08/01/2024
💊 PSA practice question - A 68-year-old man presents to the ambulatory medical clinic with left calf swelling.
He has recently had a total knee joint replacement under the orthopaedic surgeons.
Write a prescription for ONE drug that is most appropriate to treat the DVT.
Answer - B ✅
A variety of anticoagulants may now be used to treat venous thromboembolisms (VTE) including direct-oral anticoagulants, low-molecular weight heparin and warfarin.
Direct-acting oral anticoagulants (DOACs) are now commonly used first line. It is important to choose the current dose as this differs depending on whether the indication is treatment or prophylaxis of VTE. In addition, it is important to consider the patients’ age, weight and renal function as these can also influence the dose prescribed. Some DOACs such as edoxaban require a period of parenteral anticoagulation (e.g. low-molecular-weight heparin) before initiation. Warfarin is a vitamin K antagonist that inhibits vitamin-K dependant clotting factors (II, VII, IX, X). However, it inhibits protein C and protein S (anticoagulation factors) activity faster meaning it is initially prothrombotic. Therefore, warfarin should be given alongside treatment dose low molecular weight heparin until the INR is therapeutic.
The dose of enoxaparin here is the prophylactic dose. It should be 120 mg subcutaneously once daily. The dose of apixaban is the prophylaxis reduced dose. In this patient, it should be 10 mg oral twice daily.
NOTE: In the exam the Prescribing Section is not in the single-best answer format. Instead you are asked to give a drug, the route, dose, and frequency. As such there can be more than one correct answer as well as partially correct answers. See the accompanying video for more details.
