This chapter provides expert guidance on mechanism of action of lithium, valproate, and carbamazepine as well as their formulations, indications, plasma levels, adverse effects, and prescribing for special patient groups. Calcium‐related genes have been implicated by genetic studies in bipolar disorder (BD). Clinical studies of the treatment of affective disorders variably use sodium valproate, semi‐sodium valproate, ‘valproate’ or valproic acid. Antipsychotics have been used in acute and maintenance treatment of BD since the 1960s, with evidence to suggest effectiveness at both poles of the illness, as well as mixed states. Oral paliperidone prevents manic relapse in BD and case reports describe good outcomes with the long‐acting injections form. Bipolar depression shares the same diagnostic criteria for a major depressive episode in major depressive disorder but episodes may differ in severity, time course, liability to recurrence and response to drug treatment.