The antibacterial properties of silver (Ag) have been known for centuries[1]. The increasing problems of antibiotic resistance[2], along with concerns about the safety and toxicity of topical antiseptics, has resulted in the need for an agent that can be used to treat colonised and infected wounds effectively. The presentation of silver in advanced wound care dressings has been found to be effective against bacterial, fungal and viral pathogens[3,4]. This article describes two sustained-release silver product ranges ACTICOAT™ and ALLEVYN™ Ag (Smith & Nephew), which can be used to help prevent and reduce the risk of infection in a variety of wounds.

What is the role of sustained release silver dressings?
Recognising and managing wounds at risk of infection is vital for optimal wound management[5]. Patients may present with minor symptoms such as pain, swelling or discharge, or more major life-threatening conditions such as sepsis[6,7]. Wounds, particularly chronic wounds, support a variety of micro-organisms, many of which are pathogens, acting as a source for cross-infection. Such micro-organisms also provoke an increase in exudate and malodour.

Dressings are needed that provide an effective barrier[8,9] together with a sustained release of an antimicrobial agent, such as silver, to reduce the bioburden throughout the dressing wear time, while providing limited opportunity for systemic absorption. The sustained release of effective levels of ionic silver over a period of time also removes the need for frequent dressing changes, with potential cost savings.


What amounts of silver are effective?
All topical silver products, regardless of their formulation (eg silver nitrate solution, silver sulfadiazine cream or dressings containing elemental or ionised silver), only exert antimicrobial effects when they release the ionic form of silver (Ag+). This usually occurs when the dressing comes into contact with wound fluid.

It is important to recognise that the amount of silver released from a wound dressing (bio-availability) will be different to the amount highlighted on the packaging of silver dressings. It has not been possible to measure bio-available levels, but it has been suggested that at least 20-40 parts per million (ppm) are required to be microbiologically effective (see box below)[9,10].

What factors affect product choice?
When choosing an appropriate antimicrobial dressing, the priority should be to regain control of bacterial growth. In addition to reducing bacterial load, clinicians need to consider how different antimicrobial products support moist wound healing, manage exudate levels and assist wound bed preparation[11,12]. Specific products should be chosen to reflect the overall requirements of the wound following a thorough wound assessment.

Two such products ACTICOAT and ALLEVYN Ag (Smith & Nephew) are considered here for use as topical antimicrobials in patients with full and partial thickness wounds where the wound is at risk of infection, showing early signs of local infection or where increased bacterial bioburden is suspected.

What is ACTICOAT?
The ACTICOAT range of antimicrobial barrier dressings includes ACTICOAT, ACTICOAT 7, ACTICOAT Absorbent and more recently ACTICOAT Flex 3 and 7, and ACTICOAT Site (see Table 3). A number of these dressing have absorptive capabilities but all of the dressings utilise SILCRYST^TM technology, which provides fast-acting antimicrobial action. This technology was developed specifically to form the dressing interface that comes into direct contact with the wound surface (Box 1).


How does ACTICOAT work?
The SILCRYST silver layer in ACTICOAT, which comes into contact with the wound surface, is a highly soluble form of silver. These tiny crystals provide a larger surface area of silver than other silver technology systems (see Box 1) and have a greater contact with the wound, releasing a highly effective concentration of silver over a sustained time period. This feature ensures that bacteria are killed rapidly and consistently over time[13].

ACTICOAT dressings release the positively charged silver ion (Ag+). SILCRYST silver also contains Ag0 which is present in the tiny atomic clusters and can be solubilised[19]. This acts as a form of 'back-up battery' to replenish Ag+ to maximise effective kill. Additional data suggest that as a result of this antimicrobial action ACTICOAT may be responsible for modulating protease activity to promote healing[20,21]. SILCRYST silver starts to work in as little as 30 minutes[15,22-24], which is particularly important for infected wounds in high-risk patients or wounds at high risk of infection.