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Biomedical subjects

N L Benowitz

Publications and source records attributed to N L Benowitz.

At least 109 records · Page 6Linked to original sources
PubMed1994

Caffeine and coffee: effects on health and cardiovascular disease.

Caffeine is a methylxanthine whose primary biological effect is the competitive antagonism of the adenosine receptor. Its presence in coffee, tea, soda beverages, chocolate and many prescription and over-the-counter drugs makes it a commonly consumed stimulant. Coffee and/or caffeine consumption has been linked to many human diseases in epidemiologic studies. Causal relationships have been difficult to substantiate. Initial investigations, showing an association between coffee and coronary heart disease, suffer from confounding variables and have been difficult to replicate. Recent studies, showing a significant effect over long follow-up periods and with high coffee intake, have again raised the question of a role for coffee and/or caffeine consumption in the pathogenesis of atherosclerotic heart disease. Contrary to common belief, the published literature provides little evidence that coffee and/or caffeine in typical dosages increases the risk of infarction, sudden death or arrhythmia.

Caffeine↗
PubMed1994

Environmental tobacco smoke hazards and benefits of work-site nonsmoking programs.

The Council on Scientific Affairs of the California Medical Association presents the following inventory of items of progress in occupational medicine. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, and scholars to stay abreast of these items of progress in occupational medicine that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another. The items of progress listed below were selected by the Advisory Panel to the Section on Occupational Medicine of the California Medical Association, and the summaries were prepared under its direction.

Adult↗
PubMed1994

Nicotine metabolic profile in man: comparison of cigarette smoking and transdermal nicotine.

The objectives of this study were to 1) quantitatively assess human exposure to various metabolites of nicotine, 2) examine the influence of inhalation vs. transdermal administration on the patterns of nicotine metabolism, and 3) assess the extent of recovery of nicotine as various metabolites in people whose systemic intake of nicotine has been measured. Twelve smokers were studied while smoking cigarettes and while receiving transdermal nicotine. Urinary excretion of nicotine and eight of its metabolites was measured under steady state conditions. The systemic intake of nicotine in these subjects was determined using plasma concentrations and intravenous clearance data, so the percentage of their daily dose of nicotine excreted as various metabolites could be computed. The major findings of the study are as follows: 1) a high percentage (averaging 88%) of a systemic dose of nicotine can be accounted for by measurement of nicotine and its metabolites; 2) the pattern of metabolism is generally similar when nicotine is inhaled or absorbed transdermally; 3) while there is considerable interindividual variability in the pattern of metabolism, the pattern is consistent for an individual; and 4) within individuals, the extent of conjugation of nicotine and cotinine is highly correlated, but neither is correlated with the extent of conjugation of 3'-hydroxycotinine. This suggests that similar enzymes are involved in the conjugation of nicotine and cotinine, and that a different enzyme may be involved in the conjugation of 3'-hydroxycotinine.

Administration, Cutaneous↗
PubMed1993

Gas chromatographic-mass spectrometric method for determination of anabasine, anatabine and other tobacco alkaloids in urine of smokers and smokeless tobacco users.

A selected ion monitoring method for determination of the tobacco alkaloids anabasine, anatabine, nornicotine, metanicotine, dihydrometanicotine, and 2,3'-bipyridyl in urine of smokers and smokeless tobacco users is described. The method involves conversion of the secondary amine alkaloids to tertiary amine derivatives by reductive alkylation using an aldehyde and sodium borohydride, and chromatography on a 5% phenylmethylsilicone capillary column. These derivatives have good chromatographic properties, allowing determination of concentrations as low as 1 ng/ml. The alkaloid 2,3'-bipyridyl is unaffected by the derivatization procedure and may be determined simultaneously with the other alkaloids. The structural analogues 2-(3-pyridyl)hexahydroazepine, 5-methyldihydrometanicotine, and 6-methyl-2,3'-bipyridyl were synthesized for use as internal standards. Using the method, concentrations and 24 h excretion of anabasine, anatabine, and nornicotine in urine of twenty-two smokers, eight chewing tobacco users, and six oral snuff users were determined and compared with concentrations and excretion of nicotine and its metabolite cotinine. Excretion of nicotine and cotinine was similar in all tobacco users, but excretion of anabasine, anatabine and nornicotine was substantially greater in urine of smokeless tobacco users, presumably due to absence of pyrolysis of these alkaloids in smokeless tobacco products.

Alkaloids↗
PubMed1993

The chronic infusion of nicotine into the developing chick embryo does not alter the density of (-)-[3H]nicotine-binding sites or vestibular function.

(-)-Nicotine (1.2 mg/day) or saline was infused into chick embryos (Gallus domesticus) for 10 days beginning 12 h beyond the eight day of incubation (E8 + 12 h). Twelve h beyond the eighteenth day of incubation (E18 + 12 h), the eggs were opened to access the embryos and subcutaneous skull electrodes placed. Short latency vestibular response thresholds and input/output functions were determined to assess neurophysiological consequences of chronic nicotine administration. Samples of serum and extraembryonic (amniotic and albumen) fluid were analyzed by gas chromatography-mass spectrometry to determine the levels of nicotine and its major metabolite, cotinine. The brains were removed and divided into diencephalon and mesencephalon and the density of (-)-[3H]nicotine binding sites in each brain area was measured. Nicotine and cotinine were found in the serum and extraembryonic fluid, but nicotinic receptors were not up-regulated in the brains of animals infused with nicotine in comparison to controls. Vestibular response thresholds also did not differ between nicotine-treated and control animals.

Animals↗
PubMed1993

A clinical pharmacological study of subcutaneous nicotine.

The stable isotope-labeled compound 3',-3'-dideuteronicotine (nicotine-d2) was used to investigate the disposition kinetics and effects of nicotine administered subcutaneously to 6 smokers. Plasma nicotine-d2 concentrations were measured for 8 h after subcutaneous injection of 4 doses (0.4, 0.8, 1.2, and 2.4 mg). Peak plasma nicotine concentration correlated well with the dose, averaging 2.8 to 14.8 ng/ml, 19 to 25 min after injection of the 0.4 mg and 2.4 mg doses, respectively. The plasma clearance over bioavailability ratio (CL/f) averaged 12 to 13 ml.min-1.kg-1, similar to the clearance reported previously for intravenously administered nicotine. Thus, bioavailability appears to be approximately 100%. The heart rate response was more sensitive to the nicotine dose than the blood pressure response. Subjective effects showed large interindividual variability. The results reported herein may be useful in planning future studies. Administration of nicotine by the subcutaneous route appears to be a practical and safe method for studying the human pharmacology of nicotine.

Adult↗
PubMed1993

Clinical significance of genetic influences on cardiovascular drug metabolism.

Inherited differences in metabolism may be responsible for individual variability in the efficacy of drugs and the occurrence of adverse drug reactions. Among the cardiovascular drugs reported to exhibit genetic polymorphism are debrisoquine, sparteine, some beta-adrenoceptor antagonists, flecainide, encainide, propafenone, nifedipine, procainamide, and hydralazine. The implications of genetic differences in the metabolism of these drugs for cardiovascular therapeutics is the subject of this review.

Adrenergic beta-Antagonists↗
PubMed1993

Higher levels of nicotine in arterial than in venous blood after cigarette smoking.

We examined differences between arterial and venous concentrations of nicotine in human subjects. Shortly after smoking a cigarette, levels of nicotine in arterial plasma were more than double those in venous plasma. The time course of the rise in arterial nicotine levels and the magnitude of the arteriovenous difference varied considerably among subjects. For some subjects, arterial nicotine concentrations after one cigarette were similar to venous concentrations typically observed after 20 cigarettes and were nearly 10 times greater than venous concentrations. Our findings have implications for understanding the high degree of addictiveness and cardiovascular toxicity of smoked forms of drugs.

Adult↗
PubMed1993

Nicotine effects on eicosanoid formation and hemostatic function: comparison of transdermal nicotine and cigarette smoking.

OBJECTIVES: The purpose of this study was to examine the possible role of nicotine in enhancing coagulation and to assess the potential cardiovascular toxicity of transdermal nicotine therapy for smoking cessation. BACKGROUND: Cigarette smoking increases the risks of acute coronary events. A likely contributing mechanism is activation of coagulation. The role of nicotine in enhancing coagulability has not been resolved. METHODS: We compared in a crossover study the effects of cigarette smoking, transdermal nicotine and placebo transdermal nicotine, each for 5 days, in 12 healthy smokers. RESULTS: Cigarette smoking increased the urinary excretion of 11-dehydro-thromboxane B2 (reflecting thromboxane A2 generation) and increased plasma concentration of the platelet alpha-granule constituents, platelet factor 4 and beta-thromboglobulin, compared with placebo treatment, indicating in vivo platelet activation. Cigarette smoking was also associated with higher levels of fibrinogen in plasma. Transdermal nicotine produced plasma levels of nicotine in the same range as those during smoking but had no effect on thromboxane A2 metabolite excretion, platelet alpha-granule release or plasma fibrinogen, compared with placebo. Excretion of 2,3-dinor-6-keto-PGF1 alpha (reflecting prostacyclin generation) was not significantly influenced by any treatment. These results suggest that nicotine as such is not responsible for the platelet activation or elevation of plasma fibrinogen seen in smokers. However, we cannot exclude the possibility that intermittent bolus-like dosing of nicotine from cigarettes could have different effects from those produced by continually released transdermal nicotine. Other findings were that cigarette smoking and transdermal nicotine treatment were both associated with a higher white blood cell count compared with the placebo patch condition, suggesting a direct effect of nicotine to increase circulating white cells. Factor VII coagulant activity (VIIc) was significantly lower during cigarette smoking, than during either nicotine or placebo patch conditions. CONCLUSIONS: Transdermal nicotine has less effect on platelet activation and catecholamine release than does cigarette smoking, and its use in smoking cessation treatment of patients with coronary heart disease is likely to be safer than cigarette smoking.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Seizures associated with poisoning and drug overdose.

A retrospective review of cases consulted by the San Francisco Bay Area Regional Poison Control Center during a 2-year period was performed to determine the causes and consequences of seizures associated with poisoning and drug intoxication. Of 233 charts coded as involving seizures, 191 occurred in humans and were available for analysis. The leading causes of seizures reported to the Poison Control Center were cyclic antidepressants (55 cases, 29%); cocaine and other stimulants (55 cases, 29%); diphenhydramine and other antihistamines (14 cases, 7%); theophylline (10 cases, 5%); and isoniazid (10 cases, 5%). Stimulants and diphenhydramine were more likely than other drugs to produce brief, self-limited seizures. In contrast, poisoning by cyclic antidepressants, cardiodepressant antiarrhythmic agents, or theophylline was more likely to be associated with death. Seizures in elderly patients were more likely to result in complications and death. The frequency of seizure-related cases by substance type was also compared with the results of an earlier survey performed in 1981, and found a striking increase in the proportion of seizures caused by cocaine and (23% in 1988 to 1989 compared with 4% in 1981). Poison Control Center data can provide valuable information about the causes and consequences of drug-related medical complications, as well as highlight changing trends in drug-related injury.

Adolescent↗
PubMed1993

Nicotine and cotinine elimination pharmacokinetics in smokers and nonsmokers.

Published research suggests that smokers metabolize nicotine and its major metabolite cotinine more rapidly than nonsmokers. To evaluate this possibility, we studied the disposition pharmacokinetics of intravenous deuterium-labeled nicotine in 11 smokers (administered 2.0 and 0.5 micrograms/kg/min x 30 minutes) and in 11 nonsmokers (0.5 micrograms/kg/min). Smokers did not metabolize nicotine more rapidly; the clearance of nicotine normalized for body weight was significantly slower in smokers than in nonsmokers. Cotinine elimination rates were similar in the two groups. The disposition pharmacokinetics of nicotine was similar for the low and high doses in the smokers, indicating that metabolism is dose-independent. Our findings argue against "metabolic tolerance" as a mechanism for the dose escalation observed in smokers after initiation of smoking. Our findings suggest that nicotine and cotinine kinetic parameters for smokers may be extrapolated to nonsmokers for estimating exposures to environmental tobacco smoke in nonsmokers.

Adult↗
PubMed1993

Pharmacokinetic-pharmacodynamic modeling of caffeine: tolerance to pressor effects.

We propose a parametric pharmacokinetic-pharmacodynamic model for caffeine that quantifies the development of tolerance to the pressor effect of the drug and characterizes the mean behavior and inter-individual variation of both pharmacokinetics and pressor effect. Our study in a small group of subjects indicates that acute tolerance develops to the pressor effect of caffeine and that both the pressor effect and tolerance occur after some time delay relative to changes in plasma caffeine concentration. The half-life of equilibration of effect with plasma caffeine concentration is about 20 minutes. The half-life of development and regression of tolerance is estimated to be about 1 hour, and the model suggests that tolerance, at its fullest, causes more than a 90% reduction of initial (nontolerant) effect. Whereas tolerance to the pressor effect of caffeine develops in habitual coffee drinkers, the pressor response is regained after relatively brief periods of abstinence. Because of the rapid development and regression of tolerance, the pressor response to caffeine depends on how much caffeine is consumed, the schedule of consumption, and the elimination half-life of caffeine.

Adult↗
PubMed1993

Altered patterns of drug metabolism in patients with acquired immunodeficiency syndrome.

Caffeine was used to assess acetylation status and indexes of oxidative drug metabolism (demethylation, xanthine oxidation, and 8-hydroxylation) in a control group and in three groups of patients infected with human immunodeficiency virus (HIV): patients with acquired immunodeficiency syndrome (AIDS) who had acute illnesses, stable patients with AIDS, and asymptomatic patients infected with HIV. The prevalence of apparent slow acetylation was greater in AIDS patients with acute illnesses compared with control subjects (27 of 29 [93%] versus 18 of 29 [62%]). Indexes of demethylation were decreased and 8-hydroxylation increased in these patients. Xanthine oxidation was the same as that in the control subjects. In the stable AIDS patients, oxidative pathways were altered in a manner similar to that observed in the AIDS patients with acute illnesses, but acetylation was the same as that in the control subjects. In HIV-infected asymptomatic patients, drug metabolism was the same as that in the control subjects. The increased prevalence of apparent slow acetylation and the altered activity of the oxidative pathways in AIDS patients with acute illnesses may partly explain the increased incidence of adverse drug reactions in these patients.

Acetylation↗
PubMed1993

Bioavailability and absorption kinetics of nicotine following application of a transdermal system.

1. The absolute bioavailability and absorption kinetics of nicotine were investigated in 13 healthy adult male smokers following single and multiple applications of a nicotine transdermal system (NTS), designed to release nicotine at an approximate rate of 1.5 mg h-1 over 24 h. The absorption of nicotine from the single NTS application was calculated with reference to a simultaneous intravenous infusion (i.v.) of deuterium-labelled nicotine. 2. The mean input time (MIT) and mean absorption time (MAT) for nicotine following application of NTS for 24 h were 7.7 and 4.2 h, respectively. 3. Following NTS removal, the mean apparent nicotine elimination half-life was 2.8 h, compared with 2.0 h following i.v. nicotine, reflecting continued absorption of nicotine following NTS removal. 4. The mean amount of nicotine absorbed from the NTS after the 24 h application was 20.9 mg, which represents about 68% of the amount released from the system; the remaining 32% was lost from the system during daily activities. 5. The ratio of AUC values for the metabolite cotinine relative to nicotine was similar whether nicotine was administered transdermally or intravenously. 6. Following i.v. administration, the mean nicotine clearance was 72 l h-1 (coefficient of variation 29%). Since coefficients of variation in AUC values following NTS and i.v. treatments were similar, transdermal administration of nicotine was not associated with increased interindividual variability in plasma nicotine concentrations. 7. No significant changes were seen in the pharmacokinetics of nicotine between single and multiple applications of NTS. 8. As expected from the higher total plasma nicotine concentrations, the incidence of adverse effects was higher following simultaneous intravenous and transdermal administration of nicotine. The most frequently reported systemic side effects were nervousness and headache: mild itching was the most frequent topical effect.

Administration, Cutaneous↗
PubMed1993

Clinical pharmacology and toxicology of cocaine.

Cocaine abuse has produced a major epidemic health problem in North America in the 1980s. The abuse of cocaine is maintained by the drug's effects on brain reward systems, mediated at least in part by its dopaminergic action. The patterns and consequences of use are best understood by considering the pharmacokinetics (rapid absorption and delivery to the brain, relatively short half-life) and the pharmacodynamics (intense central and peripheral neural stimulation). Cocaine is used therapeutically as a topical and local anaesthetic. Toxicity occurs primarily in cocaine abusers, but also occasionally after therapeutic dosing. Medical complications reflect primarily excessive central nervous system stimulation and excessive vasoconstriction, the latter resulting in severe hypertension and/or organ ischaemia with associated organ injury. Most deaths that result from medical complications of cocaine intoxication are sudden and occur before medical intervention is possible. Other complications of cocaine abuse with severe personal and social consequences include traumatic deaths and injuries, and reproductive disturbances, as well as transmission of infectious diseases, especially AIDS. Cocaine addiction is clearly a problem, although the number of addicts is unknown. Pharmacologic treatment of cocaine addiction has as yet been unsuccessful. Psychosocial approaches remain the mainstay of therapy.

Cocaine↗
PubMed1993

Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers.

The safety, efficacy and pharmacokinetic parameters of 5 g of hydroxocobalamin given intravenously, alone or in combination with 12.5 g of sodium thiosulfate, were evaluated in healthy adult men who were heavy smokers. Sodium thiosulfate caused nausea, vomiting, and localized burning, muscle cramping, or twitching at the infusion site. Hydroxocobalamin was associated with a transient reddish discoloration of the skin, mucous membranes, and urine, and when administered alone produced mean elevations of 13.6% in systolic and 25.9% in diastolic blood pressure, with a concomitant 16.3% decrease in heart rate. No other clinically significant adverse effects were noted. Hydroxocobalamin alone decreased whole blood cyanide levels by 59% and increased urinary cyanide excretion. Pharmacokinetic parameters of hydroxocobalamin were best defined in the group who received both antidotes: t1/2 (alpha), 0.52 h; t1/2 (beta), 2.83 h; Vd (beta), 0.24 L/kg; and mean peak serum concentration 753 mcg/mL (560 mumol/L) at 0-50 minutes after completion of infusion. Hydroxocobalamin is safe when administered in a 5 gram intravenous dose, and effectively decreases the low whole blood cyanide levels found in heavy smokers.

Adult↗