The Nurse Practitioner prescribes a patient Escitalopram (Lexapro) for Major Depressive Disorder. How long does it take for the medication to show efficacy?

A. Five to ten days: Initial pharmacologic activity at the serotonin transporter begins early, but clinical improvement in depressive symptoms is not typically observed within this short timeframe. Early side effects may appear, but efficacy is delayed. B. Six to twelve hours: Escitalopram reaches peak plasma levels within a few hours, yet symptomatic relief of depression does not occur this quickly. Pharmacokinetics do not directly translate into immediate therapeutic effects. C. Two to four hours: While absorption is rapid, antidepressant effects require cumulative changes in neurotransmitter regulation and receptor sensitivity. Symptom improvement within hours is not expected. D. Four to six weeks: SSRIs like escitalopram require several weeks for neuroadaptive changes in serotonin pathways, receptor sensitivity, and downstream neuroplasticity. Clinical guidelines indicate that significant improvement in mood, motivation, and functional status is usually seen between four and six weeks of consistent dosing.