Drug Interactions of Anticoagulants (Part 1)

Drug Interactions of Warfarin:

 More Presenttions from Dr.Naina Mohamed Pakkir Maideen

ª    Warfarin is used to treat patients with Deep Vein Thrombosis (DVT) or Pulmonary Embolism.

ª    Warfarin is also used to prevent thrombosis in high risk patients with Atrial Fibrillation, Heart attack and knee or hip surgeries.

ª    Warfarin can cause serious interactions with many commonly used medicines and it also can interact with certain foods.

ª    Regular blood monitoring of INR (International Normalized Ratio) is recommended to check for effectiveness and safety.

ª    Mechanism of Action of Warfarin:

ª    Drugs increasing the risk of Warfarin associated bleeding, include…

·      Tamoxifen

·      Simvastatin

·      Amiodarone

·      Enoxaparin

·      Danaparoid

·      Antiplatelet agents (Aspirin, Clopidogrel, etc)

·      Penicillins (Amoxicillin, Cloxacillin, Ticarcillin, Methicillin, etc)

·      Cephalosporins (Cefixime, Cefepime, Ceftazidime, etc)

·      Macrolide Antibiotics (Azithromycin, Clarithromycin, Roxithromycin, etc)

·      Fluoroquinolones (Ciprofloxacin, Levofloxacin, Moxifloxacin, etc)

·      Sulphonamides (Sulfamethoxazole, Sulfisoxazole, etc)

·      Azole Antifungals (Fluconazole, Ketoconazole, Posaconazole, Miconazole, Itraconazole, etc)

·      Chemotherapeutic Agents (Cyclophosphamide, Methotrexate, Doxorubicin)

·       Fish oil (Omega 3 Fatty Acids) supplements

·      Pomegranate

·      Alcohol

    Prothrombine time/INR should be monitored closely and frequently while using listed drugs along with Warfarin. Patients should be educated to report any signs of bleeding.

ª    Habits reducing Warfarin efficacy, include…

·      Vitamin K rich Foods (Kale, Spinach, Brussels sprouts, Collard greens, Mustard greens, etc)

·      St.John's Wort

·      Green tea

·      Tobacco smoking

        Large changes in dietary consumption of foods high in vitamin K or Green Tea should be avoided. Close monitoring of warfarin therapy is recommended when there is a change in smoking status of patients.

ª    Drugs increasing Anticoagulants associated bleeding risk, include…

·      NSAIDs (Ibuprofen, Diclofenac, Naproxen, etc)

·      Selective serotonin reuptake inhibitors (SSRIs) (Fluvoxamine, Paroxetine, Vortioxetine,  Escitalopram, Sertraline, Nefazodone, vilazodone)

·      Selective Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs) (Venlafaxine, Desvenlafaxine, Duloxetine, Milnacipran, Levomilnacipran, Sibutramine)

·      Ginkgo

·      Garlic

·      Papaya

·      Chamomile (Matricaria chamomilla)

ª    TIPS for Warfarin Patients:

·      Limit the intake of Vitamin K rich foods kale, collards, broccoli, spinach and other green leafy vegetables.

·      Do not double the dose to compensate a missed one.

·      Do not forget to discuss with your surgeon or dentist about the regular use of Warfarin prior to any surgery.

·      Contact your doctor if you develop severe diarrhea, an infection or a fever.

·      Seek immediate medical advice if there is signs of bleeding such as blood in your stools or urine, nose-bleeds, bleeding gums, excessive menstrual bleeding or excessive bruising.

·      Be careful with knives and try to minimize the risk of falling.

·      Always adhere to the prescribed dosage schedule.

·      Wear or carry an identification stating that You are on Warfarin.

·      Stick with the same brand of warfarin to maintain INR levels stable.

ª    Drug interactions can result in significant morbidity and mortality and thus minimizing the risk for drug interactions should be a goal in drug therapy.

ª    The patients with clotting disorders should bring a list of all of the drugs they are taking including prescription drugs, over-the-counter drugs, and any supplements, herbal or otherwise, during their visit to the doctor or pharmacist.

ª    The risk of adverse effects could be reduced by healthcare professionals through the screening, education, and follow up on suspected drug interactions.

ª    If possible, the patients are recommended to fill all their prescriptions at one pharmacy.

ª    Pharmacists can play a crucial role in identifying possible drug interactions by asking Warfarin patients about their herbal and other alternative medicine product use.