ELEMENTAL MERCURY NEUROTOXICITY FROM SELF-INJECTION

Mercury and Movement Disorders: The Toxic Legacy Continues

Mercury (Hg) exists in the environment as inorganic (metallic Hg vapor, mercurous and mercuric salts) or organic (bonded to a structure containing carbon atoms) forms. Neurotoxic effect of Hg is known for years. While the organic form (methylmercury (meHg)) led to the Minamata incidence in Japan and "wonder-wheat" disaster in Iraq, the "mad hatters" and "Danbury shakes" were related to the inorganic elemental form (Hg vapor). Human exposure to toxic Hg continues in the modern world to a large extent by artisanal gold mining, biomass combustion, chloralkali production, and indigenous medicine use to name a few. Heavy industrial use of Hg contaminates air and landfills, affecting the aquatic ecosystem and marine food chain. A detailed social and occupational history with a high index of clinical suspicion is required to not miss this toxic etiology for movement disorders like ataxia, tremor, or myoclonus. In this review, we have discussed the past and present global health impact of Hg from a movement disorder perspective. The connection of Hg with neurodegeneration and autoimmunity has been highlighted. We have also discussed the role of chelating agents and the preventive strategies to combat the neurotoxic effects of Hg in the modern world.

Fingolimod and cardiac risk: latest findings and clinical implications

Fingolimod is an oral medication approved for the treatment of relapsing multiple sclerosis (MS). It is unique compared with other approved disease-modifying therapies for MS in that it is the first oral agent and it has a novel mechanism of action. In clinical trials and postmarket use, it demonstrates clear therapeutic efficacy. However, it is associated with certain risks including cardiac concerns. The recent reports of cardiac events potentially associated with the drug prompted a regulatory agencies review of the use of fingolimod for MS in the USA and Europe. After completion of their review, the US Food and Drug Administration and the European Medicines Agency concluded that its benefits outweighed the risks. However, certain recommendations were made for appropriate patient selection for fingolimod and for more cautious first-dose monitoring. We review the use of fingolimod for MS in light of the recently reported potential cardiac risks. We conclude that with appropriate patient selection and careful monitoring, it appears to have a favorable benefits/risks profile and can be a valuable treatment option for relapsing MS. Continued postmarketing surveillance and data from the extension phase of its clinical trials will be very important in understanding the long-term efficacy and safety of fingolimod and to help determine its place in the treatment algorithm for multiple sclerosis.

A placebo-controlled trial of oral fingolimod in relapsing multiple sclerosis

BACKGROUND

Oral fingolimod, a sphingosine-1-phosphate-receptor modulator that prevents the egress of lymphocytes from lymph nodes, significantly improved relapse rates and end points measured on magnetic resonance imaging (MRI), as compared with either placebo or intramuscular interferon beta-1a, in phase 2 and 3 studies of multiple sclerosis.

METHODS

In our 24-month, double-blind, randomized study, we enrolled patients who had relapsing-remitting multiple sclerosis, were 18 to 55 years of age, had a score of 0 to 5.5 on the Expanded Disability Status Scale (which ranges from 0 to 10, with higher scores indicating greater disability), and had had one or more relapses in the previous year or two or more in the previous 2 years. Patients received oral fingolimod at a dose of 0.5 mg or 1.25 mg daily or placebo. End points included the annualized relapse rate (the primary end point) and the time to disability progression (a secondary end point).

RESULTS

A total of 1033 of the 1272 patients (81.2%) completed the study. The annualized relapse rate was 0.18 with 0.5 mg of fingolimod, 0.16 with 1.25 mg of fingolimod, and 0.40 with placebo (P<0.001 for either dose vs. placebo). Fingolimod at doses of 0.5 mg and 1.25 mg significantly reduced the risk of disability progression over the 24-month period (hazard ratio, 0.70 and 0.68, respectively; P=0.02 vs. placebo, for both comparisons). The cumulative probability of disability progression (confirmed after 3 months) was 17.7% with 0.5 mg of fingolimod, 16.6% with 1.25 mg of fingolimod, and 24.1% with placebo. Both fingolimod doses were superior to placebo with regard to MRI-related measures (number of new or enlarged lesions on T(2)-weighted images, gadolinium-enhancing lesions, and brain-volume loss; P<0.001 for all comparisons at 24 months). Causes of study discontinuation and adverse events related to fingolimod included bradycardia and atrioventricular conduction block at the time of fingolimod initiation, macular edema, elevated liver-enzyme levels, and mild hypertension.

CONCLUSIONS

As compared with placebo, both doses of oral fingolimod improved the relapse rate, the risk of disability progression, and end points on MRI. These benefits will need to be weighed against possible long-term risks. (ClinicalTrials.gov number, NCT00289978.)