What is the expected time for Celexa (citalopram) 30mg to be eliminated from the body?

Elimination Time of Citalopram 30mg from the Body

Citalopram 30mg will take approximately 5-7 days to be completely eliminated from the body, as it has a half-life of about 35 hours in adults. 1

Pharmacokinetics of Citalopram

Citalopram has a well-established pharmacokinetic profile with the following key characteristics:

• Half-life: The mean terminal half-life is approximately 35 hours 1
• Steady state: With once-daily dosing, steady state plasma concentrations are achieved within approximately one week 1
• Elimination: At steady state, the extent of accumulation of citalopram in plasma is expected to be 2.5 times the plasma concentrations observed after a single dose 1

Metabolism and Elimination Pathway

Citalopram undergoes extensive metabolism primarily in the liver:

• Metabolized mainly through CYP3A4 and CYP2C19 enzymes 1
• The systemic clearance is approximately 330 mL/min, with about 20% due to renal clearance 1
• Following intravenous administration, approximately 10% of citalopram and 5% of its metabolite demethylcitalopram (DCT) are recovered in urine 1

Factors Affecting Elimination Time

Several factors can significantly impact how long citalopram remains in the body:

Age

• In individuals over 60 years of age, citalopram's half-life is increased by approximately 30-50% compared to younger adults 1
• This means older adults may require up to 9-10 days for complete elimination

Hepatic Function

• Patients with reduced hepatic function have a 37% reduction in oral clearance and doubled half-life 1
• For these patients, elimination time could extend to 10-14 days

Genetic Factors

• CYP2C19 poor metabolizers have 107% increased AUC and 68% increased Cmax 1
• This genetic variation can significantly extend elimination time to approximately 10-14 days

Complete Elimination Timeline

For a standard 30mg dose in an average adult with normal hepatic and renal function:

• After 35 hours (1 half-life): 15mg remains
• After 70 hours (2 half-lives): 7.5mg remains
• After 105 hours (3 half-lives): 3.75mg remains
• After 140 hours (4 half-lives): 1.88mg remains
• After 175 hours (5 half-lives): 0.94mg remains
• After 210 hours (6 half-lives): 0.47mg remains

This equates to approximately 5-7 days for over 98% elimination of the drug from the body.

Clinical Implications

Understanding the elimination time is important for:

1. Medication switches: When transitioning to another antidepressant, particularly MAOIs
2. Drug interactions: Potential interactions may persist for up to a week after discontinuation
3. Side effect management: Some adverse effects may continue for several days after stopping the medication

Comparison to Other SSRIs

Citalopram's elimination time is moderate compared to other SSRIs:

• Shorter than fluoxetine (half-life: 2-4 days, with active metabolite half-life of 7-15 days) 2
• Similar to escitalopram (half-life: 27-33 hours) 3
• Longer than some other antidepressants with shorter half-lives

The 35-hour half-life makes citalopram suitable for once-daily dosing while allowing relatively quick elimination after discontinuation compared to longer-acting SSRIs like fluoxetine.