The full, clinically endorsed recommendation should be obtained from Lareb.  

Rationale for drug selection  

Citalopram is a selective serotonin reuptake inhibitor (SSRI) used in pregnancy to treat depressive, panic, and anxiety disorders. Because pregnancy alters the activity of drug metabolizing enzymes, dose-adjustments may be necessary to maintain effective concentrations during pregnancy.

Pharmacokinetics of citalopram in pregnancy 

Citalopram is mainly metabolized by hepatic CYP enzymes such as CYP2C19, CYP3A4 and CYP2D6. While the activity of CYP2C19 decreases during pregnancy, the activity of CYP3A4 and CYP2D6 is significantly elevated. 

Pharmacokinetic studies confirm that citalopram concentrations can decrease by 40% during pregnancy, particularly in the second and third trimester. As a result, some pregnant women may benefit from an increased dosage when a reduced effect of citalopram is observed. Citalopram crosses the placenta, with fetal levels that are approximately 60–80% of maternal concentrations.

Benefits and risks with the proposed dose adjustments 

The expected benefits and associated risk of a higher dosing regimen of citalopram during pregnancy.

In short 

Pregnancy may reduce maternal plasma concentrations throughout pregnancy, especially later gestation, with possible symptom deterioration. Therefore, dose adjustments may be necessary. Based on the weighing of benefits and risks, the working committee derived an appropriate dose adjustment. Consult Lareb for the model-informed dosing recommendations.