Polyvinyl chloride (PVC) represents as much as one-third of the volume of polymers used in the manufacture of medical devices. Common device applications for PVC include intravenous (IV) tubing and blood bags. Environmental and health advocates have expressed concerns for years regarding the use of the polymer in medical applications, and the FDA issued an advisory warning regarding the health risks of PVC several years ago; however, this has not stopped the use of this economical polymer in the competitive medical device market.
There have been two concerns regarding the use of PVC. The first is an environmental concern associated with the manufacture and disposal of PVC. This concern is applicable to flexible and rigid forms of PVC, as well as medical and non-medical applications. In short, PVC is a chlorinated plastic that forms dioxin during production and when incinerated. Theses dioxins that are released can be toxic and carcinogenic.
The second is a health concern associated specifically with flexible PVC in medical applications that directly or indirectly contact the human body. This is attributed to one particular additive used to make PVC flexible: di (2-ethylhexyl) phthalate, or DEHP. Specifically, the concern is that DEHP is not chemically bound to the polymer and it can be released when heated or can leach out when in contact with certain media, such as blood, drugs, saline or water. Leaching of DEHP has been linked to reproductive issues in several studies.
To digress, PVC is inherently rigid at room temperature due to the proximity of molecular chains within the polymer, which provides strong intermolecular forces. Plasticizers can be blended into PVC in its molten form to act as spacers between the PVC molecular chains, resulting in flexibility of the polymer at room temperature. While DEHP is perhaps the most common plasticizer used in PVC, other phthalate plasticizers include diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), which collectively account for roughly three-quarters of the plasticizers used for PVC in all applications. Flexible PVC used for IV and blood bags can contain 30 to 40% DEHP, and flexible medical tubing can contain up to 80% DEHP.
Yet, PVC remains a very practical and economical polymer for medical devices. Alternatives, such as thermoplastic elastomers and silicones can result in higher cost devices. Many manufacturers have identified alternative plasticizers to DEHP for PVC (commonly referred to as DEHP-free PVC). While not eliminating the environmental concerns associated with PVC, these can alleviate the health concerns for flexible PVC in medical devices.
As recently as May 2016, the FDA provided clearance for a urological catheter that can be manufactured from PVC. This single use, disposable device allows for drainage of the patient’s urine into a collection bag. The FDA considers these class II medical devices that present sufficient risk and require demonstrably similar safety and efficacy as existing devices in the market (510(k) regulatory path). Nevertheless, drainage catheters are far from uncommon or not without competitive and market price pressures. PVC remains an economical and functional polymer in applications such as these. One would presume the ultimate material of choice given current awareness would be a DEHP-free PVC.
Sources:
Medical Device & Diagnostic Industry, 2006
PVC Information Council Denmark, www.pvc.dk, Plastics in Medical Devices Conference, Brussels 23 April 2009
http://www.mddionline.com/article/polyurethane-film-alternative-pvc-and-latex