Long-acting injectables (LAIs) are sustained drug delivery systems specifically designed so that medication is released into the body gradually over an extended period of time.
Image Credit: Powder Systems
The concept of extending the release of active pharmaceutical ingredients (APIs) has been around for some time, with oral formulations available on the market since 2001. Long-acting injectables were initially approved by the US Food and Drug Administration (FDA) in the early 1990s and are now becoming more popular for a variety of reasons which will be explored in this article.
Despite a significant uptake and applicability, processing LAR injectables remains a major challenge, even though long-acting injectables have proven to be successful in hormone replacement therapy, pain treatment, and many other applications.
Several materials are suitable as drug delivery vehicles, but biodegradable microspheres remain at the forefront. They can easily be combined with various APIs and have been demonstrably formulated into depot injections with clear success in prolonging drug delivery with first-rate efficacy.
What are long-acting injectables?
Long-acting injectables are typically referred to as “depot” injections as they “deposit” a drug load into the tissue to create a store of medication at the injection site. Over the course of weeks or sometimes even months after injection, the drug is gradually absorbed.
The compound material is what makes the sustained release possible. For example, polymeric microspheres encapsulate the API molecules and degrade gradually in vivo, releasing the drug load slowly into the body. The microspheres' release rate depends on their composition, shape, and size, meaning drug manufacturers can fine-tune a drug’s release of its active compounds kinetics to optimize therapeutics for improved pharmaceutical outcomes.
A simple reference point to work from is that a smaller microsphere will typically release a load faster than a larger one. Therefore, drug release rates can be modified by adjusting the microsphere particle size and particle size distribution (PSD). Where composition is concerned, there is an increased number of biocompatible candidate polymers that may be suitable for depot injections. Polylactic acid (PLA) and polyethylene glycol (PEG) are among the main candidates, as they demonstrate enzymatic degradation over time when injected via a standard syringe.
What are the advantages of long-acting injectables?
Compliance
Patients can better manage their medication regimen as LAIs require less frequent dosing.
Convenience
With less dosing, LAIs offer patients greater convenience, particularly for those who have difficulty remembering to take their medication or those with mobility issues.
Targeting
Clinicians can target localized anatomical areas as LAIs can be injected into specific body parts. This enhances the drug’s specificity and limits the risk of systemic exposure.
Cost-effective
LAIs can reduce costs over time as fewer clinical visits and less frequent medication refills are necessary.
Reduced risk of overdose
As LAIs release a steady and sustained level of the active drug, there is a reduced risk of overdose, especially when compared to oral medications.
Reduced risk of medication interactions
LAIs limit the risk of medication interactions as they do not have to be taken at specific times with food or in coordination with other medications.
Reduced risk of diversion
LAIs are not easily shared or sold on compared to oral medications. This reduces the risk of diversion and abuse.
Stable blood levels
The steady and sustained release of LAIs maintain consistent levels of the active drug in the body, which can help boost efficacy and reduce the likelihood of breakthrough symptoms or side-effects.
How are long-acting injectables processed?
Long-acting injectable medications are usually manufactured using one of two methods: microencapsulation or depot formulation. Microencapsulation involves a polymeric material that encapsulates the API to produce microspheres, which are subsequently suspended in an aqueous phase.
In contrast, depot formulation deviates from this route. The API is still coupled with a polymer but is formulated uniquely to deposit as a solid store following injection. Both methods deliver the sustained release required, but encapsulation often produces more consistent results.
About Powder Systems
Powder Systems Limited (PSL) provides a full range of solid liquid separation solutions for filtration, drying, and processing from research and development activities up to larger commercial production scale. Quality and innovation are central to everything they do. They are proud of their award-winning track record and have been working with industry partners for over 35 years. PSL supports clients by developing solutions to overcome challenging manufacturing processes and provide first-class aftercare services.
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