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Biomedical subjects

T Y Chan

Publications and source records attributed to T Y Chan.

At least 91 records · Page 5Linked to original sources
PubMed1996

Characterization of the antioxidant effects of melatonin and related indoleamines in vitro.

The antioxidant and possible pro-oxidant effects of melatonin and related indoleamines (tryptophan, serotonin, N-acetylserotonin, and 5-methoxytryptamine) were studied in vitro. In two model membrane systems, i.e., phospholipid liposomes and rat erythrocytes, lipid peroxidation induced by Fe2+ and H2O2, respectively, were reduced by the tested indoleamines except for tryptophan. The 5-hydroxy-indoleamines, serotonin, and N-acetylserotonin exhibited pro-oxidant actions in the bleomycin assay by reducing Fe3+ to Fe2+, which leads to DNA damage. The 5-methoxy-indoleamines, melatonin and 5-methoxytryptamine, were devoid of any pro-oxidant actions in this assay. Serotonin, but not N-acetylserotonin, scavenged the superoxide anion. None of the indoleamines tested had any reactivity towards H2O2. All the indoleamines, including tryptophan, were, however, shown to react with hypochlorous acid. These findings support an antiperoxidative and antioxidant action of melatonin which is devoid of pro-oxidant effect on non-lipid substrates.

Animals↗
PubMed1996

The risk of severe salicylate poisoning following the ingestion of topical medicaments or aspirin.

Apart from isolated reports of severe salicylate poisoning after ingesting an unusually large amount of a medicinal oil, there are no published data on the threat arising from attempted suicide with topical medicaments containing methyl salicylate or wintergreen oil compared with aspirin tablets. In this retrospective study, the admission plasma salicylate concentrations and clinical presentations were compared in 80 subjects who had taken aspirin tablets (n = 42) or topical medicaments (n = 38). The proportions of subjects being symptomatic were similar in the two groups. Although the admission plasma salicylate concentrations were generally higher in subjects who had ingested aspirin tablets, the two highest readings (4.3 and 3.5 mmol/1) belonged to two of the subjects who had taken topical medicaments. Because of its liquid, concentrated form and lipid solubility, methyl salicylate poses the threat of severe, rapid-onset salicylate poisoning. The toxic potential of topical medicaments containing methyl salicylate or wintergreen oil should be fully appreciated by both physicians and the general public.

Adolescent↗
PubMed1996

Usage and adverse effects of Chinese herbal medicines.

The great majority of Chinese herbal preparations are safe, and in the past, some useful Western drugs have been derived from these herbs. Nearly all serious poisonings are due to the few preparations containing aconitine, podophyllin or anticholinergics or else proprietary preparations containing dangerous Western drugs or heavy metals. Both medical professionals and the general public should be alerted to the potential toxicity of herbal remedies. There should be frequent monitoring of Chinese herbal medicines or their derivatives, such as some Chinese proprietary medicines, for undeclared Western drugs and heavy metals. Mothers should be discouraged from treating their children with herbal or proprietary medicines. There should be continuing efforts to collect safety information on these widely used products.

Animals↗
PubMed1996

Potential dangers from topical preparations containing methyl salicylate.

Methyl salicylate (oil of wintergreen) is widely available in many over-the-counter liniments, ointments, lotions or medicated oils for the relief of musculoskeletal aches and pains. Ingestion of methyl salicylate poses the threat of severe, rapid-onset salicylate poisoning because of its liquid, concentrated form and lipid solubility. Excessive usage of these preparations in patients receiving warfarin may result in adverse interactions and bleedings. Methyl salicylate in topical analgesic preparations may cause irritant or allergic contact dermatitis and anaphylactic reactions. Physicians should fully appreciate the potential dangers from topical preparations containing methyl salicylate.

Administration, Oral↗
PubMed1996

Pulmonary aspiration following Dettol poisoning: the scope for prevention.

1. After ingestion, Dettol liquid (4.8% chloroxylenol, pine oil, isopropyl, alcohol), a common household disinfectant, can cause central nervous system depression and corrosion of the oral mucosa, larynx and the gastrointestinal tract. The main risk from Dettol poisoning is pulmonary aspiration, leading to pneumonia, adult respiratory distress syndrome (ARDS) and/or sudden cardiorespiratory arrest. 2. To determine to what extent pulmonary aspiration in Dettol poisoning could be prevented, 13 patients treated in a general teaching hospital in Hong Kong were studied. Their clinical details were compared with those of control Dettol poisoning cases without pulmonary aspiration in order to identify possible risk factors for this complication. 3. At presentation, evidence of pulmonary aspiration was present in eight of the 13 patients prior to gastric emptying, but the use of gastric lavage without adequate protection of the airways could have aggravated the problem in three. In two other patients, evidence of aspiration was only present after gastric lavage was performed. The consequences of pulmonary aspiration were pneumonia (n = 10), ARDS (n = 2), acute exacerbation of asthma or chronic obstructive airway disease (n = 2) and sudden cardiorespiratory arrest (n = 1). Three patients with aspiration pneumonia (n = 2), ARDS (n = 1) and/or sudden cardiorespiratory arrest (n = 1) died. 4. Compared with the controls, the median amount of Dettol ingested was considerably larger (400 vs 150 ml), vomiting (100% vs 72.6%) and drowsiness/ confusion (60.2% vs 19.4%) occurred more often. 5. Amongst the 13 patients with Dettol poisoning and pulmonary aspiration, gastric lavage using the nasogastric tube technique without adequate production of the airways had been responsible for the occurrence or worsening of aspiration in two and three patients, respectively. Thus, gastric lavage particularly when using a nasogastric tube appeared to carry more harm than benefits in patients with Dettol poisoning. If the procedure is considered necessary, say because of the concomitant ingestion of the other poisons, the airways must first be well protected and the oropharyngeal aspiration and lavage technique using a wide bore Jacques tube is recommended. 6. Comparison with a control group has identified other risk factors for pulmonary aspiration: the amount of Dettol ingested, the occurrence of vomiting, drowsiness or confusion.

Adult↗
PubMed1996

Utilization of antidiabetic drugs in Hong Kong: relation to the common occurrence of antidiabetic drug-induced hypoglycemia amongst acute medical admissions and the relative prevalence of NIDDM.

Antidiabetic drug-induced hypoglycemia as a cause of acute medical admissions is more common in Hong Kong (1.7%) than in other countries (0.1-0.5%). To determine if this higher incidence may be related to the frequent use of some sulphonylureas, we have studied the overall prescribing patterns in the public sector in 1994 by reviewing the utilization of antidiabetic drugs in the general out-patient/general practice clinics (GOPD) and Hospital Authority public hospitals and affiliated specialist clinics (HA). The vast majority of patients (90.5%) receiving antidiabetic treatment were taking sulphonylureas and/or metformin, confirming that diabetes mellitus in Hong Kong is predominantly of the noninsulin-dependent type. The GOPD and the HA each accounted for approximately half of the sulphonylureas (55% vs 45%) and metformin (43% vs 57%) prescribed. Glibenclamide (84.9% vs 79.1%, 83.7% overall) and gliclazide (12.8% vs 16.6%, 14.5% overall) were the 2 most frequently used sulphonylureas. Only 9.5% of patients on antidiabetic drugs were receiving insulin and 92% of this was prescribed by the HA. For comparison, Singapore has a similar prevalence of diabetes mellitus but a much lower incidence of antidiabetic drug-induced hypoglycemia amongst acute medical admissions (0.5%). Tolbutamide was the most frequently used there sulphonylurea (66.6-72.2%) with glibenclamide only contributing 20.8-28.6%. Thus, the predominant use of glibenclamide in Hong Kong may contribute to the high incidence of antidiabetic drug-induced hypoglycemia amongst acute medical admissions.

Acute Disease↗
PubMed1996

Medicated oils and severe salicylate poisoning: quantifying the risk based on methyl salicylate content and bottle size.

In Hong Kong, medicated oils containing methyl salicylate account for 48% of acute salicylate poisoning cases treated in the general medical ward of the Prince of Wales Hospital. To quantify better the risk to average persons who have intentionally ingested these medicated oils, the methyl salicylate content and bottle size of 7 commonly available formulations were examined. Koong Yick Hung Far Oil had the highest methyl salicylate content (67%) and was available only in 60-ml bottles. If the entire bottle of this product were ingested, the equivalent of 184 adult 300-mg aspirin tablets would have been swallowed. Accidental ingestions of as little as 6 ml of Koong Yick Hung Far Oil by a child can be fatal. Six other products contained 15-40% methyl salicylate and their biggest bottle sizes range from 28-57 ml. Among medicated oils commonly found in Hong Kong, Koong Yick Hung Far Oil poses the greatest threat for severe salicylate poisoning if swallowed because of its high salicylate content and its availability in 60-ml bottles. The threat from medicated oils can probably be reduced by restricting their bottle size and methyl salicylate concentration. Physicians and clinical toxicologists should appreciate the toxic potential of these products.

Adult↗
PubMed1996

Use of a plasma salicylate assay service in a medical unit in Hong Kong: a follow-up study.

We have previously showed that routine screening of all patients with acute poisoning for salicylates in Hong Kong is unnecessary. We suggested that plasma measurements should be restricted to those suspected of having ingested salicylates. Our results and suggestion have since been presented and discussed in our medical unit meetings. The impact of our suggestion on the use of our plasma salicylate assay service was determined in this follow-up study of 196 patients presenting between October 1994 and April 1995. In 24 patients (12%), ingestion of salicylates was suspected, and of these, 3 (12.5%) had detectable plasma salicylate concentrations (> or = 0.3 mmol/L). The incidence in those who had taken identifiable drugs, unidentifiable drugs but nature known, and topical medicaments was 20%, 0% and 29%, respectively. Urinary alkalinization was necessary in the only patient with moderate to severe symptoms. In 172 patients (88%), ingestion of salicylates was not suspected; 3 (1.7%) had plasma salicylate concentrations of 0.47-2.05 mmol/L but mild symptoms only. We confirmed that routine screening for salicylates in all patients with acute poisoning was unnecessary. Despite our suggestion, 88% of plasma salicylate measurements in this follow-up study (76% in January 1992-June 1993) involved patients not suspected of having ingested salicylates.

Adolescent↗
PubMed1996

The relationship between upper gastrointestinal hemorrhage and drug use: a case control study.

The relationship between upper gastrointestinal hemorrhage and drug use was studied in 251 Chinese patients (179 men, 72 women) admitted to the Prince of Wales Hospital, Hong Kong, and control subjects matched for age and sex. There was a highly significant difference between the cases and control subjects in the use of NSAIDs (odds ratio 14.0, p < 0.00001), ulcer healing drugs (odds ratio 12.5, p < 0.00001), and Chinese proprietary medicines (odds ratio 16.0, p < 0.00001). There was also a significant difference in the use of analgesics (odds ratio 14.0, p = 0.001), paracetamol (odds ratio 2.5, p = 0.01), antacids (odds ratio 2.7, p < 0.001) and unknown drugs (odds ratio 4.7, p < 0.001). Cases also differed from control subjects regarding the use of tobacco (odds ratio 2.3, p < 0.001) and alcohol (odds ratio 1.7, p = 0.02), and the presence of peptic ulcer symptoms (odds ratio 29.8, p < 0.00001). Significantly more control subjects than cases were receiving aspirin, cardiovascular drugs, bronchodilators, oral hypoglycemic drugs/lipid-lowering drugs, and anticonvulsants/hypnotics, due to the inevitable differences in disease pattern between the 2 groups. NSAID use was a major factor associated with upper gastrointestinal hemorrhage from primarily peptic ulcers. Differences in the use of other drugs may reflect variations in disease patterns between cases and controls, the common practice of self-medication in Hong Kong, and the concomitant use of NSAIDs and ulcer healing drugs/antacids.

Adolescent↗
PubMed1996

Urinary dopamine outputs do not rise in healthy Chinese subjects during gradually increasing oral sodium intake over 8 days.

1. All previous studies on the effects of changes in sodium intake on the renal dopamine (DA) response (increase in urinary DA output) have used sudden, large changes in oral sodium intake. The present study was designed to study the role of renal DA and the suppression of sympathetic nervous system activity in the natriuretic response to step-wise, gradual increases in sodium intake. 2. Seven healthy, male Chinese subjects (23-25 years) were studied. During the 12-day study period (day -3 to 8), subjects were given the same basic diet containing 1900 calories, 75 g protein, 20 mmol sodium and 45 mmol potassium. From days 1 to 8, subjects also received 'Slow sodium' tablets (Ciba-Geigy) equivalent to 50 mmol on day 1, 100 mmol on day 2, 150 mmol on day 3,200 mmol on day 4, 250 mmol on day 5, and 300 mmol on days 6 to 8. Body weight was recorded and blood pressure was measured after lying supine for 10 min in the morning before breakfast on entry and at the end of the low and high sodium intake periods. Urine was collected for 24 h on day -3 and from days 0 to 8 for the measurement of sodium, potassium, creatinine, free DA and free noradrenaline (NA). 3. After 4 days of sodium restriction, mean arterial pressure (mean +/- SEM) had decreased from 83.0 +/- 1.3 to 79.4 +/- 0.5 (P < 0.05) and body weight from 70.2 +/- 3.1 to 68.3 +/- 3.0 (P < 0.02). Following sodium loading, MAP and body weight did not change, but pulse rate had decreased from 64.1 +/- 2.8 to 57.4 +/- 2.6 (P < 0.02). 4. There was a 13-fold increase in sodium excretion (P < 0.02) by the last day of the high sodium intake period. There were no significant changes in urine volume and urinary excretion of potassium, creatinine and free DA throughout the high sodium intake period. In contrast, there was a 19.9-26.5% decrease in urine NA 4 and 6 days after the start of the increase in sodium intake. 5. Healthy Chinese subjects do not have a renal DA response to gradually increasing sodium intake over an 8-day period. Any tendency to hypervolaemia-related rises in blood pressure during the high sodium intake period may be partly offset by a reduction in sympathetic nervous system activity.

Adult↗
PubMed1996

An estimate of the incidence of pesticide poisoning in Hong Kong.

The exact incidence of vegetable-borne and other types of acute pesticide poisoning among the 6.2 million population of Hong Kong is difficult to determine. Vegetable-borne pesticide poisoning is notifiable and, in 1992, 47 outbreaks of such poisoning (all caused by methamidophos) affected about 329 persons. No similar figures are available for non-vegetable-borne pesticide poisoning, but we calculated it based on our experience at the Prince of Wales Hospital (PWH) and on reports to our territory-wide Drug and Poisons Information Bureau (DPIB). The PWH serves the 1.2 million population in the New Territories East, where much of the remaining farmland in Hong Kong is situated. Extrapolating from our regional data to the whole of Hong Kong, we estimate that, in subjects aged > or = 15 y between 1988 and 1991, the annual incidence of non-vegetable-borne acute pesticide poisoning from parasuicides, non-farming accidents and work-related accidents was 59, 4 and 1, respectively. Between 1988 and 1992, 5 pediatric cases of non-vegetable-borne pesticide poisoning were reported to the DPIB annually. In the New Territories East, 80% of the acute pesticide poisoning deaths were due to 24% paraquat solution. In Hong Kong, acute pesticide poisoning is relatively uncommon. By maintaining a close surveillance of imported vegetables for excessive methamidophos residues, replacing high concentration paraquat with less toxic formulations, and placing pesticides out of reach of children, much of this morbidity and mortality associated with acute pesticide poisoning can be prevented.

Adolescent↗
PubMed1996

Factors responsible for continuing morbidity after paracetamol poisoning in Chinese patients in Hong Kong.

To determine those factors responsible for continuing prevalence of liver damage after paracetamol poisoning, 222 Chinese patients presenting to the Prince of Wales Hospital, Hong Kong from 1988 to 1993 were studied. Of the 27 patients with plasma paracetamol concentrations above the recommended "treatment line", 13 developed liver damage. Time elapsed between ingestion and treatment with intravenous N-acetylcysteine (NAC) was the most important prognostic factor. Failure to give NAC appropriately (50%) and late presentation (23%) were the main reasons for the continuing morbidity. Liver damage in some of the remaining patients (30%) could have been prevented if NAC was started in the Emergency Department within 8-15 hours of ingestion. Liver damage after paracetamol poisoning remains common (5.9%) in Hong Kong because of the failure to give NAC appropriately or late presentation. We hope to improve patient management by repeatedly emphasising the importance of adherence to the standard protocols and having the toxic plasma level results phoned directly to the duty registrars.

Acetaminophen↗
PubMed1996

The epidemiology of acetaminophen (paracetamol) poisoning in Hong Kong.

The prince of Wales Hospital is in a unique position for the study of the actual incidence of acetaminophen poisoning in Hong Kong because it is the sole general teaching hospital in the New Territories East and the age and sex distribution of the population in the region are readily available. Between 1991 and 1994, the rate of admission in subjects aged > or = 15 years slightly increased from 5.7 to 7.3/100,000. In both 1991 and 1994, the highest rates in women were in the 15-19 age group (from 22.8 to 53.0/100,000) and in men in the 25-29 age group (from 10.5 to 6.0/100,000). The rates of admission with toxic plasma acetaminophen concentrations were higher in 1994 than in 1991 (10.8 vs 0.6/100,000). The annual incidence of acetaminophen-induced liver damage remained unchanged (0.3/100,000). None of the patients with liver damage developed fulminant liver failure. There were no deaths. Thus, acetaminophen poisoning appears to cause less fulminant liver failure and deaths in Hong Kong than in other Western societies. Reasons for such differences need to be better understood.

Acetaminophen↗
PubMed1996

Osteomalacia during rifampicin and isoniazid therapy is rare in Hong Kong.

Prolonged therapy with rifampicin and isoniazid can cause vitamin D deficiency or osteomalacia, particularly in patients with marginal vitamin D stores. In the New Territories East of Hong Kong, there were at least 1,526 new cases of tuberculosis over a 14-month period in 1994-1995. Any severe cases of osteomalacia were expected to be hospitalized in the sole general teaching hospital of the region. However, among all the general medical patients with one of their discharge ICD codes being 268 (vitamin D deficiency) or 275 (disorders of mineral metabolism), none had osteomalacia due to rifampicin and isoniazid chemotherapy. Thus, this complication appears to be rare in Hong Kong whose residents generally have a higher vitamin D status than those of the U.K.

Antitubercular Agents↗