chick embryonic CAM assay) has also been used to determine antiangiogenic activity with shark cartilage preparations. Since thalidomide, a known teratogenic agent, has antiangiogenic effects as one of its mechanisms, it is reasonable to have concerns that the long-term use of shark cartilage preparations could produce teratogenic effects. Antiangiogenic effects might contribute to abnormal fetal development and other physiological conditions (i.e., delayed tissue repair) in which angiogenesis is crucial to the formation of normal structures.
Neurotoxicity: Clinical trials are under way based on the presumption that shark cartilage has antiangiogenic activity in vivo. Based on limited animal and in vitro studies, there is no evidence to suggest neurotoxicity. Antiangiogenic agents, based on limited animal and in vitro studies, show no evidence that suggests neurologic toxicity. However, both peripheral and central nervous system toxicity have been reported in a review of short-term clinical studies. Adverse effects included central and peripheral neuropathies (e.g., sustained paralysis, cerebellar ataxia, spastic diplegia, sensory neuropathy, sedation, headache), with some toxicities resolving upon discontinuation of the antiangiogenic agent.
These clinical observations support a potential association between shark cartilage preparations with purported antiangiogenic activity and adverse neurological effects. It should be recognized that the subjects in the shark cartilage clinical trials had advanced cancer, other chronic disease, and/or were taking concurrent medications. Many angiogenic mediators can act as neurotrophic factors, and this bioactivity may contribute to neurological abnormalities. Additional studies are warranted to establish the neurotoxic risk from antiangiogenic agents.
It is very difficult to address the safety of this substance because of the lack of its characterization. There is no generally accepted standard composition of shark cartilage supplements. There are several different products labeled as shark cartilage, and composition differs among them. It is not known if composition changes by batch as well as by product, thereby potentially influencing safety. No active ingredient of shark cartilage preparations has been defined. Furthermore, the effect of processing during the preparation of different products on the bioactivity/bioavailability of the components of shark cartilage is unknown. At this time it cannot be determined whether any of the potential safety issues are relevant to specific shark cartilage preparations or to shark cartilage in general.