Sinha V R, Trehan A
University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh, India.
Crit Rev Ther Drug Carrier Syst. 2005;22(6):535-602. doi: 10.1615/critrevtherdrugcarriersyst.v22.i6.20.
Nowadays, emphasis is being laid to development of controlled release dosage forms. Interest in this technology has increased steadily over the past few years. Although oral administration of drugs is a widely accepted route of drug delivery, bioavailability of drug often varies as a result of gastrointestinal absorption, degradation by first-pass effect, and hostile environment of gastrointestinal tract. Transdermal administration for percutaneous absorption of drug is limited by the impermeable nature of the stratum corneum. Ocular and nasal delivery is also unfavorable because of degradation by enzymes present in eye tissues and nasal mucosa. Hence, the parenteral route is the most viable approach in such cases. Of the various ways of achieving long-term parenteral drug delivery, biodegradable microspheres are one of the better means of controlling the release of drug over a long time. Because of the lipidic nature of liposomes, problems such as limited physical stability and difficulty of freeze-drying are encountered. Similarly, for emulsions, stability on long-term basis and in suspensions, rheological changes during filling, injecting, and storage poses limitation. Also, in all these systems, the release rate cannot be tailored to the needs of the patient. Parenteral controlled-release formulations based on biodegradable microspheres can overcome these problems and can control the release of drug over a predetermined time span, usually in the order of days to weeks to months. Various FDA-approved controlled-release parenteral formulations based on these biodegradable microspheres are available on the market, including Lupron Depot Nutropin Depot and Zoladex. This review covers various molecules encapsulated in biodegradable microspheres for parenteral delivery.
如今，人们正着重于控释剂型的开发。在过去几年里，对这项技术的关注度稳步上升。尽管口服给药是一种广泛接受的药物递送途径，但由于胃肠道吸收、首过效应导致的降解以及胃肠道的恶劣环境，药物的生物利用度常常有所不同。经皮给药用于药物的经皮吸收受到角质层不透性的限制。眼部和鼻腔给药也不理想，因为眼组织和鼻黏膜中存在的酶会导致药物降解。因此，在这种情况下，肠胃外给药途径是最可行的方法。在实现长期肠胃外药物递送的各种方式中，可生物降解微球是长期控制药物释放的较好手段之一。由于脂质体的脂质性质，会遇到诸如物理稳定性有限和冷冻干燥困难等问题。同样，对于乳剂，长期稳定性以及在悬浮液中，填充、注射和储存过程中的流变学变化也存在局限性。此外，在所有这些系统中，释放速率无法根据患者的需求进行调整。基于可生物降解微球的肠胃外控释制剂可以克服这些问题，并能在预定的时间段内控制药物释放，通常为数天至数周再到数月。市场上有各种基于这些可生物降解微球的、已获美国食品药品监督管理局批准的肠胃外控释制剂，包括醋酸亮丙瑞林微球、生长激素释放因子微球和戈舍瑞林。这篇综述涵盖了封装在可生物降解微球中用于肠胃外递送的各种分子。
