Inkjet printing as a novel medicine formulation technique

Abstract

We demonstrate the viability of using an ink-jet printer to produce a formulation capable of controlling the release of a drug. This is shown for the drug felodipine, an antihypertensive, with polyvinyl pirrolidone (PVP) as an excipient. As felodipine is a poorly water soluble drug, its molecular dispersion in a soluble polymer (ie. PVP) is a commonly used approach to improve bioavailability. Various ratios of felodipine and PVP in an ethanol-DMSO mixture (95/5) were dispensed in picoliter quantities using a piezoelectric 'ink-jet' head onto a hydrophobic substrate. The resultant formulation spots were characterized using atomic force microscopy, localized nano-thermal analysis, ATR-IR and imaging confocal Raman spectroscopy. Intimate mixing of the felodipine and PVP within the micro-dots was observed. ATR-IR confirmed the known molecular level interaction of felodipine and PVP through hydrogen bonding. Nanothermal analysis indicated a single glass transition point, indicative of an intimate polymer drug mixture, which is lowered as the drug concentration increases. Confocal Raman microscopy mapping on single micro-scale droplets allowed the visualization of the drug distribution in the spots as well as facilitating characterization of the release of the drug. The drug release can be altered through control of the drug loading. As inkjet printing is an inherently scalable technology, this proof of principal work with single deposited micro-spot formulations demonstrates the potential of this approach to print practical dosage forms (e.g. as an array of many thousands of spots with different release profiles). This, for example, raises the possibility in the future of producing dosage forms at points of care with one or more drugs which have been formulated for the needs of individual patients.