Antidepressant-warfarin interaction and associated gastrointestinal bleeding risk in a case-control study

Area of Science:

• Pharmacovigilance
• Drug Safety
• Clinical Pharmacology

Background:

• Gastrointestinal (GI) bleeding is a significant adverse event associated with warfarin therapy.
• Concurrent use of interacting medications that potentiate warfarin can elevate bleeding risk.

Purpose of the Study:

• To investigate whether initiating antidepressant therapy increases the risk of hospitalization for GI bleeding in patients using warfarin.

Main Methods:

• An observational, nested case-control study was conducted using Medicaid claims data from 1999-2005.
• The study included 430,455 warfarin users, analyzing 407,370 person-years of exposure.
• Cases of GI bleeding hospitalization were matched with 50 controls based on index date and state.

Main Results:

• The incidence rate of GI bleeding hospitalization was 4.48 per 100 person-years.
• Initiation of citalopram, fluoxetine, paroxetine, and amitriptyline was associated with increased odds of GI bleeding.
• Mirtazapine, not typically considered to interact with warfarin, also showed an increased risk of GI bleeding.

Conclusions:

• Warfarin users initiating citalopram, fluoxetine, paroxetine, or amitriptyline face a higher risk of GI bleeding hospitalization.
• The increased risk observed with mirtazapine suggests potential non-drug-interaction factors contributing to GI bleeding events.