Concentrations Of Amoxycillin Research Articles

A Simple Spectrophotometric Determination of Amoxicillin in Drug Samples

In this study, a fast and simple spectrophotometric method was developed for the determination of amoxicillin in drugs without any extraction steps. The developed method is based on the formation of a colored ion pair complex between bromocresol green and amoxycillin in dimethyl sulfoxide-acetonitrile (50 % v/v) medium. The absorbance of the bluish green complex is measured at a wavelength of 630 nm. The factors that affect the ion pair complex formation, such as time, reagent concentration, etc., have been optimized. Under the optimum conditions, the developed method had an average recovery of 98.16% with a relative standard deviation of 3.62 % and showed a very good linear behavior obeying Lambert-Beer's law in the range 1-18 µg mL-1 of amoxycillin concentration. The developed method has been successfully applied to both tablet and powder forms of pharmaceutical preparations. The standard addition method and statistical parameters were applied to test the accuracy of the proposed method, and the obtained results from the two methods showed good agreement with each other.

Influence of ibuprofen-arginine on the concentration of amoxicillin in the plasma and tissues of rats with induced periapical lesion

ABSTRACT Objective The aim of this study was to evaluate the influence of ibuprofen-arginine on the concentration of amoxycillin in the plasma and periapical tissues of rats with induced apical periodontitis. Methods Twenty-eight Wistar rats were divided into the following four groups: PL: placebo (saline); AM: amoxycillin (100 mg/kg); IB: ibuprofen-arginine (100 mg/kg); and AM+IB: amoxycillin (100 mg/kg) + ibuprofen-arginine (100 mg/kg). The animals were submitted to pulp exposure in the first lower left molar, which remained open for fifteen days; this was then closed with composite resin and remained for a further seven days. The treatments were performed using a single dose of the medication (gavage) one hour before taking the samples. Two mL of blood was collected from the aorta to obtain the blood plasma and the periapical tissue samples, which were homogenized to obtain the supernatant. The samples (plasma and the supernatant periapical tissue) were used to obtain the antibiogram for the analysis of the levels of amoxycillin in the plasma and periapical tissues. Results The amoxycillin concentration was higher in the AM group compared to the other groups (p < 0.05, ANOVA with Tukey’s test). Ibuprofen-arginine interfered with plasma concentration of amoxycillin; however, the AM+IB group had a higher concentration of amoxycillin than the PL and IB groups (p < 0.05, ANOVA with Tukey’s test). The analysis of the supernatant from the periapical tissues showed no significant difference between the groups (p > 0.05, Kruskal-Wallis test). Conclusion Ibuprofenarginine can interfere with the plasma concentration of amoxycillin but this study failed to show the effect of ibuprofen-arginine on the concentration of amoxycillin in the periapical tissues .

Stability of Amoxycillin, Clindamycin and Meropenem in Peritoneal Dialysis Solution

ABSTRACTAimTo determine the stability of amoxycillin, clindamycin and meropenem in peritoneal dialysis solution containing glucose 2.5% at 37 °C over 6 hours.MethodA stability‐indicating high‐performance liquid chromatography assay was used to determine the concentration of amoxycillin, clindamycin and meropenem in peritoneal dialysis solution (Dianeal PD‐4). Antibiotic solutions (amoxycillin 1 g, clindamycin 300 mg, meropenem 1 g) were prepared in 2 L peritoneal dialysis bags and stored at 37 °C. These were analysed at 0, 3 and 6 hours. A degradation profile was constructed for each antibiotic using linear regression and concentration remaining at 6 hours was calculated.ResultsClindamycin and meropenem retained at least 90% or greater of the original concentration in the peritoneal dialysis solution over 6 hours, while amoxycillin displayed marginal stability.ConclusionClindamycin and meropenem are stable for 6 hours in peritoneal dialysis solution containing 2.5% glucose. Amoxycillin's stability was marginal, which could be improved with a modified formulation.

Drug resistance pattern and clonality in H. pylori strains

This aim of this work was to determine the in vitro activity of clarithromycin, amoxycillin, metronidazole and tetracycline against Helicobacter pylori and clonality among resistant and sensitive strains isolated from North India. A total of 68 H. pylori isolates from peptic ulcer disease and non ulcer dyspepsia patients were examined. These strains were subjected for determination of minimum inhibitory concentration of clarithromycin, amoxycillin, metronidazole and tetracycline. For molecular characterization of resistant and sensitive strains, enterobacterial repetitive intergenic consensus sequences (ERIC) and random amplified polymorphic DNA-PCR (RAPD-PCR) methods were used. All the tested isolates were found resistant to metronidazole, while 65% were resistant to amoxycillin and 4.7% were resistant to clarithromycin. However, none of the isolates were found to be resistant to tetracycline. Molecular fingerprinting and cluster analysis of resistant and sensitive strains did not give clues for clonal spread of resistant strains. Various chromosomal mutations were seen in the putative resistance genes of resistant strains, possibly indicating selection pressure as the major cause of high resistance.

An indirect atomic absorption spectrometric determination of ciprofloxacin, amoxycillin and diclofenac sodium in pharmaceutical formulations

A highly sensitive indirect atomic absorption spectrophotometric (AAS) method has been developed for the determination of very low concentrations of ciprofloxacin, amoxycillin and diclofenac sodium. The method is based on the oxidation of these drugs with iron(III). The excess of iron(III) was extracted into diethyl ether and then the iron(II) in the aqueous layer was aspirated into an air-acetylene flame and determined by AAS. The linear concentration ranges were 25-400, 50-500 and 60-600 ng ml-1 for ciprofloxacin, amoxycillin and diclofenac sodium, respectively. The results were statistically compared with the official method using t- and f-test at p < 0.05. There were insignificant interferences from most of the excipients present. The intra- and inter-day assay coefficients of variation were less than 6.1 % and the recoveries ranged from 95 to 103 %. The method was applied for the analysis of these drug substances in their commercial pharmaceutical formulations.

Flow injection-chemiluminescence determination of amoxycillin using potassium permanganate and formaldehyde system

It was found that amoxycillin can react with potassium permanganate in an acidic medium to produce chemiluminescence, which is greatly enhanced by formaldehyde. The optimum conditions for this chemiluminescent reaction were studied in detail using a flow-injection system. The experimental results indicate that, under optimum conditions, the chemiluminescence intensity is linearly related to the concentration of amoxycillin in the range 5.48 x 10(-8)-2.74 x 10(-6) mol/L, with a detection limit (3sigma) of 4.1 x 10(-8) mol/L. The relative standard deviation was 1.0% at 1.1 x 10(-6) mol/L amoxycillin (n = 11 measurements). This method has the advantages of high sensitivity, fast response and ease of operation. The method was successfully applied to the determination of amoxycillin in raw medicines and capsules.

Evaluation of a single dose versus a divided dose regimen of amoxycillin in treatment of Actinobacillus pleuropneumoniae infection in pigs

The theory of a time-dependent effect of amoxycillin was examined in a model of porcine Actinobacillus pleuropneumoniae (Ap)-infection using clinically relevant dosage regimens. Twenty hours after infection of fourteen pigs, when clinical signs of pneumonia were present, one group of pigs received a single dose of amoxycillin (20 mg/kg, i.m.), whereas another group received four doses of 5 mg/kg injected at 8-h intervals. A similar AUC of the plasma amoxycillin concentration versus time curve was obtained in the two groups, whereas the maximum concentration was threefold higher using the single high dose. Plasma amoxycillin was above the MIC for twice as long using the fractionated dosage scheme. The condition of the animals was evaluated by clinical and haematological observations combined with quantification of biochemical infection markers: C-reactive protein, zinc and ascorbic acid. Within 48 h of treatment, the pigs in both treatment groups recovered clinically. No significant differences in the time-course of clinical observations or plasma concentrations of the biomarkers of infection were observed between the two treatments. In conclusion, the efficacy of these two dosage regimens of amoxycillin was not significantly different in treatment of acute Ap-infection in pigs.

Pharmacokinetics of amoxycillin and the rate of depletion of its residues in pigs

Six pigs were used in a two-period crossover study to investigate the pharmacokinetics of amoxycillin after single intravenous and oral doses of 20 mg/kg bodyweight. Twelve pigs were used to...

Comparative Pharmacokinetics and Bioavailability of Amoxycillin in Chickens after Intravenous, Intramuscular and Oral Administrations

The pharmacokinetics and systemic bioavailability of amoxycillin were investigated in clinically healthy, broiler chickens (n = 10 per group) after single intravenous (i.v.), intramuscular (i.m.), and oral administrations at a dose of 10 mg/kg body weight. The plasma concentrations of amoxycillin were determined using high-performance liquid chromatography (HPLC) and the data were subjected to compartmental and non-compartmental kinetic analyses. Following single i.v. injection, all plasma amoxycillin data were described by a two compartment-open model. The elimination half-lives of amoxycillin were 1.07 h, 1.09 h and 1.13 h after single i.v., i.m. and oral administration, respectively. The total body clearance (Cl(B)) of amoxycillin was 0.80 (L/h)/kg and the volume of distribution calculated as V(d(area)) was 1.12 L/kg, respectively after i.v. administration. Substantial differences in the resultant kinetic data were obtained by comparing the plasma concentration profiles after i.m. injection with that after oral administration. The systemic i.m. bioavailability of amoxycillin was higher (77.21%) than after oral (60.92%) dosing. In vitro, the mean plasma protein binding of amoxycillin amounted to 8.27%. Owing to high clearance of amoxycillin in birds in our study, a plasma level was maintained above 0.25 microg/ml for only 6 h after i.m. and oral routes of administration and consequently frequent dosing may be necessary daily.

The efficacy and safety of oral pharmacokinetically enhanced amoxycillin–clavulanate 2000/125 mg, twice daily, versus oral amoxycillin–clavulanate 1000/125 mg, three times daily, for the treatment of bacterial community-acquired pneumonia in adults

This double-blind, double-dummy, parallel-group study was designed to show that a pharmacokinetically enhanced formulation of oral amoxycillin–clavulanate (16:1, 2000/125 mg), twice daily, is at least as effective clinically and microbiologically as oral amoxycillin–clavulanate 1000/125 mg, three times daily, in the 10 day treatment of community-acquired pneumonia (CAP) in adults. The pharmacokinetically enhanced formulation is designed to provide higher serum concentrations of amoxycillin for a longer period than standard dosing to achieve coverage of Streptococcus pneumoniae isolates with amoxycillin–clavulanic acid minimum inhibitory concentrations (MICs) up to and including 4 mg/l. A total of 344 patients with CAP from 77 centres received amoxycillin–clavulanate 2000/125 mg twice daily for 10 days (169 patients) or amoxycillin–clavulanate 1000/125 mg three times daily for 10 days (175 patients). The most common pathogen isolated was S. pneumoniae (52.3% of patients, amoxycillin–clavulanate 2000/125 mg group; 46.8% of patients, amoxycillin–clavulanate 1000/125 mg group). In the clinical per-protocol (PP) population at test of cure (days 18–39), the clinical success rate in the amoxycillin–clavulanate 2000/125 mg group was at least as good as in the amoxycillin–clavulanate 1000/125 mg group (91.5 and 93.0%, respectively; 95% CI, −8.3, 5.4). The radiological and bacteriological success rates at test of cure for the PP populations were 92.4 and 90.6% in the amoxycillin–clavulanate 2000/125 mg group and 93.9 and 84.4% in the amoxycillin–clavulanate 1000/125 mg group, respectively. The clinical, bacteriological and radiological success rates at the end of therapy (days 11–17) for the PP populations were all over 85%. Both regimens were well tolerated, with no differences in adverse events between the groups. Amoxycillin–clavulanate 2000/125 mg, twice daily, is well tolerated and at least as effective clinically as amoxycillin–clavulanate 1000/125 mg, three times daily, in patients with CAP and may also be appropriate for the treatment of infections due to S. pneumoniae strains with high-level penicillin resistance.

Sensitive spectrophotometric methods for the determination of amoxycillin, ciprofloxacin and piroxicam in pure and pharmaceutical formulations

Two simple, sensitive and accurate spectrophotometric methods have been proposed for the determination of amoxycillin (AMX), ciprofloxacin (CPF) and piroxicam (PIR) in pure and pharmaceutical preparations. The methods are based on the measurement of absorbances of tris( o-phenanthroline) iron(II) [method A] and tris (bipyridyl) iron(II) [method B] complexes at 510 and at 522 nm, respectively. Reaction conditions have been optimized to obtain coloured complexes of higher sensitivity and longer stability. The absorbances were found to increase linearly with increase in concentrations of AMX, CPF and PIR which were corroborated by correlation coefficient values. The complexes obeyed Beer's law over the concentration range of 0.06–5.2, 0.04–7.2 and 0.2–6.5 μg ml −1 for AMX, CPF and PIR, respectively, in method A, and of 0.05–8.5, 0.05–9.0 and 0.05–6.5 μg ml −1 for AMX, CPF and PIR, respectively, in method B. The developed methods have been successfully applied for the determination of AMX, CPF and PIR in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in their determinations. The results obtained by the proposed methods have been statistically compared by means of Student t-test and by the variance ratio F-test.

CHEMILUMINESCENCE FLOW INJECTION ANALYSIS OF AMOXYCILLIN BY A PERMANGANATE-BASED REACTION

ABSTRACT A new application of chemiluminescence for the determination of amoxycillin in flow injection mode is presented. The method is based upon the direct chemiluminescence reaction of amoxycillin with KMnO4 in acidic medium in presence of quinine sulfate. The chemiluminescence intensity was linearly related to the concentration of amoxycillin within 0.05–10 µg mL−1 range with a detection limit (3σ) of 0.02 µg mL−1 and a sample measurement frequency of 90 samples h−1. The relative standard deviation is 2.3% for 1.0 µg mL−1 amoxycillin solution in 11 repeated measurements. The method was successfully applied to the analysis of amoxycillin in capsules.

UV absorption method should not be applied for determining amoxycillin in acidic dissolution test medium

In order to clarify the suitability of assay method, the stability of amoxycillin (AMX) in the acidic solution at pH 1.2 was determined by two different methods, ultraviolet absorption (UV) and HPLC methods. The determination was simultaneously performed for the same sample solutions. The data from HPLC method indicated that AMX degraded and the concentration of AMX in the acidic solution was decreased. The apparent first-order rate constant ( k obs) for the degradation was 9.83×10 −2 h −1, and the half-life was calculated to be 7.04 h. On the other hand, the data obtained from UV method apparently represented that the concentration of AMX increased with time-course. This phenomena was brought about by the increase of UV absorption at 272 nm, which accompanied with the degradation of AMX. These results clearly indicate that UV method can not be used for determining the samples accompanying the degradation of AMX. In general, the dissolution test (drug release test) has been used for the evaluation of a sustained-release dosage form of AMX. It is impossible to avoid the degradation of AMX in the test under acidic conditions. The results indicated that the UV method should not be used for the determination of AMX in the test.

Prevalence of Helicobacter pylori resistant strains in the southern part of Switzerland

Discovered in the last decade, Heliobacter pylori is now known to play a role in the onset of chronic gastritis and peptic ulcer and also to be strongly associated with gastric cancer and MucosaAssociated Lymphoid Tissue (MALT) lymphoma [1,2]. These findings have revolutionized the therapeutical approach to gastric pathology. Moreover, the wide spread of dyspeptic symptoms has contributed to the development of a variety of noninvasive diagnostic assays, such as the urea breath test, serologic and whole blood tests, most of which are available to the primary care physicians for the rapid diagnosis of H. pylori infection. As a consequence, antibiotic eradication therapy has been widely applied, often without endoscopic examination which is essential for the identification of the cause of the gastric pathophysiological disturbances. At present, the most commonly used treatment is the triple therapy: a proton pump inhibitor and two antibiotics (metronidazole plus clarithromycin, or amoxycillin plus clarithromycin, or metronidazole plus amoxycillin) [3]. Because of the abuse of this therapeutic scheme, a consistent increase in metronidazole and clarithromycin resistance among H. pylori strains has been monitored [4,5]. Recently the first case of an amoxycillin-resistant H. pylori strain has also been reported [6]. The appearance of resistant strains is one of the major causes of treatment failure [7]. Thus, monitoring the prevalence of resistant strains and establishing the local susceptibility level to the commonly used drugs is at least as important as the development of new antimicrobial agents. For this reason and because of the high incidence of gastric cancer in our region [8,9] (the southern part of Switzerland together with the northern part of Italy) we collected 142 H. pylori strains from different patients living in the Cantone Ticino (southern part of Switzerland) in 1996 and 1997. These strains were tested for susceptibility to metronidazole, clarithromycin and amoxycillin. Minimum inhibitory concentrations (MICs) of 142 H. pylori strains were determined using the E-test method (AB Biodisk, Solna, Sweden) according to the manufacturer’s instructions. The MIC breakpoint values for H. pylori resistance were chosen according to the available data published in the literature: 8 mg/L for both metronidazole and clarithromycin, and 2 mg/L

Simultaneous quantification of amoxycillin and metronidazole in plasma using high-performance liquid chromatography with photodiode array detection

A simple, robust HPLC method was developed to measure simultaneously the plasma concentrations of amoxycillin and metronidazole in order to assess their disposition in the eradication of Helicobacter pylori. Plasma samples were protein precipitated, pH adjusted and the supernatant injected onto the HPLC system which used a C 18 column, paired-ion aqueous mobile phase and photodiode array detection of amoxycillin at 230 nm and metronidazole at 313 nm. Intra- and inter-day precision and inaccuracy were less than 10% for concentrations between 5 and 20 mg/l. The limit of quantification was 1 mg/l. Samples were stable on the HPLC injector for 48 h at room temperature and multiple freeze–thaw cycles led to no decomposition.

Bactericidal properties of moxifloxacin and post-antibiotic effect.

The time-kill kinetics and post-antibiotic effect (PAE) of moxifloxacin were studied for strains of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Staphylococcus aureus and Escherichia coli. Moxifloxacin had a bactericidal effect against all strains tested, with the least rapid bactericidal effect being against S. pyogenes and the most rapid effect against S. aureus and E. coli. The PAE of moxifloxacin was similar to that of other fluoroquinolones and increased with increasing concentration. No association was found between the bactericidal effect of moxifloxacin and the duration of PAE. Gram-positive and gram-negative organisms were also exposed to concentrations of moxifloxacin, sparfloxacin and amoxycillin that simulated the drug concentrations obtained in human serum after standard oral dosing schedules. Simulation of moxifloxacin concentrations in human serum reduced viable counts more effectively and more rapidly than shown in time-kill experiments; in contrast, sparfloxacin and amoxycillin were less effective than when constant concentrations of these antibacterials were used.

Effects of co-trimoxazole, erythromycin, amoxycillin, tetracycline and chloroquine on sperm function in vitro.

This in-vitro study was designed to investigate the effects of commonly prescribed antibiotics on sperm movement characteristics, viability and the ability of spermatozoa to undergo the acrosome reaction. Spermatozoa were obtained by swim-up from normozoospermic semen and cultured for 24 h with increasing concentrations of co-trimoxazole, erythromycin, amoxycillin, tetracycline and chloroquine. Tetracycline at concentrations as low as 2.5 microg/ml led to a significant dose-dependent inhibition in percent rapid-moving spermatozoa, mean path velocity (VAP), straight-line velocity (VSL) and curvilinear velocity (VCL), but at 50 microg/ml tetracycline all spermatozoa were static. Erythromycin had significant effects on rapid movement, VAP, VSL and VCL only at concentrations >100 microg/ml. In contrast, percent rapid-moving spermatozoa was significantly enhanced at low concentrations of chloroquine (5 microg/ml), but significantly inhibited by higher concentrations. Co-trimoxazole did not adversely affect percent rapid-moving spermatozoa below 500 microg/ml, at which concentration movement was decreased by 34%. The mean lateral head displacement (ALH) was significantly enhanced by 5 microg/ml co-trimoxazole and reduced at 1 mg/ml erythromycin. The effects of these drugs were mostly irreversible. Amoxycillin had no effect on sperm movement characteristics over the dose range used, though it inhibited viability at high doses. Viability was significantly reduced at concentrations of all drugs which affect rapid sperm movement; these concentrations of drugs did not appear to affect the ability of spermatozoa to undergo the acrosome reaction. The results from this study, when combined with known effects on spermatogenesis, should facilitate the choice of drugs for the treatment of both genitourinary and unrelated infections in men who are attempting to conceive.

Penetration of amoxycillin to the respiratory tract tissues and secretions in Actinobacillus pleuropneumoniae infected pigs

The pharmokinetic properties of amoxycillin, and its penetration into respiratory tract tissue, were determined in 18 Actinobacillus pleuropneumoniae infected pigs, after a single i.v. dose of 8·6 mg amoxycillin kg −1 bodyweight. Pleuropneumoniae was produced experimentally in pigs by an aerosol infection model. The infection created a homogenous response, characterised by depression of breathing and increased body temperature. The clinical symptoms were accompanied by increased haptoglobin levels and circulating white blood cell counts. At necropsy the findings were characterised by a bilateral fibrinous pleuropneumonia. Twenty hours after infection, the pigs were administered amoxycillin i.v. The plasma concentration-time curve was described by a three compartment open model. The mean residence time and the elimination half-life were l·5 and 3·4 hours, respectively. The steady-state volume of distribution was 0·67 litres kgl, and the clearance was 0·46 litres kg −1 hour −1. There were no significant differences between these values and those reported previously for healthy pigs. The concentration of amoxycillin in bronchial secretions, lung tissue and diseased lung tissue peaked two hours after intravenous drug administration, while amoxycillin concentration in pleural fluid, lymph nodes and tonsil tissue peaked at the first sampling point one hour after drug administration. The concentration of amoxycillin in secretions and tissue decreased by a slower rate than amoxycillin concentration in plasma, resulting in an increasing tissue-to-plasma concentration ratio. The distribution ratios (AUC tissue/JAUC plasma) was 0·53 for bronchial secretions, 0·44 for pneumonic lung tissue, 0·42 for lung tissue, 1·04 for pleural fluid, 0·58 for lymph nodes and 0·37 for tonsil tissue. The distribution of amoxycillin to secretions was increased compared with that previously reported for healthy pigs, while only minor changes were observed in lung tissue.

Penetration of amoxycillin into the respiratory tract tissues and secretions in pigs

The pharmacokinetic properties of amoxycillin, and its penetration into respiratory tract tissues (alveolar macrophages, bronchial secretions, bronchial mucosa, lung tissue and lymph nodes), were determined in 20 healthy female pigs weighing 29 to 55 kg, after a single intravenous dose of 8·6 mg kg −1 bodyweight. Following intravenous administration the plasma concentration-time curves were best described by a three-compartment open model. The elimination half-life and the mean residence time were 2·5 and 1.4 hours, respectively. The volume of distribution at steady state was 0·52 litres kg −1, and the body clearance was 0·40 litres hour −1 kg −1. In all structures (except alveolar macrophages) amoxycillin concentration peaked at the first sampling point, one hour after drug administration. The tissue to plasma ratio (based on AUC values) were 0·33 for bronchial secretions, 0·37 for bronchial mucosa, 0·39 for lung tissue and 0·68 for lymph nodes. Traces of amoxycillin were found in alveolar macrophages, but the concentrations were below the limit of quantification. The concentration of amoxycillin in secretions and tissue decreased by a slower rate than the concentration in plasma, resulting in increasing secretion- and tissue-to-plasma concentration ratios.

Bioavailability of amoxycillin in pigs.

Amoxycillin was administered to pigs intravenously (i.v.), intramuscularly (i.m.) and orally (p.o.), in a cross-over design to examine the bioavailability (F) of various drug formulations. These included: a sodium salt for reconstitution in water and administration i.v.; trihydrate salt in an oil base for intramuscular administration producing 'conventional' duration of plasma concentrations; a trihydrate salt in oil base giving prolonged (LA) duration, and a trihydrate powder for oral administration in solution. The concentration of amoxycillin in plasma was measured by high-performance liquid chromatography, and its pharmacokinetic variables were assessed for the individual pigs by use of noncompartmental methods. Following i.v. administration (8.6 mg/kg), amoxycillin was eliminated rapidly with a mean residence time (MRT) of 1.4 h. After i.m. administration of the conventional formulation (14.7 mg/kg), the plasma amoxycillin concentration peaked at 2 h at 5.1 micrograms/mL. The bioavailability was 0.83. Intramuscular administration (14.1 mg/kg) of the long acting formulation (i.m. LA), lead to two peaks in plasma at 1.3 and 6.6 h. The bioavailability was calculated to be 1.11. After p.o. administration to fasted pigs, peak concentration was reached after 1.9 h, and the bioavailability was 0.33. In fed pigs, the corresponding values were 3.6 h and 0.28. Data showed that treatment of respiratory tract diseases in pigs by p.o. dosing alone, may not be optimal, because of the relatively low bioavailability and the fact that infections often result in reduced feed and water consumption. A rational treatment regime for susceptible respiratory pathogens includes an initial i.m. injection, followed by p.o. dosing every 12 h. Alternatively, the long acting formulation may be administered i.m. in a dose of 15 mg/kg, which would lead to active plasma concentrations for approximately 48 h.