Summary
For a drug to be effectivein vivo in-vitroprotection must be translated to studies of both global (transient forebrain ischemia) to discern “cellular” neuroprotection (cytoprotection) and focal ischemia to evaluate “parenchymal” neuroprotection (infarct reduction). Drug concentrations that suggest that the mechanism is activein vitromust translate to drug levels that achieve cytoprotection and infarct volume reductions which are not only significant but sustained (indefatigable). Initiation of experimental therapy should be delayed in order to have clinical relevance. Most importantly, the “effective dose” plasma level reached in rodents to achieve a neuroprotective effect must be matched in humans, in the absence of overt toxicity.
To date there are a number of shortcomings with “cytoprotective drugs” - in rats, in particular, their inability to protect white matter and striatum. The drugs have to be given early and the cytoprotective dose in rats has yet to be achieved in humans.
This review covers mechanisms of cell death following both focal and global ischemia such as excitotoxicity, acid and Ca’ overload, free radical-mediated injury, inflammation and apoptosis.
Drugs which block NMDA and AMPA receptors, as well as downstream events, have now made it to the clinic and they will be critically reviewed. Hypothermia following both global and focal ischemia is protective and at least for global ischemia has now been translated two successful clinical trials in patients resuscitated from cardiac arrest. For the first time neuroprotection has been demonstrated in patients who achieved better neurological outcomes. The review will finish with some rules for the translation of experimental work to clinical trials.