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Biomedical subjects

G Koren

Publications and source records attributed to G Koren.

At least 307 records · Page 17Linked to original sources
PubMed1996

The pharmacokinetics and pharmacodynamics of the oral iron chelator deferiprone (L1) in relation to hemoglobin levels.

Recently, we demonstrated that administration of the orally active iron chelating agent deferiprone (1,2-dimethyl-3-hydroxypyrid-4-one (L1)) at 6-hour intervals results in significantly greater urinary iron excretion than that induced during administration of the drug at 12-hour intervals. That study was conducted in thalassemia patients, all of whom had received a packed red cell transfusion of 15 cc/kg. 72 hours prior to evaluation of urinary iron excretion, at a time when endogenous erythropoiesis would be expected to be at its lowest. In clinical practice however, thalassemia patients, suppression of endogenous erythropoiesis is not sustained between transfusions. We set out to determine the influence that administration of deferiprone has on urinary iron excretion at lower hemoglobin concentrations, immediately prior to transfusion. We hypothesized that hemoglobin levels will affect the ability of deferiprone to chelate iron. Ten regularly transfused patients with homozygous beta-thalassemia (HBT) aged mean +/- SD, 20.9 +/- 4.7, range 13 - 27 years, receiving long-term therapy with deferiprone, were treated with deferiprone 75 mg/kg/day, administered every 6 hours (or every 12 hours) for 72 hours immediately prior to a blood transfusion in the first month. One month later each patient received the other of the 2 dosing regimens for 72 hours immediately prior to transfusion. The deferiprone-induced 24-hour urinary iron excretion was similar during both dosing regimens; 0.56 +/- 0.45 mg/kg when L1 was given every 6 hours and 0.48 +/- 0.52 mg/kg when L1 was administered every 12 hours (p = 0.79). However, the calculated 24-hour area under the plasma concentration-time curve (AUC0-24) of deferiprone was significantly lower when deferiprone was administered at 6-hour intervals (6,762.8 +/- 1,601.6 mg*min/l), than that observed when deferiprone was administered every 12 hours (8,250.1 +/- 1,235.7 mg*min/l) (p = 0.04). The pharmacokinetics of deferiprone when administered immediately prior to transfusions are different from those following transfusions. More studies assessing total body iron excretion are needed to determine the contribution of the fecal route in iron excretion.

Adolescent↗
PubMed1996

Nicotine and cotinine in maternal and neonatal hair as markers of gestational smoking.

OBJECTIVE: To determine the extent of fetal exposure to cigarette smoke, which cannot be clearly extrapolated from maternal reports, the authors measured concentrations of nicotine and cotinine in maternal and neonatal hair and corroborated these measures with maternal history and measures of pregnancy outcome. DESIGN: Prospective study of 94 mother-infant pairs. SETTING: Newborn nurseries of two hospitals in Toronto. PARTICIPANTS: 93 mothers, including active smokers, passive smokers and nonsmokers, and their newborns (including one set of twins). INTERVENTIONS: Hair collected from mothers and neonates shortly after birth was analysed by radio-immunoassay. MAIN OUTCOME MEASURES: Maternal data on demographic variables, obstetric history, diseases, drugs taken and smoking; infant data on demographic variables and birth indicators (gestational age, method of delivery, weight, head circumference, length, presence of meconium, need for resuscitation, need for special care and congenital malformations); hair concentrations of nicotine and cotinine. RESULTS: Neonates of active smokers had more adverse outcomes than other infants, including lower birth weight, smaller head circumference, shorter length and more perinatal complications. The difference was statistically significant. Amounts of cotinine extracted from mothers' and infants' hair showed significant differences among active smokers, passive smokers and non-smokers. When other people in the household and the mother smoked, neonatal hair concentrations of nicotine and cotinine in the infants were threefold higher than those in the infants of mothers who were the only smokers in their households. CONCLUSIONS: Hair concentrations of nicotine and cotinine are a powerful biological marker of the extent of intrauterine exposure to tobacco smoke.

Adolescent↗
PubMed1996

Combining cyclosporin with chemotherapy controls intraocular retinoblastoma without requiring radiation.

Chemotherapy without radiation has not controlled most intraocular retinoblastoma, perhaps because of the common high expression of multidrug resistance P-glycoprotein that we found in retinoblastoma. Cyclosporin blocks P-glycoprotein-induced efflux of vincristine and teniposide in vitro, and possibly modulates responses to carboplatin. To avoid eye irradiation in bilateral retinoblastoma patients with RB1 germline mutations, which incurs a high second malignancy rate, we added cyclosporin A to a vincristine-teniposide-carboplatin protocol and consolidated chemotherapy responses with focal therapy. We scored patients requiring irradiation, enucleation, or focal ablation of central vision as failures. In 21 study patients, the overall relapse-free rate at a median follow-up of 3.3 years was 76%, with a rate of 92% for newly diagnosed and 50% for previously treated, relapsed retinoblastoma. Our results for the most unfavorable tumors with vitreous seeds (86% at 3.5 years) are better than published success rates of irradiation for similar tumors, or irradiation with the same chemotherapy without cyclosporin (45% at 2. 6 years). These results also exceeded our historic success rate with similar chemotherapy without cyclosporin, focal therapy, and/or radiation in 19 equivalently poor-risk patients (relapse-free rate 37% at a median follow-up of 5.6 years, P = 0.032), 16 of whom were previously untreated (relapse-free rate also 37%, P = 0.012). A better outcome occurred with higher cyclosporin blood levels and projected tissue exposure. Cyclosporin did not enhance the usual chemotoxicity. This clinical study suggests that cyclosporin improves the long-term response of retinoblastoma to chemotherapy, possibly by more than one mechanism.

Antineoplastic Agents↗
PubMed1995

GH3 cell-specific expression of Kv1.5 gene. Regulation by a silencer containing a dinucleotide repetitive element.

A silencer element (Kv1.5 repressor element; KRE) was characterized by deletion analyses in the promoter of Kv1.5, a voltage-gated potassium channel. The silencer element selectively decreases expression of Kv1.5- and thymidine kinase-chloramphenicol acetyl-transferase reporter gene constructs in cell lines that do not express Kv1.5 polypeptide. It contains a dinucleotide repetitive element (poly(GT)19(GA)1(CA)15(GA)16), and self-associates spontaneously in vitro to form complexes with slow electrophoretic mobility. Deletion of the repetitive element abolished self-association in vitro and the silencing activity in transient transfection experiments in vivo. Electromobility gel shift assays of KRE with GH3 cells nuclear extracts detected the formation of a unique DNA-protein complex, which was not detectable in Chinese hamster ovary and COS-7 cells. This complex does not react with an antibody against nonhistone high mobility group 1 protein, which binds KRE in gel retardation assays. These observations establish that a dinucleotide tandem repeat sequence, capable of self-association, forms part of a cell-specific silencer element in a mammalian gene.

Animals↗
PubMed1995

Camphorated oil: still endangering the lives of Canadian children.

Camphor is a volatile, aromatic compound familiar to many people as a principal ingredient in topical home remedies for colds. It is highly toxic when ingested. Although camphorated oil in concentrations of 11% or greater is not longer sold in the United States, preparations containing concentrations of up to 20% are still sold over the counter in Canada. The authors describe two children who suffered severe poisoning after accidental ingestion of a small amount of camphorated oil. Both children exhibited generalized tonic-clonic seizures with subsequent respiratory depression. Treatment was symptomatic, consisting of seizure control and respiratory assistance. The authors argue that because camphorated oil is of questionable benefit and poses a danger to the public it should be removed from the market.

Administration, Oral↗
PubMed1995

Iron-chelation therapy with oral deferiprone in patients with thalassemia major.

BACKGROUND: To determine whether the orally active iron chelator deferiprone (1,2-dimethyl-3-hydroxy-pyridin-4-one) is efficacious in the treatment of iron overload in patients with thalassemia major, we conducted a prospective trial of deferiprone in 21 patients unable or unwilling to use standard chelation therapy with parenteral deferoxamine. METHODS: Hepatic iron stores were determined yearly by chemical analysis of liver-biopsy specimens or magnetic-susceptibility measurements. Detailed clinical and laboratory studies were used to monitor safety and compliance. RESULTS: The patients received deferiprone therapy for a mean (+/-SE) of 3.1 +/- 0.3 years. Ten patients in whom previous chelation therapy with deferoxamine had been ineffective had initial hepatic iron concentrations of at least 80 mumol per gram of liver, wet weight -- values associated with complications of iron overload. Hepatic iron concentrations decreased in all 10 patients, from 125.3 +/- 11.5 to 60.3 +/- 9.6 mumol per gram (P < 0.005), with values that were less than 80 mumol per gram in 8 of the 10 patients (P < 0.005). In all 11 patients in whom deferoxamine therapy had previously been effective, deferiprone maintained hepatic iron concentrations below 80 mumol of iron per gram. CONCLUSIONS: Oral deferiprone induces sustained decreases in body iron to concentrations compatible with the avoidance of complications from iron overload. The risk of agranulocytosis associated with deferiprone may restrict its administration to patients who are unable or unwilling to use deferoxamine.

Administration, Oral↗
PubMed1995

Effect of neonatal circumcision on pain responses during vaccination in boys.

Using data from one of our randomised trials, we investigated post-hoc whether male neonatal circumcision is associated with a greater pain response to routine vaccination at 4 or 6 months. Pain response during routine vaccination with diphtheria-pertussis-tetanus (DPT) alone or DPT followed by Haemophilus influenzae type b conjugate (HIB) was scored blind. 42 boys received DPT and 18 also received HIB. After DPT, median visual analogue scores by an observer were higher in the circumcised group (40 vs 26 mm, p = 0.03). After HIB, circumcised infants had higher behavioural pain scores (8 vs 6, p = 0.01) and cried longer (53 vs 19 s, p = 0.02). Thus neonatal circumcision may affect pain response several months after the event.

Circumcision, Male↗
PubMed1995

Measurement of drugs in neonatal hair; a window to fetal exposure.

Because the hair neonates are born with grows during the last 3 months of pregnancy, the presence of drugs (e.g. cocaine) or environmental toxins (e.g. nicotine) reflects fetal exposure to such compounds. In the case of cocaine, hair measurement are several fold more sensitive than maternal history or urine measurements. Measurements of cotinine in neonatal hair are capable of distinguishing between fetal exposure to passive versus active smoking. Because most cocaine users also smoke cigarettes, neonatal measurements of both cocaine and cotinine will allow cumulative quantification of fetal risk.

Cocaine↗
PubMed1995

Use of a eutectic mixture of local anesthetics for prolonged subcutaneous drug administration.

The efficacy of a eutectic mixture of local anesthetics (EMLA) in alleviating the pain associated with subcutaneous needle insertion for infusion of the iron-chelating agent, deferoxamine, was examined in 12 patients with homozygous beta-thalassemia. As reported by the patient using a 100-mm visual analogue scale, the pain of insertion was rated as significantly less after application of EMLA (mean +/- SD, 1.5 +/- 2.2 mm) than the pain associated with needle insertion without EMLA (34.8 +/- 33.5 mm, P = .005). Subsequently, in a double-blind randomized trial of 10 beta-thalassemia patients, EMLA was significantly better (5.7 +/- 8.2 mm) than placebo (27.0 +/- 22.8 mm, P = .01) in reducing the pain of needle insertion for deferoxamine infusion. No adverse effects were reported with the use of EMLA cream. These results suggest that EMLA may be effective in reducing the pain associated with needle insertion for subcutaneous deferoxamine infusion in beta-thalassemia patients, which may lead to improved compliance with this irritating, prolonged therapy. The safety of EMLA use in these patients, and others receiving regular parenteral therapy, should now be examined.

Anesthetics, Local↗
PubMed1995

Radiologic features of gastric outlet obstruction in infants after long-term prostaglandin administration.

Long-term prostaglandin (PG) therapy has recently been associated with gastric mucosal hyperplasia. We reviewed the clinical and radiologic (especially sonographic) records of eight patients with complex congenital heart disease who were on PG therapy. Feeding problems, vomiting, and abdominal distension were present in six patients. Barium meal revealed antral narrowing in three patients, suggestive of hypertrophic pyloric stenosis in two. Sonography showed a variable degree of increased gastric mucosal lobulation often accompanied by a marked polypoid or lobular appearance. Cortical hyperostosis related to PG therapy was seen in three patients. PG-associated gastric mucosal hyperplasia can cause feeding problems and pronounced gastric lobulation.

Alprostadil↗
PubMed1995

Initiation and duration of breast-feeding in women receiving antiepileptics.

OBJECTIVE: Our purpose was to characterize breast-feeding initiation and the duration of breast-feeding in women receiving antiepileptics. STUDY DESIGN: A cohort study was performed on 34 pregnant epileptic women receiving antiepileptics and 34 pregnant age-matched controls. RESULTS: Fifty percent of the group receiving antiepileptics chose breast-feeding as the initial feeding method, which was significantly less than the controls (85%, p = 0.004). The decision to choose initial feeding methods was closely associated with advice from physicians and other sources. The 17 women in the antiepileptics group who chose breast-feeding initially terminated breast-feeding significantly earlier than did the control group (4.7 +/- 2.6 vs 9.3 +/- 5.7 months post partum, p < 0.005). CONCLUSIONS: Mothers receiving antiepileptics tend to choose formula feeding. Even when they choose breast-feeding initially, its duration is shorter than usual. Consensus and guidelines on this matter among experts remain to be reflected on and effectively implemented in current medical practice.

Adult↗
PubMed1995

Safety of metronidazole in pregnancy: a meta-analysis.

OBJECTIVE: Our purpose was to determine from published experience in humans whether metronidazole exposure during the first trimester of pregnancy is associated with an increased teratogenic risk. STUDY DESIGN: All published articles reporting on metronidazole use during pregnancy were screened by two independent reviewers to select those including pregnant patients exposed during the first trimester and comparing the outcomes of their pregnancies with that of patients either not exposed to metronidazole or exposed only during the third trimester. The outcome under consideration was the occurrence of birth defects in live-born infants. The overall odds ratios of first-trimester exposure versus no first-trimester exposure was calculated by combining the selected studies in a meta-analysis according to the procedure of Mantel and Haenszel. RESULTS: From 32 identified studies, 7 met the inclusion criteria for meta-analysis. Six were prospective and included 253 women exposed to the drug in the first trimester of pregnancy; one was retrospective and reported on 1083 exposed women. The overall weighted odds ratio of exposure versus no exposure during the first trimester calculated by meta-analysis of the 7 studies was 0.93 (95% confidence interval 0.73 to 1.18). The odds ratio calculated from the 6 prospective studies was 1.02 (95% confidence interval 0.48 to 2.18). CONCLUSION: Metronidazole does not appear to be associated with an increased teratogenic risk.

Abnormalities, Drug-Induced↗