Final answer:
The intercostals region has the highest absorption rate for anesthesia, contributing to a greater risk of toxicity due to its rich vascular supply.
Step-by-step explanation:
When considering the complication of toxicity, the area of the body with the highest absorption rate for anesthesia is the intercostals. This is due to the rich vascular supply in the intercostal spaces, which allows for rapid systemic absorption of local anesthetic agents.
Absorption in these areas can lead to higher plasma levels of the drug, increasing the risk of systemic toxicity if not administered with care.