What Does the Boxed Warning Tell Us? Safe Practice of Using Ferumoxytol as an MRI Contrast Agent

BACKGROUND AND PURPOSE

Despite the label change and the FDA's boxed warning added to the Feraheme (ferumoxytol) label in March 2015, radiologists have shown increasing interest in using ferumoxytol as an MR imaging contrast agent as a supplement or alternative to gadolinium. The goals of this study were to provide information regarding ferumoxytol safety as an imaging agent in a single center and to assess how the Feraheme label change may affect this potential, currently off-label indication.

MATERIALS AND METHODS

This retrospective study evaluated the overall frequency of ferumoxytol-related adverse events when used for CNS MR imaging. Patients with various CNS pathologies were enrolled in institutional review board-approved imaging studies. Ferumoxytol was administered as multiple rapid bolus injections. The risk of adverse events was correlated with demographic data/medical history.

RESULTS

The safety of 671 ferumoxytol-enhanced MR studies in 331 patients was analyzed. No anaphylactic, life-threatening, or fatal (grade 4 or 5) adverse events were recorded. The overall proportion of ferumoxytol-related grade 1-3 adverse events was 10.6% (8.6% occurring within 48 hours), including hypertension (2.38%), nausea (1.64%), diarrhea (1.04%), and headache (1.04%). History of 1 or 2 allergies was associated with an increased risk of adverse events (14.61% versus 7.51% [no history]; P = .007).

CONCLUSIONS

The frequency of mild ferumoxytol-related adverse events was comparable with literature results, and no serious adverse event was recorded. Although the recommendations in the boxed warning should be followed, serious adverse events appear to be rare, and with proper precautions, ferumoxytol may be a valuable MR imaging agent.

Removal of dissolved brown algal phlorotannins using insoluble polyvinylpolypyrrolidone (PVPP)

Tannins, a large and diverse group of phenolic secondary metabolites, are common in terrestrial plants and marine brown algae. It is sometimes desirable to remove the tannins from plant or algal extracts, e.g., when isolating enzymes and nucleic acids, when using certain colorimetric methods to quantify the tannin content, or to create reliable controls when using tannins in experimental studies. Insoluble polyvinylpolypyrrolidone (PVPP) can be used to specifically remove tannins from solution. In the present study, we evaluated the effect of different factors (amount of PVPP, number of PVPP treatments, type of solvent, pH, and incubation time) on the PVPP removal of dissolved brown algal phlorotannins. Our results imply that there is a limited amount of phlorotannins that can bind to a given amount of PVPP, and that it is preferable to use low quantities of PVPP repeatedly, compared to using fewer treatments with a high amount of PVPP. Furthermore, we found no consistent effect on the removal of phlorotannins due to solvent type (acetone, methanol, distilled water or filtered seawater). There was a slight decrease in the amount of phlorotannins removed from extracts with increasing pH when repeatedly treated with PVPP. All phlorotannins were removed from extracts with pH < or = 6.2, and 89% of the initial phlorotannin content was removed at pH 9.7. These results are compared with previous methodological studies on tannin removal with PVPP. Furthermore, the implications of phlorotannin removal in analytical and ecological investigations are discussed.

Water-borne cues induce chemical defense in a marine alga (Ascophyllum nodosum)

It is well known that herbivores can induce chemical defenses in terrestrial vascular plants, but few examples of inducible production of defense chemicals have been reported for aquatic macrophytes. Furthermore, it is well established that water-borne chemical cues from predators or predator-wounded conspecifics can induce defensive changes of aquatic prey animals, but no such communication between aquatic herbivores and seaweeds has been reported. Here we show that water-borne cues from actively feeding herbivorous gastropods, flat periwinkles (Littorina obtusata), can serve as external signals to induce production of defense chemicals (phlorotannins) in unharmed individuals of seaweeds, knotted wrack (Ascophyllum nodosum), and that the increased levels of defense chemicals deter further feeding by periwinkles. Because seaweeds have poorly developed internal-transport systems and may not be able to elicit systemic-induced chemical defenses through conveyance of internal signals, this mechanism ensures that seaweeds can anticipate future periwinkle attacks without receiving direct damage by herbivores.