Two cases of rapid onset Parkinson's syndrome following toxic ingestion of ethylene glycol and methanol

Ethylene glycol and methanol are toxic alcohols commonly found in a variety of commercial products. We report two cases, one associated with ethylene glycol and one with methanol poisoning, which both led to acute hemorrhagic necrosis of the basal ganglia and resulted in acute Parkinson's syndrome. It is unlikely that oxalate crystal deposition is the only mechanism for such basal ganglia necrosis, because similar findings were seen following methanol intoxication. We discuss other possible mechanisms that may contribute towards this unusual neurotoxicity. Both of our patients survived their toxic ingestions, but then developed acute Parkinson's syndrome within 10 days of the ingestion. However, the patient who ingested methanol developed respiratory muscle stiffness/weakness, which responded poorly to anti-Parkinsonian drug therapy. Treatment with carbidopa/levodopa improved cogwheel rigidity and bradykinesia in both patients. We conclude that acute Parkinsonism is one of the lesser-recognized devastating complications of both ethylene glycol and methanol poisoning.

American Board of Clinical Pharmacology fellowship training and certification in clinical pharmacology: educational value and future needs for the discipline

Currently, the training and education of young clinical pharmacologist who represent the future of our discipline rest almost entirely on institutions/organizations with established and productive fellowship training programs. Here, we discuss the role of the American Board of Clinical Pharmacology (ABCP) in accrediting fellowship training programs and certifying individual clinical pharmacologists. We also explore how ABCP certification adds value to both individual trainees and the discipline in the evolving world of clinical therapeutics and research in human pharmacology.

Non-melanoma skin cancers and glucocorticoid therapy

Non-melanoma skin cancer (NMSC) is an important cause of morbidity and long-term mortality in organ transplant recipients receiving immunosuppressive drugs such as azathioprine and cyclosporin, often combined with adrenocortical steroids (glucocorticoids). At lower doses, glucocorticoids alone are prescribed for other conditions including musculoskeletal, connective tissue and respiratory disorders. Presently, it is unknown whether patients taking glucocorticoids are at an increased risk of skin malignancies. In a population-based case-control study in New Hampshire, USA, we compared use of glucocorticoids in 592 basal cell carcinoma (BCC) and 281 squamous cell carcinoma (SCC) cases and in 532 age and gender matched controls; neither cases nor controls had a history of organ transplantation. Participants underwent a structured personal interview regarding history of medication use and skin cancer risk factors. We used unconditional logistic regression analysis to compute odds ratios associated with glucocorticoid use for 1 month or longer while controlling for potential confounding factors. Risk of SCC was increased among users of oral glucocorticoids (adjusted odds ratio = 2.31; 95% CI = 1.27, 4.18), and risk of BCC was elevated modestly (adjusted odds ratio = 1.49; 95% CI = 0.90, 2.47). In contrast, risk of both SCC and BCC were unrelated to use of inhaled steroids. Our data suggest that use of oral glucocorticoids may increase risk of NMSC, and SCC in particular, among patients other than organ transplant recipients. We hypothesize that immunosuppression induced by oral glucocorticoids may allow these cancers to emerge from immunosurveillance.

Fatal poisoning from liquid dimethylmercury: a neuropathologic study

Since ancient times, mercury has been recognized as a toxic substance. Dimethylmercury, a volatile liquid organic mercury compound, is used by a small number of chemistry laboratories as a reference material in nuclear magnetic resonance spectroscopy. To our knowledge, dimethylmercury has been reported in only three cases of human poisoning, each proving fatal. Very small amounts of this highly toxic chemical can result in devastating neurological damage and death. We report the neuropathologic findings in a fatal case of dimethylmercury intoxication occurring in a laboratory researcher that resulted from a small accidental spill. We compare these findings to those reported in one previously reported fatal case of dimethylmercury poisoning, and to earlier reports of monomethylmercury poisoning, and discuss the clinicopathologic correlation.

The impact of early clinical training in medical education: a multi-institutional assessment

With funding from The Robert Wood Johnson Foundation's Generalist Physician Initiative, Dartmouth Medical School (DMS), New York Medical College (NYMC), and Virginia Commonwealth University School of Medicine (VCU-SOM) adopted early community-based training models for longitudinal clinical experiences. These schools developed different evaluation strategies to assess these models. This paper describes each program, the method used to evaluate an aspect of the program, lessons learned about early clinical teaching and learning, and challenges encountered. Each program used cross-sectional evaluation, and the analysis methods included descriptive statistics, chi-square, t-tests, analysis of variance, and generalized linear models. Dartmouth determined that the type of preceptor does not greatly influence the development of clinical skills, although case-specific differences were discovered. NYMC learned that students taught clinical skills in community-based settings performed as well as or better than their peers who received early patient experience on hospital wards. Virginia Commonwealth discovered that community experiences contributed positively to students' education, critical thinking, and problem-solving skills. Students value early clinical experiences and make important achievements in clinical skills and knowledge development, although logistic challenges exist in conducting these courses. Evaluations are critical to ensure competency, and faculty development must be linked to the evaluation process.

The use of "vertical integration groups" to help define and update course/clerkship content

Faculty at many medical schools are working hard to improve the quality of their curricula. While the world "curriculum" means different things to different people, curricular change often includes improving the structure of the teaching/learning environment (e.g., seminars or problem-based learning groups vs lectures), the content of courses and clerkships (the core set of knowledge, skills, and attitudes that should be learned), and the manner in which student learning of knowledge and skills is evaluated (the sense that evaluation can help "drive" the curriculum). The author describes how "vertical integration groups" have been used over four years at Dartmouth Medical School to improve and modernize the content of courses and clerkships. In this approach, students and faculty work together to address and improve content areas that normally are not associated with traditional, discipline-centered courses or clerkships. The author discusses the advantages of this approach, the challenges encountered during implementation, and examples of how the approach has been put into action.

The challenge of "teaching" large groups of learners: strategies to increase active participation and learning

While teaching in a tutorial, seminar, or problem-based learning group format may be the most fun and most active/interactive for both learner and faculty mentor, there are situations in medical student education in which various constraints require the use of the "lecture" format. Similar constraints may occur in the field of continuing medical education, or graduate medical education, as well. When this occurs, the faculty mentor can increase the active participation of the learners in the audience by continuously stressing seven key pedagogical (androgogical) principles. These include: 1) begin the learning exercise with a clinical example or anecdote to show the relevance of the material to the student; 2) frequently ask the students whether they have ever seen examples of what you describe in their previous experience with patients, personal experience, experience with relatives, etc.; 3) ask students frequently whether they have heard similar material presented differently in other courses; 4) recruit students to help solve "mystery cases"; 5) show examples of similar material from real life (e.g., patient descriptions, or even excerpts from favorite TV shows); 6) ask students to help summarize key points at the end of the session; and 7) allow, or even encourage, whispering during the class. Using some or all of these techniques can help turn a "lecture format" into a much more fun, interactive, and valuable session that emphasizes "learning" rather than "teaching."

Olsalazine and 6-mercaptopurine-related bone marrow suppression: a possible drug-drug interaction

A patient with refractory Crohn's disease had two separate episodes of bone marrow suppression while receiving 50 to 75 mg 6-mercaptopurine a day and 1000 to 1750 mg olsalazine a day. This adverse reaction necessitated dose reduction of 6-mercaptopurine on the first occasion and withdrawal of 6-mercaptopurine and olsalazine on the second occasion. The patient's red blood cell thiopurine methyltransferase (TPMT) activity was 1.2 U per milliliter red blood cells (low normal range) and her TPMT genotype was wild-type sequence for all known alleles of TPMT that result in low TPMT enzyme activity. In vitro enzyme kinetic studies confirmed the hypothesis that olsalazine and olsalazine-O-sulfate are potent noncompetitive inhibitors of recombinant human TPMT. We suggest that the patient's relatively low baseline level of TPMT activity was inhibited by olsalazine and olsalazine-O-sulfate, leading to decreased clearance of 6-mercaptopurine and its accumulation. This ultimately increased intracellular 6-thiopurine nucleotide levels to toxic concentrations, which caused bone marrow suppression.

Effects of 4 y of oral supplementation with beta-carotene on serum concentrations of retinol, tocopherol, and five carotenoids

beta-Carotene has been studied widely as a potential cancer-preventing agent. Recent studies found that subjects who took beta-carotene supplements orally had increases in their serum concentrations of alpha-carotene and lycopene that were large (> 150% increase) and significantly greater than such increases in subjects who received placebo and that similar supplementation was associated with a decrease of approximately 37% in plasma lutein concentrations. A biologic interaction between beta-carotene and other carotenoids was suggested. We measured concentrations of retinol, alpha-tocopherol, and five carotenoids in serum specimens from a random sample of subjects enrolled in a clinical trial of the use of antioxidant vitamins in preventing colonic adenomas. We used serum specimens obtained at enrollment and after the subjects took placebo (n = 54) or 25 mg beta-carotene/d (n = 54) orally for 4 y. In a multivariate analysis, baseline serum concentrations of the analytes, sex, body mass index, diet, smoking status, and age were associated with variable changes in some analytes over the 4-y period but supplementation with beta-carotene was related only to a mean increase in serum beta-carotene itself of 151%. We excluded with 95% confidence an increase in lycopene > 4.9%, an increase in alpha-carotene > 17.6%, and a decrease in lutein > 14.7% in subjects given beta-carotene. These results confirm previous findings that supplementation with beta-carotene given orally does not alter serum concentrations of retinol or alpha-tocopherol. The findings also indicate that beta-carotene supplementation, which results in a moderate increase in serum beta-carotene concentration, does not significantly change serum concentrations of other carotenoids.

Mortality associated with low plasma concentration of beta carotene and the effect of oral supplementation

OBJECTIVE

To examine the relationship between beta carotene plasma concentration and beta carotene supplementation and risk of death from major disease causes.

DESIGN

Cohort study of plasma concentrations; randomized, controlled clinical trial of supplementation.

SETTING

Medical school-affiliated dermatology practices.

PATIENTS

A total of 1188 men and 532 women with mean age of 63.2 years, who had enrolled in a randomized clinical trial of beta carotene supplementation to prevent nonmelanoma skin cancer.

INTERVENTION

Oral beta carotene, 50 mg per day for a median of 4.3 years.

MAIN OUTCOME MEASURES

All-cause mortality and mortality from cardiovascular disease and cancer.

RESULTS

During a median follow-up period of 8.2 years, there were 285 deaths. Persons whose initial plasma beta carotene concentrations were in the highest quartile (>0.52 micromol/L [27.7 microg/dL]) had a lower risk of death from all causes (adjusted relative rate [RR], 0.52; 95% confidence interval [CI] 0.44 to 0.87) and from cardiovascular diseases (adjusted RR, 0.57; 95% CI, 0.34 to 0.95) compared with persons with initial concentrations in the lowest quartile (<0.21 micromol/L [11.2 microg/dL]). Patients randomly assigned to beta carotene supplementation showed no reduction in relative mortality rates from all causes (adjusted RR, 1.03; 95% CI, 0.82 to 1.30) or from cardiovascular disease (adjusted RR, 1.16; 95% CI, 0.82 to 1.64). There was no evidence of lower mortality following supplementation among patients with initial beta carotene concentrations below the median for the study group.

CONCLUSIONS

These analyses provide no support for a strong effect of supplemental beta carotene in reducing mortality from cardiovascular disease or other causes. Although the possibility exists that beta carotene supplementation produces benefits that are too small or too delayed to have been detected in this study, noncausal explanations should be sought for the association between plasma concentrations of beta carotene and diminished risk of death.

Analysis of within-subject variation of caffeine metabolism when used to determine cytochrome P4501A2 and N-acetyltransferase-2 activities

Cytochrome P4501A2 (CYP1A2) and N-acetyltransferase-2 (NAT2) are hepatic enzymes that may activate some procarcinogens. Previous reports have determined CYP1A2 and NAT2 phenotypes by quantitating relative amounts of urinary caffeine and metabolites. However, a number of experimental issues with this approach remain. To address these, we measured caffeine and 4 metabolites in urine samples from 20 healthy volunteers on 3 separate occasions at 7-day intervals. Two additional volunteers were studied to measure the pattern of excretion of these analytes in urine over time. The molar ratio of two compounds (1,7-dimethylxanthine/1,3,7-trimethylxanthine) was used to phenotype CYP1A2, while the molar ratio of two other compounds (5-acetylamino-6-formylamino-3-methyluracil/1-methylxanthine) served to phenotype NAT2. Within-subject variation was less than 25% for most participants. In instances when within-subject variation of the metabolic ratio was > 25%, metabolite peaks were usually present in one or more control urine samples. Some caffeine metabolites were observed in urine samples at detectable levels up to 48 h after caffeine ingestion. We conclude that: (a) this assay for determining CYP1A2 and NAT2 activities (phenotyping) has an acceptably low within-subject variation over 3 consecutive weeks for most subjects who were caffeine-free for 36 h prior to study; (b) collecting and analyzing urine samples prior to testing can indicate if subjects are excreting caffeine metabolites and will aid in locating metabolite peaks on chromatograms; (c) refraining from caffeine for 48 h before testing is the best compromise between convenience for the subject and obtaining reproducible results; (d) determining metabolite molar ratios in urine collected 4-5 h after ingesting caffeine provides an acceptable time for the measurement; and (e) different ratios of metabolites for determining CYP1A2 phenotype have different advantages.

Steady-state serum concentration of alpha tocopherol not altered by supplementation with oral beta carotene. The Polyp Prevention Study 1 Group

BACKGROUND

The antioxidants beta carotene and vitamin E may play a role in cancer prevention. However, some studies have suggested that oral supplements of beta carotene may cause a decrease in serum levels of alpha tocopherol (vitamin E).

PURPOSE

We conducted this study to determine if beta carotene supplements affect serum levels of vitamin E and vice versa.

METHODS

Five hundred five patients in a clinical trial of antioxidant vitamins, used to prevent recurrences of colonic polyps, received either a placebo, 25 mg of beta carotene per day, 1 g ascorbic acid plus 400 mg alpha tocopherol per day, or all three agents combined. Serum levels of beta carotene and vitamin E were measured before and after 9 months of supplementation, using high-performance liquid chromatography.

RESULTS

Vitamin E levels changed very little among the groups receiving placebo or beta carotene and went up substantially and equally in the groups receiving vitamin E plus ascorbic acid or all three agents together. Conversely, beta carotene levels changed very little for the groups receiving placebo or ascorbic acid plus vitamin E but went up substantially and equally for the groups receiving beta carotene alone or all three agents.

CONCLUSIONS

We conclude that oral supplementation with beta carotene for 9 months does not alter serum concentration of vitamin E and that supplementation with vitamin E plus ascorbic acid does not alter serum beta carotene levels.

Serum concentrations of retinol, d-alpha-tocopherol and beta-carotene: effects of storage at -70 degrees C for five years

To investigate the effects of prolonged storage of serum samples at -70 degrees C on concentrations of micronutrients, we measured concentrations of retinol, d-alpha-tocopherol, and beta-carotene in serum samples drawn in 1986. We compared values we measured in 1991 to values we obtained in 1986, using the same analytical methods. The relative concentrations obtained in 1991 (mean +/- S.D.) were: retinol 99.7 +/- 12.6% (n = 23), d-alpha-tocopherol 100.7 +/- 6.4% (n = 19), and beta-carotene 103.4 +/- 13.7% (n = 28). Using these techniques of sample preparation and high-performance liquid chromatographic analysis, we found that the effects of storage of serum at -70 degrees C for five years appear insignificant in a small population of patients. However, we did identify clinically important changes in concentration (> 20% difference) in several individual subjects.

Treatment of nocturnal leg cramps. A crossover trial of quinine vs vitamin E

OBJECTIVE

This study compared the efficacy and safety of quinine sulfate, vitamin E, and placebo in the treatment of nocturnal leg cramps.

DESIGN

A random-order, double-blind, placebo-controlled crossover trial was performed.

SETTING

The study was conducted at the Veterans Affairs Medical Center, White River Junction, Vt.

PARTICIPANTS

Twenty-seven male veterans, aged 38 to 73 years, who experienced at least six leg cramps per month were recruited through the general medicine walk-in clinic or were referred from other clinics. Fifty-five subjects were contacted, 30 were enrolled consecutively, and 27 completed the study.

INTERVENTION

Subjects received, in random order, quinine sulfate (200 mg at supper and 300 mg at bedtime), vitamin E (800 U at bedtime), or placebo for 4-week periods. These periods were separated by 4-week washout intervals.

OUTCOME MEASURES

Patients reported cramp frequency, severity, and sleep disturbance caused by cramps.

RESULTS

Compared with treatment with placebo, quinine reduced the frequency of cramps and sleep disturbance, but not the average cramp severity. Thirteen of 27 patients had at least a 50% reduction in the number of cramps while receiving quinine; the response was usually seen within 3 days. There was evidence of a mild increase in side effects while subjects received quinine. Vitamin E was not effective in reducing leg cramp frequency, severity, or sleep disturbance.

CONCLUSIONS

Quinine sulfate, but not vitamin E, is superior to placebo in the treatment of nocturnal leg cramps.

A method for determining concentrations of retinol, tocopherol, and five carotenoids in human plasma and tissue samples

To explore the relation between plasma and tissue concentrations of seven fat-soluble micronutrients (retinol, alpha-tocopherol, lutein, cryptoxanthin, lycopene, alpha-carotene, and beta-carotene), we developed methods for clarifying plasma and tissue samples and quantitating these seven analytes simultaneously by using HPLC with ultraviolet detection. Clarification of tissue samples was performed by using enzymatic digestion followed by mechanical homogenization; saponification was avoided and tocopherol nicotinate was used as an internal standard. Precision and sensitivity for small samples of plasma and solid tissues were determined. Accuracy for plasma samples was assessed by comparing results obtained by using this method with those obtained by using older, standardized methods. Results from application of this method to patient samples of plasma and various tissues are presented. This method will be of interest to investigators seeking to quantitate these seven micronutrients in solid tissue samples, but desiring to avoid the usual saponification step required in most other reported techniques.

Diurnal and seasonal variation of five carotenoids measured in human serum

We studied within-person variation over time in serum concentrations of five carotenoids. In a diurnal study involving 33 subjects, only the 1700 h blood samples demonstrated carotenoid concentrations different from the original 0800 values. Correlations between serum concentrations of the same carotenoids drawn 1 d apart ranged from 0.93 to 0.98. In a seasonal study involving 29 subjects, no systematic trends were observed for serum concentrations of these carotenoids. Correlations between concentrations of the same carotenoids drawn 1 y apart ranged from 0.57 to 0.82. Concentrations of different carotenoids within an individual tended to be correlated with each other. Obtaining one blood sample from subjects is a relatively imprecise way to estimate their usual serum concentrations of carotenoids. If an epidemiological study was to be based on only one determination of serum carotenoids, within-person variability in serum concentrations would attenuate true regression coefficients by 4-13% and would increase the required numbers of study subjects by 19-65%.

Mineral spirits inhalation associated with hemolysis, pulmonary edema, and ventricular fibrillation

A previously healthy 42-year-old woman developed severe dyspnea, chest discomfort, and malaise several hours after prolonged exposure to concentrated vapors from mineral spirits. On the way to the hospital, she sustained a cardiopulmonary arrest; on arrival several minutes later, she was found to be in ventricular fibrillation and was resuscitated. Her hospital course included slowly resolving cardiac abnormalities, amnesia, noncardiogenic pulmonary edema, abrupt hemolytic anemia, sustained rhabdomyolysis, and other metabolic abnormalities. It is highly probable that this syndrome represented acute and near-lethal toxicity caused by the inhalational exposure to the petroleum distillate known as mineral spirits. It is important that physicians be aware of this syndrome in order to recognize it on presentation and to warn patients of the risk of such toxic exposure.

Determinants of increase in plasma concentration of beta-carotene after chronic oral supplementation. The Skin Cancer Prevention Study Group

We studied the relationship between eight variables, including age, sex, baseline plasma beta-carotene (BC) concentration, and smoking status and the increase in plasma BC in 582 subjects receiving oral supplementation with 50 mg BC/d. Median plasma BC concentrations after 1 y of supplementation increased from 335 nmol/L at entry to 3163 nmol/L. Changes in plasma BC concentrations ranged widely from -313 to 16,090 nmol/L (median 2721 nmol/L). Multivariate analysis revealed that the subject's plasma BC concentration before supplementation was the most important indicator of the amount of increase after supplementation. Nonsmokers, women, and leaner subjects all had larger increases in plasma concentrations although the statistical model could account for relatively little of the variability in subjects' plasma response to BC supplementation (R2 = 0.14). We conclude that between-subject variability in response to daily supplementation with oral BC is very large and that the best predictor of this response is the initial plasma BC concentration.

Neuroleptic malignant syndrome: occurrence in a child after reconstructive surgery

The occurrence of the rare but potentially fatal neuroleptic malignant syndrome must be considered by the surgeon treating a patient who develops hyperthermia, mental abnormalities, autonomic instability, and muscle rigidity after exposure to phenothiazines or other neuroleptic drugs. The dopamine agonist bromocriptine appears to be the treatment of choice in adults and seemed to be effective and well tolerated in our patient. Although the syndrome cannot be prevented, recognition is crucial, since effective general and specific therapy is available. Differentiating neuroleptic malignant syndrome from malignant hyperthermia allows early appropriate treatment with bromocriptine.

Lack of effect of chronic administration of oral beta-carotene on serum cholesterol and triglyceride concentrations

Previous studies suggest that chronic oral administration of retinol and other retinoids causes elevation of plasma triglyceride concentrations. The effects of chronic oral administration of beta-carotene, a carotenoid partially metabolized to retinol, on plasma lipid concentrations have not been well studied; therefore, we studied 61 subjects over 12 mo while they were enrolled in a skin-cancer-prevention study in which patients were randomly assigned to receive either placebo (n = 30) or 50 mg beta-carotene/d orally (n = 31). At study entry and 1 y later, fasting blood samples were obtained for measurement of triglycerides, total cholesterol, HDL cholesterol, retinol, and beta-carotene. Retinol concentrations changed minimally in both groups; beta-carotene concentration increased an average of 12.1 +/- 47 nmol/L in the placebo group and 4279 +/- 657 nmol/L in the active-treatment group. Both groups experienced similar small increases in triglyceride and total cholesterol concentrations and small decreases in HDL cholesterol. Daily oral administration of 50 mg beta-carotene/d did not affect plasma lipid concentrations.

A clinical trial of beta carotene to prevent basal-cell and squamous-cell cancers of the skin. The Skin Cancer Prevention Study Group

BACKGROUND

Beta carotene has been associated with a decreased risk of human cancer in many studies employing dietary questionnaires or blood measurements, and it has had protective effects in some animal models of carcinogenesis.

METHODS

We tested the possible cancer-preventing effects of beta carotene by randomly assigning 1805 patients who had had a recent nonmelanoma skin cancer to receive either 50 mg of beta carotene or placebo per day and by conducting annual skin examinations to determine the occurrence of new nonmelanoma skin cancer.

RESULTS

Adherence to the prescribed treatment was good, and after one year the actively treated group's median plasma beta carotene level (3021 nmol per liter) was much higher than that of the control group (354 nmol per liter). After five years of follow-up, however, there was no difference between the groups in the rate of occurrence of the first new nonmelanoma skin cancer (relative rate, 1.05; 95 percent confidence interval, 0.91 to 1.22). In subgroup analyses, active treatment showed no efficacy either in the patients whose initial plasma beta carotene level was in the lowest quartile or in those who currently smoked. There was also no significant difference between treated and control groups in the mean number of new nonmelanoma skin cancers per patient-year.

CONCLUSIONS

In persons with a previous nonmelanoma skin cancer, treatment with beta carotene does not reduce the occurrence of new skin cancers over a five-year period of treatment and observation.

Determinants of plasma levels of beta-carotene and retinol. Skin Cancer Prevention Study Group

The associations of retinol and beta-carotene plasma concentrations with eight personal variables and the use of seven classes of cardiovascular drugs were studied in over 1,750 patients with nonmelanoma skin cancer enrolled at four American study centers in a cancer prevention clinical trial. Dietary carotene and female sex were positively related to beta-carotene levels, while cigarette smoking and Quetelet index were negatively related. Use of vitamins, beta blockers, or other antihypertensive drugs were also related to beta-carotene levels, but were associated with much smaller changes in these levels. Age and use of other types of cardiovascular drugs were not associated with beta-carotene levels to a statistically significant extent. There was no statistically significant interaction of smoking and dietary carotene in predicting plasma beta-carotene levels. The multiple correlation coefficient between log plasma beta-carotene and the full model was R = 0.50. Retinol levels were positively related to male sex and use of vitamins, diuretics, beta blockers, other cardiovascular drugs, and menopausal estrogens, and negatively related to current cigarette smoking and use of nitrates. The multiple correlation coefficient between plasma retinol and the full model was R = 0.33. These findings confirm the importance of several previously reported predictors of plasma retinol and beta-carotene levels. They also identify several new predictors of these micronutrient levels.

Diurnal variation in plasma levels of retinol, tocopherol, and beta-carotene

Diurnal changes in human plasma levels of the fat-soluble vitamins retinol (R), alpha-tocopherol (E), and beta-carotene (CAR) have not been determined. Plasma levels of these three vitamins in 15 healthy volunteers were measured five times over a 24-hour period. Highly sensitive and specific HPLC assays were used. Mean +/- SEM levels for R, E, and CAR were 591 +/- 36 ng/mL, 10.3 +/- 0.6 micrograms/mL, and 271 +/- 28 ng/mL, respectively. Differences between subjects' mean levels were large and highly significant (p less than 0.0001). Relative to the first 8 AM fasting plasma sample, nonfasting plasma levels drawn over the next 24 hours showed no statistically significant or clinically important changes. The percent increases in standard deviation among subjects due to diurnal variation were 1.5%, 3.3%, and 2.3%, respectively, for R, E, and CAR. This implies that sample sizes for cross-sectional studies investigating differences between two treatments in these vitamin plasma levels would need to be increased by 3%, 7%, and 5%, respectively, if measurements are to be taken throughout the day. Plasma levels may be obtained at random during the day, and need not be 8 AM fasting levels. The small addition in variation introduced by diurnal fluctuations would have minimal impact upon the precision of estimates of treatment effect and sample sizes.

Measuring drug levels in the office: rationale, possible advantages, and potential problems

New technologies allow plasma levels of several drugs to be measured in the physician's office. Although such assays have the advantage of increased convenience for both physician and patient, they have a number of potential problems as well. Regardless of where plasma assays are performed, the physician must understand the rationale and pitfalls of therapeutic drug monitoring.

Drug inhibition of penicillin tubular secretion: concordance between in vitro and clinical findings

Using the rabbit kidney slice model of active tubular secretion, I studied the active accumulation of penicillin (PEN) in the absence and presence of competing drugs to evaluate the feasibility of using in vitro uptake to predict in vivo secretion. Active accumulation of PEN by these slices was saturable at high PEN concentrations and was inhibited by incubation conditions which decreased ATP production. PEN uptake in the presence of 1 mM concentrations of mannitol, tolazoline and tetraethylammonium was unchanged. However, PEN uptake in the presence of eight weak organic acid drugs (probenecid, phenylbutazone, sulfinpyrazone, salicylate, sulfamethizole, chlorothiazide, sulfamethoxypyridazine and indomethacin) was inhibited significantly. This inhibition appeared to be competitive in nature and the inhibitor-transport carrier protein dissociation constant (Ki) for each inhibitory drug was calculated (range, 0.38-74.8 X 10(-5) M). When these values for Ki obtained with PEN were compared to values obtained with methotrexate and p- aminohippurate, the values of Ki were similar, implying the presence of a similar transport carrier protein for PEN, methotrexate and p-aminohippurate. The effects of these eight drugs upon PEN clearance in vivo were extrapolated from the medical literature. The relative inhibitory strengths of these drugs based upon in vitro findings (drug plasma concentration/Ki ratios) and clinical findings (inhibition of PEN clearance) were concordant. This in vitro model for assessing inhibition of renal tubular secretion may be of general utility in predicting clinically important drug interactions between weak organic acid drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of tocopherol and tocopherol acetate concentrations in human feces using high-performance liquid chromatography

A method of sample clarification and high-performance liquid chromatography (HPLC) specifically developed to permit simple and rapid determination of vitamin E (alpha-tocopherol, E) and vitamin E acetate (EA) in feces is reported. Retinol acetate (RA) was used as an internal standard. The vitamins of interest were extracted from an aqueous stool suspension into an organic phase (ethyl acetate-butanol), which was injected directly onto the reversed-phase HPLC system. An isocratic mobile phase of methanol-water (97:3) was employed, with ultraviolet detection at 275 and 285 nm (to permit simultaneous monitoring and absorbance ratio determination). Recoveries of exogenous RA, E, and EA from stool suspensions (relative to water) were 99.0 +/- 7.0, 100.9 +/- 7.0, and 101.2 +/- 13.3%, respectively (n = 10). The organic matrix could be stored at -35 degrees C overnight with no change in E or EA results. Sensitivities for E and EA were 80 and 102 micrograms/g of stool, respectively. Each analysis required nine min. The within-day coefficients of variation were 2.9, 3.6, and 3.0% (n = 7) for RA, E, and EA, respectively. Neither E nor EA were detected in baseline fecal samples from fourteen subjects, but both were present in high but varied concentrations after four weeks supplementation with oral d,l-EA. E but not EA was present in blood samples drawn during periods of oral supplementation with EA. There was poor correlation between fecal levels of E and EA, and the increase in serum levels of E. This method permits rapid, selective, and precise determination of E and EA in human fecal samples.

The effects of a required fourth-year clinical pharmacology course on student attitudes and subsequent performance

Beginning with the class graduating June 1984, Dartmouth Medical School introduced a required clinical pharmacology course. Approximately 89% of the fourth-year students felt that the course was "essential" to their future careers as physicians. As interns, 80% found the course frequently useful or essential during their internships; 84% felt that they were either slightly or much better prepared than their fellow interns with respect to their therapeutic knowledge and skills. Average student performance on a pretest (33% correct answers) improved dramatically on a posttest (87% correct; P less than 0.001). Finally, although student performance on all sections of Part II of the national board examinations showed statistically nonsignificant trends toward improvement (from the 48th to the 52nd percentile), performance on questions testing core concepts in clinical pharmacology improved from the 38th percentile to the 74th percentile (P less than 0.0001). This required fourth-year course in clinical pharmacology was evaluated favorably by our students and resulted in objective improvement in their therapeutic knowledge and skills.

A clinical trial of nafazatrom (Bay g 6575) in advanced cancer

Nafazatrom (Bay g 6575) has been shown to be a potent inhibitor of tumor metastasis in preclinical models. It is believed to work by stimulating endogenous prostacyclin production. The drug has also been shown to inhibit the growth of certain experimental tumors, to be cytostatic for certain cell lines in tissue culture, and to induce differentiation in HL-60, neuroblastoma, and Friend erythroleukemia cell lines. Furthermore, no toxicity has been seen in animals or human volunteers. We report here a clinical trial of oral nafazatrom at five dose levels in patients with advanced cancer. Thirty patients with a wide variety of advanced malignancies were treated for 26-638+ days (median 82 days). No tumor responses were seen. Toxicity included two cases with mild skin rashes, one case with nausea and vomiting, and one case with diarrhea. Nafazatrom is a safe and well-tolerated agent. Maximum activity would be predicted to occur in the adjuvant treatment of cancer and we feel that further efforts should proceed to identify the appropriate dose for such a trial.

Determination of vitamins A and E in serum and plasma using a simplified clarification method and high-performance liquid chromatography

A method of sample clarification and high-performance liquid chromatography specifically developed to permit precise and rapid determination of vitamin A (retinol) and vitamin E (alpha-tocopherol) in serum and plasma is reported. Serum proteins were denatured by the addition of acetonitrile containing alpha-tocopherol acetate, the internal standard; the vitamins were subsequently extracted into an organic matrix consisting of ethyl acetate-butanol (1:1); no solvent evaporation step was required. The three vitamins of interest were eluted from a reversed-phase C18 column with an isocratic mobile phase methanol-water (95:5); detection was accomplished by measuring ultraviolet absorption at 280 nm. Recoveries of retinol, alpha-tocopherol and alpha-tocopherol acetate from spiked aqueous samples averaged 100.0, 100.0 and 98.8%, respectively. Recoveries of retinol, alpha-tocopherol and alpha-tocopherol acetate from plasma and serum relative to water were 102.6, 96.9 and 96.5%, respectively. Retinol and alpha-tocopherol were stable in the extraction matrix for up to 3.5 h, and were stable in heparinized plasma stored at room temperature for two days. Oxalate, citrate and EDTA caused significant losses of retinol and alpha-tocopherol, while vitamin levels in serum and heparinized plasma were similar. Limits of detection for retinol and alpha-tocopherol were 60 ng/ml and 0.9 micrograms/ml, respectively. Each run required 12 min. Same-day coefficients of variation were 3.5 and 3.6% for retinol and alpha-tocopherol, respectively (n = 11). Between-day coefficients of variation for retinol and alpha-tocopherol were 4.8 and 5.5%, respectively (n = 5). This method permits simple, rapid, sensitive, selective and precise determination of retinol and alpha-tocopherol using 0.5 ml of serum or heparinized plasma.

Serum and plasma beta-carotene levels measured with an improved method of high-performance liquid chromatography

An isocratic high-performance liquid chromatographic method specifically developed to allow simple and rapid determination of beta-carotene concentrations in serum and plasma is reported. Using a method modified from a previously published technique, serum and plasma proteins are denatured by exposure to perchloric acid, and beta-carotene is subsequently extracted into an organic matrix consisting of ethyl acetate-tetrahydrofuran (1:1); no evaporation step is required. Separation is achieved using isocratic elution from a reversed-phase C18 column with UV detection at 436 nm. Recovery of beta-carotene from water and plasma was greater than 98.1%; beta-carotene was stable in the extraction matrix for at least 4 h. Three anticoagulants (oxalate, citrate, and EDTA) caused losses of beta-carotene; perchloric acid and tetrahydrofuran could also destroy beta-carotene under certain conditions. Each run required less than 15 min; within-day coefficient of variation for identical samples averaged 2.3%, between-day coefficient of variation was 4.4% and sensitivity was better than 10 ng/ml. Stability of beta-carotene in plasma was also examined. This method permits a simple, rapid, sensitive, precise, and accurate determination of beta-carotene using 0.5 ml of serum or heparinized plasma.

Determination of serum and plasma concentrations of retinol using high-performance liquid chromatography

An isocratic high-performance liquid chromatographic method specifically developed to allow simple and rapid determination of retinol concentrations in serum and plasma is reported. Retinol and retinol acetate (the internal standard) are extracted into butanol-ethyl acetate, with no subsequent evaporation step. Separation is achieved on a reversed-phase C-18 column, with a mobile phase consisting of acetonitrile-1% ammonium acetate (89:11), and UV detection at 313 nm. Recoveries of both retinol and the internal standard were 100%, and both compounds were stable in the extraction solvent for at least 2.5 h. Three anticoagulants (oxalate, citrate, EDTA) and perchloric acid (used in some methods to denature protein) all caused losses of retinol. Each run required 9 min; same-day coefficient of variation (C.V.) for identical samples averaged 2.5%; between-day C.V. was 6.4%; sensitivity was better than 10 ng/ml, while clinical concentrations were 400-1200 ng/ml. This method permits simple, rapid, sensitive, precise, and accurate determination of retinol using 0.5 ml serum or heparinized plasma.

Selective killing of transformed cells by methotrexate with histidine deprivation or with alpha-amino alcohols

The effects of amino acid deprivation and treatment with amino alcohols upon the growth, viability, and susceptibility to methotrexate (MTX) cytotoxicity were examined in BALB/3T3 cells and their virally transformed counterparts, SV-T2 cells. Cells were deprived of either histidine or tyrosine plus phenylalanine, or they were treated with amino alcohol analogues of histidine and tyrosine (histidinol and tyrosinol). When incubated in medium lacking histidine and supplemented with dialyzed serum (histidine-deficient medium), the BALB/3T3 cells remained viable for at least 3 days, but they ceased logarithmic growth, and the cell number reached an early plateau. In contrast, the SV-T2 cells continued to divide in histidine-deficient medium. Neither cell line ceased division in medium deficient in both phenylalanine and tyrosine. Incubation of the BALB/3T3 cells with 1.5 mM histidinol or 1.0 mM tyrosinol caused an early plateau similar to the effect of histidine deprivation. SV-T2 cells were not affected by these concentrations of histidinol or tyrosinol, but growth was arrested at higher concentrations. Any of the conditions used which caused a plateau in the number of BALB/3T3 cells substantially protected the treated cells from cell death caused by MTX. Therefore, pretreatment of BALB/3T3 cells with histidine deprivation, 1.5 mM histidinol, or 1.0 mM tyrosinol protected this cell line against MTX-induced cell death, while the same pretreatment conditions failed to protect SV-T2 cells. (SV-T2 cells were protected by 4.0 mM histidinol.) Thus, the ability of MTX to kill cells in vitro can be selectively modified by conditions which protect cells which retain normal growth control characteristics, but which do not protect virally transformed cells.