Comparative and Veterinary Pharmacology

main cause of observed inter-species differences and the veterinary literature is
regularly enriched with new examples. Species differences in drug action and
effect, i.e. of PD, reflect differences in target functions (anatomy, physiology,
pathology) and/or target receptors including those of parasites and bacteria.

1.4

1.6

06

0.8

1

1.2

a

0

0.2

0.4

Plasma concentrations

mg/mL

Time (h)

AUC [0, 24 h] Distribution

Frequency (%)

b

12

14

16

2

4

6

8

10

0

2

AUC (mg.h.mL–1)

3 4 5 6 7 8 9 1011121314151617181920

–5 0 5 10 15 20 25 30

Fig. 2(a): Plasma concentration of doxycycline in 215 pigs under field conditions. Doxycycline
was administered by the oral route as a metaphylactic treatment: the first dose (5 mg/kg, nominal
dose) was given at 18–19 h (evening dose) and the second dose (5 mg/kg, nominal dose) was
administered at 8–9 h (morning dose) on the following day. Blood samples were obtained
approximately 30 min before, and approximately 1.8, 4.5, 6.7, and 11.5 h after the second
administration. For 25% of the pigs, a final blood sample was obtained 24 h after the second
administration. Visual inspection of the raw data reveals the large variability of plasma doxycycline
concentrations. (b): Histogram of the area under the concentration-time curve (AUC from 0 to
24 h) for the 215 pigs. The range of exposure is approximately 4–5 (from Lees et al. 2006 )

Species Differences in Pharmacokinetics and Pharmacodynamics 27