d-Fenfluramine produces neuronal degeneration in localized regions of the cortex, thalamus, and cerebellum of the rat.
d-Fenfluramine is a potent serotonin (5-HT) reuptake inhibitor/releaser and, until its recent recall, was prescribed as an anoretic agent. This study demonstrates that 10 mg/kg d-fenfluramine i.p., when administered to rats in a warm (27 degrees C) environment, produces neuronal degeneration within select brain regions. Degeneration was detected and localized using a recently developed fluorescent marker of neuronal degeneration, Fluoro-Jade. The most extensive cortical damage was in the anterior cingulate region. In the medial thalamus, degeneration was frequently seen within the intralaminar nuclei, and somewhat less frequently observed within the paraventricular nucleus, the mediodorsal nucleus, and the gelatinosis nucleus. Cerebellar damage occurred primarily in medial Purkinje cells and occasionally in granule cells or basket cells. Degeneration was not observed in either saline-injected control animals or in rats given even higher doses of 25 mg/kg d-fenfluramine but kept in a cooler environment (23 degrees C). The degeneration was clearly most prominent in animals with body temperatures of 41 degrees to 42 degrees C, but this degeneration was not seen in animals given saline that became extremely hyperthermic in a 37 degrees C environment. Behavioral signs such as tremors, myoclonus, rigidity, and splayed legs were seen in all animals with extensive neurodegeneration. The areas damaged by d-fenfluramine, when hyperthermia occurs, could play a role in the expression of the serotonin syndrome. Elevated extracellular 5-HT levels alone are probably not sufficient for neurotoxicity, and additional factors such as hyperthermia, regional specificity of 5-HT receptor subtypes, blood flow, and/or neuronal networks may be involved. (+info)
Use of dexfenfluramine, fenfluramine and phentermine and the risk of stroke.
AIMS: To estimate the incidence of newly diagnosed idiopathic stroke among users of fenfluramine, dexfenfluramine and phentermine compared to obese nonusers. METHODS: We conducted a cohort study with nested case-control analysis utilizing data from the General Practice Research Database in the UK. Eight thousand four hundred and twenty-three subjects aged 69 years or less at the start of follow-up were exposed to at least one of the three study drugs and 17 225 similarly obese subjects were not exposed to any of the study drugs. RESULTS: We identified 45 incident cases of idiopathic CVA in this cohort of subjects. The incidence of CVA among all current users of a diet drug was 1.3/1000 person-years (95% CI 0.5, 3.5). The incidence for current fenfluramine users (n=2) was 2.6/1000 person-years (95% CI 0.7, 9.6), for current dexfenfluramine users (n=1) 1.1/1000 person-years (95% CI 0.3, 3.8), and for current phentermine users 0/1000 person-years (95% CI 0.0, 12.9). The incidence in obese nonusers was 0.6/1000 person-years (95% CI 0.4, 0. 9). The adjusted matched odds ratio (OR) for thrombotic stroke from the case-control analysis comparing current use of a diet drug to nonuse was 2.4 (95% CI 0.6, 9.1). There was only one exposed subject among seven who had haemorrhagic stroke. CONCLUSIONS: The incidence of CVA in generally young obese subjects during use of fenfluramine, dexfenfluramine or phentermine is low. Although we found an OR of 2. 4 comparing users of any of the anorexiants with nonusers, this is based on only three exposed cases and the confidence limits are wide. We conclude that our study does not support a substantial increased risk of stroke attributable to the use of fenfluramine, dexfenfluramine or phentermine. (+info)
The anorexic agent dexfenfluramine causes the development of primary pulmonary hypertension in susceptible patients by an unknown mechanism that may include changes in K+-channel activity and intracellular Ca2+ concentration ([Ca2+]i). We investigated the dose-dependent effects of dexfenfluramine on [Ca2+]i, K+ current, and membrane potential in freshly dispersed rat pulmonary artery smooth muscle cells. Dexfenfluramine caused a dose-dependent (1-1,000 microM) increase in [Ca2+]i, even at concentrations lower than those necessary to inhibit K+ currents (10 microM) and cause membrane depolarization (100 microM). The [Ca2+]i response to 1 and 10 microM dexfenfluramine was completely abolished by pretreatment of the cells with 0.1 microM thapsigargin, whereas the response to 100 microM dexfenfluramine was reduced. CoCl2 (1 mM), removal of extracellular Ca2+, and pretreatment with caffeine (1 mM) reduced but did not abolish the response to 100 microM dexfenfluramine. We conclude that dexfenfluramine increases [Ca2+]i in rat pulmonary artery smooth muscle cells by both release of Ca2+ from the sarcoplasmic reticulum and influx of extracellular Ca2+. (+info)
Dexfenfluramine elevates systemic blood pressure by inhibiting potassium currents in vascular smooth muscle cells.
Appetite suppressants, such as dexfenfluramine (dex), are associated with primary pulmonary hypertension, valvular heart disease, and systemic vascular complications, such as coronary, cerebral, or mesenteric ischemia. These drugs suppress appetite by enhancing release and inhibiting reuptake of serotonin in the central nervous system. The effects of dex on the systemic circulation have not been studied. K(+) channels regulate vascular tone in most vascular beds. We hypothesized that dex is a systemic vasoconstrictor acting primarily by inhibiting K(+) channels, independent of effects on serotonin. The effects of clinically relevant concentrations of dex (10(-6) to 10(-4) M) on outward K(+) current and membrane potential were studied with whole-cell patch clamping in freshly isolated smooth muscle cells from rat renal, carotid, and basilar arteries. Tone was measured in tissue baths. Blood pressure, cardiac output, and left ventricular end diastolic pressure were assessed in open- and closed-chest anesthetized rats. At 10(-4) M, dex inhibits outward K(+) current (50%) and increases membrane potential (by >35 mV), an effect comparable with 4-aminopyridine (5 mM). Furthermore, dex constricts rings and acutely elevates systemic pressure (+17 +/- 3 mm Hg) and systemic vascular resistance in the presence of ketanserin. Dex vasoconstriction is dose-dependent (threshold dose 10(-6) M; 156 microg/ml) and enhanced in L-NAME-fed rats. We conclude that dex causes acute systemic vasoconstriction, at least in part by inhibition of voltage-gated K(+) channels, independent of effects on serotonin. To our knowledge, this is the first time that a commonly prescribed drug with voltage-gated K(+) channel-blocking properties is shown to have significant hemodynamic effects in vivo. (+info)
Prevalence and determinants of valvulopathy in patients treated with dexfenfluramine.
BACKGROUND: Valve regurgitation has been associated with dexfenfluramine, but its prevalence and severity are uncertain. Additional factors that may contribute to valve regurgitation in patients exposed to this drug are poorly understood. METHODS AND RESULTS: Echocardiography was performed on subjects recruited from 26 prescribing sites in 15 states. The total sample of 412 subjects included 172 dexfenfluramine patients and 172 unexposed controls matched for age, sex, and body mass index and 68 unmatched subjects meeting the same entry criteria (51 dexfenfluramine patients and 17 controls). Mean treatment duration was 6.9 months; mean interval from treatment discontinuation to echocardiogram was 8.5 months. Each echocardiogram was interpreted independently by 3 echocardiographers. FDA-grade regurgitation (at least mild aortic regurgitation or at least moderate mitral regurgitation) was significantly more frequent in dexfenfluramine patients (7.6% versus 2.1% for controls; P=0.01; odds ratio, 3.82). This difference was primarily due to more frequent mild aortic regurgitation in dexfenfluramine patients (6.3% versus 1.6% in controls; P<0.02; odds ratio, 4.15). No differences were found in sclerosis or mobility for either the aortic or mitral valve. Factors independently related to FDA-grade regurgitation or any grade of aortic regurgitation were older age, higher diastolic blood pressure at the time of echocardiography, and shorter time from drug discontinuation to echocardiogram. CONCLUSIONS: Dexfenfluramine use is associated with an increase in the prevalence of abnormal valve regurgitation. Age and blood pressure may also affect the prevalence of regurgitation. Dexfenfluramine-related valve regurgitation may regress after drug discontinuation. (+info)
Prevalence of valvular-regurgitation associated with dexfenfluramine three to five months after discontinuation of treatment.
OBJECTIVES: The goal of this study was to determine the prevalence of valvular regurgitation and abnormal valve morphology in patients three to five months after discontinuation of dexfenfluramine (Dexfen) therapy. BACKGROUND: We previously reported the results of a randomized, double-blind, placebo-controlled trial of valvular structure and function in 1,073 patients treated either with Dexfen, with an investigational sustained-release dexfenfluramine (Dexfen SR), or with a placebo, with echocardiograms performed approximately one month from the last dose. Using FDA criteria (aortic regurgitation [AR] > or =mild and/or mitral regurgitation [MR] > or =moderate) we found no statistical difference among the groups, but when all degrees of valvular regurgitation were considered and when the two Dexfen groups were combined, there was a higher prevalence of any degree of AR, any degree of MR, and restricted posterior mitral leaflet mobility. However, it was unknown whether these differences in prevalence persisted. METHODS: The double blind was maintained, and all patients were invited to return for a follow-up echocardiogram. Echocardiograms were acquired using a standardized protocol and assessed blindly to determine the degree of valvular regurgitation and valve leaflet thickness and mobility. We had an 80% power to detect a statistically significant change in paired proportions using the McNemar test (alpha = 0.05). RESULTS: Echocardiograms were obtained on 941 patients with a median of 137 days after drug discontinuation. Aortic regurgitation (of any degree) was present in 13.8% of Dexfen (p = 0.41 compared to placebo), 10.7% of Dexfen SR (p = 0.64 compared to placebo), and 11.9% of placebo patients. The minor differences between patients treated with active drug versus placebo, which were found in the previous study, were no longer significant even when the groups were combined (p = 0.83 compared to placebo). Mitral regurgitation (of any degree) was present in 71.5% (p = 0.15 compared to placebo), 69.8% (p = 0.30 compared to placebo), and 70.5%, respectively. This was also not significantly different from placebo when both Dexfen groups were combined (p = 0.16). There was no difference in the prevalence of restricted posterior mitral leaflet mobility among the three groups (p = 0.19). CONCLUSIONS: The small increase in prevalence of minor degrees of AR and MR in patients treated with two to three months of Dexfen previously reported is no longer present three to five months after discontinuation of medication. These data suggest that the degree of regurgitation observed in patients who used Dexfen for a relatively short duration does not progress over time. (+info)
Brain-derived neurotrophic factor-deficient mice develop aggressiveness and hyperphagia in conjunction with brain serotonergic abnormalities.
Brain-derived neurotrophic factor (BDNF) has trophic effects on serotonergic (5-HT) neurons in the central nervous system. However, the role of endogenous BDNF in the development and function of these neurons has not been established in vivo because of the early postnatal lethality of BDNF null mice. In the present study, we use heterozygous BDNF(+/-) mice that have a normal life span and show that these animals develop enhanced intermale aggressiveness and hyperphagia accompanied by significant weight gain in early adulthood; these behavioral abnormalities are known to correlate with 5-HT dysfunction. Forebrain 5-HT levels and fiber density in BDNF(+/-) mice are normal at an early age but undergo premature age-associated decrements. However, young adult BDNF(+/-) mice show a blunted c-fos induction by the specific serotonin releaser-uptake inhibitor dexfenfluramine and alterations in the expression of several 5-HT receptors in the cortex, hippocampus, and hypothalamus. The heightened aggressiveness can be ameliorated by the selective serotonin reuptake inhibitor fluoxetine. Our results indicate that endogenous BDNF is critical for the normal development and function of central 5-HT neurons and for the elaboration of behaviors that depend on these nerve cells. Therefore, BDNF(+/-) mice may provide a useful model to study human psychiatric disorders attributed to dysfunction of serotonergic neurons. (+info)
Effects of diet and serotonergic agonist on hepatic apolipoprotein B-100 secretion and endothelial function in obese men.
We studied the effects of a hypocaloric diet with or without a serotonergic agonist (dexfenfluramine, Df) on the hepatic secretion of very-low-density-lipoprotein (VLDL) apoB and endothelial function of the forearm microcirculation in 20 viscerally obese men. The kinetics of VLDL apoB were studied using an infusion of 1-((13)C)-leucine. Isotopic enrichment of apo B was measured using gas-chromatography mass spectrometry, and a multicompartmental model was used to estimate kinetic functions. Forearm vasodilatation was measured following an ischaemic stimulus using strain-gauge plethysmography, and visceral adipose tissue mass using magnetic resonance imaging. Compared with leaner subjects, the obese men had significantly higher hepatic apoB secretion (p<0.05) and lower forearm flow debt repayment (p<0.001). Both treatments produced similar decreases (p<0.05) in body weight, waist circumference, visceral adipose tissue and fasting plasma insulin. With diet alone, there was a significant decrease (p<0.05) in the plasma concentration and pool size hepatic secretion rate of VLDL apoB, as well as a significant increase (p<0.05) in post-ischaemic flow debt repayment. With diet plus Df, there were parallel responses in these variables, but only decreased forearm vascular resistance (p<0.05) was statistically significant. Combining both data sets, there was a highly significant reduction in hepatic apoB secretion rate (20. 9+/-2.0 vs. 14.7+/-1.6 mg/kg fat-free mass/day, p=0.005), as well as an increase in both maximal forearm blood flow (16.8+/-7.5 vs. 22. 2+/-8.5 ml/100 ml/min, p=0.006) and flow debt repayment (3.5+/-2.1 vs. 5.4+/-2.8 ml/100 ml, p=0.01), and a decrease in vascular resistance (6.7+/-3.7 vs. 5.1+/-4.4 mmHg/ml/100 ml/min, p=0.007). Obese men have increased hepatic secretion of apoB and endothelial dysfunction of the forearm microcirculation, and decreasing their visceral adipose tissue mass by diet (with or without a serotonergic agonist) improves these abnormalities. This may provide a mechanistic basis for the reduction in cardiovascular risk in obese patients who lose weight. (+info)