hematological analyses. The study
protocol, conforming to EU regulations (86/609/EEC), was approved by the ethics
committee of the University of Pisa, Italy (authorization no. 9403).
Test preparations were made according to an open balanced cross-over design:
animals were assigned to two treatment groups, using a single dose and two periods.
Each animal received a single dose of 2.5 mg/kg tramadol (Altadol; Formevet,
Milan, Italy) via IV or IM. A catheter was placed into the left jugular vein to
facilitate slow IV drug administration (2 min). The IM injection was placed in the
upper outer quadrant of the buttocks. After the wash-out period of 2 weeks, the
groups were inverted. By another catheter placed into the right jugular vein, blood
samples (5 mL) were collected at 0, 5, 15, 30, and 45 min, and 1, 1.5, 2, 4, 6, 8, 10,
and 24 h after administration of tramadol into collection tubes containing lithium
heparin. The blood samples were centrifuged at 3,000 rpm within 30 min after
collection, and the harvested plasma was stored at
20
C until use within 30 days
of collection (de Sousa et al.
2008
).
The concentrations of tramadol, M1, M2, and M5, in plasma were evaluated
using HPLC according to the method described by Giorgi et al. (
2007
). The HPLC
system was an LC Workstation Prostar (Varian Corporation, Walnut Creek, CA)
consisting of an LC Prostar 230 pump, combined with an RF-10A spectrofluoromet-
ric detector. Excitation and emission wavelengths were 275 and 300 nm, respec-
tively. Chromatographic separation was performed twice on a Luna C18 ODS2
analytical column (150 mm
2.1 mm i.d., 3-
m
m, Phenomenex, Bologna, Italy)
0.5
C with a flow rate of 0.7 mL/min. The mobile phase
consisted of metanolo/formic acid (99:1 v/v) and buffer (5 mM ammonium acetate,
adjusted to pH 4.5 with acetic acid; 40:60 v/v). The pharmacokinetic calculations
were performed using the WinNonLin v. 5.2.1 program (Pharsight Corp.,
Cary, NC).
maintained at 23
