Total Gentamicin Research Articles

Comparative Pharmacokinetics of Gentamicin C1, C1a and C2 in Healthy and Infected Piglets.

Gentamicin, an aminoglycoside antibiotic, is a mixture of therapeutically active C1, C1a, C2 and other minor components. Despite its decades-long use in pigs and other species, its intramuscular (IM) pharmacokinetics/pharmacodynamics (PKs/PDs) are unknown in piglets. Furthermore, the PKs of many drugs differ between healthy and sick animals. Therefore, we investigated the PKs of gentamicin after a single IM dose (10 mg/kg) in healthy piglets and piglets that were intranasally co-infected with Actinobacillus pleuropneumoniae and Pasteurella multocida (PM). The plasma concentrations were measured using validated liquid chromatography/mass spectrometry. The gentamicin exposure was 36% lower based on the area under the plasma concentration-time curve and 16% lower based on the maximum plasma concentration (Cmax) in the infected piglets compared to the healthy piglets, while it was eliminated faster (shorter half-life and larger clearance) in the infected piglets compared to the healthy piglets. The clearance and volume of distribution were the highest for the C1 component. C1, C1a and C2 accounted for 22-25%, 33-37% and 40-42% of the total gentamicin exposure, respectively. The PK/PD target for the efficacy of aminoglycosides (Cmax/minimum inhibitory concentration (MIC) > 10) could be exceeded for PM, with a greater magnitude in the healthy piglets. We suggest integrating this PK information with antibiotic susceptibility data for other bacteria to make informed antibiotic and dosage regimen selections against piglet infections.

Pharmacokinetics of Gentamicin Components C1, C1a, and C2/C2a/C2b and Subsequent Decline in Glomerular Filtration Rate in Neonates.

Gentamicin is a commonly used antibiotic in neonates. Its components C1, C1a, C2, C2a, and C2b may have different nephrotoxic potential. We aimed to describe pharmacokinetics and nephrotoxic potential of gentamicin components in a joint model in neonates. Neonates with gestational age ≥ 32weeks treated with gentamicin blood samples were collected at a steady state. Pharmacokinetics of C1, C1a, and C2/C2a/C2b were modelled in NONMEM and included competitive uptake into kidney proximal tubular cells and decrease in glomerular filtration rate. The nephrotoxic potential of total gentamicin, C1, C1a, and C2/C2a/C2b was evaluated by simulations. A total of 30 neonates (median (range) gestational age 36.4 (32-42) weeks, postnatal age 3 (1-5) days, creatinine value 47.5 (17-78) µmol/L) were included. Pharmacokinetics of all components was best described by a two-compartment model. Clearance of C1 was smaller than clearances of C1a and C2/C2a/C2b, and other parameters were similar. The model with different Km (concentration for which half-maximal uptake into kidney proximal tubular cells is achieved) for C1, C1a, and C2/C2a/C2b (37.5, 18, 15mg/L) provided a better fit than the model with equal Km (15mg/L). According to simulations, decrease in glomerular filtration rate in the case of once-daily dosing of 4mg/kg/day was the largest for C2/C2a/C2b (median (5th and 95th percentile) 0.22% (0.00-8.12%)), followed by total gentamicin (0.20% (0.00-4.10%)), C1a (0.11% (0.00-7.57%)), and C1 (0.04% (0.00-1.55%)). Different gentamicin components C1, C1a, and C2/C2a/C2b exhibited different pharmacokinetic profiles. Once-daily dosing of 4mg/kg/day results in low nephrotoxicity in neonates, in line with previous studies.

Liquid chromatography-tandem mass spectrometry method for quantification of gentamicin and its individual congeners in serum and comparison results with two immunoanalytical methods (fluorescence polarization immunoassay and chemiluminiscent microparticle immunoassay)

BackgroundTotal gentamicin is a sum of five congeners C1, C1a, C2, C2a and minor C2b, which differ from each other in their methylation on the purpurosamine ring. Liquid chromatography with mass detection (LC-MS/MS) and specified calibration material enables the concentration of total gentamicin and its individual congeners to be analysed. Methods50 µL serum was precipitated with acetonitrile in the presence of 0.5 mol/L formic acid. A RP BEH C18 1.7 µm 2.1x50 mm column maintained at 30 °C and tobramicin as the internal standard were used. Mass detection was performed in positive electrospray. The gentamicin results were compared with fluorescence polarization immunoassay (FPIA) and chemiluminiscent microparticle immunoassay (CMIA). Passing-Bablock regression analysis and Bland-Altman analysis were used. ResultsCalibration curves for individual gentamicin congeners were linear with correlation coefficients between 0.997 and 0.998. Recovery was 91.6–102.0% and the coefficients of variation 1.4–8.4%. The total gentamicin concentration was compared with immunoassay FPIA (LC-MSgen = 0.9798xPFIAgen) and CMIA (LC MSgen = 0.9835xCMIAgen) both with significant correlation (p < 0.001). ConclusionThe LC-MS/MS method is fast and precise and can be applied to routine TDM in patients. Comparing it to immunoassays makes it possible to measure concentration of gentamicin congeners, which may be important in the case of their different pharmacokinetics.

Antibacterial Layer‐by‐Layer Films of Poly(acrylic acid)–Gentamicin Complexes with a Combined Burst and Sustainable Release of Gentamicin

AbstractThere is an urgent need for the development of effective antibacterial coatings to cope with more and more resistant bacterial strains in medical environments, and particularly to prevent nosocomial infections following bone implant surgery. Polyelectrolyte multilayers (PEMs) based on poly‐l‐lysine (PLL) and complexes of poly(acrylic acid) (PAA) and gentamicin have been fabricated here applying the layer‐by‐layer (LbL) technique. Complexes are prepared by mixing PAA and gentamicin solutions in 500 × 10−3 m NaCl at pH 4.5. The assembly of PLL and the complexes follows an exponential growth allowing a high loading of gentamicin in a four bilayer PEM. Although PEMs are stable and do not degrade at physiological pH, there is a continuous release of gentamicin at pH 7.4. PEMs show an initial burst release of gentamicin in the first 6 h, which liberates 58% of the total gentamicin released during the experiment, followed by a sustainable release lasting over weeks. This release profile makes the coating appealing for the surface modification of bone implants as a high concentration of antibiotics is necessary during implant surgery while a lower antibiotic concentration is needed until tissue is regenerated. PEMs are effective in preventing the proliferation of the Staphylococcus aureus strain.

Gentamicin vestibulotoxicity with modern systemic dosing regimens: a prospective study using video-oculography

Objectives: To determine the incidence of gentamicin vestibulotoxicity with current dosing regimens, and to evaluate the feasibility of routine video-oculography on all patients given gentamicin.Materials and methods: In this prospective incidence study serial horizontal vestibulo-ocular reflex (HVOR) gain measurements were recorded using video-oculography on adult inpatients receiving intravenous gentamicin. The primary outcome was the proportion of patients developing impairment of their HVOR gain.Results: After exclusions, 42 patients were included in the analysis. Three patients (7.1%) developed asymptomatic vestibulotoxicity, exact 95% confidence interval 1.5–19.5%. In two of these patients the deficit resolved within several hours. No patients developed symptomatic vestibulotoxicity. There was no evidence for a generalised reduction in group HVOR gain with time. HVOR gain was not associated with total gentamicin dose, dynamic visual acuity or subjective imbalance.Conclusions and significance: Gentamicin may cause reversible, asymptomatic vestibulotoxicity. Video-oculography may be useful to monitor for vestibulotoxicity in patients treated with gentamcin; however, testing all patients routinely may be challenging.

Effect of trabecular metal on the elution of gentamicin from Palacos cement.

Periprosthetic joint infections continues to be a common complication in total joint arthroplasty, resulting in significant morbidity, mortality, and additional cost. Trabecular metal implants with an internal cemented interface may be customizable drug delivery devices with an ingrowth interface. Thirty-six acetabular implants were assembled in vitro, half with a trabecular metal shell and half without. The antibiotic loaded bone cement was prepared via three different mixing techniques and at two different mixing times. Mixing time had a significant effect on the total amount of gentamicin eluted. The long mixing protocol eluted up to 126% (p = 0.001) more gentamicin than the short mixing protocol at 4 h and 192% (p < 0.001) more at 7 days. Hand or mechanical mixing technique had no significant effect on elution at 4 h. At 7 days, the mechanical mixing system under vacuum eluted over 50% (p = 0.031) more gentamicin than without a vacuum and nearly 60% (p = 0.040) more gentamicin than hand mixing. The use of a trabecular metal shell had no significant effect on the bulk elution of gentamicin at 4 h (p > 0.05) but significantly reduced total gentamicin elution under certain mixing protocols at 7 days. A possible optimization strategy to improve elution kinetics would be to use a long mixing time with a mechanical mixing system under vacuum. The establishment of trabecular metal as an effective delivery vehicle for antibiotics makes possible an entirely new class of drug eluting device designs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

An LC-MS/MS based candidate reference method for the quantification of total gentamicin in human serum and plasma using NMR characterized calibrator material

BackgroundAccurate measurement of gentamicin concentration in serum and plasma is required for therapeutic drug monitoring to ensure appropriate treatment of patients. In this work, we present a validated LC-MS/MS-based candidate reference measurement procedure for total gentamicin quantification to be used for standardization and harmonization of routine assays applied for therapeutic drug monitoring of this compound. Total gentamicin is the sum of the concentrations of five known congeners C1, C1a, C2, C2a and C2b. To our knowledge, there is so far no LC-MS method for quantification of total gentamicin in human serum described in literature. MethodsSample preparation was based on sample dilution with an aqueous internal standard solution followed by protein precipitation. Stable derivatives of gentamicin-glycine congeners were prepared by chemical synthesis and used as internal standards. The primary calibration material used in this assay was characterized by NMR spectroscopy and the pattern of the gentamicin congeners was determined. The total gentamicin was reported as the sum of the congeners which were quantified individually by LC-MS/MS. ResultsThe method allows the measurement of total gentamicin in human serum and plasma in the concentration range of 0.1 to 12.0μg/ml with an assay imprecision of ≤6% CV and an assay accuracy between 96% and 114%. LOD and LOQ for the total gentamicin were 0.04μg/ml and 0.13μg/ml, respectively. Comparative measurement of 128 native patient samples using this method implemented at two laboratory sites showed an excellent agreement. ConclusionsValidation results proved that this protocol describes a robust and reliable method which is suggested as reference measurement procedure for the standardization and harmonization of routine assays for the quantification of total gentamicin.

Pharmacokinetics and Absorption of Paromomycin and Gentamicin from Topical Creams Used To Treat Cutaneous Leishmaniasis

This study evaluated the pharmacokinetics of topical creams containing 15% paromomycin ("paromomycin alone") and 15% paromomycin plus 0.5% gentamicin (WR 279,396) in patients with cutaneous leishmaniasis. The investigational creams were applied topically to all lesions once daily for 20 days. Plasma samples were analyzed for simultaneous quantitation of paromomycin and gentamicin isomers and total gentamicin. Pharmacokinetic parameters for gentamicin could not be calculated because detectable levels were rarely evident. After one application, the paromomycin area under the concentration-time curve from 0 to 24 h (AUC0-24) was 2,180 ± 2,621 ng · h/ml (mean ± standard deviation [SD]) for the paromomycin-alone group and 975.6 ± 1,078 ng · h/ml for the WR 279,396 group. After 20 days of application, the paromomycin AUC0-24 and maximum concentration of drug (Cmax) were 5 to 6 times greater than those on day 1 for both treatment groups. For the paromomycin-alone group, the AUC0-24 was 8,575 ± 7,268 ng · h/ml and the Cmax was 1,000 ± 750 ng/ml, compared with 6,037 ± 3,956 ng · h/ml and 660 ± 486 ng/ml for the WR 279,396 group, respectively. Possibly due to large intersubject variability, no differences (P ≥ 0.05) in the AUC0-24 or Cmax were noted between treatment or between sites on day 1 or 20. The percentage of dose absorbed on day 20 was 12.0% ± 6.26% and 9.68% ± 6.05% for paromomycin alone and WR 279,396, respectively. Paromomycin concentrations in plasma after 20 days of application were 5 to 9% of those after intramuscular administration of 15 mg/kg of body weight/day to adults for the systemic treatment of visceral leishmaniasis. Effective topical treatment of cutaneous leishmaniasis appears to be possible with limited paromomycin and gentamicin systemic absorption, thus avoiding drug accumulation and toxicity. (The work described here has been registered at ClinicalTrials.gov under registration no. NCT01032382 and NCT01083576.).

Pharmacokinetics of Gentamicin C after IV, IM, SC and Oral Administration , C , C 1 1a and C 2 in Broiler Chickens 2a

The pharmacokinetics and bioavailability of four major gentamicin components (C 1 , C 1a , C 2 and C 2a ) in chicken plasma administered at 5 mg/kg body weight by different routes of administration (IV, IM, SC and oral) was determined using reversed-phase high performance liquid chromatography (RP-HPLC) and pre-column derivatization with Phenylisocyanate (PIC). All the components, except for C 1a were well absorbed (bioavailability of 60% or greater) following administration by the IM and SC routes. The bioavailability of C 1a was 58% and 35% following IM and SC administration, respectively. The apparent volume of distribution (V ss and Vd area ) for the C 1 component was significantly smaller than for any of the other components individually or combined. In addition, the C 1 component had a significantly shorter t½β and MRT following intravenous administration and a higher C max /Dose following intramuscular administration. This study showed significant differences in some pharmacokinetics parameters between four gentamicin components (C 1a , C 2a , C 1 and C 2 ) after administration of single mixture of gentamicin by different routes in chickens. The differences may have clinical and toxicological implications, and could explain the high variation in total gentamicin pharmacokinetics.

Gentamicin ototoxicity: a 23‐year selected case series of 103 patients

To review patients with severe bilateral vestibular loss associated with gentamicin treatment in hospital. A retrospective case series of presentations to a balance disorders clinic between 1988 and 2010. Relationship between vestibulotoxicity and gentamicin dose or dosing profile; indications for prescribing gentamicin. 103 patients (age, 18-84 years; mean, 64 years) presented with imbalance, oscillopsia or both, but none had vertigo. Only three noted some hearing impairment after having gentamicin, but audiometric thresholds for all patients were consistent with their age. In all patients, the following tests gave positive results: a bilateral clinical head-impulse test, a vertical head-shaking test for vertical oscillopsia, and a foam Romberg test. In 21 patients, imbalance occurred during gentamicin treatment (ignored or dismissed by prescribers in 20) and in 66 after treatment; the remaining 16 could not recall when symptoms were first noticed, except that it was after gentamicin treatment in hospital. Total gentamicin dose range was 2-318 mg/kg (mean, 52 mg/kg), daily dose range was 1.5-5.6 mg/kg (mean, 3.5mg/kg), and duration was 1-80 days (mean, 17 days). Six patients had only a single dose; 26 had five or fewer doses. Serum gentamicin levels, measured in 82 patients, were in the recommended range in 59. Time to diagnosis ranged from 4 days to 15 years. Nephrotoxicity developed in 43 patients. Gentamicin dosage complied with contemporary or current Australian antibiotic guidelines in under half the patients. Gentamicin ototoxicity is vestibular, not cochlear, producing permanent loss of balance, but not of hearing. Gentamicin can be vestibulotoxic in any dose, in any regimen, at any serum level.

Local Antibiotics to Prevent Surgical Site Infections

JAMA Effect of an Implantable Gentamicin-Collagen Sponge on Sternal Wound Infections Following Cardiac Surgery: A Randomized Trial Elliott Bennett-Guerrero, MD; T. Bruce Ferguson Jr, MD; Min Lin, PhD; Jyotsna Garg, MS; Daniel B. Mark, MD, MPH; Vincent A. Scavo Jr, MD; Nicholas Kouchoukos, MD; John B. Richardson Jr, MD; Renee L. Pridgen, BS; G. R. Corey, MD; for the SWIPE-1 Trial Group Context: Despite the routine use of prophylactic systemic antibiotics, sternal wound infection still occurs in 5% or more of cardiac surgical patients and is associated with significant excess morbidity, mortality, and cost. The gentamicin-collagen sponge, a surgically implantable topical antibiotic, is currently approved in 54 countries. A large, 2-center, randomized trial in Sweden reported in 2005 that the sponge reduced surgical site infection by 50% in cardiac patients. Objective: To test the hypothesis that the sponge prevents infection in cardiac surgical patients at increased risk for sternal wound infection. Design, Setting, and Participants: Phase 3 single-blind, prospective randomized controlled trial, 1502 cardiac surgical patients at high risk for sternal wound infection (diabetes, body mass index >30, or both) were enrolled at 48 US sites between December 21, 2007, and March 11, 2009. Intervention: Single-blind randomization to insertion of 2 gentamicin-collagen sponges (total gentamicin of 260 mg) between the sternal halves at surgical closure (n = 753) vs no intervention (control group: n = 749). All patients received standardized care including prophylactic systemic antibiotics and rigid sternal fixation. Main Outcome Measures: The primary end point was sternal wound infection occurring through 90 days postoperatively as adjudicated by a clinical events classification committee blinded to study treatment group. The primary study comparison was done in the intent-to-treat population. Secondary outcomes included (1) superficial wound infection (involving subcutaneous tissue but not extending down to sternal fixation wires), (2) deep wound infection (involving the sternal wires, sternal bone, and/or mediastinum), and (3) score for additional treatment, presence of serous discharge, erythema, purulent exudate, separation of the deep tissues, isolation of bacteria, and duration of inpatient stay (ASEPSIS; minimum score of 0 with no theoretical maximum). Results: Of 1502 patients, 1006 had diabetes (67%) and 1137 were obese (body mass index >30) (76%). In the primary analysis, there was no significant difference in sternal wound infection in 63 of 753 patients randomized to the gentamicin-collagen sponge group (8.4%) compared with 65 of 749 patients randomized to the control group (8.7%) ( P = .83). No significant differences were observed between the gentamicin-collagen sponge group and the control group, respectively, in superficial sternal wound infection (49/753 [6.5%] vs 46/749 [6.1%]; P = .77), deep sternal wound infection (14/753 [1.9%] vs 19/749 [2.5%]; P = .37), ASEPSIS score (mean [SD], 1.9 [6.4] vs 2.0 [7.2]; P = .67), or rehospitalization for sternal wound infection (23/753 [3.1%] vs 24/749 [3.2%]; P = .87). Conclusion: Among US patients with diabetes, high body mass index, or both undergoing cardiac surgery, the use of 2 gentamicin-collagen sponges compared with no intervention did not reduce the 90-day sternal wound infection rate. Trial Registration: clinicaltrials.gov Identifier:NCT00600483

Construction of predictive models for gentamicin contents in aqueous solution using specific near infrared spectral regions

Component control is a key step of the quality control process in gentamicin (GM) production. The near infrared (NIR) method allows the rapid analysis of various components for the on-line control in the production process. In this study, we selected specific NIR spectral regions and eliminated solvent interference in constructing the predictive models of GM content in aqueous solution. We found that two factors could lead to better NIR predictions: (i) the combined use of specific NIR spectral regions related to both structural characteristics and content; and (ii) the analysis of sample spectra based on solvent reference spectra to identify and extract spectral information of testing components. We constructed predictive models for total GM C components, GM C1a (C1a), micronomicin (MCR) and sisomicin (SISO) in aqueous solution, respectively. These models can be used for the quick content analysis of different components in various types of GM injection samples.

Effect of an Implantable Gentamicin-Collagen Sponge on Sternal Wound Infections Following Cardiac Surgery&lt;subtitle&gt;A Randomized Trial&lt;/subtitle&gt;

Despite the routine use of prophylactic systemic antibiotics, sternal wound infection still occurs in 5% or more of cardiac surgical patients and is associated with significant excess morbidity, mortality, and cost. The gentamicin-collagen sponge, a surgically implantable topical antibiotic, is currently approved in 54 countries. A large, 2-center, randomized trial in Sweden reported in 2005 that the sponge reduced surgical site infection by 50% in cardiac patients. To test the hypothesis that the sponge prevents infection in cardiac surgical patients at increased risk for sternal wound infection. Phase 3 single-blind, prospective randomized controlled trial, 1502 cardiac surgical patients at high risk for sternal wound infection (diabetes, body mass index >30, or both) were enrolled at 48 US sites between December 21, 2007, and March 11, 2009. Single-blind randomization to insertion of 2 gentamicin-collagen sponges (total gentamicin of 260 mg) between the sternal halves at surgical closure (n = 753) vs no intervention (control group: n = 749). All patients received standardized care including prophylactic systemic antibiotics and rigid sternal fixation. The primary end point was sternal wound infection occurring through 90 days postoperatively as adjudicated by a clinical events classification committee blinded to study treatment group. The primary study comparison was done in the intent-to-treat population. Secondary outcomes included (1) superficial wound infection (involving subcutaneous tissue but not extending down to sternal fixation wires), (2) deep wound infection (involving the sternal wires, sternal bone, and/or mediastinum), and (3) score for additional treatment, presence of serous discharge, erythema, purulent exudate, separation of the deep tissues, isolation of bacteria, and duration of inpatient stay (ASEPSIS; minimum score of 0 with no theoretical maximum). Of 1502 patients, 1006 had diabetes (67%) and 1137 were obese (body mass index >30) (76%). In the primary analysis, there was no significant difference in sternal wound infection in 63 of 753 patients randomized to the gentamicin-collagen sponge group (8.4%) compared with 65 of 749 patients randomized to the control group (8.7%) (P = .83). No significant differences were observed between the gentamicin-collagen sponge group and the control group, respectively, in superficial sternal wound infection (49/753 [6.5%] vs 46/749 [6.1%]; P = .77), deep sternal wound infection (14/753 [1.9%] vs 19/749 [2.5%]; P = .37), ASEPSIS score (mean [SD], 1.9 [6.4] vs 2.0 [7.2]; P = .67), or rehospitalization for sternal wound infection (23/753 [3.1%] vs 24/749 [3.2%]; P = .87). Among US patients with diabetes, high body mass index, or both undergoing cardiac surgery, the use of 2 gentamicin-collagen sponges compared with no intervention did not reduce the 90-day sternal wound infection rate. clinicaltrials.gov Identifier: NCT00600483.

The effect of the antimicrobial peptide, Dhvar-5, on gentamicin release from a polymethyl methacrylate bone cement

The objective of this study was to investigate the release mechanism and kinetics of the antimicrobial peptide, Dhvar-5, both alone and in combination with gentamicin, from a standard commercial polymethyl methacrylate (PMMA) bone cement. Different amounts of Dhvar-5 were mixed with the bone cement powders of Osteopal and the gentamicin-containing Osteopal G bone cement and their release kinetics from the polymerized cement were investigated. Additionally, the internal structure of the bone cements were analysed by scanning electron microscopy (SEM) of the fracture surfaces. Secondly, porosity was investigated with the mercury intrusion method and related to the observed release profiles. In order to obtain an insight into the mechanical characteristics of the bone cement mixtures, the compressive strength of Osteopal and Osteopal G with Dhvar-5 was also investigated. The total Dhvar-5 release reached 96% in the 100 mg Dhvar-5/g Osteopal cement, whereas total gentamicin release from Osteopal G reached only 18%. Total gentamicin release increased significantly to 67% with the addition of 50 mg Dhvar-5/g, but the Dhvar-5 release was not influenced. SEM showed an increase of dissolved gentamicin crystals with the addition of Dhvar-5. The mercury intrusion results suggested an increase of small pores (<0.1 μm) with the addition of Dhvar-5. Compressive strength of Osteopal was reduced by the addition of Dhvar-5 and gentamicin, but still remained above the limit prescribed by the ISO standard for clinical bone cements. We therefore conclude that the antimicrobial peptide, Dhvar-5, was released in high amounts from PMMA bone cement. When used together with gentamicin sulphate, Dhvar-5 made the gentamicin crystals accessible for the release medium presumably through increased micro-porosity (<0.1 μm) resulting in a fourfold increase of gentamicin release.

Gentamicin‐loaded bone cement with clindamycin or fusidic acid added: Biofilm formation and antibiotic release

The formation of staphylococcal biofilms on experimental bone cements, loaded with 0.5 or 1.0 g of active gentamicin and an additional equivalent amount of gentamicin, clindamycin, or fusidic acid was investigated. The biofilms were formed in a modified Robbins device over a 3-day time span and the influence of the additional antibiotics was quantified by expressing the number of colony forming units relative to the corresponding bone cement containing only gentamicin. Combinations of gentamicin with either fusidic acid or clindamycin reduced growth of clinical isolates of both gentamicin-sensitive Staphylococcus aureus and gentamicin-resistant coagulase-negative staphylococci to approximately 28%. To determine whether adding a second antibiotic has influence on the gentamicin release, cement blocks were placed in phosphate buffer and aliquots were taken at designated sampling intervals. The influence of the additional antibiotics was quantified by expressing the percentage released of the total amount of antibiotic incorporated in the different bone cements. After 3 days, all bone cements had released similar percentages of gentamicin, whereas more clindamycin and fusidic acid were released after doubling their concentration in the bone cements. In conclusion, bone cements loaded with combinations of gentamicin and clindamycin or fusidic acid are more effective in preventing biofilm formation than bone cements with gentamicin as a single drug. In addition, the presence of clindamycin or fusidic acid in gentamicin-loaded bone cement has no influence on the total gentamicin release.

Development and validation of a novel LC/ELSD method for the quantitation of gentamicin sulfate components in pharmaceuticals

The equivalent response of evaporative light scattering detector (ELSD) for compounds of similar structure is exploited to develop an LC/ELSD method for the simultaneous quantitation of the four main components of gentamicin sulfate, using as external standard the one main component kanamycin. A C 18 column was used along with a mobile phase consisting of H 2O (containing 35.4 μg/ml of trichloroacetic acid and 0.89 μl/ml of trifluoroacetic acid)–methanol–acetonitrile (990:5:5, v/v/v), in an isocratic mode at 1.1 ml/min. Parameters of ELSD were 50 °C for evaporation temperature and 3.0 bar for pressure of carrier gas (N 2). A logarithmic calibration curve was obtained for sulfate ( t R = 1.9 min) from 4.2 to 150 μg/ml ( r > 0.994) with a precision of 0.18%R.S.D. Kanamycin and the four gentamicin components (C 1a, C 2, C 2a and C 1) were eluted at 3.2, 4.6, 5.9, 7.1 and 8.7 min, respectively, with good resolution (Rs > 1.5). Logarithmic calibration curve was obtained for each component ( r > 0.99) with statistically equal slopes varying from 2.457 to 2.558. The mass range of total gentamycin was 35–240 μg/ml. The proposed method was applied for the determination of gentamicin components and sulfate in raw materials and pharmaceutical formulations (injection, drops and cream) without any pretreatment except cream, for which liquid–liquid extraction was required. Recovery from standard addition experiments in commercial formulations was 99–100% regarding total gentamicin and 89–108% regarding individual components, with a precision (%RSD, n = 4) 0.7–5.8%.

Effect of metal ions on the binding of gentamicin to the peptidoglycan of Micromonospora echinospora

Peptidoglycan (PG), the major part of the cell wall (CW) of Micromonospora echinospora var 49–925, could bind about 90% of the total gentamicin (GM) absorbed on the CW and when the concentrations of PG and GM were 6 mg/ml and 500 U/ml, respectively, the amount of bound GM was approximately 88 000 U/g of PG (dry weight) and no free GM was detected in the solution. Metal ions were used to release GM from PG. Mg 2+ and Na + restrained intensively the binding of GM at GM concentration less than 1000 U/ml. Amine could compete with GM for the binding sites as well. About 50% increase of GM titre was achieved when Mg 2+ or Na + was supplemented to the fermentation broth.

Depletion of gentamicin and its major components from various tissues of turkeys.

To determine tissue depletion profiles for gentamicin and its 3 major components (C1, C1a, and C2) in turkeys. Twenty 10-week-old male turkeys. birds were maintained as untreated controls. The remaining birds were treated with gentamicin sulfate at a dosage of 2 mg/kg, IM, once daily for 5 days. Treated birds were euthanatized 45, 60, 75, and 90 days (4 birds at each sample time) after the last dose of gentamicin was administered, and samples of muscle, liver, kidney, and skin and fat were collected. Control birds were euthanatized on day 45. Concentrations of the 3 major components of gentamicin were measured by means of reversed-phase high-performance liquid chromatography. Total gentamicin concentration (ie, sum of the concentrations of the 3 major components) was < 100 microg/kg for all muscle and skin and fat samples by day 45 and all liver samples by day 75. At all sample times, concentration of the gentamicin C1 component was higher than concentrations of the C1a and C2 components in all tissues. Results suggest that tissue depletion profiles of the 3 major components of gentamicin differ from each other. Withdrawal time, therefore, may depend on the ratio of the components in the pharmaceutical preparation used.

The effect of mixing on gentamicin release from polymethylmethacrylate bone cements.

We compared the release of gentamicin from 6 different commercially available, antibiotic-loaded PMMA bone cements used for vacuum- and hand-mixed cement using a Cemvac vacuum mixing system. We also measured the release of gentamicin after manual addition of the antibiotic to different commercial, unloaded bone cements after hand-mixing. The porosity of cements was reduced in all vacuum-mixed cements, as compared with hand-mixed cements, concurrent with a statistically significant reduction (3 of 6) or increase (1 of 6) in the total amounts of gentamicin released. The total gentamicin release was studied in 3 of the brands after manual addition and mixing of the antibiotics. We found that the release of antibiotics was lower than in samples made from industrial mixing. In conclusion, the manual addition and mixing of gentamicin in PMMA bone cements leads to a lower release of antibiotics than that in corresponding commercially available antibiotic-loaded cements, while vacuum-mixing only leads to a minor reduction in antibiotic release, as compared to hand-mixing.

Pharmacokinetics of gentamicin C1, C1a and C2 in horses after single intravenous dose.

Gentamicin pharmacokinetics has not been studied in horses. Pharmacokinetics of gentamicin C1, C1a and C2 components following i.v. administration of total gentamicin at 6.6 mg/kg bwt to 6 healthy mature horses was determined. Significant differences in clearance, half-life (t 1/2), and mean residence time (MRT) between the gentamicin Cia and the 2 other components were found. The total body clearance (CL) of gentamicin C1a was 1.62 +/- 0.50 ml/min x kg and similar to the glomerular filtration rate (GFR) reported for horses. The CL of gentamicin C1 and C2 were 1.03 +/- 0.08 ml/min x kg and 1.10 +/- 0.15 ml/min x kg, respectively, and significantly slower than that of gentamicin C1a. The values of apparent volume of distribution at steady state were 0.22 +/- 0.05, 0.26 +/- 0.12 and 0.23 +/- 0.05 l/kg for gentamicin C1, C1a and C2, respectively. The MRT values were mean +/- s.d. 3.6 +/- 0.5, 2.7 +/- 0.3 and 3.5 +/- 0.4 h and the t 1/2 values were 3.1 (2.5-4.0), 2.4 (2.0-3.2) and 33 (2.4-4.3) h (harmonic mean and range) for gentamicin C1, C1a and C2, respectively. The MRT and t 1/2 values for gentamicin C1a were significantly shorter than those of gentamicin C1 and C2. It was concluded that the difference in pharmacokinetics between the gentamicin components has potential pharmacological and toxicological implications.