Can prednisone increase Partial Thromboplastin Time (PTT) and International Normalized Ratio (INR)?

Prednisone's Effect on PTT and INR

Prednisone does not typically increase PTT or INR values; in fact, it may have the opposite effect by promoting a procoagulant state in some patients. 1

Effects of Prednisone on Coagulation Parameters

• Prednisone and other corticosteroids can induce a procoagulant state in healthy individuals, as evidenced by increases in peak thrombin, velocity index, plasminogen-activator inhibitor type-1 (PAI-1), and von Willebrand factor (VWF) after 10 days of treatment 1
• Rather than increasing INR values, prednisone has been observed to potentially increase INR in patients already on warfarin therapy, suggesting an interaction with vitamin K antagonists rather than a direct effect on coagulation parameters 2
• Corticosteroids can shorten activated partial thromboplastin time (APTT) and raise both intrinsic and extrinsic coagulation factors in certain clinical contexts, such as in children with nephrotic syndrome 3

Clinical Implications

• The American College of Cardiology notes that INR was specifically designed and validated to assess coagulation status only in patients receiving vitamin K antagonist therapy, not as a general predictor of bleeding risk or to evaluate the effects of medications like prednisone 4
• When monitoring patients on prednisone who are also receiving anticoagulant therapy, clinicians should be aware that changes in INR values may reflect drug interactions rather than direct effects of prednisone on coagulation 2
• In patients with liver disease, the European Association for the Study of the Liver states that INR is a poor predictor of bleeding risk, regardless of concurrent prednisone use 4

Special Considerations

• For patients on both prednisone and anticoagulant therapy:
  • More frequent monitoring of INR may be warranted when starting or stopping prednisone in patients on warfarin 2
  • Consider alternative anticoagulants that are not monitored by global coagulation assays (e.g., fondaparinux) in situations where accurate monitoring is critical 5
  • Be aware that abnormal coagulation test results at baseline can provide an important clue regarding the risk of subsequent anticoagulant failure due to PTT or INR confounding 5

Potential Mechanisms

• Corticosteroids may affect coagulation through multiple mechanisms:
  • Increasing levels of coagulation factors II, V, VIII, IX, X, and XI 3
  • Promoting a procoagulant state by increasing peak thrombin and velocity index 1
  • Potentially inhibiting fibrinolysis through increased PAI-1 levels 1

Common Pitfalls to Avoid

• Do not assume that elevated INR or PTT values in patients on prednisone are caused by the medication itself; multiple other factors can affect these values 5
• Avoid overreliance on INR as a predictor of bleeding risk in patients not on vitamin K antagonist therapy, as the American Heart Association warns that INR lacks validation for predicting bleeding risk in other clinical scenarios 4
• Remember that platelet function tests appear to be unaffected by prednisone treatment, even after 6 weeks of therapy 6