Physical Frailty and Risk of Needing Long-Term Care in Community-Dwelling Older Adults: a 6-Year Prospective Study in Japan.

OBJECTIVE: To examine the association between physical frailty and risk of needing long-term care, and compare the predictive value and clinical usefulness of a simple frailty scale (FRAIL) with that of the original Cardiovascular Health Study (CHS) criteria. DESIGN AND SETTING: A 6-year prospective cohort study of community-dwelling older adults in a west Japanese suburban town. PARTICIPANTS: 1,554 older adults aged 65 years and over who were initially free of long-term care needs at baseline. MEASUREMENTS: Physical frailty was defined by the CHS criteria and the FRAIL scale. The onset of needing long-term care was ascertained using national records of certification of long-term care needs. Cox proportional hazard models were used to estimate the association between physical frailty and risk of needing long-term care. Decision curve analysis was performed to compare the clinical usefulness of the two physical frailty criteria. RESULTS: During a median follow-up of 5.8 years, 244 were ascertained as needing long-term care. Baseline physical frailty was significantly associated with elevated risk of needing long-term care, with a multivariable-adjusted hazard ratio (HR) of 2.00 (95% confidence interval [CI], 1.32-3.02) for being frail and 1.50 (95% CI, 1.10-2.03) for being pre-frail as defined by the CHS criteria, compared with being robust (p for trend = 0.001). Similar results were found for physical frailty defined by the FRAIL scale, with a multivariable-adjusted HR (95% CIs) of 2.11 (1.25-3.56) for being frail and 1.73 (1.28-2.35) for being pre-frail vs. being robust (p for trend < 0.001). The two physical frailty criteria had similar net benefits in identifying individuals at high risk for needing long-term care. CONCLUSIONS: Physical frailty is significantly associated with an increased risk of needing long-term care in community-dwelling older adults in Japan. Compared with the original CHS criteria, the simple FRAIL scale has comparable predictive value and clinical usefulness for identifying individuals at risk for needing long-term care.

Physical Frailty Is Associated with Longitudinal Decline in Global Cognitive Function in Non-Demented Older Adults: A Prospective Study.

OBJECTIVES: To assess the relationship between physical frailty and subsequent decline in global cognitive function in the non-demented elderly. DESIGN AND SETTING: A prospective population-based study in a west Japanese suburban town, with two-year follow-up. PARTICIPANTS: Community-dwellers aged 65 and older without placement in long-term care, and not having a history of dementia, Parkinson's disease and depression at baseline, who participated in the cohort of the Sasaguri Genkimon Study and underwent follow-up assessments two years later (N = 1,045). MEASUREMENTS: Global cognitive function was assessed using the Montreal Cognitive Assessment (MoCA). Physical frailty was identified according to the following five components: weight loss, low grip strength, exhaustion, slow gait speed and low physical activities. Linear regression models were used to examine associations between baseline frailty status and the MoCA scores at follow-up. Logistic regression models were used to estimate the risk of cognitive decline (defined as at least two points decrease of MoCA score) according to baseline frailty status. RESULTS: Seven hundred and eight non-demented older adults were included in the final analyses (mean age: 72.6 ± 5.5 years, male 40.3%); 5.8% were frail, and 40.8% were prefrail at baseline. One hundred and fifty nine (22.5%) participants experienced cognitive decline over two years. After adjustment for baseline MoCA scores and all confounders, being frail at baseline was significantly associated with a decline of 1.48 points (95% confidence interval [CI], -2.37 to -0.59) in MoCA scores, as compared with non-frailty. Frail persons were over two times more likely to experience cognitive decline (adjusted odds ratio 2.28; 95% CI, 1.02 to 5.08), compared to non-frail persons. CONCLUSION: Physical frailty is associated with longitudinal decline in global cognitive function in the non-demented older adults over a period of two years. Physically frail older community-dwellers should be closely monitored for cognitive decline that can be sensitively captured by using the MoCA.

Clinical significance of Aspergillus species isolated from respiratory specimens in patients with Mycobacterium avium complex lung disease.

Chronic pulmonary aspergillosis (CPA) is associated with mortality in patients with Mycobacterium avium complex lung disease (MAC-LD). An Aspergillus-positive respiratory specimen often reflects colonization, and thus the clinical significance of Aspergillus isolation in MAC-LD patients is not well understood. The objective of this study was to investigate the clinical characteristics and outcomes of MAC-LD patients in whom Aspergillus was isolated from respiratory specimens. We performed a retrospective review of the medical records of 329 MAC-LD patients. We compared the characteristics and mortality rates between patients with Aspergillus isolation and those without. All Aspergillus species detected from respiratory specimens within the follow-up period were reviewed. Aspergillus was detected in 40 (12.2%) of the 329 patients. There were no significant differences in the clinical characteristics and mortality rates between patients with and without Aspergillus isolation. Among the 40 patients with Aspergillus isolation, 9 (22.5%) developed CPA. CPA was most often caused by A. fumigatus. In the 40 Aspergillus-positive patients, patients with A. fumigatus isolation had a significantly higher mortality rate than those without (P < 0.001). The multivariate Cox proportional hazards model showed older age (P = 0.050), presence of respiratory comorbidities (P = 0.008), hypoalbuminemia (P < 0.001), and isolation of A. fumigatus (P = 0.005) to be prognostic factors for mortality in MAC-LD patients. There was no significant difference in the mortality rates between patients with Aspergillus isolation and those without. However, isolation of A. fumigatus may be associated with poor prognosis in MAC-LD patients.

Clinical significance of the radiological severity score in Mycobacterium avium complex lung disease patients.

SETTING: Practical methods for assessing the radiographic findings of Mycobacterium avium complex lung disease (MAC-LD) have not been established. OBJECTIVE: To identify a correlation between the radiological score and semi-quantitative culture results of respiratory samples, and to assess the prognostic impact of this radiological score in MAC-LD patients. DESIGN: We retrospectively studied 218 MAC-LD patients. Radiographic findings were classified as nodule (N), infiltration shadow (I), cavity (C) and bronchiectasis (E), scored individually according to the area occupied on six lung field divisions, and added to give the radiological severity score. RESULTS: The radiological score positively correlated with the semi-quantitative culture score (P = 0.003). In univariate analysis, the radiological score was a significant negative prognostic factor for overall survival. On multivariate analysis, factors I, C and E were independent negative prognostic factors for overall survival. We compared the prognostic value of the total score of all four factors and the three significant factors (I, C and E) using receiver operating characteristic curve analysis; the corresponding areas under the curves were respectively 0.628 and 0.763 (P < 0.001). CONCLUSIONS: The radiological score correlates with prognosis. The combined score of factors I, C and E may more accurately predict prognosis in MAC-LD patients.

Pharmacokinetics of amoxicillin trihydrate in male Asian elephants (Elephas maximus) following intramuscular administration.

The purpose of this study was to investigate the pharmacokinetic characteristics of amoxicillin (AMX) trihydrate in male Asian elephants, Elephas maximus, following intramuscular administration at two dosages of 5.5 and 11 mg/kg body weight (b.w.). Blood samples were collected from 0.5 up to 72 h. The concentration of AMX in elephant plasma was measured using liquid chromatography electrospray ionization mass spectrometry. AMX was measurable up to 24 h after administration at two dosages. Peak plasma concentration (Cmax ) was 1.20 ± 0.39 µg/mL after i.m. administration at a dosage of 5.5 mg/kg b.w., whereas it was 3.40 ± 0.63 µg/mL at a dosage of 11 mg/kg b.w. A noncompartment model was developed to describe the disposition of AMX in Asian elephants. Based on the preliminary findings found in this research, the dosage of 5.5 and 11 mg/kg b.w. produced drug plasma concentrations higher than 0.25 mg/mL for 24 h after i.m. administration. Thereafter, i.m. administration with AMX at a dosage of 5.5 mg/kg b.w. appeared a more suitable dose than 11 mg/kg b.w. However, more studies are needed to determine AMX clinical effectiveness in elephants.

Polybacterial aetiology and outcomes in patients with community-acquired pneumonia.

SETTING: Community-acquired pneumonia (CAP) is a common cause of morbidity and mortality worldwide. While interactions among bacterial pathogens in the respiratory tract have been studied, the impact of polybacterial aetiology on mortality has not been fully elucidated. OBJECTIVE: To investigate the impact of polybacterial aetiology on mortality, prevalence, microbial patterns and clinical characteristics among CAP patients. DESIGN: Retrospective data analysis. RESULTS: Bacterial aetiology was established in 711 (46.0%) of 1544 enrolled hospitalised CAP patients. Of these, polybacterial aetiology was identified in 89 (12.5%): Streptococcus pneumoniae was the most frequently identified pathogen (n = 55, 61.8%). The most prevalent microbial combination was S. pneumoniae and Haemophilus influenzae (n = 19, 21.3%). Alcoholism and lack of previous antibiotic therapy were independent predictors of polybacterial aetiology. The proportion of patients with severe pneumonia was significantly higher in the polybacterial aetiology group than in the monobacterial group. Multivariate analysis showed that polybacterial aetiology was a predictor of 30-day mortality (OR 2.14, 95%CI 1.07-4.24, P = 0.030), independently of severe pneumonia status, pneumonia severity index, chronic obstructive pulmonary disease and inappropriate empirical therapy. CONCLUSION: Polybacterial CAP tends to advance in severity, and indicates adverse outcomes.

Dispositions and tissue depletion of melamine in ducks.

To evaluate the toxicokinetics and persistence of residues of melamine (MEL) in ducks, MEL was administered intravenously (i.v.) or orally (p.o.) to ducks at a dosage of 5.5 mg/kg body weight. The concentration of MEL in the plasma and various tissues was detected using HPLC equipped with an ultraviolet detector. The plasma concentration of MEL in ducks was determined up to 12 h after both i.v. and p.o. administrations. The average value of elimination half-life (t1/2ß) of MEL was 2.16 ± 0.37 and 2.01 ± 0.56 h after i.v. and p.o. administration, respectively. The absolute p.o. bioavailability was 90.79%. MEL was measurable in the liver and kidney after p.o. administration with maximum levels of 15.80 ± 1.81 and 15.49 ± 2.12 µg/g at 6 h, respectively. The results suggest that most of the administered MEL is efficiently absorbed from the gastro intestinal tract, and it has the ability to distribute into various tissues of the duck.

Impact of bacterial coinfection on clinical outcomes in pneumococcal pneumonia.

The aim of this study was to investigate the influence of bacterial coinfection on patients with pneumococcal pneumonia. We retrospectively analyzed the incidence, clinical features, microbial distributions, and outcomes of patients with bacterial coinfection in a cohort of 433 hospitalized patients with pneumococcal pneumonia. Eighty-five patients (19.6 %) were diagnosed with bacterial coinfection; the most frequent pathogens were Haemophilus influenzae (25 patients, 33.3 %), methicillin-susceptible Staphylococcus aureus (MSSA) (15 patients, 20.0 %), and Moraxella catarrhalis (13 patients, 17.3 %). The CURB-65 score and pneumonia severity index (PSI) were significantly higher in patients with bacterial coinfection (both P < 0.001). In addition, the proportion of patients with bacterial coinfection who met the Infectious Disease Society of America (IDSA)/American Thoracic Society (ATS) severe pneumonia criteria was significantly higher (P < 0.001). Multivariate logistic regression analysis identified three risk factors for bacterial coinfection in patients with pneumococcal pneumonia: alcoholism (odds ratio [OR], 5.12; 95 % confidence interval (95 % CI), 1.60-16.4; P = 0.006), hospitalization for 2 days or more within 90 days preceding admission (OR, 2.02; 95 % CI, 1.03-3.98; P = 0.041), and residence in a nursing home or extended care facility (OR, 3.22; 95 % CI, 1.48-6.97; P = 0.003). Multivariate analysis for 30-day mortality showed that bacterial coinfection was a significant adverse prognostic factor (OR, 2.50; 95 % CI, 1.13-5.53; P = 0.023), independent of IDSA/ATS severe pneumonia, PSI, or healthcare-associated pneumonia. In conclusion, bacterial coinfection may have an adverse impact on severity and outcomes of pneumococcal pneumonia.

Toxicokinetics and absolute oral bioavailability of melamine in broiler chickens.

The objective of this study was to investigate the toxicokinetic characteristics of melamine in broilers due to the limited information available for livestock. Melamine was then administered to broiler chickens at an intravenous (i.v.) or oral (p.o.) dosage of 5.5 mg/kg of body weight, and plasma samples were collected up to 48 h. The concentration of melamine in each plasma sample was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Melamine was measurable up to 24 h after i.v. and p.o. administration. A one-compartment model was developed to describe the toxicokinetics of melamine in broilers. Following i.v. administration, the values for the elimination half-life (t(1/2ß)), the volume of distribution (Vd ), and the clearance (CL) were 4.42 ± 1.02 h, 00.52 ± 0.18 L/kg, and 0.08 ± 0.01 L/h/kg, respectively. The absolute oral bioavailability (F) was 95.63 ± 3.54%. The results suggest that most of the administered melamine is favorably absorbed from the alimentary tract and rapidly cleared by the kidneys in broiler chickens.

Excitation-photon-energy selectivity of photoconversions in halogen-bridged Pd-chain compounds: Mott insulator to metal or charge-density-wave state.

Ultrafast photoinduced transitions of a one-dimensional Mott insulator into two distinct electronic phases, metal and charge-density-wave (CDW) state, were achieved in a bromine-bridged Pd-chain compound [Pd(en)2Br](C5-Y)2H2O (en=ethylenediamine and C5-Y=dialkylsulfosuccinate), by selecting the photon energy of a femtosecond excitation pulse. For the resonant excitation of the Mott-gap transition, excitonic states are generated and converted to one-dimensional CDW domains. For the higher-energy excitation, free electron and hole carriers are produced, giving rise to a transition of the Mott insulator to a metal. Such selectivity in photoconversions by the choice of initial photoexcited states opens a new possibility for the developments of advanced optical switching and memory functions.

Impact of seafood regulations for Vibrio parahaemolyticus infection and verification by analyses of seafood contamination and infection.

Consumption of seafood contaminated with Vibrio parahaemolyticus causes foodborne infections, which are on the rise owing to increased consumption of raw seafood in Asia, Europe, North America, and other regions. V. parahaemolyticus infections have been common in Japan since the 1960s. Following an epidemic in 1997, the Japanese Ministry of Health, Labour, and Welfare instituted regulations for seafood in 1999, which appear to be reducing V. parahaemolyticus infections. In this review, we describe the scientific findings for these regulations. Analyses of the V. parahaemolyticus serotypes and isolate characteristics in samples from infected patients and contaminated seafood are discussed. In addition, based on the results of a survey, we show that new food safety regulations have led to improvements in food hygiene at many seafood retail shops, food service facilities, and restaurants. This example from Japan could be of immense help to control foodborne infections in other countries.

Efficacy of neoadjuvant chemotherapy followed by radical hysterectomy in locally advanced non-squamous carcinoma of the uterine cervix: a retrospective multicenter study of Tohoku Gynecologic Cancer Unit.

OBJECTIVE: Radical hysterectomy (RH) is a standard treatment for locally advanced non-squamous cell carcinoma (N-SCC) of the uterine cervix, but there have been no reports on whether neoadjuvant chemotherapy (NAC) followed by radical hysterectomy could improve the outcome of patients with this disease. MATERIALS AND METHODS: This multicenter retrospective study enrolled 77 patients with Stage IB2 to IIB N-SCC of the uterine cervix. Of these, 27 patients were treated with NAC prior to radical hysterectomy (NAC group) and 50 with RH alone (RH group). The two-year recurrence-free survival (RFS) rate, progression-free survival (PFS), and overall survival (OS) were compared between the two groups. Clinical parameters such as clinical stage, histological type, and postoperative treatment were also examined between the groups. RESULTS: While the two-year RFS rates were 81.5% and 70.0% in NAC and RH groups, respectively (p = 0.27) and the median PFS was 51 months and 35 months in NAC and RH groups, respectively (p = 0.35), the median OS was 58 months and 48 months in NAC and RH groups, respectively, which was significant (p = 0.0014). The median OS of patients with mucinous adenocarcinoma in NAC group was significantly higher than that in RH group: 58 months versus 37 months (p = 0.03). CONCLUSION: NAC prior to RH may offer the prognostic advantage of patients with locally advanced N-SCC of the uterine cervix, especially mucinous adenocarcinoma.

Simulation of deoxynivalenol intake from wheat consumption in Japan using the Monte Carlo method.

The aim of this study was to evaluate the current advisory level in Japan for deoxynivalenol (DON) in foods. To this end, we estimated the intake of DON based on its presence in wheat using a probabilistic computer simulation method. Values for the concentration of DON in wheat were based on those reported in surveys of 638 wheat samples conducted from 2002 to 2004. Data regarding consumption of 108 wheat-based products according to age group were obtained from the 2002 Japan national survey on food consumption. Two data sets on the consumption of wheat-based products and contamination of DON in wheat were analysed using three DON regulatory scenarios: no regulation, 1100 µg kg(-1) and 2000 µg kg(-1). Because consumption distributions contained two peaks for each age category, it was assumed that two log-normal distributions for each age category were needed to achieve a better fit to the distribution models. The results of simulated DON intake using the Monte Carlo method showed that children aged 1-6 years have the highest DON intake. However, the 95th percentile of simulated intake of DON in each age group was below the provisional maximum tolerable daily intake (TDI) of 1 µg kg(-1) body weight using any regulation scenario. The 99th percentile of simulated DON intake in the 1-6-year-old group was greater than TDI at approximately 2 µg kg(-1) body weight. These results suggest that the current dietary intake of DON from wheat consumption does not exert a significant health effect, but we may need to reconsider the current regulation value for the 1-6-year-old age group. In addition, we may need a better method to fit the distribution to the log-normal distribution better.

Rapid and effective DNA extraction method with bead grinding for a large amount of fungal DNA.

To identify a rapid method for extracting a large amount of DNA from fungi associated with food hygiene, extraction methods were compared using fungal pellets formed rapidly in liquid media. Combinations of physical and chemical methods or commercial kits were evaluated with 3 species of yeast, 10 species of ascomycetous molds, and 4 species of zygomycetous molds. Bead grinding was the physical method, followed by chemical methods involving sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB), and benzyl chloride and two commercial kits. Quantity was calculated by UV absorbance at 260 nm, quality was determined by the ratio of UV absorbance at 260 and 280 nm, and gene amplifications and electrophoresis profiles of whole genomes were analyzed. Bead grinding with the SDS method was the most effective for DNA extraction for yeasts and ascomycetous molds, and bead grinding with the CTAB method was most effective with zygomycetous molds. For both groups of molds, bead grinding with the CTAB method was the best approach for DNA extraction. Because this combination also is relatively effective for yeasts, it can be used to extract a large amount of DNA from a wide range of fungi. The DNA extraction methods are useful for developing gene indexes to identify fungi with molecular techniques, such as DNA fingerprinting.

Exposure to aflatoxins in Japan: risk assessment for aflatoxin B1.

The intake of total aflatoxins (AFT) and aflatoxin B(1) (AFB(1)) from food in Japan was estimated from AFT and AFB(1) concentration and frequency data in 24 foods (884 samples) from a 3-year retail market survey from the summer of 2004 to the winter of 2006, and by food consumption data from the National Health and Nutrition Survey performed in 2005. The AFT and AFB(1) survey revealed that peanut, peanut products, cocoa, chocolate, pistachio, white pepper, red pepper, almond, job's tears, buckwheat and corn grits are considered to be contributors of AFT (or AFB(1)) intake in Japan (maximum AFB(1) (AFT) levels ranged from 0.21 to 28.0 microg kg(-1) (from 0.21 to 9.0 microg kg(-1))) in AFT-contaminated food. A probabilistic approach using the Monte Carlo method was carried out to simulate an estimate of the AFT (or AFB(1)) intake distributions in each age group in Japan. In this study, AFB(1) intake ranged from 0.003 to 0.004 ng kg(-1) body weight day(-1) (from lower to upper limits), and the potential risk for cancer using a formula devised by the Joint Food and Agricultural Organization/World Health Organization (FAO/WHO) Expert Committee on Food Additives (JECFA) was estimated at 0.00004-0.00005 person/year/100,000 persons, even though this was in the higher levels (95.0th percentile) of the consumer population. The results suggest that the current dietary intake of AFB(1) in Japan has no appreciable effect on health.

Brain-derived neurotrophic factor treatment increases the skeletal muscle glucose transporter 4 protein expression in mice.

The purpose of the present study was to investigate whether peripheral brain-derived neurotrophic factor (BDNF) treatment induced metabolic adaptations in mouse skeletal muscle. BDNF (20 mg/kg/day) was injected subcutaneously for successive 14 days. BDNF treatment significantly reduced the total food intake and inhibited the weight gain in comparison to the control group. The glucose transporter 4 (GLUT4) protein expression in the gastrocnemius muscle was significantly increased by BDNF treatment in comparison to the control and pair-fed groups. Neither the oxidative nor the glycolytic enzyme activities in the gastrocnemius muscle changed after the BDNF treatment. These results suggest that the peripheral BDNF treatment promotes the skeletal muscle GLUT4 protein expression as well as hypophagia.

The toxic effects and fate of intravenously administered zearalenone in goats.

To clarify the toxic effects and fate of zearalenone (ZEA) in ruminants, we studied histopathological changes and toxicokinetic profiles in goats administered with a single intravenous (iv) injection of ZEA at doses of 2.4 mg/kg bw and 1.2 mg/kg bw, respectively. The expression of the mRNA of estrogen receptor (ER) alpha and beta in tissues was also investigated. The histopathological study revealed that ZEA caused hepatocellular swelling and lymphocytic infiltration in the liver, kidney, and uterus. The expression of ERalpha mRNA was enhanced by ZEA in association with the histopathological changes, indicating the possible involvement of ERalpha in the toxic effects of ZEA. For toxicokinetic profiles, blood plasma, urine, and feces were collected consecutively after iv injection of ZEA and analyzed for ZEA and its metabolites with high performance liquid chromatography (HPLC). alpha-Zearalenol (ZOL) and beta-ZOL were detected with ZEA, but alpha-zearalanol (ZAL), beta-ZAL, and zearalanone were below the detection limits. The distribution half-life (t(1/2alpha)) and elimination half-life (t(1/2beta)) of ZEA were 3.15 and 28.58h, respectively. ZEA, alpha-ZOL, and beta-ZOL were excreted in urine and feces, with beta-ZOL being the predominant metabolite. The ZEA and ZOL in urine were largely in their glucuronide and/or sulphate conjugated forms, while those in feces were largely in their free forms. This study showed the toxic effect of zearalenone and its metabolites, and their pharmacokinetic characteristics in goats.

Impact of smoking as a risk factor for developing rheumatoid arthritis: a meta-analysis of observational studies.

OBJECTIVES: To assess whether smoking is a risk factor for developing rheumatoid arthritis (RA). DESIGN: Meta-analysis. DATA SOURCES: were observational studies that examined the association between smoking history and the risk of developing RA identified through Medline and EMBASE (from 1966 to December 2006), relevant books and a reference search. Two authors independently extracted the following: authors' names, publication year, sample size, participant characteristics, odds ratios (OR) or relative risks, adjustment factors, study design and area where the study was conducted. Data syntheses were based upon random effects model. Summarised syntheses effects were expressed by OR. RESULTS: Sixteen studies were selected from among 433 articles. For men, summary OR for ever, current and past smokers were 1.89 (95% CI 1.56 to 2.28), 1.87 (1.49 to 2.34) and 1.76 (1.33 to 2.31), respectively. For rheumatoid factor-positive (RF+) RA, summary OR for ever, current and past smokers were 3.02 (2.35 to 3.88), 3.91 (2.78 to 5.50) and 2.46 (1.74 to 3.47), respectively. Summary OR for 20 or more pack-years of smoking was 2.31 (1.55 to 3.41). For women, summary OR for ever, current and past smokers were 1.27 (1.12 to 1.44), 1.31 (1.12 to 1.54) and 1.22 (1.06 to 1.40), respectively. For RF+ RA, summary OR for ever, current and past smokers were 1.34 (0.99 to 1.80), 1.29 (0.94 to 1.77) and 1.21 (0.83 to 1.77). Summary OR for 20 or more pack-years of smoking was 1.75 (1.52 to 2.02). CONCLUSION: Smoking is a risk factor for RA, especially RF+ RA men and heavy smokers.

Dispositions and residue depletion of enrofloxacin and its metabolite ciprofloxacin in muscle tissue of giant freshwater prawns (Macrobrachium rosenbergii).

Fates and residue depletion of enrofloxacin (ER) and its metabolite ciprofloxacin (CP) were examined in giant freshwater prawns, Macrobrachium rosenbergii, following either single oral (p.o.) administration of ER at a dosage of 10 mg/kg body weight (b.w.) or medicated-feed treatment at the feeding concentration of 5 g/kg of feed for five consecutive days. The concentrations of ER and CP in prawn muscle tissues were measured simultaneously using high-performance liquid chromatography (HPLC) equipped with a fluorescence detector. Muscle tissue concentrations of ER and CP were below the detection limit (LOD, 0.015 microg/g for ER; 0.025 microg/g for CP) after 360 and 42 h, following single p.o. administration respectively. Peak muscle concentration (C(max)) of ER was 1.98 +/- 0.22 microg/g whereas CP was measurable at concentrations close to the detection limit of the analytical method after p.o. administration at a single dosage of 10 mg/kg b.w. The concentration of ER in prawn muscle tissue with respect to time was analyzed with a non-compartmental pharmacokinetic model. The elimination half-life and area under the curve of ER were 39.33 +/- 7.27 h and 168.7 +/- 28.7 microg x h/g after p.o. administration at a single dose of 10 mg/kg x b.w. respectively. In medicated-feed treated group, ER was detectable in prawn muscle tissue 11 days postdosing at the dose of 5 g/kg of feed for five consecutive days, which is the value corresponding to the maximum residue limit (MRL) of ER in animal products. The maximum concentrations of ER and CP were 2.77 +/- 0.91 and 0.06 +/- 0.006 microg/g during medicated-feed treatment and postdosing respectively. The values of elimination half-life and absorption half-life of ER after single p.o. administration at a dosage of 10 mg/kg b.w. corresponded well with the values determined from medicated-feed treated group, showing 41.01 +/- 6.62 and 11.36 +/- 3.15 h respectively in M. rosenbergii. Based on data derived from this study, to avoid the ER residue in prawn muscle, it should take at least 11 days postcessation of medicated feed containing ER at the dose concentration of 5 g/kg of feed twice a day at a rate of 1% of total body weight for five consecutive days to wash out the drug from the muscle of M. rosenbergii.