**Core Concept**
Mefloquine and chloroquine-resistant malaria areas require alternative chemoprophylaxis strategies to prevent Plasmodium falciparum infection. Artemisinin-based combination therapies (ACTs) are a recommended option for travelers to these regions.

**Why the Correct Answer is Right**
Artemether-lumefantrine (Coartem) is an ACT that combines the fast-acting artemether with the longer-acting lumefantrine. This combination provides effective prophylaxis against P. falciparum, as well as against other Plasmodium species. The use of ACTs in malaria chemoprophylaxis has significantly reduced the incidence of malaria in travelers to high-risk areas.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the scenario described.
**Option B:** Although doxycycline is an alternative chemoprophylaxis option for malaria, it is not the preferred choice for travelers to areas with high resistance to chloroquine and mefloquine.
**Option C:** Atovaquone-proguanil (Malarone) is another ACT used for malaria chemoprophylaxis, but it is not the primary choice for travelers to areas with high resistance to chloroquine and mefloquine.

**Clinical Pearl / High-Yield Fact**
When prescribing chemoprophylaxis for malaria, consider the destination country's malaria transmission patterns, the traveler's itinerary, and the presence of resistance to commonly used antimalarial drugs. Always provide clear instructions and warnings about potential side effects and drug interactions.

**Correct Answer: A. Artemether-lumefantrine (Coartem)**