Endovascular Drug Delivery and Drug Elution Systems: First Principles

Evolution of drug-eluting biomedical implants for sustained drug delivery

In the field of drug delivery, the most commonly used treatments have traditionally been systemically delivered using oral or intravenous administration. The problems associated with this type of delivery is that the drug concentration is controlled by first pass metabolism, and therefore may not always remain within the therapeutic window. Implantable drug delivery systems (IDDSs) are an excellent alternative to traditional delivery because they offer the ability to precisely control the drug release, deliver drugs locally to the target tissue, and avoid the toxic side effects often experienced with systemic administration. Since the creation of the first FDA-approved IDDS in 1990, there has been a surge in research devoted to fabricating and testing novel IDDS formulations. The versatility of these systems is evident when looking at the various biomedical applications that utilize IDDSs. This review provides an overview of the history of IDDSs, with examples of the different types of IDDS formulations, as well as looking at current and future biomedical applications for such systems. Though there are still obstacles that need to be overcome, ever-emerging new technologies are making the manufacturing of IDDSs a rewarding therapeutic endeavor with potential for further improvements.

Cost-effectiveness of Drug-Eluting Stents in Percutaneous Coronary Intervention in Brazil's Unified Public Health System (SUS)

Fundamento

O uso do stent farmacológico (SF) comparado ao stent não farmacológico (SNF) na intervenção coronariana percutânea (ICP) reduziu o percentual de reestenose, porém sem impacto na mortalidade, com aumento no custo. A literatura carece de estudos randomizados que comparem economicamente esses dois grupos de stents na realidade do Sistema Único de Saúde (SUS).

Objetivo

Estimar a razão custo-efetividade incremental (RCEI) entre SF e SNF na coronariopatia uniarterial em pacientes do SUS

Métodos

Pacientes com coronariopatia uniarterial sintomática foram randomizados em 3 anos para uso de SF ou SNF durante a ICP, na proporção de 1:2, com seguimento clínico de 12 meses. Foram avaliados reestenose intrastent (RIS), revascularização da lesão-alvo (RLA), eventos adversos maiores e custo-efetividade (CE) de cada grupo. Os valores de p < 0,05 foram considerados significativos.

Resultados

No grupo SF, dos 74 pacientes (96,1%) que completaram o acompanhamento, ocorreu RIS em 1(1,4%), RLA em 1 (1,4%), óbito em 1 (1,4%), sem trombose. No grupo SNF, dos 141 pacientes (91,5%),ocorreu RIS em 14 (10,1%), RLA em 10 (7,3%), óbito em 3 (2,1%) e trombose em 1 (0,74%). Na análise econômica, o custo do procedimento foi de R$ 5.722,21 no grupo SF e de R$4.085,21 no grupo SNF. A diferença de efetividade a favor do grupo SF por RIS e RLA foi 8,7% e 5,9%, respectivamente, com RCEI de R$ 18.816,09 e R$ 27.745,76.

Conclusões

No SUS, o SF foi custo-efetivo, em concordância com o limiar de CE preconizado pela Organização Mundial da Saúde. (Arq Bras Cardiol. 2020; 115(1):80-89)

Defining drug and target protein distributions after stent-based drug release: Durable versus deployable coatings

BACKGROUND

Innovations in drug eluting stent designs make it increasingly important to develop models for differentiating performance through spatial definition of drug, receptor binding and cell state.

METHODS

Two designs of sirolimus analog eluting stents were implanted into porcine coronary arteries for 28, 60 or 90 days (n = 9/time point), durable coating (Xience) and deployable absorbable coating (MiStent). Explanted arteries were evaluated for drug content (n = 3/time point) by LC-MS/MS and for drug and target protein (mTOR) distributions by immunofluorescence (IF, n = 6/time point). A computational model was developed to predict drug release and arterial distribution maps.

RESULTS

Both stents released the majority of drug load by 28 days, with different tissue retention efficiencies (91.4 ± 4.9% MiStent versus 21.5 ± 1.9% Xience, P < 0.001). Computational modeling of MiStent coating deployment and microcrystal dissolution recapitulated in vivo drug release and net tissue content and predicted that >98.5% of deployed drug remains crystalline through 90 days. Immunofluorescence and computational modeling showed peristrut drug localization for both stents, with similar peaks, but high interstrut levels only at sites of coating deployment from the absorbable coating. Co-localization of mTOR-IF with drug-IF for both devices showed persistent drug effects, though with differential drug-receptor pharmacokinetics.

CONCLUSIONS

Immunofluorescence and computational modeling provide insights into drug distribution and binding status that can help differentiate drug delivery technologies. Herein we found that tissue deployment of slow dissolving crystalline drug particles results in temporally and spatially more uniform drug delivery to interstrut zones that might otherwise be under-dosed without excess peristrut drug.