Small Ruminant Research 73 (2007) 242–245

Technical note

Pharmacokinetics of ciprofloxacin in sheep followingintravenous and subcutaneous administration

Anu Rahal c,∗, Amit Kumar b, A.H. Ahmad c, J.K. Malik a

a Division of Veterinary Pharmacology & Toxicology, IVRI, Izzatnagar, Bareilly 243122, Indiab UP State Government, India

c Department of Veterinary Pharmacology & Toxicology, College of Veterinary & Animal Sciences,GBPUA&T, Pantnagar 263145, UA, India

Received 14 October 2005; received in revised form 17 January 2007; accepted 17 January 2007Available online 23 March 2007

Abstract

Pharmacokinetics of ciprofloxacin was studied in sheep after intravenous and subcutaneous administration at a dose of 10 mg kg−1.Blood was collected using indwelling jugular catheter at predetermined time intervals. Plasma was extracted and analyzed forciprofloxacin by reverse phase high performance liquid chromatography. Following i.v. and s.c. administration, ciprofloxacin

followed two-compartment and one-compartment open model, respectively. Subcutaneous route was found to possess a very lowbioavailability of 40%. Ciprofloxacin was found to exert its pharmacological effect for more than 28 and 14 h after i.v. and s.c.administration, respectively.© 2007 Elsevier B.V. All rights reserved.

ous; Sh

Keywords: Pharmacokinetics; Ciprofloxacin; Intravenous; Subcutane

Ciprofloxacin is a fluoroquinolone which has beenshown to be highly active against the most strains ofbacteria including Haemophilus, Bordetella bronchisep-tica, Pasteuralla multocida and Mycoplasma (Greeneand Budsberg, 1993). In general, flouroquinolones pos-sess good oral bioavailability in all monogastric animals(upto 80%) but poor in ruminants (approximately 10%)which necessitates the use of parenteral routes of admin-istration (Jenkins, 1990). Pharmacokinetic studies ofciprofloxacin have already been investigated in calves

and pigs (Nouws et al., 1988), dogs (Abadia et al., 1994),ponies (Dowling et al., 1995) and broiler chicken (Attaand Sharif, 1997). Previously, ciprofloxacin has been

∗ Corresponding author. Tel.: +91 5944 233617.E-mail address: rahalanu72@yahoo.com (A. Rahal).

0921-4488/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.smallrumres.2007.01.015

eep

employed at two dose levels 7.5 mg kg−1 intramuscu-larly in sheep (Munoz et al., 1996) and subcutaneously ingoats (Ramesh, 2001) and 10 mg kg−1 in lactating cows(Jayakumar et al., 2000). The objective of this study wasto determine the plasma concentrations and pharmacoki-netics of ciprofloxacin following single dose intravenousand subcutaneous administration in sheep.

Six crossbred healthy female sheep (weighing25–30 kg) were quarantined for 2 weeks for use in thestudy. They were dewormed and maintained on concen-trate, green fodder and water was provided at libitum.The animals used for the pharmacokinetic study fol-lowing intravenous administration were reused for study

following subcutaneous administration after observing awashout period of 15 days.

Ciprofloxacin (pure hydrochloride salt, AurobindoPharmaceuticals, Chennai, India) was injected as

A. Rahal et al. / Small Ruminant Research 73 (2007) 242–245 243

Fig. 1. Mean plasma concentration (�g mL−1) vs. time plot ofci

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Table 1Plasma concentrations (�g mL−1) of ciprofloxacin following singledose (10 mg kg−1) i.v. and s.c. administration of ciprofloxacin in sheep(n = 6)

Time post-administration (h)

Ciprofloxacin,intravenous route

Ciprofloxacin,subcutaneous route

0.03 2.60 ± 0.32 0.15 ± 0.030.08 1.67 ± 0.11 0.21 ± 0.040.16 1.35 ± 0.07 0.26 ± 0.040.25 1.01 ± 0.09 0.32 ± 0.060.5 0.79 ± 0.07 0.34 ± 0.060.75 0.71 ± 0.05 0.22 ± 0.031 0.58 ± 0.05 0.17 ± 0.031.5 0.46 ± 0.04 0.12 ± 0.022 0.37 ± 0.03 0.09 ± 0.023 0.29 ± 0.02 0.07 ± 0.024 0.22 ± 0.03 0.05 ± 0.015 0.19 ± 0.03 0.05 ± 0.016 0.13 ± 0.03 0.03 ± 0.01

iprofloxacin following single dose (10 mg kg−1) i.v. and s.c. admin-stration of ciprofloxacin in sheep (n = 6).

0 mg kg−1 (3% solution in sterile water) in the jugu-ar vein and in the flank region for i.v. and s.c. study,espectively.

. Materials and methods

Blood samples (3 mL each) were collected by jugularndwelling catheter into heparinised glass tubes at 0, 0.016,.033, 0.083, 0.16, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 10, 12nd 24 h after drug administration. Plasma samples were storedt −20 ◦C until assayed. The concentration of ciprofloxacin inlasma was determined according to Nielsen and Gyrd-Hansen1997). The calibration curves prepared by spiking externaltandards in the pooled drug free sheep plasma were linear inhe range of 0.02–0.8 �g mL−1 for ciprofloxacin with coeffi-ient of variation (r2) of 0.86. Recovery for ciprofloxacin was4.9%. The limit of quantification was 0.02 �g mL−1. The intrand inter-day assay variation for ciprofloxacin was 5.8 and.4%.

The plasma concentration versus time data of each animalfter i.v. and s.c. administration of ciprofloxacin (10 mg kg−1)ere analyzed with the aid of a nonlinear iterative curve-fitting

omputer programme (Statis Version 3, M/s Clydesoft, Glas-ow, UK) based on the method described by Gibaldi and Parrier1982) and Baggot (1977).

. Results and discussion

A plasma concentration of 0.1 �g mL−1 was con-idered to be therapeutically adequate, as minimalnhibitory concentration (MIC) of ciprofloxacin againstensitive bacteria (Prescott and Yielding, 1990). The

7 0.09 ± 0.03 0.02 ± 0.018 0.05 ± 0.02 –

therapeutic concentrations were maintained for 6 hafter i.v. injection. Moreover, fluoroquinolones exhibitconcentration-dependent killing, i.e. as the concentra-tion of the drug increases from two to eight times theMIC, the rate and extent of bacterial killing increasesproportionately (Drusano et al., 1993).

The plasma concentration time profile (Fig. 1) wasadequately described by a two-compartment open model(based on the Akaike, r2 and positive and negativeresiduals) following intravenous administration, as hasalready been reported by Munoz et al. (1996). Thecorrelation coefficient (r2) of the fit of the curvewas 0.98. The derived pharmacokinetic parameters areshown in Table 1. The drug was detectable up to 10 hpostadministration. The initial plasma drug concen-tration was 2.60 �g mL−1, which rapidly declined to1.01 �g mL−1 at 0.25 h. This sharp fall in the plasmaconcentrations can be attributed to high distribution rateconstant (α, 10.83 h−1). The elimination rate constants(β) was 0.41 h−1. Munoz et al. (1996) reported α as0.364 h−1 and β as 0.01 h−1 after i.v. administrationof ciprofloxacin (7.5 mg kg−1). Jayakumar et al. (2000)reported α and β as 0.182 and 0.0053 min−1, respectivelyafter i.v. administration of ciprofloxacin (10 mg kg−1)in lactating cows. The distribution of ciprofloxacin wasrapid in sheep (t1/2α, 0.08 h) as seen in cow and dog(t1/2α, 3.2 min) (Abadia et al., 1994). The elimination

half-life was comparable to that observed in goat after i.v.administration of 7.5 mg kg−1 of ciprofloxacin (Ramesh,2001). Much slower elimination has been reported inlactating cows.

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244 A. Rahal et al. / Small Rum

The apparent volume of distribution (Vdarea) ofciprofloxacin was 10.25 L kg−1 following i.v. adminis-tration. The fluoroquinolones, in general, have a largevolume of distribution and penetrates all organs and cell(Bugyei et al., 1999). Ciprofloxacin has excellent tissuepenetration in sheep. The clearance of ciprofloxacin was4.01 L kg−1 h−1. Ciprofloxacin is reported to undergominimal metabolism into any of the active metabolites,the clearance is mainly attributed to urinary excretion(Campoli-Richards et al., 1988). Wide variations havebeen reported in clearance of ciprofloxacin in ruminantseg. for cow calves, it is 0.014 L kg−1 h−1 (Kumar et al.,1997) while for buffalo calves, it is 0.122 L kg−1 h−1

(Raina et al., 2000).Following subcutaneous administration, the plasma

concentration-time curve (r2 = 0.86) followed one-compartment open model with first order absorption. Thederived pharmacokinetic parameters are represented inTable 2. The absorption and elimination rate constantswere calculated as 1.55 and 0.79 h−1, respectively. Theabsorption of ciprofloxacin from the SC site was rapidand in accordance with earlier studies (Munoz et al.,1996). On analyzing the SC parameters, it can be said thatthe drug was made available to the animal body at a rate atpar with the distribution rate constant but the eliminationwas faster compared to the i.v. route. The plasma concen-

trations were significantly (p < 0.05) lower compared toi.v. administration. The therapeutic concentration couldbe maintained only for 1.5 h post-administration. Thebioavailability was 40.5%. Low bioavailability values

Table 2Pharmacokinetic parameters of ciprofloxacin following single dose (10 mg kg

Kinetic parameters Unit Ciprofloxacin

A �g mL−1 2.41 ± 0.59B �g mL−1 0.93 ± 0.08α/Ka h−1 10.83 ± 2.01β h−1 0.41 ± 0.06t1/2α/t1/2Ka h 0.08 ± 0.01t1/2β h 1.87 ± 0.21AUC �g h mL−1 2.67 ± 0.28AUMC �g h2 mL−1 7.03 ± 0.30MRT h 2.48 ± 0.30Vdarea L kg−1 10.25 ± 0.90Vc L kg−1 3.44 ± 0.40Vp L kg−1 5.98 ± 0.64Vdss L kg−1 9.42 ± 0.85ClB L kg−1 h 4.01 ± 0.42F % –

A, zero time intercept of distribution slope in the two-compartment model; B, zα, distribution rate constant; β, elimination rate constant; Ka, absorption rate cabsorption half-life; ClB, clearance of drug; Vdarea, apparent volume of districompartment; Vdss, volume of distribution at steady state; AUC, total area umoment concentration time-curve; MRT, mean residence time; F, bioavailabi

search 73 (2007) 242–245

have been reported in intramuscular studies in sheep(approximately 48%, Munoz et al., 1996) and in goats(approximately 33%, Ramesh, 2001). The poor avail-ability may be due to poor absorption from the site ofadministration or due to presence of a deep seated tis-sue compartment from which the drug is slowly releasedover a long period of time.

Fluoroquinolones antimicrobials exhibit concentra-tion dependent killing, i.e. rate and extent of bacterialkilling depends upon the drug concentration. Studiesdealing with pharmacodynamics and pharmacokineticproperties of fluoroquinolones have indicated that thecritical breakpoints determining the therapeutic efficacyof these drugs are Cmax/MIC ≥10 and AUIC (AUC/MIC)≥100 (Walker, 2000; Nightingale et al., 2000). In thepresent study, the AUC0–24 h (2.45 and 0.63 �g mL−1 fori.v. and s.c. routes, respectively) is sufficiently higherthan the MIC required to suppress the growth of thesusceptible organism.

Although MIC values of enrofloxacin reported earlierfor veterinary pathogens Escherichia coli, Haemophilussomnus, Moraexella bovis and Salmonella speciesranged from 0.01 to 0.06 �g mL−1, P. multocida andYersinia species (usual MICs 0.008–0.01 �g mL−1) arehighly susceptible to the drug (Prescott and Yielding,1990). The usual therapeutic concentration (MIC)

of enrofloxacin against most veterinary pathogens isreported to be ≤0.1 �g mL−1 (Kaartinen et al., 1997).Ciprofloxacin is a more potent antimicrobial than the par-ent drug (Prescott and Yielding, 1990). Using the value of

−1) i.v. and s.c. administration of ciprofloxacin in sheep (n = 6)

, intravenous route Ciprofloxacin, subcutaneous route

–0.51 ± 0.14

12.55 ± 3.230.79 ± 0.200.08 ± 0.021.38 ± 0.390.63 ± 0.141.61 ± 0.642.12 ± 0.55

–––––

40.52 ± 9.41

ero time intercept of elimination slope in the two-compartment model;onstant; t1/2α, distribution half-life; t1/2β, elimination half-life; t1/2Ka ,bution; Vc, volume of central compartment; Vp, volume of peripheralnder the concentration time-curve; AUMC, total area under the firstlity.

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Ramesh, S., 2001. Pharmacokinetics and bioavailability studies of

A. Rahal et al. / Small Rum

.1 �g mL−1, a single i.v. dose of ciprofloxacin yieldedCmax/MIC of 26 and AUIC 24.5 while for s.c. route the

espective values are 5.1 and 6.3.Since fluoroquinolones kill bacteria in a concentra-

ion dependent manner and exert a post-antibiotic effectasting for 4–8 h (Brown, 1996), it is not necessary to

aintain their plasma concentration above MIC duringhe whole dosing interval. Moreover, if the duration ofharmacological effect, td (Levy and Nelson, 1965) isalculated as

d = 2.3log(Ao/Amin)

β

here Ao is the dose in mg kg−1 and Amin is the mini-um effective concentration, it comes to be more than

4 h for s.c. route and 28 h for i.v. route. Thus, on theasis of pharmacokinetic and pharmacodynamic vari-bles obtained in the present study it is suggested thatiprofloxacin may be used at a dosage of 10 mg kg−1

very 12 h subcutaneously and every 24 h intravenouslyn sheep. Further studies are required to establish thefficacy and safety of this dosage in a clinical setting.

As far as route of administration is concerned, bothmax and AUC show a significant differences for i.v.nd s.c. routes (p < 0.001). Thus, we can say that the i.v.oute is much superior to s.c. route for administration ofiprofloxacin.

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