Long-acting injectable (LAI) formulations have revolutionized veterinary pharmaceuticals by improving patient compliance, minimizing dosage frequency, and improving therapeutic efficacy. These formulations utilize advanced drug delivery technologies, including microspheres, liposomes, oil solutions/suspensions, in situ-forming gels, and implants to achieve extended drug release. Biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA), and polycaprolactone (PCL) have been approved by the USFDA and are widely employed in the development of various LAIs, offering controlled drug release and minimizing the side effects. Various classes of veterinary medicines, including non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, and reproductive hormones, have been successfully formulated as LAIs. Some remarkable LAI products, such as ProHeart^® (moxidectin), Excede^® (ceftiofur), and POSILACTM (recombinant bovine somatotropin), show clinical relevance and commercial success. This review provides comprehensive information on the formulation strategies currently being used and the emerging technologies in LAIs for veterinary purposes. Additionally, challenges in characterization, in vitro testing, in vitro in vivo correlation (IVIVC), and safety concerns regarding biocompatibility are discussed, along with the prospects for next-generation LAIs. Continued advancement in the field of LAI in veterinary medicine is essential for improving animal health.

Background/Objectives: Current clinical evidence suggests that cannabidiol (CBD) demonstrates therapeutic potential in the management of chronic pain, particularly in conditions involving inflammation. However, its therapeutic potential is severely limited by poor oral bioavailability, extensive first-pass metabolism, and the need for frequent high-dose administration, which compromises patient adherence and tolerability. Long-acting injectable (LAI) delivery systems offer a strategy to overcome these limitations by providing sustained plasma concentrations and reducing dosing frequency. This study aimed to develop and optimise CBD-loaded poly (lactic-co-glycolic acid) (PLGA) microspheres for LAI delivery and to evaluate poly(2-ethyl-2-oxazoline) (POx) as a functional and biocompatible alternative to the conventionally used poly (ethylene glycol) (PEG). Methods: CBD-loaded microspheres were prepared using emulsion–solvent evaporation technique. The formulations were optimised based on entrapment efficiency (EE), drug loading (DL), particle size distribution, surface morphology, thermal behaviour, in vitro release kinetics, and cytocompatibility using NIH 3T3 fibroblasts. Multiple in vitro release methodologies, including dialysis bag, shaking-flask, and USP Apparatus IV, were evaluated to identify the most discriminative and practical approach for long-term release assessment. Results: The optimised POx-based microspheres demonstrated superior control over particle size, yielding significantly smaller and more uniform particles compared with PEG-based microspheres (124 ± 1.47 µm vs. 218 ± 13.5 µm, respectively). Differential scanning calorimetry (DSC) confirmed molecular dispersion of CBD within the polymer matrix. In vitro release studies demonstrated sustained drug release over 20 days. Conclusions: POx represents a promising alternative to PEG for the formulation of CBD-loaded PLGA microspheres, offering enhanced physicochemical stability and biological compatibility. This platform supports the development of safe and effective long-acting injectable CBD therapies and consideration of POx as an alternative to PEG.

Long-acting injectable (LAI) systems may offer an alternative approach to antidepressant treatment by reducing reliance on daily oral medication, supporting adherence, limiting pharmacokinetic fluctuations, and maintaining therapeutic drug exposure over extended periods. These potential advantages may be particularly relevant for patients with recurrent depression or difficulty sustaining regular oral treatment. However, converting conventional antidepressants into clinically useful LAIs remains challenging because many drugs require substantial maintenance doses, have formulation-limiting physicochemical properties, and may require dose adjustment or prompt discontinuation in response to adverse effects. This review evaluates the feasibility of established and emerging depot technologies, including polymeric microspheres, in situ-forming depots, lipid- and oil-based systems, hydrogels, and hybrid or stimulus-responsive platforms, for sustained antidepressant delivery. It compares these approaches according to drug-loading capacity, release mechanisms, achievable dosing interval, injection-volume constraints, manufacturing scalability, sterilization, product robustness, safety, local tissue tolerability, and regulatory maturity. Major translational barriers include the high total drug mass required for many antidepressants, acceptable injection-volume limits, solvent and excipient safety, injection-site reactions, limited reversibility after administration, pharmacokinetic drug-interaction risk, difficulty developing predictive in vitro–in vivo correlations and demanding regulatory expectations for complex injectable products. The review also considers opportunities for coordinated long-acting combination therapy, personalized patient selection, digital adherence monitoring, and emerging biomaterials. Overall, successful LAI antidepressant development will require careful matching of the drug molecules, delivery platform, pharmacokinetic target, and intended patient population. Early products are most likely to rely on established depot technologies and prior confirmation of oral efficacy and tolerability before long-term administration.

The management of Alzheimer’s disease requires continuous therapeutic intervention due to its progressive nature. Currently, the FDA has approved ace