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PharmTech.com Trends in Formulatio eBook September 2024 Pharmaceutical Technology ® 31 T he lungs are one of the most complicated or- gans in the body. Therefore, there are several considerations that come into play when for- mulating a new inhaled drug. "I don't think I would be exaggerating if I [said] that [the] lungs are probably one of the most complex organs in the body," said Vivek Gupta, PhD, associate professor, Pharmaceutical Sciences, College of Pharmacy & Health Sciences, St. John's University, in an inter- view with Pharmaceutical Technology® (1). "We are talking about multiple branching going from trachea to brochi, and … millions of air sacs, where most of the blood gas exchange happens, [and] where the lungs will give oxygen into the blood for circulation all over the body." Because t he trachea branches of f, t he deliver y pathway decreases. Therefore, according to Evonne Brennan, consultant at Evonne Brennan Consulting, "To reach its region of impact, a precise micronized dose of drug substance will need to be delivered in an aerosolized state, through the aid of a device and a formulation designed for deliver y f rom that de- vice, through simple actuation or a synchronized under taking by the patient, the aerosolized par ti- cles travel with the patient's airf low through a series of pathways where it is deposited." Obstacles caused by disease could restrict delivery further and cause increased mucus, remarks Bren- nan. "Deposition of the drug substance is required to deliver its pharmacological response," Brennan stresses. Other complications for deliver y of drug s ubs t a nce v i a i n h a l at ion ca n be cau sed by age, post-ref lux cough, and patient compliance. "For a given indication and drug substance, there are many physiological factors that need to be con- sidered during product development for inhalation, s uch a s pat ient pu l mon a r y f u nc t ion , c lea ra nce mechanisms, etc., and these are addressed in an in- Susan Haigney Formulating Inhaled Medicines Excipient and delivery device selection play crucial roles in the formulation of inhaled drugs. DAVIZRO PHOTOGRAPHY- STOCK.ADOBE.COM