What is the half-life of Lexapro (escitalopram)?

Half-Life of Lexapro (Escitalopram)

The half-life of Lexapro (escitalopram) is approximately 27-32 hours, which is consistent with once-daily dosing. 1

Pharmacokinetic Profile of Escitalopram

Escitalopram, the S-enantiomer of citalopram, has well-established pharmacokinetic properties:

• Absorption: Following oral administration, escitalopram is rapidly absorbed, reaching maximum plasma concentrations in approximately 3-4 hours after either single or multiple doses 2
• Distribution: Escitalopram has low protein binding (56%) and is widely distributed throughout tissues 2
• Metabolism: Primarily hepatic, involving CYP enzymes:
  • Metabolized mainly by CYP3A4 and CYP2C19 1
  • The principal metabolite is S-demethylcitalopram (S-DCT), which is present at approximately one-third the level of escitalopram but has minimal activity 2

Steady-State Characteristics

• Steady-state plasma concentrations are achieved within approximately 7-10 days of once-daily administration 2
• At steady state, the extent of accumulation of escitalopram in plasma in young healthy subjects is 2.2-2.5 times the plasma concentrations observed after a single dose 1

Clinical Implications of Escitalopram's Half-Life

The 27-32 hour half-life of escitalopram has several important clinical implications:

1. Dosing frequency: Supports once-daily dosing regimen 1
2. Steady state: Requires approximately one week to reach steady-state concentrations 1
3. Missed doses: The relatively long half-life provides some buffer against occasional missed doses compared to medications with shorter half-lives

Special Populations

The pharmacokinetics of escitalopram may be altered in certain populations:

• Elderly patients: Escitalopram AUC and half-life were increased by approximately 50% in elderly subjects, though Cmax was unchanged 1
• Hepatic impairment: Patients with reduced hepatic function show reduced oral clearance (37% reduction) and doubled half-life compared to normal subjects 1
• Renal impairment: In mild to moderate renal impairment, oral clearance is reduced by 17% compared to normal subjects 1

Common Pitfalls and Considerations

1. Dose adjustments: Lower starting doses (10 mg) are recommended for elderly patients and those with hepatic impairment due to altered pharmacokinetics 1

2. Drug interactions: While escitalopram has minimal effects on CYP enzymes, certain medications can affect its metabolism:

   • Cimetidine and omeprazole can increase escitalopram exposure (72% and 51% respectively) 2
   • Caution should be exercised when combining with other serotonergic medications due to risk of serotonin syndrome

3. Discontinuation: The relatively long half-life may help reduce discontinuation symptoms compared to shorter-acting SSRIs, though abrupt discontinuation should still be avoided

The pharmacokinetic profile of escitalopram, particularly its half-life of 27-32 hours, contributes to its favorable clinical utility across a broad range of patients with anxiety and depressive disorders.