In which type of toxicity is Dimercaprol (BAL) contraindicated?

Dimercaprol, also known as British Anti-Lewisite (BAL), is a chelating agent that is primarily used to treat poisoning from certain heavy metals. However, it is contraindicated in cases of iron toxicity due to the potential for exacerbating the situation. This is particularly relevant as dimercaprol can release free iron from transferrin, causing a further increase in free iron levels and leading to additional oxidative stress and organ damage.

With cadmium toxicity, dimercaprol is also contraindicated. While BAL is effective for heavy metal chelation, it is not used in cadmium poisoning because it may actually enhance the toxicity of cadmium. The mechanism behind this includes the potential mobilization of cadmium from tissues or increasing its bioavailability.

Thus, the correct answer indicates that dimercaprol is contraindicated in both cadmium and iron toxicity, highlighting the importance of selecting appropriate chelation therapy based on the specific heavy metal involved in poisoning scenarios.