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Biomedical subjects

G Koren

Publications and source records attributed to G Koren.

At least 91 records · Page 5Linked to original sources
PubMed2001

Finasteride. Does it affect spermatogenesis and pregnancy?

QUESTION: A few women have asked me whether finasteride, taken by their partners for male pattern baldness, will affect their pregnancies. The product monograph is very alarming: it sounds as if even handling the medication could cause harm, especially to a male fetus. Should a man stop taking finasteride if his partner is planning pregnancy or is pregnant? What is the risk to the fetus if its mother accidentally handles crushed or broken tablets? ANSWER: To date, there are no reports of adverse pregnancy outcomes among women exposed to finasteride. Taking 1 mg of finasteride daily did not have any clinically significant effect on men's semen. Absorption through the skin while handling tablets is extremely unlikely to cause fetal exposure or harm. There is no reason to discontinue the drug. Motherisk is currently following up women who are pregnant or planning pregnancy and whose partners are taking finasteride.

Administration, Cutaneous↗
PubMed2000

Prenatal exposure to misoprostol and vascular disruption defects: a case-control study.

Prenatal exposure to misoprostol has been associated with Moebius and limb defects. Vascular disruption has been proposed as the mechanism for these teratogenic effects. The present study is a multicenter, case-control study that was designed to compare the frequency of prenatal misoprostol use between mothers of Brazilian children diagnosed with vascular disruption defects and matched control mothers of children diagnosed with other types of defects. A total of 93 cases and 279 controls were recruited in eight participating centers. Prenatal exposure was identified in 32 infants diagnosed with vascular disruption defects (34.4%) compared with only 12 (4.3%) in the control group (P<0.0000001). Our data suggest that prenatal exposure to misoprostol is associated to the occurrence of vascular disruption defects in the newborns.

Abnormalities, Drug-Induced↗
PubMed2000

Evidence of renal metabolism of ifosfamide to nephrotoxic metabolites.

Nephrotoxicity is a limiting factor in the use of ifosfamide in children. Despite the co-administration of uroprotective agents such as sodium 2-mercaptoethanesulfonate (mesna), ifosfamide chemotherapy is associated with nephropathy characterized by glomerular toxicity and Fanconi syndrome in many children treated with this drug. This is in distinction to cyclophosphamide, an analogue which differs solely by the position of a chloroethyl group, and which is not associated with nephrotoxicity. We hypothesized that ifosfamide is metabolized by cytochrome P450 (CYP) enzymes located in the renal tubular cell to the toxic metabolite chloroacetaldehyde; and, that the higher production of chloroacetaldehyde from ifosfamide than from cyclophosphamide explains the clinical differences in nephrotoxicity. We found that in both pig renal cortical microsomes and whole human kidney microsomes incubated with 1 mM ifosfamide for 3 hr, 2 and 3 dechloroethylifosfamide (DCEI) were produced. Our study provides evidence that porcine and human kidney microsomes are capable of biotransforming ifosfamide to DCEI metabolites that are produced in equimolar amounts with chloroacetaldehyde, indicating that chloroacetaldehyde is locally produced by renal cells as a possible mechanism for nephrotoxicity.

Animals↗
PubMed2000

Pregnancy outcome following gestational exposure to echinacea: a prospective controlled study.

BACKGROUND: Echinacea products are among the most popular phytomedicines on the North American market. Since at least half of all pregnancies are unplanned, many women inadvertently use echinacea in their first trimester. Presently, there is a paucity of information regarding the gestational safety of this herb. The primary objective of this study was to evaluate the safety of echinacea in pregnancy when used for upper respiratory tract ailments. PATIENTS AND METHODS: The study group consisted of women who were prospectively followed up after contacting the Motherisk Program regarding the gestational use of echinacea. This cohort was disease-matched to women exposed to nonteratogenic agents by maternal age, alcohol, and cigarette use. Rates of major and minor malformations between the groups were compared. RESULTS: A total of 206 women were enrolled in the study group after using echinacea products during pregnancy; 112 women used the herb in the first trimester. There were a total of 195 live births, including 3 sets of twins, 13 spontaneous abortions, and 1 therapeutic abortion. Six major malformations were reported, including 1 chromosomal abnormality, and 4 of these malformations occurred with echinacea exposure in the first trimester. In the control group, there were 206 women with 198 live births, 7 spontaneous abortions, and 1 therapeutic abortion. Seven major malformations were reported. There were no statistical differences between the study and control groups for any of the end points analyzed. CONCLUSIONS: This first prospective study suggests that gestational use of echinacea during organogenesis is not associated with an increased risk for major malformations.

Congenital Abnormalities↗
PubMed2000

Observation of spontaneous flux generation in a multi-josephson-junction loop

We describe observations of spontaneous flux generation inside a YBa(2)Cu(3)O(7-delta) loop made of 214 Josephson junctions in series. The flux is generated spontaneously during cooldown into the superconducting state. The experiment is motivated by the Kibble-Zurek scenario of formation of topological defects in condensed matter systems. The transition from decoupled superconducting segments into a coherent loop is determined by the strength of thermal fluctuations in the junctions. Values of the flux measured at the end of each cooldown follow a normal distribution, and are consistent with the instantaneous phase differences across the junctions adding up as the loop becomes coherent.

Journal Article↗
PubMed2000

Discrepancy between CYP2D6 phenotype and genotype derived from post-mortem dextromethorphan blood level.

OBJECTIVE: To describe the death of a toddler after a therapeutic dose of dextromethorphan and its investigation. STUDY DESIGN: Case report, cytochrome P450 phenotype and genotype determination in the victim and post-mortem drug redistribution study performed in rats. RESULTS: A 20-month Asian male who received 3 mg of dextromethorphan once at 09:00 h and again at 22:00 h was found dead at 04:35 h. Post-mortem examination showed signs of early bronchopneumonia (bacterial cultures were negative); dextromethorphan and dextrorphan blood concentrations taken from the heart cavity were 500 ng/ml (1. 84 micromol/l) and 200 ng/ml (0.78 micromol/l), respectively. Despite the dextromethorphan level being almost 100-fold higher than expected after therapeutic doses, intentional or unintentional overdose was extremely unlikely; other potential causes were investigated. Post-mortem drug redistribution study performed in rats showed that dextromethorphan does not undergo extensive redistribution after death (6+/-5-fold increase) and could not explain the observed dextromethorphan level. The dextromethorphan/dextrorphan concentration ratio of 2.5 found in this toddler was compatible with a slow CYP2D6 metabolizer phenotype. However, the toddler exhibited a fast metabolizer genotype. Potential reasons for this discrepancy are discussed. CONCLUSION: CYP450 phenotypes derived from post-mortem blood levels should be interpreted with caution and preferably confirmed by a genotype analysis.

Animals↗
PubMed2000

Spontaneous macroscopic magnetization at the superconducting transition temperature of YBa2Cu3O(7-delta)

A noteworthy feature of the high-temperature superconductors is the unconventional symmetry of the superconducting order parameter. Several experiments have established that the order parameter has a four-fold d(x2 - y2) symmetry under rotation of the lattice (the order parameter of conventional superconductors is, in contrast, isotropic). An intriguing and much debated possibility is that, in certain cases, an additional imaginary component might be present, having an isotropic s-wave or d(xy) symmetry. A consequence of a complex order parameter of the form d(x2 - y2) + id(xy) is that it would break both reflection (parity, P) symmetry and time-reversal (T) symmetry, a clear signature of which would be the spontaneous appearance of a macroscopic magnetization at the superconducting transition temperature. Broken T symmetry has been reported, but searches for the effects of combined P and T symmetry breaking have so far yielded null results. Here we report the observation of a weak (approximately 10(-5) gauss) magnetic field that appears spontaneously at the superconducting transition temperature of epitaxial thin films of YBa2Cu3O(7-delta). The magnetic signal originates near the edges of the samples. One interpretation for this observation is that the order parameter carries an intrinsic angular momentum, related to the breaking of P and T symmetries, but other possibilities cannot yet be excluded.

Journal Article↗
PubMed2000

Enhanced dispersion of repolarization and refractoriness in transgenic mouse hearts promotes reentrant ventricular tachycardia.

The heterogeneous distribution of ion channels in ventricular muscle gives rise to spatial variations in action potential (AP) duration (APD) and contributes to the repolarization sequence in healthy hearts. It has been proposed that enhanced dispersion of repolarization may underlie arrhythmias in diseases with markedly different causes. We engineered dominant negative transgenic mice that have prolonged QT intervals and arrhythmias due to the loss of a slowly inactivating K(+) current. Optical techniques are now applied to map APs and investigate the mechanisms underlying these arrhythmias. Hearts from transgenic and control mice were isolated, perfused, stained with di-4-ANEPPS, and paced at multiple sites to optically map APs, activation, and repolarization sequences at baseline and during arrhythmias. Transgenic hearts exhibited a 2-fold prolongation of APD, less shortening (8% versus 40%) of APDs with decreasing cycle length, altered restitution kinetics, and greater gradients of refractoriness from apex to base compared with control hearts. A premature impulse applied at the apex of transgenic hearts produced sustained reentrant ventricular tachycardia (n=14 of 15 hearts) that did not occur with stimulation at the base (n=8) or at any location in control hearts (n=12). In transgenic hearts, premature impulses initiated reentry by encountering functional lines of conduction block caused by enhanced dispersion of refractoriness. Reentrant VT had stable (>30 minutes) alternating long/short APDs associated with long/short cycle lengths and T wave alternans. Thus, optical mapping of genetically engineered mice may help elucidate some electrophysiological mechanisms that underlie arrhythmias and sudden death in human cardiac disorders.

Action Potentials↗
PubMed2000

Clinical applications of hair testing for drugs of abuse--the Canadian experience.

During the last 2 decades there has been a substantial increase in illicit drug consumption in North America. It has been repeatedly shown that the personal history of drug use is far from being accurate. Fearing legal consequences and embarrassment of admitted illicit substance use, most users tend to deny or, to under-report illicit drug consumption. These facts have stressed an urgent need for a biological marker which does not lose its sensitivity within a few days after the end of exposure and which may yield a cumulative reflection of long term exposure to illicit drugs. Hair analysis has emerged as such a marker. A variety of illicit and medicinal compounds have been shown to be incorporated into hair including trace metals, barbiturates, amphetamines, opiates, phencyclidine, cocaine, nicotine and cannabis. Hair analysis for drugs of abuse provides long-term information on an individual's drug use; its window of detection is limited only by the length of the hair and typically, ranges from a week to several months. After establishing and validating several hair tests during the last decade, we have analyzed over 1000 hair samples for different drugs of abuse. We used RIA for screening and GC-MS for confirmation of positive results. The aim of this report is to illustrate the diagnostic usefulness of hair testing in different age groups (newborns, children, adults) and circumstances: (criminal cases, athletes, child custody cases, etc.).

Adult↗
PubMed2000

Fall in mean arterial pressure and fetal growth restriction in pregnancy hypertension: a meta-analysis.

BACKGROUND: We investigated the relation between fetoplacental growth and the use of oral antihypertensive medication to treat mild-to-moderate pregnancy hypertension. METHODS: The study design was a metaregression analysis of published data from randomised controlled trials. Data from a paper that was regarded as an extreme statistical outliner were excluded from primary analyses. The change in (group) mean arterial pressure (MAP) from enrolment to delivery was compared with indicators of fetoplacental growth. FINDINGS: Greater mean difference in MAP with antihypertensive therapy was associated with the birth of a higher proportion of small-for-gestational-age (SGA) infants (slope: 0.09 [SD 0.03], r2=0.48, p=0.006, 14 trials) and lower mean birthweight significant after exclusion of data from another paper regarded as an extreme statistical outliner (slope: -14.49 [6.98] r=0.16, p=0.049, 27). No relation with mean placental weight was seen (slope -2.01 [1.62], r2=0.15, p=0.25, 11 trials). INTERPRETATION: Treatment-induced falls in maternal blood pressure may adversely affect fetal growth. Given the small maternal benefits that are likely to be derived from therapy, new data are urgently needed to elucidate the relative maternal and fetal benefits and risks of oral antihypertensive drug treatment of mild-to-moderate pregnancy hypertension.

Antihypertensive Agents↗
PubMed2000

Combined analgesia and local anesthesia to minimize pain during circumcision.

BACKGROUND: Pain of circumcision is only partially relieved by single modalities, such as penile nerve block, lidocaine-prilocaine cream, and sucrose pacifiers. OBJECTIVE: To assess the effectiveness of a combination of interventions on the pain response of infants undergoing circumcision. METHODS: Cohort study. Group 1 included infants circumcised using the Mogen clamp and combined analgesics (lidocaine dorsal penile nerve block, lidocaine-prilocaine, acetaminophen, and sugar-coated gauze dipped in grape juice). Group 2 included infants circumcised using the Gomco clamp and lidocaine-prilocaine. Infants were videotaped during circumcision, and pain was assessed using facial activity scores and percentage of time spent crying. RESULTS: There were 57 infants in group 1 and 29 infants in group 2. Birth characteristics did not differ between groups. Infants in group 1 were older than infants in group 2 (17 days vs 2 days) (P < .001). The mean duration of the procedure was 55 seconds and 577 seconds for infants in group 1 and 2, respectively (P < .001). Facial action scores and percentage of time spent crying were significantly lower during circumcision for infants in group 1 (P < .001). The percentage of time spent crying was 18% and 40% for infants in groups 1 and 2, respectively. No adverse effects were observed in infants in group 1; 1 infant in group 2 had a local skin infection. CONCLUSIONS: Infants circumcised with the Mogen clamp and combined analgesia have substantially less pain than those circumcised with the Gomco clamp and lidocaine-prilocaine cream. Because of the immense pain during circumcision, combined local anesthesia and analgesia using the Mogen clamp should be considered.

Acetaminophen↗
PubMed2000

Assessment of systemic toxicity in children receiving chemotherapy with cyclosporine for sarcoma.

BACKGROUND: Overexpression of P-glycoprotein in malignant tumors has been associated with poor responses to chemotherapy. It appears biologically plausible that addition of the P-glycoprotein inhibitor cyclosporine (CsA) to standard chemotherapy may improve the outcome. The protective functions of P-glycoprotein in healthy tissues, however, have not been fully elucidated. Addition of CsA may lead to increased systemic chemotherapy toxicity, so we compared the rate and severity of chemotherapy-associated systemic toxicity in the presence and absence of CsA. PROCEDURE: Standard chemotherapy consisted of etoposide/ifosfamide (VP16/IFOS) cycles, alternating with vincristine/dactinomycin/cyclophosphamide (VAC) cycles. CsA was given at a median dose of 20 mg/kg with unaltered doses of the antineoplastic drugs. The analysis of toxicity was performed by comparing clinically significant toxicity events recorded during and after chemotherapy cycles with and without CsA. RESULTS: Toxicity-related hospital admissions occurred after 93% of VAC cycles with CsA compared to 40% of the cycles without CsA (P < 0. 0001); 29% of VP16/IFOS cycles with CsA led to admissions vs. 12% with non-CsA cycles (P = 0.04). Infections or fever and neutropenia were the main reasons for these admissions. Thirty-seven percent of the VAC cycles with CsA were complicated by culture-proved sepsis, which did not occur in cycles without CsA (P < 0.0001). Requirements for blood and platelet transfusions were greatly increased after VAC cycles with CsA compared to VAC cycles without CsA. CONCLUSIONS: The chemosensitizer CsA increases the systemic toxicity of VAC chemotherapy in patients with sarcomas. Future trials of chemotherapy with chemosensitizers will have to take into account a potential increase in systemic toxicity. Careful monitoring of chemotherapy-related toxicity becomes mandatory in such studies.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Birth defects after maternal exposure to corticosteroids: prospective cohort study and meta-analysis of epidemiological studies.

BACKGROUND: Corticosteroids are first-line drugs for the treatment of a variety of conditions in women of childbearing age. Information regarding human pregnancy outcome with corticosteroids is limited. METHODS: We collected prospectively and followed up 184 women exposed to prednisone in pregnancy and 188 pregnant women who were counseled by Motherisk for nonteratogenic exposure. The primary outcome was the rate of major birth defects. A meta-analysis of all epidemiological studies was conducted. The Mantel-Haenszel summary odds ratio was calculated for the pooled studies with 95% confidence intervals. A cumulative summary odds ratio was also calculated by combining studies in chronological order. Chi-squared for homogeneity was determined to establish the comparability of the studies. RESULTS: In our prospective study, there was no statistical difference in the rate of major anomalies between the corticosteroid-exposed and control groups. In the meta-analysis, the Mantel-Haenszel summary odds ratio for major malformations with all cohort studies was 1.45 [95% CI 0.80, 2.60] and 3.03 [95% CI 1.08, 8. 54] when Heinonen et al. ('77) was removed. This suggests a marginally increased risk of major malformations after first-trimester exposure to corticosteroids. In addition, summary odds ratio for case-control studies examining oral clefts was significant (3.35 [95% CI 1.97, 5.69]). CONCLUSIONS: Although prednisone does not represent a major teratogenic risk in humans at therapeutic doses, it does increase by an order of 3.4-fold the risk of oral cleft, which is consistent with the existing animal studies.

Abnormalities, Drug-Induced↗
PubMed2000

A randomized prospective crossover trial of amlodipine in pediatric hypertension.

Amlodipine has potential advantages in children since it can be dissolved into a liquid preparation and has a long elimination half-life, allowing for once-daily administration. The objective of this study was to compare the efficacy and compliance of amlodipine with that of standard long-acting calcium channel blockers (felodipine or nifedipine) in hypertensive children. A randomized, prospective, crossover study of 11 hypertensive children (9-17 years of age, 10 renal transplant patients) was performed with electronic monitoring of compliance. Each treatment arm was 30 days. No significant differences were observed in mean systolic (SBP) and diastolic blood pressures (DBP) between amlodipine and the other calcium channel blockers. Using 24-h blood pressure monitoring there were no significant differences over each drug treatment period in both mean day-time and night-time SBP and DBP. Patient compliance was similar in both the amlodipine and the nifedipine/felodipine treatment periods. These data suggest that amlodipine is as effective in pediatric nephrology patients as nifedipine and felodipine. Amlodipine may be optimally suited for treatment of young children because at present it is the only calcium channel blocker which can be administered once daily as a liquid preparation.

Adolescent↗
PubMed2000

Attitudes, management and consequences of nausea and vomiting of pregnancy in the United States and Canada.

BACKGROUND: Nausea and vomiting of pregnancy (NVP) affects a large proportion of pregnant women. In 1983, Bendectin((R)), the only FDA-approved drug for NVP, was removed from the market by its manufacturer due to legal costs based on claims of teratogenicity, which were subsequently proven to be unsubstantiated. In Canada, a generic form of Bendectin (Diclectin; a doxylamine/pyridoxine combination) has continued to be available, with increasing use over the last few years. OBJECTIVE: To characterize the attitudes, management and consequences of NVP among pregnant women in the USA, where no approved drug for NVP is available, and in Canada, where such a drug is available. DESIGN: Prospective, observational study. RESULTS: Women suffering from NVP (N = 1444) were interviewed, of which 42% were American and 58% were Canadian. The two groups had similar maternal characteristics and a similar distribution of severity of NVP, although among Canadian women the NVP continued for slightly longer. American respondents were treated significantly more often by an obstetrician as their primary caregiver, were more commonly advised by their caregiver to change their diet and/or lifestyle and to use non-pharmacological agents to manage their NVP, and more often perceived anti-emetics as posing an increased risk for malformations (all P < 0.001). Canadian respondents reported a family physician as their primary caregiver significantly more often, were more commonly advised to take anti-emetic medications and perceived their NVP as causing a concern to their unborn (all P < 0.001). American women experienced significantly larger weight loss, more hospitalizations and more time lost from paid work. CONCLUSIONS: Lack of an approved drug for symptoms of NVP may be associated with unwarranted and preventable adverse health effects. Because this is an observational study, these associations do not necessarily prove causation.

Adult↗
PubMed2000

Risks and benefits of beta-receptor blockers for pregnancy hypertension: overview of the randomized trials.

OBJECTIVE: Examine the benefits/risks of beta-blockers for pregnancy hypertension. STUDY DESIGN: Meta-analysis of relevant trials identified by comprehensive literature review (1966-97). RESULTS: Included were 30 trials for pregnancy hypertension, and four others for perinatal outcomes only. For mild chronic hypertension treated throughout pregnancy (n=2 trials), oral beta-blockers (compared with no therapy) were associated with an inconsistent increase in small for gestational age (SGA) infants (OR 2.46 [1.02, 5.92]). For mild-moderate 'late-onset' pregnancy hypertension (i.e. either chronic treated only late in pregnancy, or pregnancy-induced) (n=8 trials), oral beta-blockers (compared with no therapy) were associated with a decrease in severe hypertension (OR 0.27 [0.16, 0.451), borderline decrease in development of proteinuria (OR 0.69 [0.48, 1.02]), decrease in RDS (OR 0.33 [0.13, 0.85]), but a borderline increase in SGA infants (OR 1.47 [0.96, 2.26]). Beta-blockers were equivalent to other agents (n=15 trials). For severe 'late-onset' pregnancy hypertension (n=5 trials), i.v. labetalol produced less maternal hypotension (OR 0.13 [0.03, 0.71]) and fewer cesareans (OR 0.23 [0.13, 0.63]) than i.v. hydralazine/diazoxide. CONCLUSIONS: It is not clear that the benefits outweigh the risks when beta-blockers are used to treat mild to moderate chronic or pregnancy-induced hypertension, given the unknown overall effect on perinatal outcomes. For severe 'late-onset' pregnancy hypertension, i.v. labetalol is safer than i.v. hydralazine or diazoxide.

Adrenergic beta-Antagonists↗