JANTOVEN is a narrow therapeutic range (index) drug, and its action may be affected by factors such as other drugs and dietary vitamin K. Therefore, anticoagulation must be carefully monitored during JANTOVEN therapy. Determine the INR daily after the administration of the initial dose until INR results stabilize in the therapeutic range. After stabilization, maintain dosing within the therapeutic range by performing periodic INRs. The frequency of performing INR should be based on the clinical situation but generally acceptable intervals for INR determinations are 1 to 4 weeks. Perform additional INR tests when other warfarin products are interchanged with JANTOVEN, as well as whenever other medications are initiated, discontinued, or taken irregularly. Heparin, a common concomitant drug, increases the INR [see Dosage and Administration (2.8) and Drug Interactions (7)].
Determinations of whole blood clotting and bleeding times are not effective measures for monitoring of JANTOVEN therapy.
The anticoagulant effect of JANTOVEN persists beyond 24 hours. If a patient misses a dose of JANTOVEN at the intended time of day, the patient should take the dose as soon as possible on the same day. The patient should not double the dose the next day to make up for a missed dose.
Some dental or surgical procedures may necessitate the interruption or change in the dose of JANTOVEN therapy. Consider the benefits and risks when discontinuing JANTOVEN even for a short period of time. Determine the INR immediately prior to any dental or surgical procedure. In patients undergoing minimally invasive procedures who must be anticoagulated prior to, during, or immediately following these procedures, adjusting the dosage of JANTOVEN to maintain the INR at the low end of the therapeutic range may safely allow for continued anticoagulation.
Since the full anticoagulant effect of JANTOVEN is not achieved for several days, heparin is preferred for initial rapid anticoagulation. During initial therapy with JANTOVEN, the interference with heparin anticoagulation is of minimal clinical significance. Conversion to JANTOVEN may begin concomitantly with heparin therapy or may be delayed 3 to 6 days. To ensure therapeutic anticoagulation, continue full dose heparin therapy and overlap JANTOVEN therapy with heparin for 4 to 5 days and until JANTOVEN has produced the desired therapeutic response as determined by INR, at which point heparin may be discontinued.
As heparin may affect the INR, patients receiving both heparin and JANTOVEN should have INR monitoring at least:
- 5 hours after the last intravenous bolus dose of heparin, or
- 4 hours after cessation of a continuous intravenous infusion of heparin, or
- 24 hours after the last subcutaneous heparin injection.
JANTOVEN may increase the activated partial thromboplastin time (aPTT) test, even in the absence of heparin. A severe elevation (>50 seconds) in aPTT with an INR in the desired range has been identified as an indication of increased risk of postoperative hemorrhage.
Consult the labeling of other anticoagulants for instructions on conversion to JANTOVEN.
JANTOVEN tablets are single scored, compressed tablets with one side scored and debossed with WRF above the score and 1, 2, 2½, 3, 4, 5, 6, 7½, or 10 below the score and with 832 debossed on the opposite side.
JANTOVEN tablets are supplied in the following strengths:
|10 mg||white (dye-free)|
JANTOVEN is contraindicated in women who are pregnant except in pregnant women with mechanical heart valves, who are at high risk of thromboembolism [see Warnings and Precautions (5.5) and Use in Specific Populations (8.1)]. JANTOVEN can cause fetal harm when administered to a pregnant woman. JANTOVEN exposure during pregnancy causes a recognized pattern of major congenital malformations (warfarin embryopathy and fetotoxicity), fatal fetal hemorrhage, and an increased risk of spontaneous abortion and fetal mortality. If JANTOVEN is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus [see Warnings and Precautions (5.6) and Use in Specific Populations (8.1)].
- Hemorrhagic tendencies or blood dyscrasias
- Recent or contemplated surgery of the central nervous system or eye, or traumatic surgery resulting in large open surfaces [see Warnings and Precautions (5.7) ]
- Bleeding tendencies associated with:
- Active ulceration or overt bleeding of the gastrointestinal, genitourinary, or respiratory tract
- Central nervous system hemorrhage
- Cerebral aneurysms, dissecting aorta
- Pericarditis and pericardial effusions
- Bacterial endocarditis
- Threatened abortion, eclampsia, and preeclampsia
- Unsupervised patients with conditions associated with potential high level of non-compliance
- Spinal puncture and other diagnostic or therapeutic procedures with potential for uncontrollable bleeding
- Hypersensitivity to warfarin or to any other components of this product (e.g., anaphylaxis) [see Adverse Reactions (6)]
- Major regional or lumbar block anesthesia
- Malignant hypertension
JANTOVEN can cause major or fatal bleeding. Bleeding is more likely to occur within the first month. Risk factors for bleeding include high intensity of anticoagulation (INR >4.0), age greater than or equal to 65, history of highly variable INRs, history of gastrointestinal bleeding, hypertension, cerebrovascular disease, anemia, malignancy, trauma, renal impairment, certain genetic factors [see Clinical Pharmacology (12.5)], certain concomitant drugs [see Drug Interactions (7)], and long duration of warfarin therapy.
Perform regular monitoring of INR in all treated patients. Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shortest duration of therapy appropriate for the clinical condition. However, maintenance of INR in the therapeutic range does not eliminate the risk of bleeding.
Drugs, dietary changes, and other factors affect INR levels achieved with JANTOVEN therapy. Perform more frequent INR monitoring when starting or stopping other drugs, including botanicals, or when changing dosages of other drugs [see Drug Interactions (7)].
Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding [see Patient Counseling Information (17)].
Necrosis and/or gangrene of skin and other tissues is an uncommon but serious risk (<0.1%). Necrosis may be associated with local thrombosis and usually appears within a few days of the start of JANTOVEN therapy. In severe cases of necrosis, treatment through debridement or amputation of the affected tissue, limb, breast, or penis has been reported.
Careful clinical evaluation is required to determine whether necrosis is caused by an underlying disease. Although various treatments have been attempted, no treatment for necrosis has been considered uniformly effective. Discontinue JANTOVEN therapy if necrosis occurs. Consider alternative drugs if continued anticoagulation therapy is necessary.
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