For therapeutic effect in manic depressive illness, steady-state serum lithium concentration should be maintained between
**Core Concept**
Lithium is a mood stabilizer used in the treatment of bipolar disorder, and maintaining a therapeutic steady-state serum lithium concentration is crucial for its efficacy and safety. The optimal concentration range is critical to prevent toxicity while ensuring the therapeutic effect.
**Why the Correct Answer is Right**
The therapeutic effect of lithium is achieved when the steady-state serum concentration is maintained between 0.6 and 1.2 mmol/L. This narrow concentration range is essential for its efficacy in managing manic depressive illness. Lithium exerts its therapeutic effects by inhibiting the reuptake of norepinephrine and serotonin, thereby increasing the synaptic concentration of these neurotransmitters. It also has a stabilizing effect on the sodium-potassium pump, which is crucial in maintaining the stability of neuronal membranes.
**Why Each Wrong Option is Incorrect**
* **Option A:** Concentrations below 0.6 mmol/L may not be effective in managing manic depressive illness, as they are below the therapeutic range.
* **Option B:** Concentrations above 1.2 mmol/L increase the risk of lithium toxicity, which can cause severe symptoms such as nausea, vomiting, tremors, and seizures.
* **Option D:** Concentrations above 1.5 mmol/L are considered toxic and can lead to serious complications, including renal failure and cardiac arrhythmias.
**Clinical Pearl / High-Yield Fact**
It's essential to monitor serum lithium concentrations regularly, especially when initiating or adjusting therapy, to ensure that the concentration remains within the therapeutic range. A mnemonic to remember the therapeutic range is "6-12," which represents the concentration range of 0.6-1.2 mmol/L.
**Correct Answer: C. 0.6-1.2 mmol/L**