I believe, today, we have mostly addressed the problem of improper use of mefloquine. I would suggest that there are individuals out there who have taken mefloquine many times and, for whatever reason, they are simply not susceptible to the adverse effects of this drug. We don't know why some people are susceptible and some aren't. A sizable minority of us are susceptible to this toxic encephalopathy, the neurotoxic effects of mefloquine. The drug is what we call an idiosyncratic neurotoxicant, meaning some are susceptible and some aren't, and we don't know why that is. In due course we'll determine that.
Until we determine that, we have the next best thing. We have the development of prodromal symptoms to warn us who is susceptible. It could very well be that the 5%, or however many per cent, of the current force that is choosing mefloquine are individuals who have, through experience, determined that they are not susceptible. For example, I have many colleagues in the malariology community who have used mefloquine and they seem to be fine and they wish to continue taking it. I suppose as long as the drug is available and licensed for use, that's fine. I wouldn't recommend that someone who hasn't taken mefloquine take it for the first time, because there's always a risk—even with the very first tablet—that they could develop a permanent disability. I would ague that, even if one has tolerated it in the past, we don't know if certain environmental exposures or the taking of drugs or any number of things might introduce a new susceptibility. I think it's just an inherently risky drug that we probably shouldn't encourage the use of.
I think a case can be made that the current labelling, while not perfect, is far improved over what it had previously been. If the labelling is followed; if one does immediately discontinue the drug at the onset of psychiatric or neurologic symptoms, that should reduce the risk of long-term disability. I don't think it reduces it to zero, because again, there are reliable reports of permanent disability from even a single tablet, but there has been considerable improvement in the labelling in recent years.