Variability in vascular responsiveness between Mexican-Americans and White Americans.

Ethnic differences in vascular adrenergic responsiveness have been implicated to be a potentially important mechanism which may be responsible for some of the variations in haemodynamic patterns between races. These differences may account for the variability in the prevalence of hypertension in different groups. The main aim of this study was to determine whether there was a difference in venous responsiveness to the vasoactive agents, phenylephrine and isoproterenol, between Mexican-Americans and White Americans. Isoproterenol is a potent non-selective beta-adrenergic agonist, phenylephrine is an alpha1-selective adrenergic agonist. Using the dorsal hand vein compliance technique, dose-response curves were constructed for the two vasoactive agents in 10 Mexican-American and 10 White American volunteers. The maximal venoconstriction for phenylephrine in the Mexican-American group was significantly less than that of the Whites in the study (71.2 +/- 20.1% vs 89.4 +/- 10.9%, P < 0.05). The log ED50 for isoproterenol in the Mexican-American group was also significantly greater than that for Whites (1.68 +/- 0.35[47.6 ng/min] vs 1.19 +/- 0.55[15.5 ng/min], P < 0.05). These results suggest that Mexican-Americans have a differential responsiveness to adrenergic vasoactive agents compared to White Americans and may be protected from the development of hypertension.

Serum lipid and lipoprotein levels in Ghanaians with diabetes mellitus and hypertension.

Both diabetes mellitus and hypertension alter lipid and lipoprotein metabolism and increase the risk of coronary artery disease. We have reported previously on lipid and lipoprotein levels in healthy Ghanaians, and this study deals with the levels of these biochemical parameters in Ghanaians with diabetes mellitus and hypertension. Fasting serum lipoproteins were determined on blood samples drawn from healthy male and female Ghanaians as well as age-matched individuals with either diabetes or hypertension. Cholesterol, high-density lipoprotein cholesterol (HDL-C), triglycerides, and fasting blood glucose were measured. Low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were derived. Total serum cholesterol levels were 4.43 +/- 0.22 mmol/L and 4.67 +/- 0.26 mmol/L for diabetic males and females, respectively. High-density lipoprotein was 1.55 +/- 0.09 mmol/L and 1.50 +/- 0.09 mmol/L for male and female diabetics, respectively. Lipid and lipoprotein levels in the hypertensive patients did not differ from the above values. The levels of cholesterol and lipoprotein obtained in Ghanaians with hypertension and diabetes mellitus were similar to those of their age-matched healthy controls. These results suggest a reduced risk of coronary artery disease from the atherogenic effects of cholesterol in Ghanaians with diabetes mellitus and hypertension.

Impaired beta 2-adrenergic agonist-induced venodilation in Indians of Asian origin.

OBJECTIVES: Vascular responsiveness to infusions of vasoactive substances varies between ethnic groups. Indians of Asian origin are a rapidly growing ethnic group in the United States but have not been extensively studied. We sought to determine whether there was any difference in venous responsiveness to a local infusion of vasoactive substances between Indians of Asian origin and white subjects. METHODS: We used the dorsal hand vein compliance technique to construct full dose-response curves to the beta 2-agonist isoproterenol (2 to 270 ng/min) in hand veins preconstricted with phenylephrine in 11 young white subjects and in 11 young Asian Indian subjects. In addition, six subjects in each group were randomly selected to have full dose-response curves to nitroglycerin (0.006 to 1485 ng/min) generated. RESULTS: The maximal response (E(max)) to isoproterenol was smaller in Asian Indians (33.9% +/- 41.1% in Asian Indians versus 107.0% +/- 60.1% in white subjects; p < 0.01). There was no difference in the log of the dose that produced half-maximal venodilation [log(ED50)] between the two groups (1.10 +/- 0.57 in Asian Indians versus 1.15 +/- 0.50 in white subjects). However, nitroglycerin infusion produced similar responses for both the E(max) and the log(ED50) between the two groups. CONCLUSION: These results indicate that differences may exist in beta-adrenergic responsiveness among white subjects and Indians of Asian origin. Therapy for diseases that use beta-adrenergic responses, such as hypertension, must take into account these differential vascular responses because they may affect their efficacy in Asian Indians.

Oxybutynin-induced heatstroke in an elderly patient.

OBJECTIVE: To report an elderly patient with oxybutynin-induced heatstroke and to remind clinicians of the possibility of drugs as an etiology of hyperthermia. CASE SUMMARY: An elderly man was admitted to the emergency department in a confused state. The day of admission was the hottest of the summer months in the San Francisco area. Because his rectal temperature was 40 degrees C and his skin was hot and dry, he was immediately packed in ice, given intravenous NaCl 0.9%, and a cooling fan was used to aid in external cooling. The patient was taking oxybutynin chloride, a drug with anticholinergic properties. The previous summer he had been admitted with a rectal temperature of 41.1 degrees C. No infectious etiology could be found. He was discharged in an improved state after a 48-hour observation period. The drug was discontinued. DISCUSSION: It is important to recognize heatstroke and institute prompt management because of the high mortality associated with this thermoregulatory disorder. Prompt treatment should consist of rapid cooling and vigorous cardiopulmonary support. CONCLUSIONS: The possibility of drug-induced heatstroke should be investigated in all patients admitted during the summer months with unexplained hyperthermia, especially the elderly. To our knowledge this is the first reported case of heatstroke associated with the use of oxybutynin.

Serum lipids and lipoprotein in adult Ghanaians.

OBJECTIVES: To date, no measurement of serum lipid levels in healthy adult Ghanaians have been carried out. This study was undertaken with the objective of providing reference values for serum lipid levels in the Ghanaian population. DESIGN/SETTING: Fasting serum lipid levels were measured in 79 adult Ghanaians living in an urban setting. Volunteers were randomly selected from the work force of the University of Ghana in Accra. There were 54 males and 25 females in the study population. RESULTS: The mean serum cholesterol (SC) for Ghanaian males was 4.27 +/- 1.00 mmol L-1. A value of 4.34 +/- 1.12 mmol L-1 was obtained for the females in this study. High-density lipoprotein cholesterol (HDL-C) in Ghanaian males averaged 1.37 +/- 0.44 mmol L-1 and 1.47 +/- 0.50 mmol L-1 in females. There was no statistically significant difference in low-density-lipoprotein cholesterol (LDL-C) and very-low-density-lipoprotein cholesterol (VLDL-C) levels between the females and males in this study. CONCLUSIONS: Compared to other studies, our results show that populations in Europe and North America have higher levels of total cholesterol and LDL cholesterol than Ghanaians. The levels of HDL cholesterol as well as VLDL cholesterol are higher in Ghanaians than in Europeans and Americans. Further work needs to be done to compare lipid levels in urban and rural Ghanaians as well as in those with cardiovascular disorders.

Cimetidine-induced rise in praziquantel levels in a patient with neurocysticercosis being treated with anticonvulsants.

A patient had neurocysticercosis complicated by a seizure disorder requiring anticonvulsants; previous praziquantel therapy (50 mg/kg/day) had failed to eradicate the disease. In an attempt to inhibit cytochrome P-450 metabolism of praziquantel, cimetidine (1600 mg/day) was coadministered. Before addition of cimetidine, the maximum concentration of praziquantel was 350 ng/mL; concurrent cimetidine administration increased the maximum concentration to 826 ng/mL. The elimination half-life increased from 1.7 h without cimetidine to 3.3 h with cimetidine and the area under the curve for the 12-h sampling period rose from 754 ng.h/mL to 3050 ng.h/mL. Coadministration of cimetidine raises serum praziquantel levels and may be helpful in patients treated concomitantly with praziquantel and anticonvulsants.

Drug resistance in malaria: a review of the west African situation.

Chloroquine-resistant Plasmodium falciparum malaria is an emerging problem in the West African subregion. While chloroquine remains an effective antimalarial agent in some countries of West Africa, the susceptibility patterns of P falciparum strains need to be assessed periodically. This article reviews the literature on chloroquine-resistant P falciparum malaria.