ARIXTRA (Page 5 of 10)


8.1 Pregnancy

Pregnancy Category B. Reproduction studies have been performed in pregnant rats at subcutaneous doses up to 10 mg/kg/day (about 32 times the recommended human dose based on body surface area) and pregnant rabbits at subcutaneous doses up to 10 mg/kg/day (about 65 times the recommended human dose based on body surface area) and have revealed no evidence of impaired fertility or harm to the fetus due to fondaparinux sodium. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, ARIXTRA should be used during pregnancy only if clearly needed.

8.3 Nursing Mothers

Fondaparinux sodium was found to be excreted in the milk of lactating rats. However, it is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when ARIXTRA is administered to a nursing mother.

8.4 Pediatric Use

Safety and effectiveness of ARIXTRA in pediatric patients have not been established. Because risk for bleeding during treatment with ARIXTRA is increased in adults who weigh <50 kg, bleeding may be a particular safety concern for use of ARIXTRA in the pediatric population [see Warnings and Precautions (5.3)].

8.5 Geriatric Use

In clinical trials the efficacy of ARIXTRA in the elderly (65 years or older) was similar to that seen in patients younger than 65 years; however, serious adverse events increased with age. Exercise caution when using ARIXTRA in elderly patients, paying particular attention to dosing directions and concomitant medications (especially anti-platelet medication). [See Warnings and Precautions (5.1).]

Fondaparinux sodium is substantially excreted by the kidney, and the risk of adverse reactions to ARIXTRA may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, assess renal function prior to ARIXTRA administration. [See Contraindications (4), Warnings and Precautions (5.2), and Clinical Pharmacology (12.4).]

In the peri-operative hip fracture, hip replacement, or knee replacement surgery clinical trials with patients receiving ARIXTRA 2.5 mg, serious adverse events increased with age for patients receiving ARIXTRA. The incidence of major bleeding in clinical trials of ARIXTRA by age is provided in Table 6.

Table 6. Incidence of Major Bleeding in Patients Treated With ARIXTRA by Age

<65 years

% (n/N)

65 to 74 years

% (n/N)

≥75 years

% (n/N)
Orthopedic surgerya 1.8% (23/1,253) 2.2% (24/1,111) 2.7% (33/1,277)
Extended prophylaxis 1.9% (1/52) 1.4% (1/71) 2.9% (6/204)
Abdominal surgery 3.0% (19/644) 3.2% (16/507) 5.0% (14/282)
DVT and PE treatment 0.6% (7/1,151) 1.6% (9/560) 2.1% (12/583)

a Includes hip fracture, hip replacement, and knee replacement surgery prophylaxis.

8.6 Renal Impairment

Patients with impaired renal function are at increased risk of bleeding due to reduced clearance of ARIXTRA [see Contraindications (4) and Warnings and Precautions (5.2)]. Assess renal function periodically in patients receiving ARIXTRA. Discontinue ARIXTRA immediately in patients who develop severe renal impairment while on therapy. After discontinuation of ARIXTRA, its anticoagulant effects may persist for 2 to 4 days in patients with normal renal function (i.e., at least 3 to 5 half-lives). The anticoagulant effects of ARIXTRA may persist even longer in patients with renal impairment [see Clinical Pharmacology (12.4)].

8.7 Hepatic Impairment

Following a single, subcutaneous dose of 7.5 mg of ARIXTRA in patients with moderate hepatic impairment (Child-Pugh Category B) compared to subjects with normal liver function, changes from baseline in aPTT, PT/INR, and antithrombin III were similar in the two groups. However, a higher incidence of hemorrhage was observed in subjects with moderate hepatic impairment than in normal subjects, especially mild hematomas at the blood sampling or injection site. The pharmacokinetics of fondaparinux have not been studied in patients with severe hepatic impairment. [See Dosage and Administration (2.4) and Clinical Pharmacology (12.4).]


There is no known antidote for ARIXTRA. Overdose of ARIXTRA may lead to hemorrhagic complications. Discontinue treatment and initiate appropriate therapy if bleeding complications associated with overdosage occur.

Data obtained in patients undergoing chronic intermittent hemodialysis suggest that clearance of ARIXTRA can increase by 20% during hemodialysis.


ARIXTRA (fondaparinux sodium) Injection is a sterile solution containing fondaparinux sodium. It is a synthetic and specific inhibitor of activated Factor X (Xa). Fondaparinux sodium is methyl O-2-deoxy-6-O-sulfo-2-(sulfoamino)-α-D-glucopyranosyl-(1→4)-O-β-D-glucopyra-nuronosyl-(1→4)-O-2-deoxy-3,6-di-O-sulfo-2-(sulfoamino)-α-D-glucopyranosyl-(1→4)-O-2-O-sulfo-α-L-idopyranuronosyl-(1→4)-2-deoxy-6-O-sulfo-2-(sulfoamino)-α-D-glucopyranoside, decasodium salt.

The molecular formula of fondaparinux sodium is C31 H43 N3 Na10 O49 S8 and its molecular weight is 1728. The structural formula is provided below:

fondaparinux sodium chemical structure
(click image for full-size original)

ARIXTRA is supplied as a sterile, preservative-free injectable solution for subcutaneous use.

Each single-dose, prefilled syringe of ARIXTRA, affixed with an automatic needle protection system, contains 2.5 mg of fondaparinux sodium in 0.5 mL, 5.0 mg of fondaparinux sodium in 0.4 mL, 7.5 mg of fondaparinux sodium in 0.6 mL, or 10.0 mg of fondaparinux sodium in 0.8 mL of an isotonic solution of sodium chloride and water for injection. The final drug product is a clear and colorless to slightly yellow liquid with a pH between 5.0 and 8.0.


12.1 Mechanism of Action

The antithrombotic activity of fondaparinux sodium is the result of antithrombin III (ATIII)-mediated selective inhibition of Factor Xa. By selectively binding to ATIII, fondaparinux sodium potentiates (about 300 times) the innate neutralization of Factor Xa by ATIII. Neutralization of Factor Xa interrupts the blood coagulation cascade and thus inhibits thrombin formation and thrombus development.

Fondaparinux sodium does not inactivate thrombin (activated Factor II) and has no known effect on platelet function. At the recommended dose, fondaparinux sodium does not affect fibrinolytic activity or bleeding time.

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