What I've looked up thus far for State of Wonder

Marina mentions how she had horrible nightmares whenever she went to India as a child and didn't realize until she had to go to Brazil and start anti-malarials again, what was the cause. The drug Lariam. When I was on malaria meds (less exotic than this sounds), I took plain old chloroquine and if they had adverse affects I didn't notice them between the dysentery and general craziness of being in a foreign country.

Chloroquine is a 4-Aminoquinoline and for the most part, its side effects seem benign. Itchy skin, unpleasant taste in the mouth, headache. All pretty generic and if you are in a place where malaria is prevelent, you probably feel all of the above regardless. Along with an unceasing fear you are at any minute going to shit yourself.

Lariam, or Mefloquine, was created by the army in the 1970's. It's a synthetic form of quinine, the original Malaria remedy that comes from cinchona tree bark. According to Wiki, as of 2009 Roche no longer manufactures it but you can get generic analogs still.

Although, why the hell would you want to. Take a look at these side effects: psychosis, seizures, pneumonia and abnormal heartbeat. In fact in {the website in the link says 2008 but it appears this happened in 2002}, within 6 weeks time 4 soldiers at Fort Bragg murdered their wives. Two later killed themselves. Lariam was mentioned as a possible cause.

As to why the character was taking Lariam at all, I found this on a travel website:

Generally, chloroquine is not prescribed for areas where chloroquine-resistent malaria is thriving - mainly in tropical climates. In more temporate zones, such as Argentina, chloroquine is sufficient as most areas are of no risk.

There are other options but they have other side-effects, such as doxycycline which causes photo-sensitivity (and is an antibiotic. I'm surprised it's in this list.) 

Marina mentions she is going to Manaus. Manaus is the capital of the state of Amazonas, which is the largest state in Brazil. Look where this place is:

It's 2674 miles from Rio de Janeiro. It's 1200 miles from Brasilia. It's not a tiny backwater though. The population is 2 million. It looks very pretty , more than I expected, in pictures.