John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. Venous thromboembolism is a common condition with potentially serious and life-threatening consequences, and several reviews from the Cochrane Vascular Group look at the evidence on interventions to prevent or treat it. In an updated review in October 2016, Yanzhi Song from Fudan University in Shanghai China and colleagues brought together the evidence on the use of pentasaccharides to prevent venous thromboembolism. We asked Yanzhi to tell us what they found.

Yanzhi: In recent years, pentasaccharides have been shown to work well for stopping blood clots and to be better tolerated than other drugs used to prevent venous thromboembolism, such as heparin and warfarin. There are three types of pentasaccharide: short-acting fondaparinux, long-acting idraparinux and idrabiotaparinux; and we wanted to investigate them all, but we found no trials for idraparinux or idrabiotaparinux.
The 25 randomised trials that we were able to include all studied fondaparinux and had recruited a total of 21,000 participants. Most of these patients were undergoing orthopaedic surgery but some of the trials included patients having abdominal surgery, thoracic surgery, bariatric surgery or coronary bypass surgery; acutely ill hospitalised medical patients; people requiring rigid or semirigid immobilisation; and those with superficial venous thrombosis.
We found moderate to high quality evidence that fondaparinux is effective for short-term prevention of venous thromboembolism when compared with placebo, and low to moderate quality evidence that it is more effective for short-term venous thromboembolism prevention than low molecular weight heparin. However, there is also moderate to high quality evidence that fondaparinux increases major bleeding when compared with either placebo or low molecular weight heparin.
Therefore, in summary, when fondaparinux is chosen for the prevention of venous thromboembolism, attention should be paid to the person's bleeding and thrombosis risks; and because of the focus of the trials, our conclusions predominantly pertain to patients undergoing orthopaedic surgery so we cannot be sure how applicable they are for other types of patient.

John: If you would like to read the full review, and find out more about the 25 included studies, you can find it online at Cochrane Library dot com. Just go to the website and run a simple search for the word ‘pentasaccharides’.