What the label lists and what reports show
Fondaparinux side effects
Fondaparinux's FDA label: “Hemorrhage During administration of fondaparinux sodium, the most common adverse reactions were bleeding complications [see Warnings and Precautions (5.2) ].” FAERS holds 8,047 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is anaemia (610 reports).
- Generic listed
- Boxed warning
Check it at the source: the fondaparinux FDA label on DailyMed (effective December 15, 2024, Mylan Institutional LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are possible side effects of fondaparinux sodium injection?Fondaparinux sodium injection can cause serious side effects. See “What is the most important information I should know about fondaparinux sodium injection?” • Severe bleeding. […]
Source: FDA drug label, Mylan Institutional LLC, effective December 15, 2024 (SPL set 4b65f642-87f7-4da5-a9c9-02cd1f8d9d16), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsHemorrhage During administration of fondaparinux sodium, the most common adverse reactions were bleeding complications [see Warnings and Precautions (5.2) ].
Table 8. Adverse Reactions Across Randomized, Controlled, Hip Fracture Surgery, Hip Replacement Surgery, and Knee Replacement Surgery Studies
| Reaction | Fondaparinux Sodium 2.5 mg subcutaneously once daily N = 3,616 | Enoxaparin Sodium Enoxaparin sodium dosing regimen: 30 mg every 12 hours or 40 mg once… N = 3,956 | Fondaparinux Sodium 2.5 mg subcutaneously once daily N = 327 | Placebo subcutaneously once daily N = 329 |
|---|---|---|---|---|
| Anemia | 707 (19.6%) | 670 (16.9%) | 5 (1.5%) | 4 (1.2%) |
| Insomnia | 179 (5%) | 214 (5.4%) | 3 (0.9%) | 1 (0.3%) |
| Wound drainage increased | 161 (4.5%) | 184 (4.7%) | 2 (0.6%) | 0 (0%) |
| Hypokalemia | 152 (4.2%) | 164 (4.1%) | 0 (0%) | 0 (0%) |
| Dizziness | 131 (3.6%) | 165 (4.2%) | 2 (0.6%) | 0 (0%) |
| Purpura | 128 (3.5%) | 137 (3.5%) | 0 (0%) | 0 (0%) |
| Hypotension | 126 (3.5%) | 125 (3.2%) | 1 (0.3%) | 0 (0%) |
| Confusion | 113 (3.1%) | 132 (3.3%) | 4 (1.2%) | 1 (0.3%) |
| Bullous eruption Localized blister coded as bullous eruption. | 112 (3.1%) | 102 (2.6%) | 0 (0%) | 1 (0.3%) |
| Hematoma | 103 (2.8%) | 109 (2.8%) | 7 (2.1%) | 1 (0.3%) |
| Post-operative hemorrhage | 85 (2.4%) | 69 (1.7%) | 2 (0.6%) | 2 (0.6%) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in the labeling: • Spinal or epidural hematomas [see Warnings and Precautions (5.1) ] • Hemorrhage [see Warnings and Precautions (5.2) ] • Renal impairment and bleeding risk [see Warnings and Precautions (5.3) ] • Body weight less than 50 kg and bleeding risk [see Warnings and Precautions (5.4) ] • Thrombocytopenia [see Warnings and Precautions (5.5) ] The most serious adverse reactions associated with the use of fondaparinux sodium are bleeding complications. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Clinical Trials Experience in Adults The adverse reaction information below is based on data from 8,877 patients exposed to fondaparinux sodium in controlled trials of hip fracture, hip replacement, major knee, or abdominal surgeries, and DVT and PE treatment. …
Source: FDA drug label, Mylan Institutional LLC, effective December 15, 2024 (SPL set 4b65f642-87f7-4da5-a9c9-02cd1f8d9d16), via openFDA; the full label on DailyMed
What do FAERS reports show?
8,047 reports list fondaparinux among the medicines taken, each a report of something that happened, not proof the medicine caused it; 1,438 are coded as a death and 4,269 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Fondaparinux: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions