First agent shown to be effective in maniac phase of BPD –

**Core Concept**
The treatment of the manic phase of bipolar disorder (BPD) involves pharmacological interventions to stabilize mood and reduce symptoms of mania. The first agent shown to be effective in managing mania is a key milestone in the field of psychiatry.

**Why the Correct Answer is Right**
Lithium is the first agent shown to be effective in the manic phase of BPD. It acts by inhibiting the reuptake of serotonin and norepinephrine, thereby increasing their availability in the synaptic cleft. Lithium also has a stabilizing effect on the neuronal membrane, which may contribute to its therapeutic effects. The mechanism of lithium's action is not fully understood, but it is believed to involve the inhibition of inositol monophosphate, an enzyme involved in the signaling pathway of inositol trisphosphate.

**Why Each Wrong Option is Incorrect**
**Option A:** Chlorpromazine is an antipsychotic medication primarily used to treat schizophrenia. While it may have some mood-stabilizing effects, it is not the first agent shown to be effective in the manic phase of BPD.
**Option B:** Carbamazepine is an anticonvulsant medication that is also used as a mood stabilizer in BPD. However, it was not the first agent shown to be effective in the manic phase of BPD.
**Option C:** Imipramine is a tricyclic antidepressant that is not typically used to treat mania. It may even exacerbate mania in some cases.

**Clinical Pearl / High-Yield Fact**
Lithium is a narrow therapeutic index medication, meaning that the difference between a therapeutic dose and a toxic dose is small. Regular monitoring of serum lithium levels is essential to avoid toxicity.

**Correct Answer:** A. Lithium