Systemic delivery of cetrorelix to rats by a new aerosol delivery system

Nanocarriers for pulmonary administration of peptides and therapeutic proteins

Peptides and therapeutic proteins have been the target of intense research and development in recent years by the pharmaceutical and biotechnology industry. Preferably, they are administered through the parenteral route, which is associated with reduced patient compliance. Formulations for noninvasive administration of peptides and therapeutic proteins are currently being developed. Among them, inhalation appears as a promising alternative for the administration of such products. Several formulations for pulmonary delivery are in various stages of development. Despite positive results, conventional formulations have some limitations such as reduced bioavailability and side effects. Nanocarriers may be an alternative way to overcome the problems of conventional formulations. Some nanocarrier-based formulations of peptides and therapeutic proteins are currently under development. The results obtained are promising, revealing the usefulness of these systems in the delivery of such drugs.

Clinical perspectives on pulmonary systemic and macromolecular delivery

The large epithelial surface area, the high organ vascularization, the thin nature of the alveolar epithelium and the immense capacity for solute exchange are factors that led the lung to serve as an ideal administration route for the application of drugs for treatment of systemic disorders. However, the deposition behaviour of aerosol particles in the respiratory tract depends on a number of physical (e.g. properties of the particle), chemical (e.g. properties of the drug) and physiological (e.g. breathing pattern, pulmonary diseases) factors. If these are not considered, it will not be possible to deposit a reproducible and sufficient amount of drug in a predefined lung region by means of aerosol inhalation. The lack of consideration of such issues led to many problems in inhalation drug therapy for many years mainly because physiological background of aerosol inhalation was not fully understood. However, over the last 20 years, there has been considerable progress in aerosol research and in the understanding of the underlying mechanisms of particle inhalation and pulmonary particle deposition. As a consequence, an increasing number of studies have been performed for the lung administration of drugs using a variety of different inhalation techniques. This review describes the physical and in part some of the physiological requirements that need to be considered for the optimization of pulmonary drug delivery to target certain lung regions.

Cetrorelix in the treatment of female infertility and endometriosis

The use of cetrorelix within ovarian-stimulation protocols demonstrates several advantages compared with gonadotropin-releasing hormone (GnRH) agonist-containing protocols, which include, for example, significantly less time for analogue treatment and a reduction in the amount of gonadotropins needed. Furthermore, fewer side effects can be expected. There is no difference regarding endometrium quality and hormone profiles, and the results of assisted reproduction cycles are comparable. Cetrorelix also seems to be useful in the treatment of endometriosis which, in most cases, is an estrogen-dependent disease. Furthermore, fewer side effects occur with this agent (e.g., postmenopausal symptoms) and no estradiol add-back is needed. In the future, new nonpeptic GnRH antagonists are expected to be available for oral administration. Although they are still under investigation, these agents have the potential to improve patients' comfort and compliance.

Pulmonary delivery of therapeutic peptides via dry powder inhalation: effects of micronisation and manufacturing

Pulmonary drug delivery is increasingly appreciated as a route of administration for systemically acting proteins and peptides. A respirable particle size of the drug is a key requirement, but the fragile nature of many proteins may be a limitation for the application of conventional production processes. The aim of this study was to examine the effect of different micronisation processes on the degradation and aerodynamic properties of the GnRH-antagonist cetrorelix in order to enable its application by a dry powder inhaler (Novolizer). A modified pearl mill was used for milling in fluid propellant. Furthermore, a spray drying procedure was established using a novel process of atomisation and drying. Adhesive mixtures of lactose and 5-20% of micronised cetrorelix-acetate were prepared. Analysis by laser light scattering, HPLC, Karl Fischer, cascade impactor and scanning electron microscopy were performed to characterise the manufactured powders. Both micronisation procedures succeeded in producing small range particle size distributions, suitable for deep lung deposition (D50 = 1.6 microm for milling and 3.3 microm for spray drying). The pearl milled cetrorelix showed promising results when delivered by the Novolizer: a reproducible and highly efficient dispersion of the drug was achieved (around 60% of aerosolised drug < 5 microm). The spray dried drug was not suitable when processed as adhesive mixture.

The role of particle engineering in relation to formulation and de-agglomeration principle in the development of a dry powder formulation for inhalation of cetrorelix

We formulated cetrorelix acetate, as an adhesive mixture for use in dry powder inhalation. To achieve the highest possible deposition efficiency we investigated both the influence of different micronization techniques and different inhalers. The Novolizer with an air classifier as the powder de-agglomeration principle and the ISF inhaler were used for in vitro deposition experiments (cascade impaction). Micronization by milling as the classical approach and micronization by spray drying and spray freeze drying as advanced particle engineering techniques were investigated to determine whether advanced techniques are necessary to obtain high fine particle fractions (FPF) for this specific drug. It was found that the effects obtained with a certain micronization technique depended on the complex interaction of the physical characteristics of the drug substance with the type of formulation chosen, as well as with the de-agglomeration principle used. The combination of particle engineering by spray drying and the use of the air classifier technology resulted in a fine particle fraction of 66%, while spray freeze drying yielded extremely fragile particles resulting in a FPF of only 25%. The behaviour of the milled material showed similar trends as the spray dried material but FPF values were lower. It was concluded that when a drug is to be formulated as a powder for inhalation with high fine particle fractions, it is profitable to use advanced particle engineering techniques, however the applied technique should be tuned with the characteristics of the formulation type and process as well as with device development.