Low allergenic potential with fondaparinux: results of a prospective investigation

Shake it off: A curious case of rigors

Heparin-induced Anaphylactoid reactions are rare systemic reactions to heparin exposure. Although the exact pathogenesis of the reaction is unclear, in vivo platelet activation from inflammation may play a role. The reaction involves anti-platelet factor 4, a common factor also noted to be involved in heparin-induced thrombocytopenia (HIT). Like HIT, prompt identification of the reaction, immediate discontinuation of heparin, and supportive care are the mainstays of treatment to avoid severe and potentially fatal outcomes. Previous cases have described heparin-induced anaphylactoid reactions in the setting of heparin-induced thrombocytopenia. However, we will present a case of an isolated heparin-induced anaphylactoid reaction without HIT.

Delayed-Type Heparin Allergy: Intravenous Tolerance Despite Inflammatory Skin Reaction After Subcutaneous Injection

BACKGROUND

Heparin allergy most frequently manifests as delayed-type hypersensitivity (DTH) causing an itchy inflammatory skin reaction at the site of subcutaneous injection. An important differential diagnosis is circumscribed skin necrosis due to heparin-induced thrombocytopenia.

OBJECTIVES

An inflammatory skin reaction to subcutaneously injected heparin generally entails the quest for alternative anticoagulation; concerns may particularly arise in an emergency situation requiring intravenous heparin administration.

METHODS

All heparin DTH cases seen in our department over the last 17 years underwent standardized allergy diagnostics including challenge testing, that is, subcutaneous injection of fondaparinux and intravenous administration of unfractionated heparin (UFH).

RESULTS

Of a total of 50 patients with confirmed heparin allergy, DTH was found in 48 (96.0%), and immediate-type, presumably IgE-mediated hypersensitivity was diagnosed in only 2 (4.0%). In the 48 DTH cases, intradermal testing revealed broad cross-reactivity between UFH and low-molecular-weight heparins (LMWH) including nadroparin, dalteparin, and enoxaparin. Cross-reactivity with (or concomitant sensitization to) fondaparinux was seen in only 3 (6.3%) cases. Intravenous administration of UFH was tolerated by all 45 patients challenged, despite DTH to UFH and LMWH as demonstrated by intradermal testing.

CONCLUSIONS

If an inflammatory skin reaction at the site of subcutaneously injected heparin is observed or reported without any evidence of skin necrosis or thrombocytopenia, intravenous administration of UFH seems to be sufficiently safe and may be considered without allergy testing if urgently indicated in an emergency situation. Fondaparinux is the most suitable alternative for subcutaneous application.

Fondaparinux Pre-, Peri-, and/or Postpartum for the Prophylaxis/Treatment of Venous Thromboembolism (FondaPPP)

We analyzed data for women who received fondaparinux for ≥7 days during pregnancy. The study retrospectively included women who received fondaparinux pre-, peri- and/or postpartum for ≥7 days for prophylaxis/venous thromboembolism (VTE) treatment at German specialist centers (2004-2010). Data on pregnancy, VTE risk factors, anticoagulant treatment, pregnancy outcome and adverse events were extracted from medical records. 120 women (mean age 31.5 years) were included. Among 84 women with prior pregnancies, 41.0% had ≥1 abortion. Anticoagulation was indicated for prophylaxis in 92.5% cases, including 82.5% women with an elevated VTE risk (82.8% thrombophilia, 34.2% VTE history). All women received low-molecular-weight heparin (LMWH) as first-line therapy; 3 also unfractionated heparin. Treatment changed to fondaparinux, due to heparin allergy (41.7%) or heparin-induced thrombocytopenia (10.0%). Fondaparinux was generally well tolerated. Adverse events included bleeding events (n = 5), abortion (n = 2), premature births (n = 2), stillbirth (n = 1), arrested labors (n = 2), injection site erythema (n = 4) and unspecified drug hypersensitivity (n = 6). No VTE events or increased liver enzymes occurred during treatment. In this retrospective study, fondaparinux was effective and well tolerated. Trial registration: ClinicalTrials.gov NCT01004939.

Non-immediate heparin and heparinoid cutaneous allergic reactions: a role for fondaparinux

Non-immediate allergic cutaneous reactions to heparins have been increasingly reported, typically manifesting as large, eczematous plaques at sites of subcutaneous injection. Patients may demonstrate cross-reactivity between unfractionated heparin, low molecular weight heparin and semi-synthetic heparinoids, making finding an alternative difficult. Fondaparinux has been identified as a useful alternative in such patients; here we present the first two documented cases in Australia and a literature review.

Adverse Drug Reactions and Cutaneous Manifestations Associated With Anticoagulation

Anticoagulants are amongst the most commonly prescribed medications worldwide. Although rare, localised and systemic drug reactions have been reported with anticoagulants that can lead to significant morbidity and mortality. Some of the first signs of drug reactions to anticoagulants are cutaneous changes that, when recognised early, can prevent significant complications. Dermatologists should be aware of these changes to make an early and accurate diagnosis. This is particularly important in instances of skin-induced necrosis caused by systemic toxicity to anticoagulants. This review discusses adverse drug reactions to the traditional anticoagulants, warfarin and heparin, and the newer direct oral anticoagulants (DOACs) such as the thrombin inhibitor, dabigatran, and the factor Xa inhibitors, rivaroxaban, apixaban, and edoxaban. In particular, this review provides dermatologists with a framework for early diagnosis and management of patients with drug reactions to anticoagulants and alerts them to potential bleeding complications associated with minor procedures.

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Heparin-induced skin lesions

Heparins are widely used for prophylaxis and treatment of thromboembolic diseases. Besides bleeding complications, heparin-induced skin lesions are the most frequent unwanted adverse effects of subcutaneous heparin treatment. Evidence suggests that these lesions are more common than previously thought. Lesions are most frequently due to either allergic reactions or to possibly life-threatening heparin-induced thrombocytopenia. Early recognition and adequate treatment are highly important, because although both complications initially show a similar clinical picture, their treatment should be fundamentally different. Furthermore, risk factors associated with the patient, drug, and treatment regimen have been identified. We review the clinical range of heparin-induced skin lesions, emphasise evidence and controversies in epidemiology, diagnosis, and differential diagnosis, and discuss the management of patients with these skin lesions.

Adverse effects of heparin

All the adverse effects of heparins are related to their wide variety of biological activities, with bleeding being the most important safety issue, resulting directly from the potency of heparin as an anticoagulant. However, it is hard to define the bleeding risk, since it depends on numerous parameters including the indication, dosage, method, and duration of heparin application, the clinical study design and definition of bleeding as well as patient characteristics and determinants of bleeding such as type of surgery and co-medication. Nonbleeding complications of heparins are caused by binding of heparin molecules to proteins other than antithrombin and to cells, which is generally more pronounced with unfractionated heparin than with low-molecular-weight heparins. Accordingly, heparin-induced thrombocytopenia, the most severe nonbleeding adverse reaction, occurs about 10 times less with low-molecular-weight heparins than with unfractionated heparin. Frequent and therefore important adverse reactions of heparins are skin lesions resulting from delayed-type hypersensitivity reactions. All the other undesirable effects are discussed as well, but they are mostly clinically irrelevant.

Fondaparinux - data on efficacy and safety in special situations

New anticoagulants promise to have better efficacy, more safety and/or a better manageability than traditional anticoagulants. However, knowledge is limited regarding special situations such as renal insufficiency, obesity, pregnancy, long-term therapy, heparin-induced thrombocytopenia, treatment in patients with mechanical heart valves, use for children, and in patients with a high risk of thromboembolic complications. These situations have rarely or even never been the objective of randomised controlled trials. The purpose of the present article is to summarize and discuss available data on efficacy and safety in these special situations for one of the first new anticoagulants, the indirect factor-Xa inhibitor fondaparinux. Furthermore, we discuss safety in licensed indications and management of bleeding complications and comment on measuring of drug concentration in plasma.

Application, tolerance and safety of fondaparinux therapy in a German hospital: a prospective single-centre experience

INTRODUCTION

The pentasaccharide fondaparinux is widely approved for prophylaxis and treatment of thromboembolic diseases and therapy of acute coronary syndrome. It is also used off-label in patients with acute, suspected or antecedent heparin-induced thrombocytopenia (HIT). The aim of this prospective observational cohort study was to document fondaparinux' prescription practice, tolerance and therapy safety in a representative mixed German single-centre patient cohort.

PATIENTS AND METHODS

Between 09/2008 - 04/2009, 231 consecutive patients treated with fondaparinux were enrolled. Medical data were obtained from patient's records. The patients were clinically screened for thrombosis (Wells score), sequelae of HIT (4T's score), and bleeding complications (ISTH-criteria) and subjected to further assessment (i.e. sonography, HIT-diagnostics), if necessary. The mortality rate was assessed 30 days after therapy start.

RESULTS

Overall, 153/231 patients had a prophylactic, 74/231 patients a therapeutic, and 4/231 patients a successive prophylactic/therapeutic indication. In 11/231 patients fondaparinux was used due to suspected/antecedent HIT, in 5/231 patients due to a previous cutaneous delayed-type hypersensitivity to heparins. Other indications were rare. Three new/progressive thromboses were detected. No cases of HIT, major bleedings, or fatalities occurred.

CONCLUSIONS

Fondaparinux was well tolerated and was safe in prophylaxis and therapy; prescriptions mostly followed the current approval guidelines and were rarely related to HIT-associated indications (<5% of prescriptions), which is in contrast to previous study results in the U.S. (>94% of prescriptions were HIT-associated). A trend towards an individualised fondaparinux use based on the compound's inherent properties and the patients' risk profiles, i.e., antecedent HIT, bone fractures, heparin allergy, was observed.