The hallucinatory effects of larium are so well known it has effectively been banned for SCUBA diving for a couple of decades - hallucinate underwater and you are likely to die.

The effects on other nations' troops (and the US Peace Corps) are also well known. One of our SCUBA diving partners has a daughter who took larium in the Peace Corps and she has suffered serious mood control problems ever since.

There are safer anti-malarial drugs but they need to be taken daily. So far as I can see, the fact that larium needs only be taken once a week was the deciding factor in the US, UK and Canadian governments' decisions to issue it. Daily pills might be a nuisance; for a soldier; but lifelong mental problems is a far bigger problem,  

.