The resistance of certain strains of malaria to the good old drugs of paludrine and chloroquine has become a problem for aircrew over the last few years. The most commonly prescribed prophylactics of doxycycline or mefloquine both have unacceptable side effects for aircrew.
Beware of general practioners (or worse, MHO operatives) who will prescribe mefloquine to you. As a pilot I was prescribed it by the MHO who provides a "health" service (my italics) to my airline.
When I questioned this operative (who had a medical qualification) as to the psychotic effects of the drug the answer was that it was not usually a problem but if I experienced any problem it would require psychiatric attention.
I reported this to my AME who quietly informed the MHO of their error.
To put the drug into perspective, when I got to my destination in Africa, the boat captain asked what anti-malarials I was taking. I told him paludrine and chloroquine, despite the prevalence in that area of Africa for resistance to those drugs. He replied that if I had been taking mefloquine he would not have allowed me on his boat. He told me that he had seen too many psychotic reactions in tourists who had been taking this drug such that it would endanger his small craft.
I was interested to see that QDM had no contra indications, so for some it is useful.
Also remember (and in my expererience it is often not mentioned by the prescribing doctor) that the other prophylactic for malaria, doxycycline, like most broad spectrum antibiotics can change gut absorbtion such that the contraceptive pill is reduced in efficiency. A vacation surprise that may not be in your future plans.
As QDM implies, if you have anything like flu symptoms after returning from the area seek serious professional advice. We lost a cabin crew last year for what many people think was a mis-diagnosis of cerebral malaria by her HMO.