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Carignan G, Larocque L, Stephen S, Carrier K, Ikai Y, Reimer G, Schermerhorn PG, Zitko V. Assay of Oxolinic Acid Residues in Salmon Muscle by Liquid Chromatography with Fluorescence Detection: Interlaboratory Study. J AOAC Int 2020. [DOI: 10.1093/jaoac/74.6.906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
A previously developed method that uses a simplified sample preparation and fluorometric detection of liquid chromatographic eluates for the determination of oxolinic acid in salmon muscle has been collaboratively studied. Five laboratories participated in the study to analyze, in quintuplicate, blank salmon muscle fortified at 10, 20, 50, and 100 μg/kg (ppb), and 2 incurred samples from salmon given feed with medicated oxolinic acid. The tissue, 2 g mixed with 2 g Na2S04, is extracted with ethyl acetate and centrifuged, and the solvent Is evaporated. The residue is partitioned in a mixture of hexane and 0.01 M oxalic acid, and the aqueous phase is chromatographed using fluorescence detection at 327 nm excitation and 369 nm emission. Mean recoveries ranged from 77.2 to 84.5% in spiked samples with reproducibility relative standard deviation (RSDR) ranging from 11.5 to 18.3%. Treated salmon were found to contain 8.71 and 53.8 μg/kg with RSDR of 18.6 and 16.7%, respectively. The corresponding repeatability relative standard deviations (RSDr) were 5.8-12.2%, and 7.7 and 6.2%. The method is recommended for regulatory purposes in Canada.
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Affiliation(s)
- Germain Carignan
- Health and Welfare Canada, Bureau of Drug Research, Drug Residues Section, Ottawa, ON, K1A 0L2, Canada
| | - Lyse Larocque
- Health and Welfare Canada, Bureau of Drug Research, Drug Residues Section, Ottawa, ON, K1A 0L2, Canada
| | - Sved Stephen
- Health and Welfare Canada, Bureau of Drug Research, Drug Residues Section, Ottawa, ON, K1A 0L2, Canada
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Nash C, Kelton D, Vasseur E, DeVries T, Parent D, Pellerin D, Carrier K, Pajor E, Rushen J, de Passillé A, Coe J, Haley D. A survey of practices implemented to improve cow comfort following an initial assessment on Canadian dairy farms. Can J Anim Sci 2019. [DOI: 10.1139/cjas-2018-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objectives of this study were to determine the difficulty of implementing changes to improve cow comfort on Canadian dairy farms, to determine if any changes were implemented to improve dairy cow comfort following an initial cow comfort assessment, to categorize producers based on types of changes they made, to compare how producers in these categories differed, and to identify barriers to implementing these changes. The most difficult type of change to implement was changing stall design (including building a new barn) with a mean difficulty score of 3.3 (out of 5) scored by a panel of dairy researchers. Overall, 3 of 118 (2.5%) interviewed producers were categorized as innovators, 62 (52.5%) as effective adopters, 20 (16.9%) as ineffective adopters, and 33 (28.0%) as non-adopters. The most common types of changes made were to stall management (37.3%). Participants were asked to identify all barriers to further improvement of cow comfort. The most commonly reported barriers were lack of funds (52.9%), lack of time (38.7%), and being satisfied with the level of cow comfort (31.1%). This survey study demonstrates that a cow comfort assessment can influence dairy producers to implement changes to improve cow comfort; however, certain barriers exist to implementation.
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Affiliation(s)
- C.G.R. Nash
- Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - D.F. Kelton
- Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - E. Vasseur
- Department of Animal Science, McGill University, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada
| | - T.J. DeVries
- Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - D. Parent
- Département des sciences animales, Université Laval, Québec, QC G1V 0A6, Canada
| | - D. Pellerin
- Département des sciences animales, Université Laval, Québec, QC G1V 0A6, Canada
| | - K. Carrier
- Département des sciences animales, Université Laval, Québec, QC G1V 0A6, Canada
| | - E.A. Pajor
- Department of Production Animal Health, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - J. Rushen
- Faculty of Land & Food Systems, Animal Welfare Program, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A.M. de Passillé
- Faculty of Land & Food Systems, Animal Welfare Program, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J.B. Coe
- Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - D.B. Haley
- Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada
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Siega-Riz AM, Herring AH, Carrier K, Evenson KR, Dole N, Deierlein A. Sociodemographic, perinatal, behavioral, and psychosocial predictors of weight retention at 3 and 12 months postpartum. Obesity (Silver Spring) 2010; 18:1996-2003. [PMID: 20035283 PMCID: PMC2902688 DOI: 10.1038/oby.2009.458] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Postpartum weight retention plays an important role in the pathway leading to obesity among women of childbearing age. The objective of this study was to examine predictors of moderate (1-10 pounds) and high (>10 pounds) postpartum weight retention using data from a prospective pregnancy cohort that followed women into the postpartum period; n = 688 and 550 women at 3 and 12 months, respectively. Analysis included descriptive statistics and predictive modeling using log-binomial techniques. The average weight retained at 3 and 12 months postpartum in this population was 9.4 lb (s.d. = 11.4) and 5.7 lb (s.d. = 13.2), respectively. At 3 months postpartum, prepregnancy weight, gestational weight gain, and hours slept during the night were associated with moderate or high weight retention, whereas having an infant hospitalized after going home and scoring in the upper 75th percentile of the Eating Attitudes Test (EAT) were associated only with high weight retention. At 12 months postpartum, prepregnancy weight, gestational weight gain, and maternal education were associated with moderate weight retention; and gestational weight gain, maternal age, race, employment status, and having an infant hospitalized at birth were associated with high weight retention. The results of this study illustrate the importance of prepregnancy weight and gestational weight gain in predicting postpartum weight retention. Furthermore, given the lack of successful intervention studies that exist to date to help women lose weight in the postpartum period, the results of this study may help to inform future interventions that focus on such aspects as hours of sleep, dealing with stress associated with a hospitalized infant, and nonclinical eating disorder symptomatology.
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Affiliation(s)
- Anna Maria Siega-Riz
- Department of Nutrition, University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina, USA.
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Battelli C, Blaszyk H, Carrier K, Lucas L, Florman JE, Emery IF. Molecular predictors of chemotherapy response in high-grade gliomas. J Clin Oncol 2010. [DOI: 10.1200/jco.2010.28.15_suppl.e12505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Evenson KR, Moos MK, Carrier K, Siega-Riz AM. Perceived barriers to physical activity among pregnant women. Matern Child Health J 2008; 13:364-75. [PMID: 18478322 DOI: 10.1007/s10995-008-0359-8] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Accepted: 04/29/2008] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Physical activity generally declines during pregnancy, but barriers to activity during this time period are not well understood. The objective was to examine barriers to physical activity in a large cohort of pregnant women and to explore these barriers in more depth with qualitative data derived from a separate focus group study using a socioecologic framework. METHOD A total of 1535 pregnant women (27-30 weeks' gestation) enrolled in the Pregnancy, Infection, and Nutrition Study were asked an open-ended question about their primary barrier to physical activity; responses were coded into categories according to the socioecologic framework. To further elucidate, 13 focus groups of a total of 58 pregnant women (20-37 weeks' gestation) were conducted among Hispanic, African American, and White participants. RESULTS Among the 1535 pregnant women participating in the survey, 85% reported an intrapersonal barrier to physical activity, of which almost two-thirds were health related. Only 2% of the women reported their main barrier to physical activity as interpersonal and 3% reported a neighborhood or environmental barrier. These results were supported by the focus group data, overall and by race/ethnicity and body mass index. Although women discussed barriers to physical activity at a variety of levels, the intrapersonal level was the most frequently cited and discussed factor in both studies. CONCLUSIONS Since pregnancy may trigger the development of obesity and since physical activity is recommended for healthy pregnant women, it is imperative to promote physical activity in a more relevant way. These quantitative and qualitative studies revealed many barriers to physical activity among pregnant women and some suggestions for interventions.
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Affiliation(s)
- Kelly R Evenson
- Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, 137 East Franklin Street, Bank of America Center, Suite 306, Chapel Hill, NC 27514, USA.
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Carrier K, Hans F, Sanfaçon H. Mutagenesis of amino acids at two tomato ringspot nepovirus cleavage sites: effect on proteolytic processing in cis and in trans by the 3C-like protease. Virology 1999; 258:161-75. [PMID: 10329578 DOI: 10.1006/viro.1999.9729] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tomato ringspot nepovirus (ToRSV) encodes two polyproteins that are processed by a 3C-like protease at specific cleavage sites. Analysis of ToRSV cleavage sites identified previously and in this study revealed that cleavage occurs at conserved Q/(G or S) dipeptides. In addition, a Cys or Val is found in the -2 position. Amino acid substitutions were introduced in the -6 to +1 positions of two ToRSV cleavage sites: the cleavage site between the protease and putative RNA-dependent RNA polymerase, which is processed in cis, and the cleavage site at the N-terminus of the movement protein, which is cleaved in trans. The effect of the mutations on proteolytic processing at these sites was tested using in vitro translation systems. Substitution of conserved amino acids at the -2, -1, and +1 positions resulted in a significant reduction in proteolytic processing at both cleavage sites. The effects of individual substitutions were stronger on the cleavage site processed in trans than on the one processed in cis. The cleavage site specificity of the ToRSV protease is discussed in comparison to that of related proteases.
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Affiliation(s)
- K Carrier
- Department of Botany, The University of British Columbia, 3529-6270 University Boulevard, Vancouver, British Columbia, V6T 1Z4, Canada
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Wang A, Carrier K, Chisholm J, Wieczorek A, Huguenot C, Sanfa ßon H. Proteolytic processing of tomato ringspot nepovirus 3C-like protease precursors: definition of the domains for the VPg, protease and putative RNA-dependent RNA polymerase. J Gen Virol 1999; 80 ( Pt 3):799-809. [PMID: 10092022 DOI: 10.1099/0022-1317-80-3-799] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tomato ringspot nepovirus (TomRSV) RNA-1 encodes a putative NTP-binding protein (NTB), a putative viral genome-linked protein (VPg), a putative RNA-dependent RNA polymerase (Pol) and a serine-like protease (Pro), which have been suggested to be involved in viral RNA replication. Proteolytic processing of protease precursors containing these proteins was studied in Escherichia coli and in vitro. The TomRSV protease could cleave the precursor proteins and release the predicted mature proteins or intermediate precursors. Although processing was detected at all three predicted cleavage sites (NTB-VPg, VPg-Pro and Pro-Pol), processing at the VPg-Pro cleavage site was inefficient, resulting in accumulation of the VPg-Pro intermediate precursor in E. coli and in vitro. In addition, the presence of the VPg sequence in the precursor resulted in increased cleavage at the Pro-Pol cleavage site in E. coli and in vitro. Direct N-terminal sequencing of the genomic RNA-linked VPg, of the mature protease purified from E. coli extracts and of radiolabelled mature polymerase purified from in vitro translation products revealed the sequences of the NTB-VPg, VPg-Pro and Pro-Pol dipeptide cleavage sites to be Q/S, Q/G and Q/S, respectively. In vitro processing at the NTB-VPg and Pro-Pol cleavage sites was not detected upon mutation or deletion of the conserved glutamine at the -1 position of the cleavage site. These results are discussed in light of the cleavage site specificity of the TomRSV protease.
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Laganière S, Davies RF, Carignan G, Foris K, Goernert L, Carrier K, Pereira C, McGilveray I. Pharmacokinetic and pharmacodynamic interactions between diltiazem and quinidine. Clin Pharmacol Ther 1996; 60:255-64. [PMID: 8841148 DOI: 10.1016/s0009-9236(96)90052-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES To examine the pharmacokinetic and pharmacodynamic interactions between quinidine and diltiazem because both drugs can inhibit drug metabolism. METHODS Twelve fasting, healthy male volunteers (age, 24 +/- 5 years; weight, 75 +/- 10 kg) received a single oral dose of diltiazem (60 mg) or quinidine (200 mg), alone and on a background of the other drug, in a crossover study. Background treatment consisted of 100 mg quinidine twice a day or 90 mg sustained-release diltiazem twice a day for 2 day before the study day. RESULTS Pretreatment with diltiazem significantly (p < 0.05) increased the area under the curve of quinidine from 7414 +/- 1965 to 11,213 +/- 2610 ng.hr/ml and increased its terminal elimination half-life (t1/2) from 6.8 +/- 1.1 to 9.3 +/- 1.5 hours. Its oral clearance was decreased from 0.39 +/- 0.1 to 0.25 +/- 0.1 L/hr/kg, whereas the maximal concentration was not significantly affected. Diltiazem disposition was not significantly affected by pretreatment with quinidine. Diltiazem pretreatment increased QTc and PR intervals and decreased heart rate and diastolic blood pressure. No significant pharmacodynamic differences were shown for diltiazem alone versus quinidine pretreatment. CONCLUSION Diltiazem significantly decreased the clearance and increased the t1/2 of quinidine, but quinidine did not alter the kinetics of diltiazem with the dose used. No significant pharmacodynamic interaction was shown for the combination that would not be predicted from individual drug administration.
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Affiliation(s)
- S Laganière
- Bureau of Drug Research, Health Protection Branch, Health Canada, Ottawa, Ontario, Canada
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Carignan G, Carrier K, Laganière S, Lessard M. Simultaneous determination of diltiazem and quinidine in human plasma by liquid chromatography. J Chromatogr B Biomed Appl 1995; 672:261-9. [PMID: 8581132 DOI: 10.1016/0378-4347(95)00230-g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A novel method for simultaneous determination of diltiazem and quinidine in human plasma is described. Plasma is alkalinized and extracted with methyl tert.-butyl ether. The ether phase is separated and evaporated. The residue is reconstituted in 0.2 ml of mobile phase containing 56 mM octanesulfonic acid then washed twice with n-hexane. Aliquots are chromatographed on a silanol-deactivated reversed-phase column using a mobile phase containing aqueous H2SO4 (0.01 M, pH 2)-methanol-acetonitrile (45:45:10) and 10 mM octanesulfonic acid. Peaks are monitored with a UV detector set at 237 nm and a fluorescence detector using an excitation set at 247 nm and a 270 nm UV cut-off filter at the emission. Calibration and standard curves were linear from 1 to 130 ng on-column for diltiazem and from 2 to 600 ng on-column for quinidine. Limits of quantitation were 2 and 4 ng/ml for diltiazem and quinidine, respectively. Recoveries from spiked plasma were 94.0 to 102.5% (R.S.D. 6.0-11.4%) for diltiazem and 98.5% to 104.1 (R.S.D. 7.7-8.7%) for quinidine over the ranges studied. In vitro stability was studied in spiked plasma samples stored at -80 degrees C for sixteen months. Both diltiazem and quinidine remained within 10% from nominal values. For ex vivo stability at -80 degrees C, a plasma sample obtained from a volunteer 2 h after oral administration of diltiazem (60 mg) was analysed for two days after sampling and eighteen months later. The mean deviation from initial measured was 4.7%.
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Affiliation(s)
- G Carignan
- Health Canada, Health Protection Branch, Bureau of Drug Research, Ottawa, Ontario, Canada
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Abstract
An unidentified metabolite of dimetridazole (DMZ), found in pig plasma, muscle and kidney, was shown by chromatography and spectroscopy to be 2-methyl-5-nitroimidazole (2-MNI), resulting from N-demethylation of DMZ. This route of degradation competes with the oxidation pathway previously described. The concentration of 2-MNI in the plasma of pig fed medicated diet (DMZ 0.0125%) ranged from 29 to 83 ppb, 2 hours after the morning meal, similar to DMZ, but lower than that of the major metabolite, 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI). Its elimination profile in plasma was biphasic, similar to those of HMMNI and DMZ. Early and terminal half lives were 2.6 and 9.1 h respectively. None of the metabolites could be detected in any of the tissues studied 49 hours after withdrawal.
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Affiliation(s)
- G Carignan
- Drug Residues Section, Bureau of Drug Research, Health and Welfare Canada, Ottawa, Ontario
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Beaubien AR, Ormsby E, Bayne A, Carrier K, Crossfield G, Downes M, Henri R, Hodgen M. Evidence that amikacin ototoxicity is related to total perilymph area under the concentration-time curve regardless of concentration. Antimicrob Agents Chemother 1991; 35:1070-4. [PMID: 1929245 PMCID: PMC284288 DOI: 10.1128/aac.35.6.1070] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Previous studies have failed to fully establish whether ototoxicity is related in any way to the levels of an aminoglycoside antibiotic in the perilymph. To study this we exposed guinea pigs to continuously infused amikacin at four different dosing rates under conditions parallel to those used in our previous study which related ototoxicity to total plasma area under the concentration-time curve regardless of the level in plasma. It was found that at all dosing rates, levels in the perilymph and ratios of levels in perilymph/plasma remained constant as the dosing duration increased from nonototoxic to strongly ototoxic. Plasma and perilymph amikacin levels were found to be linear functions of the dosing rate even at ototoxic dosing exposures, and ratios of levels in perilymph/plasma did not differ between dosing rates. The total perilymph area under the concentration-time curve was not different between dosing rates either for a total dose associated with threshold ototoxicity or for one associated with severe ototoxicity. The results suggest that amikacin ototoxicity is related to the integral of the concentration in the perilymph over the total time of amikacin exposure regardless of the level in the perilymph.
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Affiliation(s)
- A R Beaubien
- Drug Toxicology Division, Health Protection Branch, Ottawa, Ontario, Canada
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Carignan G, Carrier K. Quantitation and confirmation of sulfamethazine residues in swine muscle and liver by LC and GC/MS. J Assoc Off Anal Chem 1991; 74:479-82. [PMID: 1874691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The present paper describes a liquid chromatographic (LC) method for purification of crude swine tissue extracts before gas chromatographic/mass spectrometric (GC/MS) quantitation and confirmation of sulfamethazine at low ppb levels. Fractions corresponding to sulfamethazine were collected, evaporated to dryness, N-methylated with diazomethane, concentrated, and analyzed by GC/MS. A mass spectrometer was set to selected ion monitoring (SIM) mode. Ions 233, 227, 228, and 92 m/z were detected. Ratio 227/233 m/z (sulfamethazine/internal standard, [phenyl 13C6] sulfamethazine) was used for quantitation, while ratios 228/227 and 92/227 m/z, respectively, were used for confirmation. Quantitation in spiked blank muscle tissue was tested from 100 to 1 ppb and found acceptable at all concentrations studied; coefficients of variations ranged from 4.9 to 14.4%. Similar results were obtained for liver tissue from 5 to 20 ppb; coefficients of variation ranged from 1.2 to 9.1%.
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Affiliation(s)
- G Carignan
- Health and Welfare Canada, Bureau of Drug Research, Ottawa, Ontario
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13
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Beaubien AR, Desjardins S, Ormsby E, Bayne A, Carrier K, Cauchy MJ, Henri R, Hodgen M, Salley J, St Pierre A. Delay in hearing loss following drug administration. A consistent feature of amikacin ototoxicity. Acta Otolaryngol 1990; 109:345-52. [PMID: 2360443 DOI: 10.3109/00016489009125154] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The time course of threshold increase in the VIII nerve compound action potential was studied in guinea pigs following amikacin administration at four different constant infusion rates. Despite the wide range of dosing durations required to achieve drug ototoxicity (2-24 days), the full development of both high and low frequency hearing loss was invariably found to be delayed with respect to the time of drug removal. The greatest degree of delayed hearing loss generally occurred within the first 7 days after drug removal, with smaller losses occurring during later time intervals. The delay showed a tendency to decrease as the ototoxic dose was increased. Using the data from the two highest dosing rates, it was estimated that a minimum of 4 days had to elapse before any hearing loss could be detected, once an ototoxic amount of drug had been administered. These data suggest that hearing loss is always substantially delayed with respect to the receipt of an ototoxic dose of amikacin, and that this must be taken into account when conducting animal experiments and when monitoring hearing in patients for the early detection of ototoxicity.
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Affiliation(s)
- A R Beaubien
- Drug Toxicology Division, Health Protection Branch, Frederick G. Banting Building, Ottawa, Ontario, Canada
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Beaubien AR, Desjardins S, Ormsby E, Bayne A, Carrier K, Cauchy MJ, Henri R, Hodgen M, Salley J, St Pierre A. Incidence of amikacin ototoxicity: a sigmoid function of total drug exposure independent of plasma levels. Am J Otolaryngol 1989; 10:234-43. [PMID: 2764235 DOI: 10.1016/0196-0709(89)90002-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A sigmoid curve was found to closely describe the relationship between the incidence of amikacin ototoxicity (greater than or equal to 15 dB hearing loss at a given frequency) and either (1) total dose, or (2) the area under the curve (AUC) describing plasma drug concentration v time over the total period of amikacin administration (total AUC) in continuously infused guinea pigs. Total dose or total AUC estimates of the drug exposure required to produce ototoxicity in 50% of the animals (ED50s) were not significantly different over an eight-fold range of dosing rates or plasma concentrations. A theoretical explanation for this result is that ototoxicity occurs only when a critical amount of drug is accumulated at the ototoxic site by an essentially unidirectional process with a rate that is slow and linearly related to the extracellular drug concentration. The sigmoid relationships for pooled data were parallel in slope for all hearing frequencies from 2 to 32 kHz, and the ED50s showed a strong negative linear relationship to the log of the hearing frequency over this range. The magnitude of ototoxicity expressed as the number of octaves (frequency ratios of 2) for which hearing loss damage was continuous from 32 kHz downward, was correlated to both total dose (r = .605) and total AUC (r = 0.703). No relationship between ototoxicity and plasma level or dosing rate was found. The extreme steepness of the dose-effect curve for the incidence of ototoxicity greatly amplified the variability between individuals and offers an explanation for the unpredictability of aminoglycoside ototoxicity in human patients. The results indicate that either total dose or total AUC (in cases of highly unpredictable blood levels), and not peak or trough serum levels, should be used as an index of ototoxic risk and that the safety limits of drug exposure should be set conservatively.
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Affiliation(s)
- A R Beaubien
- Drug Toxicology Division, Health Protection Branch, Ottawa, Ontario, Canada
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