Biodegradable polymers for parenteral drug delivery
Functional lactide/glycolide polymers play a key role in complex parenteral drug delivery products. They are often referred to as ‘smart’ materials, as their tunability drives the performance of parenteral dosage forms. Using these polymers, formulators can deliberately change drug impact by prolonging drug release in patients and offering long-acting or extended-release options.
Long-acting, complex drug delivery products, particularly those based on injectable microparticles, nanoparticles and implants, are among the most attractive parenteral products in the pharmaceutical industry – more than 50 products on the market worldwide. In fact, long-acting injectables (LAIs) that use bioabsorbable polymers for systemic and local drug delivery are receiving a lot of attention today, improving the lives of millions of patients globally, thanks to successful outcomes for the treatment of schizophrenia, diabetes, substance abuse, cancer, and ocular, rare and hormonal diseases. These products have many advantages, such as simplifying the drug regimen by decreasing dosing frequency, helping to improve efficacy, improving treatment adherence, and releasing beneficial agents locally, including in knee joints and within the eye.
Since the first synthetic plastic, Bakelite, was developed in 1907, the field of polymer science has grown drastically. Polystyrene, nylon, Teflon, and plexiglass were all invented in the late 1920s and 1930s. This is also the timeframe in which polylactide polymers were invented and, thus, are considered to be the origins of long-acting injectables – at least for those formulations based on lactide/glycolide polymers (LG polymers). However, the next significant development for LG polymers wasn’t until a 1955 patent. Up to then the advantages of these polymers that degrade in the presence of water had not yet been recognized; so they weren’t commercialized. The 1955 patent led to the first synthetic resorbable suture.
A lot has changed in the intervening years, with medical devices leading the way. Now LG polymers are an essential formulation tool and can be thought of as the timers or clocks of drug delivery, allowing tunable and precise uptake of water which influences drug release times so that they reach the most appropriate part of the body with maximum impact. Single or blends of LG polymers can be combined in dosage forms to match target release profiles over durations ranging from days or weeks to, in principle, more than a year.
So how do you use lactide/glycolide polymers to design these clocks and distribute the drugs for maximum effectiveness at the right time?
Tom Tice, Senior Director of Global Technical Marketing at Evonik, has 43 years’ experience in bioresorbable polymers, microencapsulation, complex parenterals and drug delivery. Basically, 40 years of one polymer—lactide/glycolide polymers—and long-acting injectables. Over the past 17 years, he has also volunteered at USP, sitting on various expert committees. He’s also served for over 30 years in the McWhorter School of Pharmacy at Samford University, Birmingham, Alabama in the U.S.
Whitney Moro is currently the analytical and quality control manager for the LACTEL® polymer line within Evonik. With a background in small molecule synthetic organic chemistry, she has worked in the biodegradable polymer field for more than 10 years with experience synthesizing, scaling, analyzing, and formulating with poly(lactide-glycolide) polymers. She also volunteers with USP and resides on two expert committees.