Which of the following statements about heparin administration is NOT true?

The statement regarding the time it takes for heparin to take effect is indeed a key detail. Heparin is a medication that acts as an anticoagulant and is usually administered to prevent blood clotting. However, it typically begins to have its effects almost immediately after administration, especially when given intravenously, which is the most common route for quick anticoagulation. For subcutaneous administration, while the onset might be slightly delayed compared to intravenous use, it still does not take as long as 8 hours for heparin's effects to manifest.

In terms of the context of the other statements, using tranexamic acid to manage minor postoperative bleeding is a recognized approach; thereby affirming its relevance to managing bleeding in patients on anticoagulants. Prothrombin time measured by INR is crucial in determining the safety of dental extractions in anticoagulated patients, and an INR of 3 would generally be a threshold beyond which dental procedures are approached with caution. Lastly, the subcutaneous route is indeed a common method of administering heparin, particularly for outpatient management, pointing to the normal clinical practice regarding its administration.