Which agent is considered effective for chemoprophylaxis against all Plasmodium infections for most adults?

Chloroquine is recognized as a highly effective agent for chemoprophylaxis against all Plasmodium infections, particularly Plasmodium falciparum, which is one of the most common malaria-causing parasites. It works by interfering with the growth of parasites in the red blood cells. Chloroquine has been a standard part of malaria prevention strategies, especially in areas where the parasite is known to be sensitive to this drug.

Its effectiveness in adults is well-documented, making it a go-to option for individuals traveling to malaria-endemic regions. The considerations for using chloroquine include both regional resistance patterns and the specific type of Plasmodium the patient may be exposed to since resistance can affect its efficacy in certain areas.

While other options like quinine, mefloquine, and atovaquone are used in certain contexts for treating or preventing malaria, chloroquine stands out due to its broad effectiveness across various types of Plasmodium, particularly when knowing the strain prevalence in the area of potential exposure.