FONDAPARINUX Drug Interactions: What You Need to Know

INTERACTIONS In clinical studies performed with fondaparinux sodium, the concomitant use of oral anticoagulants (warfarin sodium), platelet inhibitors (acetylsalicylic acid), NSAIDs (piroxicam), and digoxin did not significantly affect the pharmacokinetics/pharmacodynamics of fondaparinux sodium. In addition, fondaparinux sodium neither influenced the pharmacodynamics of warfarin sodium, acetylsalicylic acid, piroxicam, and digoxin, nor the pharmacokinetics of digoxin at steady state. Agents that may enhance the risk of hemorrhage should be discontinued prior to initiation of therapy with fondaparinux sodium unless these agents are essential. If co-administration is necessary, monitor patients closely for hemorrhage [see Warnings and Precautions (5.2)] . In an in vitro study in human liver microsomes, inhibition of CYP2A6 hydroxylation of coumarin by fondaparinux (200 micromolar i.e., 350 mg/L) was 17% to 28%. Inhibition of the other isozymes evaluated (CYPs 1A2, 2C9, 2C19, 2D6, 3A4, and 3E1) was 0% to 16%. Since fondaparinux does not markedly inhibit CYP450s (CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, or CYP3A4) in vitro, fondaparinux sodium is not expected to significantly interact with other drugs in vivo by inhibition of metabolism mediated by these isozymes. Since fondaparinux sodium does not bind significantly to plasma proteins other than ATIII, no drug interactions by protein-binding displacement are expected. Discontinue agents that may enhance the risk of hemorrhage prior to initiation of therapy with fondaparinux sodium unless essential. If co-administration is necessary, monitor patients closely for hemorrhage. (7)

Fondaparinux sodium injection is contraindicated in the following conditions:

• Severe renal impairment (creatinine clearance [CrCl] less than 30 mL/min) [see Warnings and Precautions (5.3) and Use in Specific Populations (8.6)].
• Active major bleeding.
• Bacterial endocarditis.
• Thrombocytopenia associated with a positive in vitro test for anti-platelet antibody in the presence of fondaparinux sodium.
• Body weight less than 50 kg (venous thromboembolism [VTE] prophylaxis in adults only) [see Warnings and Precautions (5.4)] .
• History of serious hypersensitivity reaction (e.g., angioedema, anaphylactoid/anaphylactic reactions) to fondaparinux sodium. Fondaparinux sodium injection is contraindicated in the following conditions: (4) Severe renal impairment (creatinine clearance less than 30 mL/min) in prophylaxis or treatment of venous thromboembolism. Active major bleeding. Bacterial endocarditis. Thrombocytopenia associated with a positive in vitro test for anti-platelet antibody in the presence of fondaparinux sodium. Body weight less than 50 kg (venous thromboembolism prophylaxis in adults only). History of serious hypersensitivity reaction (e.g., angioedema, anaphylactoid/anaphylactic reactions) to fondaparinux sodium.

AND PRECAUTIONS

• Spinal or epidural hematomas, which may result in long-term or permanent paralysis, can occur. (5.1)
• Patients taking fondaparinux sodium with risk factors for bleeding are at increased risk of hemorrhage. (5.2)
• Bleeding risk is increased in renal impairment and in adult patients with low body weight less than <50 kg. (5.3, 5.4)
• Thrombocytopenia can occur with administration of fondaparinux sodium. (5.5)
• Periodic routine complete blood counts (including platelet counts), serum creatinine level, and stool occult blood tests are recommended. (5.6)

5.1 Neuraxial Anesthesia and Post-operative Indwelling Epidural Catheter Use Spinal or epidural hematomas, which may result in long-term or permanent paralysis, can occur with the use of anticoagulants and neuraxial (spinal/epidural) anesthesia or spinal puncture. The risk of these events may be higher with post-operative use of indwelling epidural catheters or concomitant use of other drugs affecting hemostasis such as NSAIDs <span class="opacity-50 text-xs">[see Boxed Warning]</span> . In the postmarketing experience, epidural or spinal hematoma has been reported in association with the use of fondaparinux sodium by subcutaneous (SC) injection. Optimal timing between the administration of fondaparinux sodium and neuraxial procedures is not known. Monitor patients undergoing these procedures for signs and symptoms of neurologic impairment such as midline back pain, sensory and motor deficits (numbness, tingling, or weakness in lower limbs), and bowel or bladder dysfunction. Consider the potential risks and benefits before neuraxial intervention in patients anticoagulated or who may be anticoagulated for thromboprophylaxis.

5.2 Hemorrhage Fondaparinux sodium increases the risk of hemorrhage in patients at risk for bleeding, including conditions such as congenital or acquired bleeding disorders, active ulcerative and angiodysplastic gastrointestinal disease, hemorrhagic stroke, uncontrolled arterial hypertension, diabetic retinopathy, or shortly after brain, spinal, or ophthalmological surgery. Cases of elevated aPTT temporally associated with bleeding events have been reported following administration of fondaparinux sodium (with or without concomitant administration of other anticoagulants) <span class="opacity-50 text-xs">[see Adverse Reactions (6.2)]</span>. Conditions associated with increased bleeding in pediatric patients include systemic lupus erythematosus, Wilms tumor, antiphospholipid syndrome, antithrombin III deficiency, Factor V Leiden, malignancy, pancytopenia, indwelling chest tubes, thoracotomy, invasive infections, hypertensive encephalopathy, intestinal lymphangiectasia and von Willebrand disease. Do not administer agents that enhance the risk of hemorrhage with fondaparinux sodium unless essential for the management of the underlying condition, such as vitamin K antagonists for the treatment of VTE. If co-administration is essential, closely monitor patients for signs and symptoms of bleeding. Do not administer the initial dose of fondaparinux sodium earlier than 6 to 8 hours after surgery. Administration earlier than 6 hours after surgery increases risk of major bleeding <span class="opacity-50 text-xs">[see Dosage and Administration (2) and Adverse Reactions (6.1)]</span> .

5.3 Renal Impairment and Bleeding Risk in Adult Patients Fondaparinux sodium increases the risk of bleeding in adult patients with impaired renal function due to reduced clearance <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.4)]</span>. The incidence of major bleeding by renal function status reported in clinical trials of adult patients receiving fondaparinux sodium for VTE surgical prophylaxis is provided in Table 4. In these patient populations, the following is recommended:

• Do not use fondaparinux sodium for VTE prophylaxis and treatment in patients with CrCl less than 30 mL/min [see Contraindications (4)] .
• Fondaparinux sodium may cause prolonged anticoagulation in patients with CrCl 30 mL/min to 50 mL/min.

Table

4: Incidence of Major Bleeding in Adult Patients Treated with Fondaparinux Sodium by Renal Function Status for Surgical Prophylaxis and Treatment of Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE)

Population

Timing of Dose Degree of Renal Impairment Normal % (n/N) Mild % (n/N) Moderate % (n/N) Severe % (n/N) CrCl (mL/min) Greater than or equal to 80 Greater than or equal to 50 to less than 80 Greater than or equal to 30 to less than 50 Less than 30 Orthopedic surgery a Overall 1.6% (25/1,565) 2.4% (31/1,288) 3.8% (19/504) 4.8% (4/83) 6 hours to 8 hours after surgery 1.8% (16/905) 2.2% (15/675) 2.3% (6/265) 0% (0/40) Abdominal surgery Overall 2.1% (13/606) 3.6% (22/613) 6.7% (12/179) 7.1% (1/14) 6 hours to 8 hours after surgery 2.1% (10/467) 3.3% (16/481) 5.8% (8/137) 7.7% (1/13) DVT and PE Treatment 0.4% (4/1,132) 1.6% (12/733) 2.2% (7/318) 7.3% (4/55) CrCl = creatinine clearance. a Hip fracture, hip replacement, and knee replacement surgery prophylaxis. CrCl=creatinine clearance. a Hip fracture, hip replacement, and knee replacement surgery prophylaxis. Assess renal function periodically in patients receiving fondaparinux sodium. Discontinue the drug immediately in patients who develop severe renal impairment while on therapy. After discontinuation of fondaparinux sodium, its anticoagulant effects may persist for 2 days to 4 days in patients with normal renal function (i.e., at least 3 to 5 half-lives). The anticoagulant effects of fondaparinux sodium may persist even longer in patients with renal impairment [see Clinical Pharmacology (12.4)] .

5.4 Body Weight Less than 50 kg and Bleeding Risk in Adults Fondaparinux sodium increases the risk for bleeding in adults who weigh less than 50 kg, compared to adults with higher weights. In adults who weigh less than 50 kg:

• Do not administer fondaparinux sodium as prophylactic therapy for adults undergoing hip fracture, hip replacement, or knee replacement surgery and abdominal surgery [see Contraindications (4)]. In randomized clinical trials of VTE prophylaxis in adults during the peri-operative period following hip fracture, hip or knee replacement surgery, and abdominal surgery, major bleeding occurred at a higher rate among adults with a body weight less than 50 kg compared to those with a body weight greater than 50 kg (5.4% versus 2.1% in adults undergoing hip fracture, hip replacement, or knee replacement surgery; 5.3% versus 3.3% in adults undergoing abdominal surgery).

5.5 Thrombocytopenia Thrombocytopenia can occur with the administration of fondaparinux sodium. Thrombocytopenia of any degree should be monitored closely. Discontinue fondaparinux sodium if the platelet count falls below 100,000/mm3. Moderate thrombocytopenia (platelet counts between 100,000/mm3 and 50,000/mm3) occurred at a rate of 3% in patients given fondaparinux sodium 2.5 mg in the peri-operative hip fracture, hip replacement, or knee replacement surgery and abdominal surgery clinical trials. Severe thrombocytopenia (platelet counts less than 50,000/mm3) occurred at a rate of 0.2% in patients given fondaparinux sodium 2.5 mg in these clinical trials. During extended prophylaxis, no cases of moderate or severe thrombocytopenia were reported. Moderate thrombocytopenia occurred at a rate of 0.5% in patients given the fondaparinux sodium treatment regimen in the DVT and PE treatment clinical trials. Severe thrombocytopenia occurred at a rate of 0.04% in patients given the fondaparinux sodium treatment regimen in the DVT and PE treatment clinical trials. Occurrences of thrombocytopenia with thrombosis that manifested similar to heparin-induced thrombocytopenia have been reported with the use of fondaparinux sodium in postmarketing experience <span class="opacity-50 text-xs">[see Adverse Reactions (6.2)]</span>.

5.6 Monitoring: Laboratory Tests Routine coagulation tests such as Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT) are relatively insensitive measures of the activity of fondaparinux sodium and international standards of heparin or LMWH are not calibrators to measure anti-Factor Xa activity of fondaparinux sodium. If unexpected changes in coagulation parameters or major bleeding occur during therapy with fondaparinux sodium, discontinue fondaparinux sodium. In postmarketing experience, occurrences of aPTT elevations have been reported following administration of fondaparinux sodium <span class="opacity-50 text-xs">[see Adverse Reactions (6.2)]</span>. Periodic routine complete blood counts (including platelet count), serum creatinine level, and stool occult blood tests are recommended during the course of treatment with fondaparinux sodium. The anti-Factor Xa activity of fondaparinux sodium can be measured by anti-Xa assay using the appropriate calibrator (fondaparinux). The activity of fondaparinux sodium is expressed in milligrams (mg) of the fondaparinux and cannot be compared with activities of heparin or low molecular weight heparins <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.2, 12.3)]</span>.