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Biomedical subjects

G Koren

Publications and source records attributed to G Koren.

At least 289 records · Page 16Linked to original sources
PubMed1996

Chemotherapy with focal therapy can cure intraocular retinoblastoma without radiotherapy.

BACKGROUND: External beam radiotherapy is standard treatment for medium and large, or visually threatening, intraocular retinoblastoma but markedly increases the risk of cosmetic deformities and second malignant neoplasms in children with germline RB1 mutations. Large tumors and those with vitreous seeds do poorly despite radiotherapy. Chemotherapy traditionally is ineffective for intraocular retinoblastoma, perhaps because many retinoblastomas overexpress the multidrug resistance protein, P-glycoprotein. OBJECTIVE: To avoid radiotherapy in the management of intraocular retinoblastoma by using chemotherapy and focal therapy. INTERVENTIONS: We shrank retinoblastomas in 40 eyes of 31 patients that conventionally should be enucleated or receive radiotherapy by using chemotherapy (ie, vincristine-teniposide, 8 eyes; additional carboplatin, 32 eyes) combined with the administration of cyclosporine, a known multidrug-resistance-reversal agent. We then consolidated these responses to chemotherapy by subsequent 532- and 1064-nm laser therapy and cryotherapy. RESULTS: At the median follow-up of 2 2/3 [corrected] years (range, 1/10-4 3/4 years), the results of treatment were excellent. The actuarial relapse-free rate was 89% in patients not previously treated (91% for 28 eyes) and 67% in patients treated after relapse from previous therapy (70% for 12 eyes). For the eyes with the worst prognosis (ie, vitreous seeds), the relapse-free rate was 88%, better than previously reported. Cyclosporine is nontoxic and did not enhance the expected toxic effects of chemotherapy. Most eyes required laser therapy, cryotherapy, or both for consolidation of tumor control. CONCLUSIONS: This pilot study suggests that most retinoblastomas are curable by combining chemotherapy with cyclosporine therapy, laser therapy, and cryotherapy, without requiring external beam radiotherapy. We propose a randomized trial to clarify the role of cyclosporine.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Outpatient treatment of croup with nebulized dexamethasone.

PURPOSE: To determine if treating children who have acute, moderate croup with nebulized dexamethasone sodium phosphate in the emergency department results in clinical improvement by 4 hours and a decrease in the hospitalization rate. DESIGN: Randomized, double-blind, placebo controlled trial. SETTING: Emergency department, children's hospital. PATIENTS: Fifty-five children with croup who were in moderate respiratory distress after treatment with mist for 30 minutes who met inclusion and exclusion criteria. MEASUREMENTS: Croup score, respiratory rate, heart rate, and oxygen saturation were assessed by one of us (D.W.J. or S.S.) before treatment and 2 and 4 hours after treatment. A staff pediatrician or senior pediatric resident, also "blind" to treatment, decided on admission to or discharge from the hospital. The differences between groups for change in croup score and hospitalization rate after treatment were analyzed. RESULTS: Evaluation of the croup scores disclosed a significant improvement in the dexamethasone-treated group compared with the placebo group at 4 hours (P=.005, Mann-Whitney U). However, the hospitalization rate was not statistically different at the end of treatment (33% vs 52%, P=.28) or after 24 hours (48% vs 60%, P=.56, Yates corrected chi(2)). Our study has 80% power to detect a two-thirds reduction in hospitalization rate. Two patients with neutropenia treated with dexamethasone had a clinical course consistent with bacterial tracheitis. CONCLUSIONS: Treatment of moderate croup with nebulized dexamethasone results in clinical improvement within 4 hours. We did not show a decrease in hospitalization rates, although our sample size was only large enough to detect a 67% reduction in the rate of hospitalization. Given the infectious complications and the absence of evidence for a sustained clinical effect, we do not recommend that patients with croup be treated with nebulized dexamethasone.

Acute Disease↗
PubMed1996

Hepatotoxicity of 6-mercaptopurine in childhood acute lymphocytic leukemia: pharmacokinetic characteristics.

Treatment with 6-mercaptopurine (6MP) is associated with adverse gastrointestinal (GI) and hepatic effects. Four patients, ages 6.9 +/- 2.6 (mean +/- S.D.) years, with acute lymphocytic leukemia (ALL) on maintenance chemotherapy including 6MP, developed nausea, vomiting, abdominal pain, elevated liver enzymes, and hyperbilirubinemia after 1.4 +/- 1.0 (range 0.5-2) years. Liver biopsy in 1 patient was suggestive of drug-induced intrahepatic cholestatis. Symptoms resolved and liver function returned to normal after discontinuation of 6MP. Pharmacokinetic data of the symptomatic patients were compared with those of 25 ALL patients on the same protocol but without GI symptoms or hepatotoxicity. Levels of 6-thioguanine nucleotides (6-TGN) and the methylated metabolites of 6MP in red blood cells of the patients with hepatotoxicity, were not significantly different when compared to patients without hepatotoxicity, suggesting similar absorption of 6MP in both groups. Time to achieve peak 6MP levels was significantly longer in the symptomatic patients compared to the asymptomatic patients (P = 0.005). Peak levels and standardized concentration versus time curve (AUC) per 1 mg of 6MP per m2 of body surface area were significantly lower in the patients with hepatotoxicity (P = 0.016; P = 0.037, respectively). A significant correlation between peak 6MP levels and standardized AUC (r = 0.729, P < 0.0001) was found. These results suggest accumulation of 6MP and its metabolites in the liver of the patients with GI symptoms, leading to hepatotoxicity.

Antimetabolites, Antineoplastic↗
PubMed1996

Excretion of fluoxetine and its metabolite, norfluoxetine, in human breast milk.

A study was conducted to measure breast milk concentrations of fluoxetine and its active metabolite, norfluoxetine, excreted in breast milk in a cohort of nursing women using fluoxetine, and to estimate infant dose from nursing. The study included 10 women nursing 11 infants (median age, 185 days). The mean fluoxetine dose was 0.39 mg/kg/day. Each patient manually collected 3 to 6 milk samples throughout a dosing interval. Concentrations of fluoxetine and norfluoxetine in milk were measured by gas-liquid chromatography. Mothers reported whether they observed adverse effects in their infants. The average infant doses of fluoxetine and norfluoxetine, as estimated for an exclusively breast-fed infant ingesting 1000 mL of milk per day, were 0.077 mg (SD = 0.054 mg) and 0.084 mg (SD = 0.043 mg), respectively. The total dose of fluoxetine and norfluoxetine (expressed as fluoxetine equivalents) was 0.165 mg (SD = 0.092 mg), which was equivalent to 10.8% (SD = 2.2%) of the maternal dose, adjusted on a mg/kg basis in a 4-kg infant. No adverse events were reported by mothers in their infants. Approximately one tenth of the adult therapeutic dose of fluoxetine is excreted in breast milk. Although short-term adverse effects in the infant from exposure through nursing were not reported in this cohort, future studies that assess the potential long-term consequences are needed.

Adult↗
PubMed1996

Safety of first trimester exposure to histamine H2 blockers. A prospective cohort study.

The objective of this study was to examine whether H2 blockers represent a major teratogenic risk. This prospective cohort study was done at the Motherisk Program, a Teratology Information Service, Toronto, Canada. The subjects included 178 women who contacted Motherisk about gestational H2-blocker use, and 178 controls matched for maternal age, smoking, and heavy alcohol consumption. The main outcome measures were primary--major malformations, and secondary--pregnancy outcome, method of delivery, gestational age, prematurity, birthweight, small for gestational age infants, neonatal health problems, and developmental milestones. No increase in major malformations was found following first trimester exposure to H2 blockers [2.1% vs 3.5% (controls), mean difference (95% CI) -1.4% (-5.2, +2.4)]. No other aspects of pregnancy outcome or neonatal health differed between groups. This study suggests that H2-blocker exposure during the first trimester does not represent a major teratogenic risk.

Abnormalities, Drug-Induced↗
PubMed1996

Cocaine inhibits hCG secretion by the human term placental cotyledon perfused in vitro.

Cocaine has been shown to adversely affect pregnancy outcome in humans, but the mechanism(s) are not well understood. Using the technique of perfusing the human term placental cotyledon in vitro, we measured the rate of hCG appearance in the maternal circulation in the presence and absence of cocaine in the maternal circulation. At a dose of 0.80 microgram/mL, hCG secretion was reduced by 46%. This reduction in hCG concentration in the maternal circulation may effect normal steroidogenesis required to maintain pregnancy and may contribute to our understanding of the reproductive toxicology of cocaine.

Chorionic Gonadotropin↗
PubMed1996

The safety of calcium channel blockers in human pregnancy: a prospective, multicenter cohort study.

OBJECTIVE: Our purpose was to examine the potential teratogenicity of calcium channel blockers. STUDY DESIGN: Six teratogen information services prospectively collected and followed up 78 women with first-trimester exposure to calcium channel blockers. Pregnancy outcome was compared (by paired t text of chi2 analysis) with that of a control group matched for maternal age and smoking. RESULTS: There was no increase in major malformation (2/66=3.0% [calcium channel blockers] vs 0% [nonteratogenic controls], p=0.27); a fivefold increase was ruled out (baseline 2%, alpha = 0.05, beta = 0.20). The defects reported were attributable to maternal diabetes or coingestion of teratogens. The increase in preterm delivery 28% [calcium channel blockers] vs 9% [nonteratogenic controls], p=0.003), attributed to maternal disease by stepwise regression, was the most important factor responsible for the observed decrease in birth weight (mean -334 gm vs nonteratogenic controls, p=0.08). CONCLUSION: This study suggests that calcium channel blockers do not represent a major teratogenic risk.

Abnormalities, Drug-Induced↗
PubMed1996

Midodrine efficacy and pharmacokinetics in a patient with recurrent intradialytic hypotension.

Recurrent intradialytic hypotension, a complication of hemodialysis, is a consequence of an inadequate compensatory response or a paradoxic response to ultrafiltration-induced volume reduction. We report the use of midodrine, an alpha agonist, in an 18-year-old man with Bardet-Biedl syndrome and recurrent intradialytic hypotension. The clinical features of the intradialytic hypotensive spells are consistent with a paradoxic withdrawal of sympathetic activity, although an underlying abnormality in autonomic dysfunction cannot be excluded. Midodrine significantly increased the intradialytic blood pressure and decreased the intradialytic hypotensive episodes requiring intervention. The pharmacokinetic characteristics of the prodrug midodrine and the active metabolite de-glymidodrine in this patient with end-stage renal disease approximate those reported for patients with normal renal function. However, the prolonged terminal half-life for the active metabolite, de-glymidodrine, warrants careful administration in patients with renal failure.

Adolescent↗
PubMed1996

Cocaine toxicity and isoflurane anesthesia: hemodynamic, myocardial metabolic, and regional blood flow effects in swine.

OBJECTIVES: Increasing numbers of people use cocaine recreationally and may require anesthesia care, having recently abused the drug. However, no data currently exist concerning potential interactions between toxic levels of cocaine and volatile anesthetic agents. This study investigated the effects of cocaine infusion on systemic hemodynamics, myocardial metabolism, and regional organ blood flow in relation to depth of isoflurane anesthesia. DESIGN: Prospective, randomized, controlled trial. SETTING: A laboratory at a university medical center. PARTICIPANTS: Twelve miniature pigs. INTERVENTIONS: An open-chest swine model was used. Isoflurane (ISO) was the sole anesthetic, administered at 0.75 and 1.5 minimum alveolar concentration (MAC), and cocaine was infused (n = 6) at a rate of 0.5 mg/kg/min. Control animals (n = 6) received an equivalent amount of normal saline. MEASUREMENTS AND MAIN RESULTS: Systemic and pulmonary arterial pressures and thermodilution cardiac output data were collected at 0.75 MAC and 1.5 MAC ISC. Regional myocardial and blood flows to other organs were measured using radiolabeled microspheres. Arrhythmias and altered ventricular conduction were noted only in the cocaine group, along with significant elevations in diastolic arterial pressure, coronary perfusion pressure, and systemic vascular resistance. Increased subendocardial blood flow occurred during cocaine infusion (p = 0.03); subepicardial perfusion was unchanged. Cerebral (p < 0.01) and spinal cord (p < 0.05) blood flows were reduced in animals receiving cocaine. Other organ blood flows were unchanged with depth of anesthesia or cocaine administration, with the exception of splenic blood flow (p < 0.04). CONCLUSIONS: Moderately toxic cocaine levels occurring during isoflurane at 0.75 MAC and 1.5 MAC are associated with hemodynamic abnormalities, a marked increase in systemic vascular resistance, and a tendency to produce cardiac arrhythmias. A reversal of endo/epicardial myocardial perfusion ratio occurs associated with cocaine infusion during ISO anesthesia. This is probably not related to a primary redistribution of subendocardial blood flow and may be related to a combination of increased myocardial oxygen demand and epicardial coronary vasoconstriction. The reductions in cerebral and spinal cord perfusion observed may explain, in part, the neurologic sequelae of cocaine toxicity.

Anesthetics, Inhalation↗
PubMed1996

Validation of self-reported smoking by analysis of hair for nicotine and cotinine.

Evidence suggesting the use of self-reports as an index of systemic exposure to cigarette smoke in selected study populations is highly inaccurate. In order to assess the use of hair analysis as a biochemical marker of cigarette smoking, we compared measurements of nicotine and cotinine in the hair and plasma of 36 volunteers whose reports of smoking were deemed to be reliable. A significant correlation was observed between the number of cigarettes smoked and hair measurements of nicotine (r = 0.48, p = 0.004) and cotinine (r = 0.57, p = 0.0008). In addition, a good correlation was found between the reported number of cigarettes smoked and plasma nicotine, plasma cotinine, and carboxyhemoglobin levels. These results suggest that hair analysis is a reliable noninvasive method of determining human exposure to cigarette smoke and is comparable to blood analysis.

Adult↗
PubMed1996

Passive smoking in children. Racial differences in systemic exposure to cotinine by hair and urine analysis.

Passive smoking has been shown to adversely affect the health of infants and children. Black children and adults appear to be more susceptible to a variety of tobacco smoke health hazards for unknown reason. The objectives of this study were as follows: (1) to correlate the number of cigarettes reported to have been smoked by parents with urine and hair concentrations of cotinine in children; and (2) to identify race differences in systemic exposure to cotinine in children. This was an observational study in a consulting pediatric office on 169 nonsmoking children between 2 and 18 years of age, not actively smoking. The outcome measures of interest were urinary cotinine concentrations corrected for milligram of creatinine and hair concentration of cotinine (per milligram of hair). There were significant correlations between the number of cigarettes the child was exposed to and urinary cotinine (r = 0.68, p = 0.0001) or hair cotinine concentrations (r = 0.19, p = 0.02), and between urinary and hair cotinine (r = 0.3, p = 0.0005). In this cohort, parents of black children (n = 21) tended to smoke less (6.6 +/- 3/d, mean +/- SEM) than white parents (n = 97) (12 +/- 1.8, mean +/- SEM) (p = 0.2). Despite being exposed to less cigarettes, black children had higher hair concentrations of cotinine than white children (0.89 +/- 0.25 ng/mg vs 0.48 +/- 0.05 ng/mg; p = 0.05). The ratio hair/urine concentrations of cotinine was twofold higher in black children (0.035 +/- 0.01 vs 0.019 +/- 0.002; p = 0.004). White children with dark hair did not differ significantly from white children with fair hair in any of these indexes. The amount of urinary cotinine per milligram of creatinine caused by 1 cigarette per day was twofold higher in black children (14.7 +/- 5.2 ng/mg of creatinine) than in white children (6.3 +/- 1.2 ng/mg of creatinine) (p = 0.02). These data suggest that black children handle cigarette smoke differently from white children and that black children have higher systemic exposure to this constituent of cigarette smoke.

Adolescent↗
PubMed1996

Efficacy of deferiprone in the treatment of acute iron intoxication in rats.

BACKGROUND: Deferiprone [(1,2-dimethyl-3-hydroxypyrid-4-one) (L1)], is the first orally active iron chelating agent to reach clinical trials in patients with chronic iron overload. Its efficacy in preventing morbidity and mortality in acute iron poisoning has not been tested. OBJECTIVE: To determine whether deferiprone can reduce the mortality of rats following toxic oral doses of iron. METHODS: Rats were administered 612 mg/kg elemental iron by gavage, corresponding to the LD58. A parallel group received the same oral dose of iron followed by deferiprone intraperitoneally at 400 mg/kg (loading dose), followed by additional intraperitoneal injections of 200 mg/kg, 100 mg/kg and 100 mg/kg of deferiprone at one hour intervals. RESULTS: Coadministering deferiprone with the iron decreased mortality from 58% (11/19) to 15% (3/20) (p = 0.013). The administration of deferiprone was associated with urinary excretion of iron (which did not occur with iron alone) and the production of the red deferiprone-iron complex. On histological examination there appeared to be less iron in the liver and gastrointestinal tract. CONCLUSION: The coadministration of deferiprone can decrease morbidity and mortality caused by acute iron overdose. Deferiprone holds promise for the treatment of iron poisoning but additional study is required.

Animals↗
PubMed1996

Folic acid and prevention of neural tube defects: a study of Canadian mothers of infants with spina bifida.

OBJECTIVES: To determine the diffusion of information about preventing neural tube defects (NTDs) through folic acid consumption by examining whether mothers of Canadian children born with spina bifida, who had become pregnant at least a year after evidence of the preventive effect of folic acid had been published, had taken sufficient amounts of folic acid in the periconceptional period and were aware of this important new information. DESIGN: Validated food-frequency questionnaire to assess folate intake. SETTING: The Hospital for Sick Children in Toronto between Jan. 4 and Aug. 16, 1994. PARTICIPANTS: Thirty mothers whose infants were being treated for spina bifida. MAIN OUTCOME MEASURES: The mothers' mean folate intake and knowledge about the protective effect of folic acid; demographic and health information. RESULTS: The mothers' mean folate intake was 0.182 mg/d (standard deviation 0.076 mg/d, range 0.02 to 0.53 mg/d), less than half the protective dose. Only 4 (13%) of the mothers had been aware of the relation between nutritional folate and NTDs when they conceived, but even they did not supplement their diets with sufficient folic acid. The medical data showed that, in addition to the failure of primary prevention of NTDs, secondary prevention through diagnostic tests during pregnancy were also inadequate. CONCLUSIONS: Our study, one of the first to be conducted after the role of folate in preventing NTDs was confirmed, reveals that, in one of the most advanced countries in the world, this new information has had no effect on patients' folate intake. Unless food is fortified with folate, the estimated 400 to 800 annual cases of NTDs in Canada will not be prevented.

Canada↗