Identifying the Risks of Anticoagulation in Patients with Substance Abuse

UMMS Affiliation

Department of Quantitative Health Sciences

Publication Date


Document Type



Cardiovascular Diseases | Epidemiology | Health Services Research | Substance Abuse and Addiction


BACKGROUND: Warfarin is effective in preventing thromboembolic events, but concerns exist regarding its use in patients with substance abuse.

OBJECTIVE: Identify which patients with substance abuse who receive warfarin are at risk for poor outcomes.

DESIGN: Retrospective cohort study. Diagnostic codes, lab values, and other factors were examined to identify risk of adverse outcomes.

PATIENTS: Veterans AffaiRs Study to Improve Anticoagulation (VARIA) database of 103,897 patients receiving warfarin across 100 sites.

MAIN MEASURES: Outcomes included percent time in therapeutic range (TTR), a measure of anticoagulation control, and major hemorrhagic events by ICD-9 codes.

RESULTS: Nonusers had a higher mean TTR (62 %) than those abusing alcohol (53 %), drugs (50 %), or both (44 %, p < 0.001). Among alcohol abusers, an increasing ratio of the serum hepatic transaminases aspartate aminotransferase/alanine aminotransferase (AST:ALT) correlated with inferior anticoagulation control; normal AST:ALT ≤ 1.5 predicted relatively modest decline in TTR (54 %, p < 0.001), while elevated ratios (AST:ALT 1.50-2.0 and > 2.0) predicted progressively poorer anticoagulation control (49 % and 44 %, p < 0.001 compared to nonusers). Age-adjusted hazard ratio for major hemorrhage was 1.93 in drug and 1.37 in alcohol abuse (p < 0.001 compared to nonusers), and remained significant after also controlling for anticoagulation control and other bleeding risk factors (1.69 p < 0.001 and 1.22 p = 0.003). Among alcohol abusers, elevated AST:ALT >2.0 corresponded to more than three times the hemorrhages (HR 3.02, p < 0.001 compared to nonusers), while a normal ratio AST:ALT ≤ 1.5 predicted a rate similar to nonusers (HR 1.19, p < 0.05).

CONCLUSIONS: Anticoagulation control is particularly poor in patients with substance abuse. Major hemorrhages are more common in both alcohol and drug users. Among alcohol abusers, the ratio of AST/ALT holds promise for identifying those at highest risk for adverse events.


Anticoagulation, Warfarin, Alcohol abuse, Drug abuse, Substance abuse

DOI of Published Version



Efird LM, Miller DR, Ash AS, Berlowitz DR, Ozonoff A, Zhao S, Reisman JI, Jasuja GK, Rose AJ. Identifying the Risks of Anticoagulation in Patients with Substance Abuse. J Gen Intern Med. 2013 Apr 26. DOI 10.1007/s11606-013-2453-x.

Journal/Book/Conference Title

Journal of general internal medicine : official journal of the Society for Research and Education in Primary Care Internal Medicine

PubMed ID


Related Resources

Link to article in PubMed