Department of Pharmacy, The Chinese University of Hong Kong, Shatin, NT, Hong Kong
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Abstract |
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Introduction |
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In this study, Sanguisorba officinalis L. (Rosaceae; SO) was selected for evaluation of its potential to interact with ciprofloxacin. Dried roots and rhizomes of SO are traditionally used for the treatments of haemoptysis, epistaxis, dysentery, haemorrhage, functional bleeding and burns. Its antibacterial activities have been demonstrated against Pseudomonas aeruginosa, Salmonella typhi, Proteus vulgaris, Salmonella paratyphi,Staphylococcus aureusand Shigella dysenteriae.3 This crude drug is therefore commonly used as a natural antimicrobial for the treatment of various infections. The major chemical components of SO were found to be triterpenoids and tannins.3 In the present study, potential drug-drug interaction between SO and ciprofloxacin was evaluated in the rat, using a pharmacokinetic approach, and the metal content of SO was independently examined.
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Materials and methods |
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Ciprofloxacin hydrochloride was kindly provided by Bayer AG (Leverkusen, Germany). Enoxacin (Sigma, St Louis, MO, USA), acetonitrile (HPLC grade, Mallinckrodt-Baker, Inc., Phillipsburg, NJ, USA), triethylamine (Riedel-de Haen AG, Seelze, Germany) and other chemical reagents were acquired commercially.
An HPLC system (Hewlett Packard series 1050, Palo Alto, CA, USA) consisting of a UV detector, autosampler, guard column (Novapak C18; Waters, Milford, MA, USA), and reverse-phase octadecyl silane column (4.6 mm i.d. x 250 mm; 5 µm; Phenomenex, Torrance, CA, USA) was employed for the quantitation of ciprofloxacin in biofluids. An inductive plasma emission spectrometer (Shimadzu ICPQ-1012, Kyoto, Japan) was used to assess the content of Zn, Fe, Cu, Ca, Mn, Mg, Sr, Cr, Pb and Ni in the SO extract. The sample was digested with an acid mixture consisting of HNO3:HClO4 (9:1), and a plant-free acid control was prepared for comparison.
For the pharmacokinetic study, male Sprague-Dawley rats (220250 g) were usedfive in each treatment group. Following anaesthetization of each study animal by an ip injection of ketamine (75 mg/kg) and xylazine (10 mg/kg), a cannular was inserted surgically into the right jugular vein. Blood sampling was scheduled 24 h after the cannulation procedure. In the test group, rats were dosed orally with the SO extract (2 g/kg crude drug) immediately followed by a single oral dose of ciprofloxacin (20 mg/kg), and then were put individually into metabolic cages. Blood (0.6 mL) was withdrawn via the cannular just before ciprofloxacin dosing (t = 0) and 5, 30, 60, 90, 120, 150, 180, 240, 300 and 360 min after dosing. Urine samples were collected over 02, 24, 46 and 624 h intervals and the total volume within each interval was recorded. Rats receiving only a single oral dose of ciprofloxacin (20 mg/kg) were used as controls. An HPLC assay developed by Nix et al.4 was used with minor modifications for the quantitation of ciprofloxacin. Acetonitrile (200 µL) was added to the plasma sample (0.3 mL) for protein precipitation, then the internal standard, enoxacin, was added (final concentration 1.0 mg/L). The mixture was centrifuged at 10,000g for 5 min and 200 µL of the supernatant was collected and concentrated at 35°C. The residue was reconstituted by 70 µL of mobile phase and a 50 µL aliquot was injected onto the HPLC system. For the urine assay, the sample was diluted initially with deionized distilled water containing 10 µg/L internal standard. The dilution factor was 1:50 for samples collected over the 02, 24 and 46 h intervals and 1:10 for samples collected over the 624 h interval. The diluted samples were centrifuged at 10,000g for 5 min, and 50 µL of the supernatant was submitted to the HPLC assay.
The HPLC mobile phase consisted of 16% acetonitrile, 1% methanol and 83% aqueous buffer (pH 3.0) containing sodium dihydrogen phosphate monohydrate (0.1 M), glacial acetic acid (1% v/v) and triethylamine (0.5% v/v). The flow rate was set at 1.1 mL/min and detection was performed at 278 nm. The calibration curves were linear over the range 03 mg/L and 1.010 µg/L for the plasma and urine assays, respectively, with correlation coefficients >0.999 for both fluids. The detection limit of ciprofloxacin for both assays was 25 ng/mL. The adequacy of this analytical methodology was supported by the 9.3% coefficient of variation for the assay variability between days. The sample stability was verified to be >4 months without significant degradation when stored at -80°C.
The plasma concentration-time data for ciprofloxacin were assessed by non-compartmental
analysis. The relative bioavailability of ciprofloxacin was estimated as the ratio of the mean
AUC0 for the animals receiving both
ciprofloxacin and SO to that for those receiving only ciprofloxacin. Statistical differences in the
derived pharmacokinetic parameter estimates between the groups were assessed by
Students t-test with the level of significance (
) set at 0.05.
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Results |
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Concentrations (µg/g) of the ten metal cations contained in the aqueous SO extract were determined to be 10,846, 2629, 479.5, 70.2, 48.8, 34.1, 9.9, 7.2, 7.0 and 1.8 µg/g for Ca, Mg, Fe, Sr, Zn, Mn, Cr, Cu, Ni and Pb, respectively.
Pharmacokinetics of ciprofloxacin in the rats
Data obtained from the rats given oral ciprofloxacin alone revealed that ciprofloxacin (20
mg/kg) was rapidly absorbed, with the maximum plasma concentration (1.31 ± 0.49
mg/L) achieved at 0.42 ± 0.17 h. The distribution of the drug was extensive, i.e.
approximately 50-fold greater than total body water (Table). This large
distribution volume of
ciprofloxacin suggests a significant degree of tissue penetration and uptake. The oral clearance
of the antibiotic was estimated to be 10.8 ± 2.7 L/h per kg and a mean t
1/2,z of 1.96 ± 0.43 h was observed. Urinary
recovery represented approximately 20% of the oral ciprofloxacin dose administered. All
pertinent pharmacokinetic parameter estimates are listed in the Table.
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The mean plasma concentration-time profiles of ciprofloxacin for the control and SO-dosed
groups are shown in the Figure. Significant alterations were observed
from the profiles when the
antibiotic was administrated concurrently with SO. In particular, the Cmax
of ciprofloxacin was reduced by 94% (P < 0.005) and Tmax was 1.7-fold longer. Drug elimination measured by t1/2,z was also two-fold slower (3.78 ± 1.36 h versus 1.96 ± 0.43
h, P< 0.05). The relative bioavailability of ciprofloxacin was estimated to be 0.22,
since AUC0
was reduced by 78% (1.97
± 0.51 mg·h/L versus 0.43 ± 0.07 mg·h/L, P<
0.005).
Similarly, urinary recovery was reduced by 79%. A larger magnitude of alteration was
detected for drug distribution and oral clearance with 8.3-fold and 4.5-fold increases,
respectively, in the presence of SO.
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Discussion |
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A 4.5-fold increase in the oral clearance estimate for ciprofloxacin was observed in the rats dosed concomitantly with SO. Such an increase could be the result of an increase in systemic clearance or a reduction in bioavailability. The magnitude of such an increase in oral clearance mirrored that of the decrease in urinary drug recovery. A decrease in bioavailability is therefore a more feasible explanation for the perturbation in this estimate. Furthermore, SO did not alter the mechanisms of renal excretion of ciprofloxacin, since the estimate of renal clearance (Cl r) was not altered (Table). The evidence suggests a 4.5-fold to 5-fold reduction in bioavailability being the cause of the pharmacokinetic perturbations observed. However, the 8.3-fold increase in the apparent volume of distribution in the presence of SO suggests a net increase in drug distribution even after correcting for the decrease in bioavailability. Because the degree of protein binding for ciprofloxacin is reported to be only 1640%,5 modifications of protein binding by SO could not possibly cause such a substantial change in tissue distribution. Therefore, the factor affecting drug absorption may play a role in the alteration of tissue drug distribution.
As demonstrated in this study, the SO extract contained a large amount of calcium (10.8 mg/g), magnesium (2.6 mg/g), iron (0.5 mg/g), zinc (0.05 mg/g), manganese (0.03 mg/g) and copper (0.007 mg/g). These metal cations accounted for 99% of the total metal in the SO extract and the chelation of these metals with ciprofloxacin has been well documented.6 Since the total chelatable metal cations measured in the SO extract was 14 mg/g, the amount of cation and ciprofloxacin dosed was actually 28 mg/kg (2 g/kg SO) and 20 mg/kg, respectively, i.e. a ratio of 1.4:1. Since each metal cation can complex with as many as three fluoroquinolone molecules,7 the metal cations present in the SO extract should be sufficient to trigger a negative effect on ciprofloxacin absorption. Moreover, since other components of SO, such as triterpenoids and tannins, cannot meet the structural requirements to be a ligand for chelation, the metal cations are the only substances likely to induce such interaction. Since the increased molecular size of the metal-ciprofloxacin chelates may reduce the permeability and increase the lipophilicity of the drug, enhancement of tissue uptake and distribution volume may be expected.
In the past decade, the use of herbal medicines has dramatically increased throughout the world as an alternative approach to compensate for certain deficiencies in conventional pharmacotherapy. Findings in this study suggest that if ciprofloxacin is to be used concurrently with herbal drugs containing high mineral content, sufficient time between administration should be allowed to reduce the possibility of interaction between them.
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Notes |
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References |
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2 . Lehto, P., Kivisto, K. T. & Neuvonen, P. J. (1994). The effect of ferrous sulphate on the absorption of norfloxacin, ciprofloxacin and ofloxacin. British Journal of Clinical Pharmacology 37, 825.[ISI][Medline]
3 . Li, G. X. (1992). Pharmacology, Toxicity and Clinic of Traditional Chinese Medicine, pp. 2078. Tianjin Science and Technique Translation Publishing House, Tianjin.
4
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Nix, D. E., De-Vito, J. M. & Schentag, J. J. (1985). Liquid chromatographic determination of ciprofloxacin in serum and urine. Clinical Chemistry 31, 6846.
5 . Campoli-Richards, D. M., Monk, J. P., Price, A., Benfield, P., Todd, P. A. & Ward, A. (1988). Ciprofloxacin: a review of its antibacterial activity, pharmacokinetic properties and therapeutical use. Drugs 35, 373447.[ISI][Medline]
6 . Li, R. C., Nix, D. E. & Schentag, J. J. (1994). Interaction between ciprofloxacin and metal cations: its influence on physiochemical characteristics and antibacterial activity. Pharmaceutical Research, 11, 91720.[ISI][Medline]
7 . Kuhlmann, J., Schaefer, H. G. & Beermann, D. (1998). Clinical Pharmacology. In Quinolone Antibacterials, (Kuhlmann, J., Galhoff, A. & Zeiler, H. J., Eds), pp. 35961. Springer, Berlin.
Received 20 July 1998; returned 2 January 1999; revised 18 January 1999; accepted 16 February 1999