Q; Which commonly use drugs in ICU may cause resistance to Heparin Therapy (failure of monitoring tests to change or higher than expected doses) ?


Answer: The most important cause of apparent resistance to heparin therapy is antithrombin III deficiency. Replacement of antithrombin III in a deficient patient may restore heparin efficacy.

Also, its important to know that following commonly use medicines may cause resistance to heparin therapy.

• intravenous nitroglycerin
• digitalis,
• nicotine (smoking),
• tetracycline
• some antihistamines
  

Reference:

Bick RL., Disorders of Thrombosis & Hemostasis. Clinical and Laboratory Practice. 1992. ASCP Press. (Figure 1-29 page 20; Table 14-7, page 305).