Long-Acting Opioid Analgesics for Acute Pain: Pharmacokinetic Evidence Reviewed

Simple Summary Pharmacokinetic (PK) studies measure the time for a dose of a drug to reach therapeutic levels in a patient's blood or tissues. This data provides a simple and precise method to compare the response to drugs made by different manufactures or the same drug provided in different delivery formats; for example, oral tablets, intravenous infusions, or subcutaneous (SC) injections. The present study provides the first review of PK data for buprenorphine, an opioid analgesic, in animals dosed with the drug in a lipid or polymer carrier. The PK data from studies using the polymer carrier system illustrate greater variability, an outcome probably related to the different manufacturing conditions of the supplying vendors. The lipid product was produced by a single vendor. Long-acting injectable (LAI) opioid formulations mitigate the harm profiles and management challenges associated with providing effective analgesia for animals. A single dose of a long-acting opioid analgesic can provide up to 72 h of clinically relevant pain management. Yet, few of these new drugs have been translated to products for veterinary clinics. Regulatory pathways allow accelerated drug approvals for generic and biosimilar drugs. These pathways depend on rigorous evidence for drug safety and pharmacokinetic evidence demonstrating bioequivalence between the new and the legacy drug. This report reviews the animal PK data associated with lipid and polymer-bound buprenorphine LAI formulations. Buprenorphine is a widely used veterinary opioid analgesic. Because of its safety profile and regulatory status, buprenorphine is more accessible than morphine, methadone, and fentanyl. This review of PK studies coupled with the well-established safety profile of buprenorphine suggests that the accelerated approval pathways may be available for this new family of LAI veterinary pharmaceuticals.