Formulating Inhaled Medicines

The lungs are one of the most complicated organs in the body. Therefore, there are several considerations that come into play when formulating 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 interview 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 the trachea branches off, the delivery 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 delivery from that device, through simple actuation or a synchronized undertaking by the patient, the aerosolized particles travel with the patient’s airflow through a series of pathways where it is deposited.”

Obstacles caused by disease could restrict delivery further and cause increased mucus, remarks Brennan. “Deposition of the drug substance is required to deliver its pharmacological response,” Brennan stresses. Other complications for delivery of drug substance via inhalation can be caused by age, post-reflux cough, and patient compliance.

“For a given indication and drug substance, there are many physiological factors that need to be considered during product development for inhalation, such as patient pulmonary function, clearance mechanisms, etc., and these are addressed in an integrated way at the formulation and device development levels,” says Eunice Costa, R&D director–Inhalation and Advanced Drug Delivery, Hovione.

Attributes such as formulation particle size and density and inhaler dispersion performance need to be controlled to ensure successful deposit of the product into the lungs, according to Costa. “Once deposited, bioavailability of the drug becomes a function of additional factors such as intrinsic chemical properties as well as solid state and formulation composition, being that dissolution and/or permeation needs to occur at a faster rate than the clearance mechanisms in place in the local diseased microenvironment,” Costa says.

Read the article in the Trends in Formulation eBook.

About the author

Susan Haigney is lead editor for Pharmaceutical Technology®.

Article details

Pharmaceutical Technology®
eBook: Trends in Formulation
September 2024
Pages: 31–33

Citation

When referring to this article, please cite it as Haigney, S. Formulating Inhaled Medicines. Pharmaceutical Technology Trends in Formulation eBook 2024, September.