Advanced Characterization and Bioequivalence Strategies for Complex Long-Acting Injectable Systems
A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Biopharmaceutics".
Deadline for manuscript submissions: 28 June 2026 | Viewed by 53
Special Issue Editor
Interests: patient-centered drug development; fattigation-platform; complex generic development; solubilization; controlled release; bioavailability control; patient-focused drug development
Special Issues, Collections and Topics in MDPI journals
Special Issue Information
Dear Colleagues,
Long-acting injectable (LAI) formulations are designed to facilitate extended drug release from days to years when administered via intramuscular, subcutaneous, intra-articular, and other parenteral routes. These systems encompass various technologies including nanocrystal-based suspensions (e.g., aripiprazole, paliperidone palmitate, olanzapine LAI suspensions), oil-based lipophilic solutions (e.g., haloperidol decanoate), biodegradable PLGA microspheres prepared via w/o/w emulsion techniques (e.g., risperidone, octreotide, naltrexone), multivesicular liposomal (MVL) systems (e.g., bupivacaine liposomes), and in situ gel-forming systems (e.g., buprenorphine extended-release injection).
Additionally, many strategies are emerging to enable sustained drug release, including innovative approaches that implement the chemical modification of APIs through fatty acid conjugation or other small-molecule attachments to create prodrug systems. These prodrug approaches modulate lipophilicity, tissue distribution, and enzymatic conversion kinetics to control drug release duration and bioavailability.
With the exception of oil-based solutions, which involve relatively simple formulation and manufacturing processes, most LAI products are classified as complex formulations due to their sophisticated drug delivery mechanisms. Nanocrystal suspensions rely on particle size reduction and stabilization to control dissolution rates, while biodegradable microspheres utilize polymer erosion and drug diffusion. MVL systems exploit osmotic gradients across lipid bilayers, and in situ gels undergo thermosensitive or ion-activated phase transitions to form sustained-release depots. These complex formulations present significant challenges in quality assessment and bioequivalence demonstration due to their multiphasic release profiles, variable absorption kinetics, and depot formation behavior.
Therefore, this Special Issue aims to provide a scientific basis for the evaluation of LAI formulations, emphasizing advanced characterization techniques, in vitro release testing methodologies, pharmacokinetic modeling approaches, and bioequivalence strategies. While these formulations are often developed as complex generics, the fundamental principles of pharmaceutical science primarily guide their development and evaluation.
Dr. Chulhun Park
Guest Editor
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Keywords
- long-acting injectables
- bioequivalence
- prodrug conjugation
- PLGA microspheres
- in situ gels
- nanocrystal suspensions
- sustained release
- injectable formulations
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