Pulmonary drug delivery sustained release

Cook, R. O., Pannu, R. K., and Kellaway, I. W. (2005), Novel sustained release microspheres for pulmonary drug delivery, / Controlled Release, 104,79-90. 

F. Modulation of Pulmonary Selectivity by Sustained-release Drug Delivery Systems... 

The pharmacokinetic/dynamic parameters involved in pulmonary drug delivery of glucocorticoids have been reviewed. Among these, low oral bioavailability, high pulmonary deposition, pronounced clearance, and sustained pulmonary release are the most important parameters to be considered. 

Application of SCF is now the subject of increasing interest especially in the pharmaceutical industry and there are three aims increasing bioavailability of poorly soluble molecules designing sustained-release formulations and formulation of active agents for new types of drug delivery that are less invasive than parental delivery (oral, pulmonary, transdermal). The most complex challenge is related to therapeutic delivery, as it is extremely difficult to obtain a satisfactory therapeutic delivery effect due to biomolecule instability and very short half-life in vivo. 

Terzano et al developed Polysorbate 20 niosomes containing beclomethasone dipropionate for pulmonary delivery to patients with chronic obstructive pulmonary disease. Singh et prepared niosomes containing the anti-inflammatory drug nimesulide and tested its physico-chemical properties including stability and in vitro release. It was shown that in vitro sustained drug release can be achieved with this approach. The research literature for niosomes in ocular drug delivery has been reviewed by Kaur et al." ... 

Another issue is reproducibility. The formulation may work perfectly in an in vitro test system, but the dosage form requires aerosolization, and lung deposition is a function of the characteristics of the aerosol (dose, mass concentration, droplet/particle size, etc.) and the nature of the inspiratory maneuver, a factor that the patient has control over. These factors can influence performance to a far greater extent than can be built into a particle, and thus the term controlled does not seem a defensible objective for pulmonary delivery. The vagaries of the deposition profile and of the amount that will deposit also imply that sustaining a certain drug concentration is a difficult proposition, but the loosest definition extended release, seems an acceptable goal within the boundaries set by the clearance mechanisms. 

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