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Thomas Y K Chan

Publications and source records attributed to Thomas Y K Chan.

11 recordsLinked to original sources
PubMed2005

A multidisciplinary approach to the toxicologic problems associated with the use of herbal medicines.

In Hong Kong, a multidisciplinary team consisting of a pharmacist, a chemical pathologist, a scientific officer, and a physician has jointly provided an advisory service on herbal safety to healthcare professionals of all public hospitals since August 2000. This paper reports the first 2 years of experience of this team to emphasize the importance of a multidisciplinary approach to herbal poisoning. Twenty referrals received from the public hospitals from August 2000 to June 2002 were reviewed. The diagnosis of herbal toxicity was made after consideration of the temporal relationship between exposure to the herb and the occurrence of the adverse event and the exclusion of other causes. The causal relationship was seen as much stronger if the herb's pharmacological effects could fully explain the adverse event, if there were similar previous reports, and if the toxicological analysis findings were supportive. In 10 patients, the adverse events were deemed unlikely to be related to the use of herbal medicines. In 3 patients, it was concluded that the adverse events were possibly related to the use of herbal medicines. In 7 patients, the causal relationship was seen to be much stronger because the adverse events in these patients simply reflected the pharmacological effects of the herbs consumed and specific toxic ingredients were isolated from herbal residues and patients' urine or serum. The clinical problems arising from the use of herbal medicines included the Aristolochia species causing acute renal failure (n = 1), aconite roots causing aconitine poisoning (n = 2), the Datura species causing anticholinergic poisoning (n = 1), and "yulan" (Stephania sinica) causing tetrahydropalmatine poisoning (n = 3). The 4 patients with acute renal failure and tetrahydropalmatine poisoning received these toxic herbs, which were not listed in the prescriptions, as a result of poor dispensing practice or for other reasons. Toxicological problems associated with the use of herbal medicines are complex and may be easily overlooked. A multidisciplinary team of experts should be made available to provide advice to frontline healthcare professionals.

Acetaminophen↗
PubMed2004

Clinical features and management of herb-induced aconitine poisoning.

STUDY OBJECTIVE: We define the potential sources, clinical manifestations, and treatment of aconitine poisoning. METHODS: The database of the National Poison Center in Taiwan was retrospectively searched for the diagnosis of aconitine poisoning for 1990 to 1999. The reasons for taking the aconite roots, the clinical features, management, and possible predisposing factors were noted. RESULTS: A total of 17 cases occurred and consisted of 9 men and 8 women aged 30 to 70 years. Thirteen patients ingested aconite roots as treatment for rheumatism and wounds. Two patients volunteered to test the effects of aconite roots in a drug study. Two patients accidentally ingested the aconite roots. After a latent period of 10 to 90 minutes, patients developed a combination of neurologic (n=17), cardiovascular (n=14), gastrointestinal (n=9), and other (n=5) features typical of aconitine poisoning. Four patients developed ventricular tachycardia. All patients received supportive treatment. Patients with ventricular tachycardia were also treated with charcoal hemoperfusion. All patients made a complete recovery. CONCLUSION: Life-threatening ventricular tachycardia can occur after the consumption of aconite roots. The risk is higher with inadequately processed aconite roots, large doses, or tincture preparations. With increasing popularity of herbal medicines, herb-induced aconitine poisoning may also be seen in Western countries.

Aconitine↗
PubMed2003

Cost-effectiveness analysis of high-dose omeprazole infusion as adjuvant therapy to endoscopic treatment of bleeding peptic ulcer.

BACKGROUND: Intravenous administration of proton pump inhibitors after endoscopic treatment of bleeding peptic ulcers has been shown to decrease the rate of recurrent bleeding and the need for subsequent surgery. Yet there is a relative lack of formal assessment of this practice. The aim of this study was to examine the cost-effectiveness of this therapy by using standard pharmacoeconomic methods. METHODS: The present study was performed in conjunction with a randomized controlled clinical trial that included 232 patients who received either omeprazole (80 mg intravenous bolus followed by infusion at 8 mg/hour for 72 hours) or placebo after hemostasis was achieved endoscopically. A cost-effectiveness analysis was performed to evaluate the different outcomes of the trial. All related direct medical costs were identified from patient records. Cost-effectiveness ratios were calculated. RESULTS: Analysis by the Kolmogorov-Smirnov test showed that the direct medical cost in the omeprazole group was lower than that for the placebo group. Cost-effectiveness ratios for omeprazole and placebo groups were, respectively, HK$ 28,764 (US$ 3688) and HK$ 36,992 (US$ 4743) in averting one episode of recurrent bleeding in one patient after initial hemostasis was achieved endoscopically. CONCLUSIONS: Intravenous administration of high-dose omeprazole appears to be a cost-effective therapy in reducing the recurrence of bleeding and need for surgery in patients with active bleeding ulcer after initial hemostasis is obtained endoscopically.

Adult↗
PubMed2003

Adverse herbal interactions causing hypotension.

A 57-year-old man consulted an herbalist for epigastric discomfort. Four hours after he drank a decoction made from 14 herbs, he developed nausea, epigastric pain, and dizziness. He also had two loose bowel movements. On arrival at the hospital 4 hours later, his blood pressure was 77/46 mm Hg, and his pulse was 60 beats/min. He was given intravenous fluids. In the next 3 hours, his blood pressure gradually returned to his usual level of 100/65 mm Hg. His other gastrointestinal symptoms gradually subsided during the next 24 hours. His white cell count was 17.8 x 109/L but was normal on recheck. Complete cell counts, renal function and liver function tests, and electrocardiogram were otherwise normal. He was discharged home on day 2. Seven of the 14 herbs taken by this patient are known to have vasodilatory or blood pressure-lowering effects, and 3 of these herbs are used to manage hypertension. In traditional Chinese medicine, practitioners often use a combination of herbs in an attempt to improve the efficacy but reduce the adverse effects of treatment. The risk of adverse herbal interactions will also be higher.

Drug Therapy, Combination↗
PubMed2003

Relationship between patients' warfarin knowledge and anticoagulation control.

OBJECTIVE: To evaluate patients' knowledge of warfarin and its relationship to anticoagulation control. METHODS: From January to March 1999, 122 patients attending the warfarin clinic of the Prince of Wales Hospital in Hong Kong were interviewed. Their knowledge of warfarin therapy and adherence to medical advice were tested by 9 questions. A score (maximum 1.0) was calculated for each patient. The number of international normalized ratios (INRs) that was within the target range in the 4 most recent clinic visits was noted. RESULTS: Fifty-six men and 66 women participated in the study (mean +/- SD age 58.0 +/- 13.0, duration of treatment 43.1 +/- 39.8 mo). Patients' warfarin knowledge was poor, with an overall score of 0.48 +/- 0.18. Participants generally knew the colors of their warfarin tablets and took them regularly. They almost always informed their physicians and dentists of their warfarin therapy. Only 40-45% of patients knew the strengths of their warfarin tablets, the reason for taking warfarin, and its effect on the body. Their deficiencies in knowledge were even more obvious with respect to the possible consequences of under- or over-anticoagulation, drugs and medicated oils that might interact with warfarin, and management of a missed dose. Knowledge was related to age (r -0.43; p < 0.001) and duration of therapy (r 0.18; p = 0.044). Sixty patients (49.2%) had read the information booklet on warfarin and had better knowledge than those who had not (0.53 +/- 0.20 vs. 0.42 +/- 0.20; p < 0.001). Illiteracy was the main reason for not reading the booklet. There was a positive correlation between patients' warfarin knowledge and the number of INR values that was within the target range in the 4 most recent clinic visits (r 0.20; p = 0.024). CONCLUSIONS: Patients' warfarin knowledge, a determinant of anticoagulation control, was generally poor. More attention should be given to the education of elderly and illiterate patients.

Adult↗
PubMed2003

Interaction between warfarin and the herbal product quilinggao.

OBJECTIVE: To describe a patient with loss of anticoagulation control and bleeding after consumption of the combination herbal product quilinggao. CASE SUMMARY: A 61-year-old man who was stable on warfarin therapy regularly consumed a jelly-like herbal product called quilinggao ("essence of tortoise shell"). Five days after the daily consumption of a second brand of quilinggao, he developed easy gum bleeding, epistaxis, and skin bruising with an international normalized ratio (INR) >6.0. Warfarin therapy was temporarily withdrawn until the INR decreased to 1.9. On the day of hospital discharge, he took a third brand of quilinggao against medical advice. Three days later, his INR was 5.2. Warfarin therapy was again temporarily withheld and the patient counseled about an apparent herb-warfarin interaction. He could not remember the name of the third brand of quilinggao. DISCUSSION: Quilinggao is a very popular Chinese herbal product. There are many different brands, and the composition of herbal products varies between manufacturers. Chuanbeimu (Fritillaria cirrhosa) in the first brand and beimu (Fritillaria spp.), chishao (Paeoniae rubra, Chinese peony), jinyinhua (Lonicera japonica), and jishi (Poncirus trifoliata) in the second brand of quilinggao have antiplatelet and/or antithrombotic effects. Loss of anticoagulation control occurred after consumption of the second and third brands of quilinggao, possibly due to the presence of a greater number of interacting herbs. An objective causality assessment revealed that the observed reaction was highly probable to be related to the ingestion of the second and third brands of quilinggao. CONCLUSIONS: Quilinggao contains herbal ingredients that can interact with warfarin. Patients on warfarin therapy should be discouraged from taking herbal medicines, especially preparations that are already known to have antiplatelet and antithrombotic effects.

Blood Coagulation↗
PubMed2003

Use of herbal medicines by patients receiving warfarin.

BACKGROUND: Patients receiving warfarin therapy are discouraged from taking herbal medicines. Whether patients adhere to this advice and, if they do not, the types of products they use, are not known. OBJECTIVE: The objective of this observational study was to estimate the magnitude of use of herbal medicines among Chinese patients attending the Warfarin Clinic of the Prince of Wales Hospital in Hong Kong. METHODS: A medical officer interviewed all patients who attended the Warfarin Clinic during May 2001. Patients were asked about the use of herbal medicines in the preceding week. Demographic data, indication and duration of warfarin therapy, and International Normalised Ratio (INR) value at the time of the visit were also noted. RESULTS: Of 107 patients interviewed, 28 (26%) claimed to have taken herbal medicines during the week prior to the clinic visit. The users of herbal medicines had lower INR values than non-users (mean INR value 2.41 +/- 0.65 vs 2.75 +/- 0.65, p = 0.019), possibly because of a lower warfarin dosage (mean dosage 2.93 mg/day +/- 1.23 vs 3.34 mg/day +/- 1.45; p = 0.185) and because a smaller proportion of such patients had heart valve replacement (21% vs 39%, p = 0.141). 'Herbal soup' (soup made at home from vegetables, meat and certain herbs for consumption with the main meals) and 'cool tea' (herbal decoction for the treatment of 'endogenous heat') were the most popular and were taken by 12 (11%) and 11 (10%) patients, respectively. Four patients took proprietary medicines each containing between one and three different herbs that could potentially enhance or antagonise the effects of warfarin. None of the patients in this study showed any evidence of thromboembolism or bleeding on the day of clinic visit. CONCLUSION: Among Chinese patients treated with warfarin at a Hong Kong clinic, the use of herbal medicines was relatively common. Healthcare professionals play an important role in educating the patients and updating the list of herbal medicines that should be avoided by patients taking warfarin.

Blood Coagulation↗
PubMed2002

Deficient dietary vitamin K intake among elderly nursing home residents in Hong Kong.

There is strong evidence supporting the importance of vitamin K in bone health and the aetiological role of vitamin K deficiency in osteoporosis. In view of the common occurrence of osteoporosis among older subjects in Hong Kong, we have studied the dietary vitamin K intakes in 100 residents of a nursing home (43 men, 57 women; median age 81.0 years) and 88 free-living subjects attending a day care centre (13 men, 75 women; median age 71.5 years). The subjects were interviewed and the average vitamin K intake in the preceding week was estimated, using a diet recall questionnaire modified from our previous surveys of dietary patterns in local Chinese people. The median vitamin K intake was much lower in nursing home residents than in free-living subjects (4.50 vs 488.09 microg/day or 0.13 vs 8.74 microg/kg/day, P<0.001). An intake that was below the recommended daily intake was far more common among nursing home residents (86.0 vs 11.4%, P < 0.001). Among nursing home residents, there was a negative correlation between age and vitamin K intake (r = -0.217, P = 0.030), but there was a positive correlation between body weight and vitamin K intake (r = 0.244, P = 0.015). No such relationship was seen among free-living subjects. Elderly nursing home residents in this study generally had a poor dietary vitamin K intake and might therefore be predisposed to osteoporosis. The importance of green leafy vegetables as a rich source of vitamin K should be emphasised.

Adult↗
PubMed2002

Incidence of herb-induced aconitine poisoning in Hong Kong: impact of publicity measures to promote awareness among the herbalists and the public.

BACKGROUND: In Hong Kong 'chuanwu' (the main root of Aconitum carmichaeli) and 'caowu' (the root of Aconitum kusnezoffii) are used by herbalists to treat patients with various musculoskeletal disorders. These aconite roots contain aconitine, mesaconitine and hypaconitine, which are neurotoxins and cardiotoxins. During 1989 to 1991, 31 patients were treated in public hospitals because of poisoning by aconite roots and there were two deaths from ventricular arrhythmias. In late 1991, healthcare officials together with cardiologists held a press conference to warn the public, healthcare professionals and herbalists of the potential toxicity of aconite roots. The risk of ventricular arrhythmias and the need for urgent medical attention were highlighted. An information leaflet was also sent to hospital doctors. Since 1992, the topic was covered periodically in the local newspapers, medical journals and continuing medical education programmes. OBJECTIVE: The objective of this study was to assess the impact of these publicity measures on the incidence of herb-induced aconitine poisoning in the New Territories East, based on the number of admissions to the Prince of Wales Hospital. METHODS: During 1989 to 1993 and 1996 to 1998, all patients admitted to our medical wards because of herb-induced aconitine poisoning were identified by on-going surveillance of medical patients, searching our computerised medical record system and reviewing reports received by the 24-hour Drug and Poisons Information Bureau. RESULTS: The number of hospitalisations due to aconitine poisoning markedly decreased from four to six per year in 1989 to 1991 to one to two per year in 1992 to 1993. The annual incidence of aconitine poisoning showed a marked decrease from 0.49 to 0.69 [overall 0.60, 95% confidence intervals (CI) 0.34 to 0.99] to 0.10 to 0.22 (overall 0.16, 95% CI 0.03 to 0.46) per 100,000 population (p = 0.024). During 1996 to 1998, herb-induced aconitine poisoning remained uncommon, with zero to two hospital admissions per year or an annual incidence of zero to 0.33 (overall 0.17, 95% CI 0.05 to 0.43) per 100,000 population (p = 0.016). DISCUSSION: It is possible that the herbalists could have used smaller doses of 'chuanwu' and 'caowu' than before. Patients could be more compliant with the instructions on how to prepare the herbal decoction at home. However, our experience suggested that publicity measures to promote awareness, among the herbalists and the public, may reduce the incidence of poisoning due to toxic herbs such as aconite roots.

Aconitine↗
PubMedDate not supplied

Comparison of Pueraria lobata with hormone replacement therapy in treating the adverse health consequences of menopause.

OBJECTIVE: Pueraria lobata (PL) is used as a traditional Chinese herbal remedy for menopausal symptoms, as well as an ingredient in preparations for conditions affecting menopausal women, such as osteoporosis, coronary heart disease, and some hormone-dependent cancers. The scientific basis for its action may be its action as a phytoestrogen. DESIGN: To examine the effects of PL in comparison with hormone replacement therapy (HRT) on lipid profile, sex hormone levels, bone turnover markers, and indices of cognitive function. For the study, 127 community-living, postmenopausal women aged 50 to 65 years were randomized to receive HRT (n = 43), PL (equivalent to 100 mg isoflavone; n = 45), or no treatment (n = 39) for 3 months. The following measurements were carried out at baseline and after 3 months for all participants: menopausal symptoms questionnaire; neuropsychological tests covering memory, attention, motor speed, and word-finding ability; quality of life (SF36); lipid profile; urinary deoxypyridinoline; dietary phytoestrogen intake and urinary phytoestrogen; estradiol; follicle-stimulating hormone; and luteinizing hormone. RESULTS: Only participants in the HRT group showed a mean reduction in cholesterol and low-density lipoprotein cholesterol that was significantly different from that of the control group. No significant changes in lipid profile or follicle-stimulating hormone and luteinizing hormone were observed in the PL group compared with the controls. However, both the HRT and PL groups showed an improvement in Mini-Mental State Examination score and attention span compared with the case of participants receiving no treatment. HRT and PL had different effects on cognitive function; HRT improved delayed recall, whereas flexible thinking seemed improved in the PL group. CONCLUSIONS: This study was unable to demonstrate a scientific basis for the use of PL for improving the health of postmenopausal women in general. However, the effect of PL on cognitive function deserves further study.

Aged↗