Plastic Prefilled Syringes: A Better Fit for Autoinjector Systems

The authors describe the ways in which plastic prefilled syringes can be an alternative that provides consistent performance, protects drugs prone to degradation, and enhances patient safety.
Nov 01, 2009
Volume 2009 Supplement, Issue 6

This article is part of PharmTech's supplement "Injectable Drug Delivery."

More than two billion prefilled syringes are developed and used each year. The rise of the prefilled syringe as the preferred container for injectable drugs began with Sanofi and Rhône-Poulenc Rorer's successful introduction of syringes for heparins to the European market in the early 1980s. The prefilled syringe market has expanded considerably because of factors such as the growth of biopharmaceuticals, the need to eliminate overfills, the need for precise delivery volumes, the desire for convenient delivery, the quest for cost effectiveness, and the goal of reducing dosage errors (1–4).

Figure 1: Daikyo Crystal Zenith prefillable syringes (Daikyo Seiko, Tokyo). (IMAGES ARE COURTESY OF WEST)
Currently, most prefilled syringes are made of glass, but plastic syringes are gaining popularity, particularly in applications for which glass is an unsuitable delivery system. In the last decade, pharmaceutical protein and peptide drug products have been approved for use with prefilled plastic syringes. One example is a peptide drug product in a Daikyo Crystal Zenith (CZ) syringe (Daikyo Seiko, Tokyo) (see Figure 1). More products using plastic prefilled syringes are in various phases of drug development.

The need for combination-drug delivery systems

Many chronic diseases such as multiple sclerosis and rheumatoid arthritis require the self-administration of injectable treatments. This need has increased interest in combination-drug delivery systems that are safe, convenient, and help improve the administration process.

Pen injectors and multidose cartridges were created for patients who need frequent injections. These devices were limited to specific therapies such as diabetes and growth hormones, which often require weighed dosages or dose titration. Although pen injectors were designed for frequent injections and for patients who require variable dose capabilities, they are not ideal for chronic users of fixed-dose medications, including patients suffering from impaired dexterity. The need for a safe, reliable, easy-to-use, single-dose injection system for these patients soon became apparent.

Figure 2: ConfiDose autoinjector (West, Lionville, PA). (IMAGES ARE COURTESY OF WEST)
Autoinjectors have been recognized as a convenient method for delivering drug products through an intuitive activation mechanism designed especially for patients whose poor dexterity affects their ability to inject a drug treatment effectively with a traditional syringe (see Figure 2). As patients and caregivers become increasingly involved in determining the best treatment option, biopharmaceutical, pharmaceutical, and device companies are adapting to meet consumers' needs.

Traditional systems' performance problems

Autoinjector systems traditionally use 1-mL glass prefilled syringes. These systems have been successful, but they have notable limitations, including performance problems. Recent studies have shown that silicone oil, which is used to increase lubricity in syringe systems, is often distributed unevenly, thus leaving certain areas of the prefilled syringe surface with insufficient lubrication (5). The inconsistent silicone-oil coating can significantly affect the piston-travel and glide forces in autoinjectors. In 2006, commercial lots of a drug product delivered by an autoinjector that contained a glass prefilled syringe were recalled in several European countries because of problems with slow or incomplete delivery of the drug (6). Uneven silicone coating may increase travel forces and cause failures such as incomplete injections.

lorem ipsum