Why is a functional renal system important when taking Lithium?

A functional renal system is crucial when taking Lithium because this medication is primarily excreted through the kidneys. Proper kidney function ensures that Lithium levels in the bloodstream remain within the therapeutic range. If renal function is compromised, Lithium can accumulate in the body, leading to toxicity. This could result in severe side effects such as nausea, tremors, confusion, or even more serious problems like renal failure or seizures.

In contrast to the other options, the metabolism of Lithium does not involve the liver, and it doesn't require liver enzymes to function effectively. While Lithium can influence cardiac function, this relates more to its effects rather than the necessity for kidney excretion. Therefore, understanding the role of the renal system is essential for safely managing Lithium therapy and preventing potential complications.