Lithium is the 'gold standard' pharmacotherapy for bipolar disorder. The drug has been available for over 50 years and its efficacy in bipolar maintenance and acute mania has been well established through numerous studies and meta-analyses. More recently, evidence has begun to mount that lithium may possess antisuicidal properties – an important consideration in bipolar disorder, which has the highest rates of suicide attempt and completion of all the psychiatric disorders. 

Even though the efficacy of lithium in the maintenance of bipolar disorder is well recognized, the drug has a poor tolerability profile and may be difficult to use due to its narrow therapeutic index. At high plasma concentrations, lithium can cause severe neurotoxicity. Plasma-concentration monitoring is therefore required (every 3 months) even on stabilized regimens during long-term treatment.

Strengths:

• 'Gold standard' of mood-stabilizing drugs
• Well-documented efficacy in acute mania and as maintenance  therpay (less so for bipolar depression)
• Documented antisuicidal effects
• Has been used for more than 50 years
• Inexpensive
  

Weaknesses:

• Narrow therapeutic index
• Difficult to use (monitoring of plasma concentration is required)
• Poor tolerability profile
• Poor compliance which may lead to premature relapse
• Predominantly effective against manic relapse