Pharmacokinetics of antidepressants must be considered when choosing and combining treatments for patients. Information on drug interactions is constantly being updated. This chapter reviews the basic principles of antidepressant pharmacokinetics, but specifics are best found in up-to-date reference sources on prescribing.

Once treatment options have been investigated, algorithms to treat depression may help the clinician in deciding the best treatment choice on a per-case basis. Current algorithms that may be utilized in the treatment of depression can be evidence-based, cost-based or symptom-based. Whereas evidence- and cost-based algorithms may be more beneficial to healthcare plans in terms of financial issues, patients often benefit most from a symptom-based approach. This may require some trial and error, but once the correct treatment option is chosen, patients may experience complete remission of depressive symptoms. Whatever approach is taken, the goal of treatment of depression is remission. Here, we emphasize the symptom-based approach to selecting and combining antidepressants, particularly for difficult cases.

MDD: major depressive disorder. NDRI: norepinephrine and dopamine reuptake inhibitors. NRI: norepinephrine reuptake inhibitors. SSRI: selective serotonin reuptake inhibitors. SNRI: serotonin norepinephrine reuptake inhibitors. SARI: serotonin antagonist/reuptake inhibitors. MAOI: monoamine oxidase inhibitors. 5HT: serotonin. NE: norepinephrine. DA: dopamine.

SSRI: selective serotonin reuptake inhibitors. SNRI: serotonin norepinephrine reuptake inhibitors. NDRI: norepinephrine and dopamine reuptake inhibitors. 5HT1A: serotonin 1A agonists. T3/T4: thyroid hormone.

SSRI: selective serotonin reuptake inhibitors. NDRI: norepinephrine and dopamine reuptake inhibitors. SNRI: serotonin norepinephrine reuptake inhibitors. ECT: electroconvulsive therapy. IPT: interpersonal therapy. VNS: vagus nerve stimulation. NRI: norepinephrine reuptake inhibitors. TCA: tricyclic antidepressants. SARI: serotonin 2A antagonist/reuptake inhibitors. MAOI: monoamine oxidase inhibitors.

SSRI: selective serotonin reuptake inhibitors. NDRI: norepinephrine and dopamine reuptake inhibitors. SNRI: serotonin norepinephrine reuptake inhibitors. DPA: dopamine partial agonists. MTHF: L-5-methyl-tetrahydrofolate.