Displaying publications 21 - 40 of 72 in total

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  1. Fulltext Comparative bioavailability study of two ketoconazole tablet preparations
    Yuen KH, Wong JW, Billa N, Choy WP, Julianto T
    Med J Malaysia, 1999 Dec;54(4):482-6.
    PMID: 11072466
    The bioavailability of a generic preparation of ketoconazole (Zorinax from Xepa-Soul Pattinson, Malaysia) was evaluated in comparison with the innovator product (Nizoral from Janssen Pharmaceutica, Switzerland). Eighteen healthy male volunteers participated in the study conducted according to a two-way crossover design. The bioavailability was compared using the parameters, total area under the plasma concentration-time curve (AUC0-infinity), peak plasma concentration (Cmax) and time to reach peak plasma concentration (Tmax). No statistically significant difference was observed between the values of the two products in all the three parameters. Moreover, the 90% confidence interval for the ratio of the logarithmic transformed AUC0-infinity and Cmax values of Zorinax over Nizoral was found to lie between 0.82-1.04 and 0.83-1.02, respectively, being within the acceptable equivalence limit of 0.80-1.25. These findings indicate that the two preparations are comparable in the extent and rate of absorption. In addition, the elimination rate constant (ke) and apparent volume of distribution (Vd) were calculated. For both parameters, there was no statistically significant difference between the values obtained from the data of the two preparations. Moreover, the values are comparable to those reported in the literature.
  2. Bioequivalence of a generic metformin tablet preparation
    Yuen KH, Wong JW, Billa N, Julianto T, Toh WT
    Int J Clin Pharmacol Ther, 1999 Jul;37(7):319-22.
    PMID: 10442505
    The bioavailability of a generic preparation of metformin (Diabetmin from Hovid Sdn Bhd) was evaluated in comparison with a proprietary product (Glucophage from Lipha Pharma Ltd., UK).
  3. Glutathione S transferase-theta (GSTT1) genetic polymorphism among Chinese, Malays and Indians in Singapore
    Lee EJ, Wong JY, Yeoh PN, Gong NH
    Pharmacogenetics, 1995 Oct;5(5):332-4.
    PMID: 8563775
    Glutathione S-transferase-theta (GSTT1) is subject to a genetic polymorphism where approximately 50% of a Caucasian population are homozygous for the null allele. Because of the possible association of the polymorphism with increased cancer risk in individuals, we genotyped by polymerase chain reaction 187 normal Chinese, 167 normal Malays and 152 normal Indians from Singapore and Malaysia. The proportion of Chinese, Malays and Indians with the null genotype were 58%, 38% and 16% respectively and mirrored previously reported frequencies of the GSTM1 null genotype in these populations. The frequency of the combined GSTM1 and GSTT1 null genotypes among Chinese, Malays and Indians were 37%, 22% and 5% respectively. The similarity with predicted frequencies indicated no interaction between the two genetic polymorphisms.
  4. Frequency of mutant CYP1A1, NAT2 and GSTM1 alleles in normal Indians and Malays
    Zhao B, Lee EJ, Wong JY, Yeoh PN, Gong NH
    Pharmacogenetics, 1995 Oct;5(5):275-80.
    PMID: 8563767
    Several xenobiotic metabolizing enzymes, including CYP1A1, NAT2 and GSTM1, are subject to genetic polymorphisms. Because these enzymes are important for the detoxification and/or bioactivation of drugs and carcinogens, these polymorphisms have important implications in therapeutics and cancer susceptibility. The distributions of CYP1A1, NAT2 and GSTM1 genotype frequencies in unrelated individuals of the Indian (n = 139) and Malay (n = 146) populations were characterized by the polymerase chain reaction. The respective allelic frequencies of wild-type and mutant alleles of CYP1A1 were 0.82 and 0.18 for the Indians, and 0.69 and 0.31 for the Malays. The frequencies of wild-type, M1, M2 and M3 of NAT2 among Indians were 0.44, 0.20, 0.32 and 0.04 respectively. The corresponding NAT2 allelic frequencies in Malays were 0.41, 0.12, 0.38 and 0.09. The GSTM1*A allele could not be amplified in 33.1% of Indians and 61.6% of Malays. At least one GSTM1*B allele was detected in 7.2% and 7.5% of the respective populations. The allelic frequencies of CYP1A1, NAT2 and GSTM1 among Malays are similar to previously reported frequencies among Chinese in the region. These findings will be of importance in the determination of cancer risks in these populations.
  5. Diode laser contact transscleral cyclophotocoagulation for refractory glaucoma in Asian patients
    Wong EY, Chew PT, Chee CK, Wong JS
    Am J Ophthalmol, 1997 Dec;124(6):797-804.
    PMID: 9402826
    PURPOSE: To evaluate the effectiveness and safety of diode laser contact transscleral cyclophotocoagulation in Asian patients with refractory glaucoma by lower energy settings with an innovative probe featuring a glass ball tip that focused the laser beam onto the ciliary body.

    METHODS: This prospective clinical study included consecutive Asian patients with dark irides and confirmed for glaucoma. Only one eye of each patient was treated. Diode laser contact transscleral cyclophotocoagulation treatment was performed with the center of the probe placed 1.5 mm behind the limbus. About 30 pulses of 810-mm laser radiation (power, 1.8 to 2.0 W; duration, 0.3 to 0.5 second) were applied around the eye. Patients were examined at fixed postoperative intervals. Intraocular pressure levels and postoperative complications were recorded. The relation between patient and disease characteristics, total laser energy delivered, and intraocular pressure effects were analyzed.

    RESULTS: Thirty-three patients were studied, with a mean follow-up period of 9.4 months. An average 56% of patients showed a 30% or greater drop in intraocular pressure. About 38% of patients achieved sustained intraocular pressure lowering to below 22 mm Hg at 18 months. Complications were few and included transient hypotony and iritis.

    CONCLUSIONS: In Asian patients with refractory glaucoma or painful glaucomatous eyes with poor visual acuity (defined for this study as worse than 20/200), low-energy-setting diode laser contact transscleral cyclophotocoagulation by means of the glass ball probe is relatively effective and safe.

  6. Fulltext The use of radiochromic EBT2 film for the quality assurance and dosimetric verification of 3D conformal radiotherapy using Microtek ScanMaker 9800XL flatbed scanner
    Sim GS, Wong JH, Ng KH
    J Appl Clin Med Phys, 2013 Jul 08;14(4):4182.
    PMID: 23835383 DOI: 10.1120/jacmp.v14i4.4182
    Radiochromic and radiographic films are widely used for radiation dosimetry due to the advantage of high spatial resolution and two-dimensional dose measurement. Different types of scanners, including various models of flatbed scanners, have been used as part of the dosimetry readout procedure. This paper focuses on the characterization of the EBT2 film response in combination with a Microtek ScanMaker 9800XL scanner and the subsequent use in the dosimetric verification of a 3D conformal radiotherapy treatment. The film reproducibility and scanner uniformity of the Microtek ScanMaker 9800XL was studied. A three-field 3D conformal radiotherapy treatment was planned on an anthropomorphic phantom and EBT2 film measurements were carried out to verify the treatment. The interfilm reproducibility was found to be 0.25%. Over a period of three months, the films darkened by 1%. The scanner reproducibility was ± 2% and a nonuniformity was ±1.9% along the direction perpendicular to the scan direction. EBT2 measurements showed an underdose of 6.2% at high-dose region compared to TPS predicted dose. This may be due to the inability of the treatment planning system to predict the correct dose distribution in the presence of tissue inhomogeneities and the uncertainty of the scanner reproducibility and uniformity. The use of EBT2 film in conjunction with the axial CT image of the anthropomorphic phantom allows the evaluation of the anatomical location of dose discrepancies between the EBT2 measured dose distribution and TPS predicted dose distribution.
  7. Simple high-performance liquid chromatographic method for the determination of tocotrienols in human plasma
    Yap SP, Julianto T, Wong JW, Yuen KH
    J Chromatogr B Biomed Sci Appl, 1999 Dec 10;735(2):279-83.
    PMID: 10670741
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of vitamin E especially delta-, gamma- and alpha-tocotrienols in human plasma. The method entailed direct injection of plasma sample after deproteinization using a 3:2 mixture of acetonitrile-tetrahydrofuran. The mobile phase comprised 0.5% (v/v) of distilled water in methanol. Analyses were run at a flow-rate of 1.5 ml/min with the detector operating at an excitation wavelength of 296 nm and emission wavelength of 330 nm. This method is specific and sensitive, with a quantification limit of approximately 40, 34 and 16 ng/ml for alpha-, gamma- and delta-tocotrienol, respectively. The mean absolute recovery values were about 98% while the within-day and between-day relative standard deviation and percent error values of the assay method were all less than 12.0% for alpha-, gamma- and delta-tocotrienol. The calibration curve was linear over a concentration range of 40-2500, 30-4000 and 16-1000 ng/ml for alpha-, gamma- and delta-tocotrienol, respectively. Application of the method in a bioavailability study for determination of the above compounds was also demonstrated.
  8. Automated otolith image classification with multiple views: an evaluation on Sciaenidae
    Wong JY, Chu C, Chong VC, Dhillon SK, Loh KH
    J Fish Biol, 2016 Aug;89(2):1324-44.
    PMID: 27364089 DOI: 10.1111/jfb.13039
    Combined multiple 2D views (proximal, anterior and ventral aspects) of the sagittal otolith are proposed here as a method to capture shape information for fish classification. Classification performance of single view compared with combined 2D views show improved classification accuracy of the latter, for nine species of Sciaenidae. The effects of shape description methods (shape indices, Procrustes analysis and elliptical Fourier analysis) on classification performance were evaluated. Procrustes analysis and elliptical Fourier analysis perform better than shape indices when single view is considered, but all perform equally well with combined views. A generic content-based image retrieval (CBIR) system that ranks dissimilarity (Procrustes distance) of otolith images was built to search query images without the need for detailed information of side (left or right), aspect (proximal or distal) and direction (positive or negative) of the otolith. Methods for the development of this automated classification system are discussed.
  9. Fulltext COVID-19 in Singapore and Malaysia: Rising to the Challenges of Orthopaedic Practice in an Evolving Pandemic
    Tay K, Kamarul T, Lok WY, Mansor M, Li X, Wong J, et al.
    Malays Orthop J, 2020 Jul;14(2).
    PMID: 32313613 DOI: 10.5704/MOJ.2007.001
    With the increasing number of COVID-19 cases and related deaths worldwide, we decided to share the development of this condition in Singapore and Malaysia. First few cases were diagnosed in the two countries at the end of January 2020, and the numbers have surged to thousands by end of March 2020. We will focus on strategies adopted by the government and also the Orthopaedic community of the two countries up till the beginning of April 2020. We hope that by sharing of relevant information and knowledge on how we are managing the COVID-19 condition, we can help other communities, and health care workers to more effectively overcome this pandemic.
  10. Comparative bioavailability study of two controlled-release pentoxifylline tablet preparations
    Yuen KH, Wong JW, Peh KK, Julianto T, Choy WP
    Drug Dev Ind Pharm, 2000 Jul;26(7):803-7.
    PMID: 10872103
    The bioavailability of a generic preparation of pentoxifylline sustained-release (SR) tablet was evaluated in comparison with a proprietary product (Trental 400). For the study, 12 healthy male volunteers participated; the study was conducted according to a randomized, two-way crossover design. The bioavailability was compared using the parameters total area under the plasma level-time curve AUC0-infinity, peak plasma concentration Cmax, and time to reach peak plasma concentration Tmax. No statistically significant difference was observed between the values of the two products in all three parameters. The 90% confidence interval for the ratio of the logarithmic transformed AUC0-infinity values of the generic pentoxifylline over those of Trental 400 was found to lie between 0.83 and 1.00, while that of the parameter Cmax was between 0.91 and 1.29. In addition, elimination half-life t1/2 and apparent volume of distribution Vd were calculated. There was no statistically significant difference between the t1/2 Vd values obtained from the data of the two preparations.
  11. Comparative bioavailability study of two atenolol tablet preparations
    Peh KK, Yuen KH, Wong JW, Toh WT
    Drug Dev Ind Pharm, 1999 Mar;25(3):357-60.
    PMID: 10071830
    A study was conducted to compare the bioavailability of a generic product of atenolol (Normaten FC) with the innovator product, Tenormin. Twelve healthy adult volunteers participated in the study conducted according to a randomized, two-way crossover design. The preparations were compared using area under the plasma concentration-time curve AUC0-infinity, peak plasma concentration Cmax, and time to reach peak plasma concentration Tmax. No statistically significant difference was obtained between the Tmax values and the logarithmic transformed AUC0-infinity and Cmax values of the two products. Moreover, the 90% confidence interval for the ratio of the logarithmically transformed AUC0-infinity values of Normaten FC over those of Tenormin was found to lie between 0.82 and 0.98, while that of the logarithmically transformed Cmax values was between 0.82 and 1.09, both being within the bioequivalence limit of 0.80-1.25. The values of elimination half-life t1/2 between the two products were also found comparable and not significantly different statistically. The t1/2 values obtained in our study were slightly longer than those reported in the literature for other population groups.
  12. Fulltext Differential expression of galectin-3 in advancing thyroid cancer cells: a clue toward understanding tumour progression and metastasis
    Htwe TT, Karim N, Wong J, Jahanfar S, Mansur MA
    Singapore Med J, 2010 Nov;51(11):856-9.
    PMID: 21140111
    INTRODUCTION: Galectin-3 is a member of the beta-galactoside-binding protein family that plays an important role in cell-to-cell adhesion and in cell-to-matrix interaction. Cellular expression of galectin-3 is correlated with cancer aggressiveness and metastasis.
    METHODS: We examined the differential expression of galectin-3 in a collection of 142 cases of thyroid lesions, including 108 cases of papillary thyroid carcinoma (PTC) and 34 cases of follicular carcinoma (FCA). An immunohistochemical method was applied and semiquantitative scoring was performed on the staining intensity of the positive tissue. Scoring was done on cells at the central portion of the tumour foci and on cells at the periphery that were adjacent to the neighbouring normal thyroid tissue matrix.
    RESULTS: A significantly higher expression (p is 0.001) of galectin-3 was observed in the advancing peripheral thyroid cancer cells compared to the centrally located cells that were not in close contact with the neighbouring stromal tissue in cases with PTC compared to those with FCA.
    CONCLUSION: This finding supported the role of galectin-3 in its cell-to-cell adhesion and cell-to-matrix interaction. Galectin-3 is a potential tumour marker for indicating local and distance metastasis, especially in cases with PTC.
  13. Fulltext A case of recurrent respiratory papillomatosis successfully removed via endoscopic argon plasma coagulation (APC) with no evidence of recurrence
    Wong JL, Tie ST, Lee J, Kannan SK, Rashid Ali MR, Ibrahim A, et al.
    Med J Malaysia, 2014 Aug;69(4):195-6.
    PMID: 25500852 MyJurnal
    Recurrent respiratory papillomatosis (RRP) is a benign disease caused by the human papilloma virus (HPV), characterized by the formation of recurrent, epithelial neoplastic lesions in the airways. While benign, they can cause significant airway obstruction in some cases. Difficulties in treatment arise from the recurrent nature of the lesions despite repeated procedures. Other known procedures that result in deep tissue damage also cause unacceptable collateral damage to the underlying airway mucosa. We describe a case of recurrent papillomatosis that was successfully treated with argon plasma coagulation ( APC) when laser and electrocautery ablation had failed in the past. After the papillomatasis was treated with APC, there is no recurrence on repeat scope at 4 months and 9 months after the initial procedure. The procedure was done as a day case and there is no complication from the procedure. The property of the APC that allows it to cause only superficial thermal damage to the tissue makes it a suitable adjunct therapy to the treatment of papillomas, which are usually superficial lesions.
  14. Fulltext Tuberculosis in adults
    Abdul Rahaman JA, Ker HB, Yusof M, Hanafi NS, Wong JL
    Malays Fam Physician, 2014;9(3):34-7.
    PMID: 26425303 MyJurnal
    Tuberculosis (TB) in Malaysia is rising due to multiple factors and issues related to its management are addressed in the updated evidence-based clinical practice guidelines. Screening for active TB should be considered in high risk groups. Light emitting diode-based fluorescence microscopy and nucleic acid amplification tests are recommended investigations. Health education and standardised 6-month daily antituberculosis (antiTB) regimen are among important elements for successful treatment. Latent TB infection screening should only be performed on high risk individuals. AntiTB regimen offered to HIV-positive adults should be the same as for HIV-negative adults and timing to initiate highly active antiretroviral therapy in patients with TB is based on CD4 count. All patients on antiTB treatment should be monitored to assess their response to treatment and to identify problems associated with it.
  15. Fulltext Detailed assessment of nutritional status and eating patterns in children with gastrointestinal diseases attending an outpatients clinic and contemporary healthy controls
    Tsiountsioura M, Wong JE, Upton J, McIntyre K, Dimakou D, Buchanan E, et al.
    Eur J Clin Nutr, 2014 Jun;68(6):700-6.
    PMID: 24424079 DOI: 10.1038/ejcn.2013.286
    BACKGROUND/OBJECTIVES: In the era of modern multidisciplinary clinical management, very little is known about the prevalence and presentation of malnutrition in children with gastrointestinal disorders (GastroD) particularly employing composite, global measures of nutritional status.
    SUBJECTS/METHODS: Anthropometry, body composition, dietary intake, eating habits and grip strength were assessed with bedside methods in 168 patients from outpatient gastroenterology clinics (n, median (IQR) years; Crohn's disease (CD): n=53, 14.2 (11.6:15.4); ulcerative colitis (UC): n=27, 12.2 (10.7:14.2); coeliac disease: n=31, 9.3 (7.5:13.6); other GastroD: n=57, 9.8 (7.2:13.8)) and compared with 62 contemporary healthy controls (n, median (IQR): 9.8 (6.9:13.8)) and the results of the recent UK, National Diet and Nutritional Survey (NDNS).
    RESULTS: Children with CD had lower BMI z-scores than controls (median (IQR): -0.3 (-0.9:0.4) vs 0.3 (-0.6:1.4); P=0.02) but only 2% were classified as thin (BMI z-score
  16. Fulltext Methacholine challenge test as an adjunctive investigative tool in patients with asthma-like symptoms: the Sabah experience
    Siew BTT, Wong JL, Beniyamin A, Ho A, Kannan SKK, Jamalul Azizi AR
    Med J Malaysia, 2012 Apr;67(2):204-6.
    PMID: 22822644 MyJurnal
    INTRODUCTION: Patients with asthma-like symptoms pose a diagnostic dilemma when physical examination is normal. The usual practice in Malaysia would be to give empirical asthma treatment. Bronchial challenge test (BCT) is widely used in many countries to diagnose asthma objectively but it is not widely available in Malaysia.
    OBJECTIVE: To describe our experience with BCT using methacholine at Queen Elizabeth Hospital as a supporting tool in the investigation of patients with asthma-like symptoms.
    METHODOLOGY: Review of case notes of patients who underwent BCT from July 2008 till April 2009. BCT was performed via dosimeter technique. Results were classified as high hyper responsiveness if the provocative dose of methacholine required to achieve 20% fall in FEV1 (PD20) was less than or equal to 0.125 micromol, moderate hyper responsiveness if PD20 was between 0.125 to 1.99 micromol or mild hyper responsiveness if PD20 was between 2.00 to 6.6 micromol. PD20 of more than 6.6 micromol constitutes a negative MCT.
    RESULTS: 29 patients had BCT during the study period. 19 cases were included in this review. The age ranged from 13 to 70 years old. There were 12 males and 7 females. Duration of symptoms ranged from 2 weeks to 23 years. BCT was positive (mild or moderate hyper responsiveness) in 10 out of 19 patients. No patient had high bronchial hyper responsiveness.
    CONCLUSIONS: BCT is a useful adjunctive tool in the investigation of patients presenting with asthma-like symptoms. This test obviates empirical asthma treatment. BCT should be made available in all major hospitals in Malaysia.
  17. Fulltext Comparative bioavailability study of a generic sustained release diclofenac sodium tablet
    Magosso E, Yuen KH, Choy WP, Ling SSN, Ng BH, Ur-Rahman N, et al.
    Med J Malaysia, 2004 Aug;59(3):352-6.
    PMID: 15727381
    The bioavailability of a generic diclofenac sodium sustained release tablet preparation (Zolterol, SR) was compared with the innovator product, Voltaren, SR. Twelve healthy adult male volunteers participated in the study, which was conducted according to a randomized, two-way crossover design with a wash out period of one week. The bioavailability of diclofenac was compared using the parameters area under the plasma concentration-time curve (AUC(0-infinity)), peak plasma concentration (Cmax) and time to reach peak plasma concentration (Tmax). No statistically significant difference was observed for both logarithmically transformed AUC(0-infinity), Cmax values and Tmax value of the two preparations.
  18. Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures
    Safari MJ, Wong JH, Ng KH, Jong WL, Cutajar DL, Rosenfeld AB
    Med Phys, 2015 May;42(5):2550-8.
    PMID: 25979047 DOI: 10.1118/1.4918576
    The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures.
  19. Improved high performance liquid chromatographic analysis of omeprazole in human plasma
    Yuen KH, Choy WP, Tan HY, Wong JW, Yap SP
    J Pharm Biomed Anal, 2001 Feb;24(4):715-9.
    PMID: 11272330
    A simple high-performance liquid chromatographic method was developed for the determination of omeprazole in human plasma. Omeprazole and the internal standard, chloramphenicol, were extracted from alkalinized plasma samples using dichloromethane. The mobile phase was 0.05 M Na2HPO4-ACN (65:35, v/v) adjusted to pH 6.5. Analysis was run at a flow rate of 1.0 ml/min at a detection wavelength of 302 nm. The method was specific and sensitive with a detection limit of 2.5 ng/ml at a signal-to-noise ratio of 4:1. The limit of quantification was set at 5 ng/ml. The calibration curve was linear over a concentration range of 5-1280 ng/ml. Mean recovery value of the extraction procedure was about 96%, while the within and between day coefficient of variation and percent error values of the assay method were all less than 14%.
  20. BRCA1 c.2845insA is a founder mutation in Singaporean Malay women with early onset breast/ovarian cancer
    Sng JH, Ali AB, Lee SC, Zahar D, Wong JE, Cross G, et al.
    Ann Acad Med Singap, 2003 Sep;32(5 Suppl):S53-5.
    PMID: 14968737
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