Effect of ionizing radiation on the stability and performance of the TAXUS Express2 paclitaxel-eluting stent

Sterilization process of polyester based anticancer-drug delivery systems

Recently, growing interest in biodegradable polyesters as drug carriers in the development of innovative anticancer drug delivery systems (DDSs) has been observed. These compounds are thermally unstable, and are therefore, particularly demanding due to the limited number of available sterilization techniques. Furthermore, the DDSs sterilization process is often limited to aseptic filtration. Ensuring aseptic production is very demanding and costly, and it is therefore necessary to work on the application of new sterilization methods. In view of this, this review presents the current state of knowledge regarding the radiation sterilization process of some anticancer drugs as well biodegradable polyester carriers (such as polylactide, polyglycolide, poly(ε-caprolactone), poly(trimethylene carbonate) and co- or terpolymers of lactide, glycolide, ε-caprolactone and trimethylene carbonate). The structural changes in anticancer DDSs under the influence of ionizing radiation and the potential degradation mechanisms of both, polyester carriers and cytostatics during the sterilization process of ionizing radiation as well as their effects on the microstructure and properties of DDSs have been discussed in this paper.

Investigation of mass-balance issue in e-beam sterilized paclitaxel eluting coronary stents by SPME/GC-MS

Paclitaxel eluting coronary stents were sterilized by e-beam in a closed system, to investigate sterilization related mass-balance issues and evaluate potential volatile paclitaxel degradation products. A solid-phase microextraction (SPME) method utilizing a polydimethyl-siloxane/divinyl-benzene (PDMS/DVB) fiber was optimized for extracting the volatiles from the head-space of the sterilized stents. GC-MS was used for separation, identification, and quantitation of the components. Benzaldehyde and benzoic acid were identified as paclitaxel related volatile degradation products. Three groups of stents were included in the study, a control group (not exposed to e-beam), a group sterilized at 25 kGy, and a final group sterilized at 75 kGy. The stents sterilized by e-beam at 75 kGy contained significantly higher levels of benzoic acid relative to the controls and the stents at 25 kGy contained intermediate levels of benzoic acid. The benzaldehyde levels increased in the 25 kGy e-beam sterilized stents relative to the control but remained fairly constant in the 75 kGy e-beam sterilized stents relative to the 25 kGy e-beam results. Mechanism for the formation of benzoic acid and benzaldehyde from paclitaxel was proposed. The levels of benzoic acid and benzaldehyde observed on the stents did not resolve the original mass-balance issue, but most likely contribute to the lack of mass balance observed for paclitaxel.

Intravascular brachytherapy versus drug-eluting stents for the treatment of patients with drug-eluting stent restenosis

Drug-eluting stents (DESs), although promising technology, still are associated with restenosis; therefore, we evaluated the safety and efficacy of intravascular radiation therapy for the treatment of DES in-stent restenosis (ISR). Treatment of DES ISR has not been established, although intravascular radiation therapy is an effective treatment for patients with ISR of bare metal stents. Other modalities are conventional percutaneous coronary intervention (PCI), including restenting with DES. Radiation for Eluting Stents in Coronary FailUrE (RESCUE) is an international, Internet-based registry of 61 patients who presented with ISR of a DES and were assigned to intravascular radiation therapy with commercially available systems after PCI. Outcomes of these patients were compared with those of a consecutive series of 50 patients who presented with ISR of a DES and were assigned to repeat DES (r-DES) treatment. Baseline clinical and angiographic characteristics were similar between groups, except for more Cypher stents as the initial DES that restenosed in the r-DES group than in the intravascular radiation therapy group (88.5% vs 69%, p = 0.01). At 8 months there were fewer overall major adverse cardiac events in the intravascular radiation therapy group compared with the r-DES group (9.8% vs 24%, p = 0.044). The need for target vessel and target lesion revascularizations was similar in the 2 groups at 8 months. There has been no report of subacute thrombosis in either group. In conclusion, intravascular radiation therapy as adjunct therapy to PCI for patients presenting with ISR of a DES is safe and should be considered an alternative therapeutic option for this difficult subset of patients.