| Pharmacotherapeutic group: antithrombotic agents. ATC code: B01AX05 Pharmacodynamic effects Fondaparinux is a synthetic and selective inhibitor of activated Factor X (Xa). The antithrombotic activity of fondaparinux is the result of antithrombin III (ATIII) mediated selective inhibition of Factor Xa. By binding selectively to ATIII, fondaparinux potentiates (about 300 times) the innate neutralization of Factor Xa by ATIII. Neutralisation of Factor Xa interrupts the blood coagulation cascade and inhibits both thrombin formation and thrombus development. Fondaparinux does not inactivate thrombin (activated Factor II) and has no effects on platelets. At the 2.5 mg dose, fondaparinux does not affect routine coagulation tests such as activated partial thromboplastin time (aPTT), activated clotting time (ACT) or prothrombin time (PT)/International Normalised Ratio (INR) tests in plasma nor bleeding time or fibrinolytic activity. However, rare spontaneous reports of aPTT prolongation have been received.Fondaparinux does not cross-react with sera from patients with heparin-induced thrombocytopaenia. Clinical studies Prevention of Venous Thromboembolic Events (VTE) in patients undergoing major orthopaedic surgery of the lower limbs treated up to 9 daysThe fondaparinux clinical program was designed to demonstrate the efficacy of fondaparinux for the prevention of venous thromboembolic events (VTE), i.e. proximal and distal deep vein thrombosis (DVT) and pulmonary embolism (PE) in patients undergoing major orthopaedic surgery of the lower limbs such as hip fracture, major knee surgery or hip replacement surgery. Over 8,000 patients (hip fracture 1,711, hip replacement 5,829, major knee surgery 1,367) were studied in controlled Phase II and III clinical studies. Fondaparinux 2.5 mg once daily started 6-8 hours postoperatively was compared with enoxaparin 40 mg once daily started 12 hours before surgery, or 30 mg twice daily started 12-24 hours after surgery.In a pooled analysis of these studies, the recommended dose regimen of fondaparinux versus enoxaparin was associated with a significant decrease (54% [95% CI, 44 %; 63%]) in the rate of VTE evaluated up to day 11 after surgery, irrespective of the type of surgery performed. The majority of endpoint events were diagnosed by a prescheduled venography and consisted mainly of distal DVT, but the incidence of proximal DVT was also significantly reduced. The incidence of symptomatic VTE, including PE was not significantly different between treatment groups.In studies versus enoxaparin 40 mg once daily started 12 hours before surgery, major bleeding was observed in 2.8% of fondaparinux patients treated with the recommended dose, compared to 2.6% with enoxaparin.Prevention of Venous Thromboembolic Events (VTE) in patients undergoing hip fracture surgery treated for up to 24 days following an initial prophylaxis of 1 weekIn a randomised double-blind clinical trial, 737 patients were treated with fondaparinux 2.5 mg once daily for 7 +/- 1 days following hip fracture surgery. At the end of this period, 656 patients were randomised to receive fondaparinux 2.5 mg once daily or placebo for an additional 21 +/- 2 days. Fondaparinux provided a significant reduction in the overall rate of VTE compared with placebo [3 patients (1.4%) vs 77 patients (35%), respectively]. The majority (70/80) of the recorded VTE events were venographically detected non-symptomatic cases of DVT. Fondaparinux also provided a significant reduction in the rate of symptomatic VTE (DVT, and / or PE) [1 (0.3%) vs 9 (2.7%) patients, respectively] including two fatal PE reported in the placebo group. Major bleedings, all at surgical site and none fatal, were observed in 8 patients (2.4%) treated with fondaparinux 2.5 mg compared to 2 (0.6%) with placebo.Prevention of Venous Thromboembolic Events (VTE) in patients undergoing abdominal surgery who are judged to be at high risk of thromboembolic complications, such as patients undergoing abdominal cancer surgeryIn a double-blind clinical study, 2,927 patients were randomised to receive fondaparinux 2.5mg once daily or dalteparin 5,000 IU once daily, with one 2,500 IU preoperative injection and a first 2,500 IU post-operative injection, for 7+2 days. The main sites of surgery were colonic/rectal, gastric, hepatic, cholecystectomy or other biliary. Sixty-nine percent of the patients underwent surgery for cancer. Patients under-going urological (other than kidney) or gynaecological surgery, laparoscopic surgery or vascular surgery were not included in the study.In this study, the incidence of total VTE was 4.6% (47/1,027) with fondaparinux, versus 6.1%: (62/1,021) with dalteparin: odds ratio reduction [95%CI] = -25.8% [-49.7%, 9.5%]. The difference in total VTE rates between the treatment groups, which was not statistically significant, was mainly due to a reduction of asymptomatic distal DVT. The incidence of symptomatic DVT was similar between treatment groups: 6 patients (0.4%) in the fondaparinux group vs 5 patients (0.3%) in the dalteparin group. In the large subgroup of patients undergoing cancer surgery (69% of the patient population), the VTE rate was 4.7% in the fondaparinux group, versus 7.7% in the dalteparin group. Major bleeding was observed in 3.4% of the patients in the fondaparinux group and in 2.4% of the dalteparin group. Prevention of Venous Thromboembolic Events (VTE) in medical patients who are at high risk for thromboembolic complications due to restricted mobility during acute illnessIn a randomised double-blind clinical trial, 839 patients were treated with fondaparinux 2.5 mg once daily or placebo for 6 to 14 days. This study included acutely ill medical patients, aged 60 years, expected to require bed rest for at least four days, and hospitalized for congestive heart failure NYHA class III/IV and/or acute respiratory illness and/or acute infectious or inflammatory disease. Fondaparinux significantly reduced the overall rate of VTE compared to placebo [18 patients (5.6%) vs 34 patients (10.5%), respectively]. The majority of events were asymptomatic distal DVT. Fondaparinux also significantly reduced the rate of adjudicated fatal PE [0 patients (0.0%) vs 5 patients (1.2%), respectively]. Major bleedings were observed in 1 patient (0.2%) of each group. Treatment of patients with acute symptomatic spontaneous superficial-vein thrombosis without concomitant Deep-Vein Thrombosis (DVT) A randomised, double blind, clinical trial (CALISTO) included 3002 patients with acute symptomatic isolated, spontaneous superficial-vein thrombosis of the lower limbs, at least 5 cm long, confirmed by compression ultrasonography. Patients were not included if they had concomitant DVT or superficial-vein thrombosis within 3 cm of the sapheno-femoral junction. Patients were excluded if they had severe hepatic impairment, severe renal impairment (creatinine clearance <30ml/min), low body weight (<50kg), active cancer, symptomatic PE or a recent history of DVT/PE (<6 months) or superficial-vein thrombosis (<90 days), or superficial-vein thrombosis associated with sclerotherapy or a complication of an IV line, or they were at high risk of bleeding. Patients were randomised to receive fondaparinux 2.5 mg once daily or placebo for 45 days in addition to elastic stockings, analgesic and/or topical NSAIDS anti-inflammatory drugs. Follow-up continued up to Day 77. The study population was 64% female, with a median age of 58 years, 4.4% had a creatinine clearance <50ml/min. The primary efficacy outcome, a composite of symptomatic PE, symptomatic DVT, symptomatic superficial-vein thrombosis extension, symptomatic superficial-vein thrombosis reoccurrence, or Death up to Day 47, was significantly reduced from 5.9% in placebo patients to 0.9% in those receiving fondaparinux 2.5 mg (relative risk reduction: 85.2%; 95% CIs, 73.7% to 91.7% [p<0.001]). The incidence of each thromboembolic component of the primary outcome was also significantly reduced in fondaparinux patients as follows: symptomatic PE [0 (0%) vs 5 (0.3%) (p=0.031)], symptomatic DVT [3 (0.2%) vs 18 (1.2%); relative risk reduction 83.4% (p<0.001)], symptomatic superficial-vein thrombosis extension [4 (0.3%) vs 51 (3.4%); relative risk reduction 92.2% (p<0.001)], symptomatic superficial-vein thrombosis reoccurrence [5 (0.3%) vs 24 (1.6%); relative risk reduction 79.2% (p<0.001)]. The mortality rates were low and similar between the treatments groups with 2 (0.1%) deaths in the fondaparinux group versus 1 (0.1%) death in the placebo group. Efficacy was maintained up to Day 77 and was consistent across all predefined subgroups including patients with varicose veins and patients with superficial-vein thrombosis located below the knee. Major bleeding during treatment occurred in 1 (0.1%) fondaparinux patient and in 1 (0.1%) placebo patient. Clinically relevant non major bleeding occurred in 5 (0.3%) fondaparinux patients and 8 (0.5%) placebo patients. | |