Pulsatile Bi-Directional Aerosol Flow Affects Aerosol Delivery to the Intranasal Olfactory Region: A Patient-Specific Computational Study

The nasal olfactory region is a potential route for non-invasive delivery of drugs directly from the nasal epithelium to the brain, bypassing the often impermeable blood-brain barrier. However, efficient aerosol delivery to the olfactory region is challenging due to its location in the nose. Here we explore aerosol delivery with bi-directional pulsatile flow conditions for targeted drug delivery to the olfactory region using a computational fluid dynamics (CFD) model on the patient-specific nasal geometry. Aerosols with aerodynamic diameter of 1 µm, which is large enough for delivery of large enough drug doses and yet potentially small enough for non-inertial aerosol deposition due to, e.g., particle diffusion and flow oscillations, is inhaled for 1.98 s through one nostril and exhaled through the other one. The bi-directional aerosol delivery with steady flow rate of 4 L/min results in deposition efficiencies (DEs) of 50.9 and 0.48% in the nasal cavity and olfactory region, respectively. Pulsatile flow with average flow rate of 4 L/min (frequency: 45 Hz) reduces these values to 34.4 and 0.12%, respectively, and it mitigates the non-uniformity of right-left deposition in both the cavity (from 1.77- to 1.33-fold) and the olfactory region (from 624- to 53.2-fold). The average drug dose deposited in the nasal cavity and the olfactory epithelium region is very similar in the right nasal cavity independent of pulsation conditions (inhalation side). In contrast, the local aerosol dose in the olfactory region of the left side is at least 100-fold lower than that in the nasal cavity independent of pulsation condition. Hence, while pulsatile flow reduces the right-left (inhalation-exhalation) imbalance, it is not able to overcome it. However, the inhalation side (even with pulsation) allows for relatively high olfactory epithelium drug doses per area reaching the same level as in the total nasal cavity. Due to the relatively low drug deposition in olfactory region on the exhalation side, this allows either very efficient targeting of the inhalation side, or uniform drug delivery by performing bidirectional flow first from the one and then from the other side of the nose.

Pulsatile Drug Delivery System Triggered by Acoustic Radiation Force

Since biological systems exhibit a circadian rhythm (24-hour cycle), they are susceptible to the timing of drug administration. Indeed, several disorders require a therapy that synchronizes with the onset of symptoms. A targeted therapy with spatially and temporally precise controlled drug release can guarantee a considerable gain in terms of efficacy and safety of the treatment compared to traditional pharmacological methods, especially for chronotherapeutic disorders. This paper presents a proof of concept of an innovative pulsatile drug delivery system remotely triggered by the acoustic radiation force of ultrasound. The device consists of a case, in which a drug-loaded gel can be embedded, and a sliding top that can be moved on demand by the application of an acoustic stimulus, thus enabling drug release. Results demonstrate for the first time that ultrasound acoustic radiation force (up to 0.1 N) can be used for an efficient pulsatile drug delivery (up to 20 μg of drug released for each shot).

Patented pulsatile drug delivery technologies for chronotherapy

INTRODUCTION

Oral-controlled and modified-release drug delivery systems with zero-order sustained-release kinetics have been developed and proven suitable for meeting increasingly sophisticated therapeutic needs. Nevertheless, the impact of basic chronobiology concepts on the practice of medicine is still ongoing and to address chronotherapy needs, various types of pulsatile drug delivery systems have been innovated. The purpose of this review is to highlight these innovations in the field of chronotherapy.

AREAS COVERED

The present review discusses in depth on recent patents and developments related to pulsatile drug delivery systems with eroding, soluble or rupturable barrier coatings, and systems with capsular structures. Besides focusing on all recent innovations, the review addresses the novelty and feasibility of all upcoming technologies being exploited considering pulsatile drug delivery systems.

EXPERT OPINION

There has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable and well-defined lag phase from the time of administration. From 1981 until the present date, patent publications related to pulsatile drug delivery have shown more promising systems with numerous developments in arena of drug delivery. Future development of chronotherapeutic medications requires proper assessment and integration with other emerging disciplines such as hydrogel and transdermal delivery systems. The selection of the appropriate chronopharmaceutical technology should take into considerations with the ease of manufacturing and the cost-effectiveness.