- VCPR
- Veterinarian-client-patient relationship — exists when a vet has examined an animal (or made a comparable clinically appropriate evaluation), knows it well enough to make a general diagnosis, and is available for follow-up. The legal foundation for prescribing and compounding decisions.
- AMDUCA
- The Animal Medicinal Drug Use Clarification Act — the federal law allowing licensed veterinarians to prescribe certain drugs for extralabel (off-label) use in animals, only within a valid VCPR and under specific conditions.
- Extralabel use
- Using an approved drug in a way not specified on its label (different species, dose, or condition) — legal only when a veterinarian directs it under AMDUCA within a valid VCPR.
- Veterinary compounding pharmacy
- A licensed pharmacy that prepares customized medication formulations for a specific animal patient, based on a veterinarian's prescription — the legitimate channel for most extralabel and specialty veterinary medications.
- Research use only (RUO)
- A regulatory label indicating a compound is intended for laboratory research, not for use in humans or animals, and has not been evaluated by the FDA for that purpose.
- Allometric scaling
- The principle that metabolic rate and drug clearance don't scale in a straight line with body weight across species — a key reason why doses can't simply be scaled down from a human to a much smaller animal.
- Glucuronidation
- A liver detoxification process many mammals use to safely clear certain compounds. Cats have a partial deficiency in this pathway, making them more sensitive to some substances that are safe for other species.
- Pharmacokinetics (PK)
- The study of how a drug moves through the body — absorption, distribution, metabolism, and excretion. A 2022 peer-reviewed study measuring BPC-157's pharmacokinetics in rats and beagle dogs is a real example: it tracked how quickly the compound was absorbed, where it accumulated (kidney and liver showed the highest concentrations), and how fast it cleared — and found real differences between the two species.
- Pharmacodynamics (PD)
- The study of what a drug does to the body — its mechanism of action and biological effects — as distinct from pharmacokinetics, which is what the body does to the drug. Two animals can have identical pharmacodynamics (the drug affects the same receptor the same way) but very different pharmacokinetics (how fast it's absorbed or cleared), which is part of why cross-species extrapolation is unreliable.
- Bioavailability
- The percentage of an administered dose that actually reaches circulation and is available to have an effect. It varies by species and route. In the BPC-157 rat-and-dog pharmacokinetics study referenced elsewhere on this site, intramuscular bioavailability was measured at roughly 14–19% in rats versus roughly 45–51% in dogs in the same study — a concrete illustration of why bioavailability can't be assumed to transfer across species.
- Half-life (elimination half-life)
- The time it takes for the concentration of a drug in the body to drop by half. Short-half-life compounds clear quickly and require different handling than long-half-life ones. Many small peptides have very short half-lives — the same BPC-157 pharmacokinetics study found an elimination half-life of under 30 minutes in both rats and dogs.
- First-pass metabolism
- The reduction in a drug's concentration that happens before it ever reaches general circulation, typically because the liver metabolizes a portion of it immediately after absorption. It's one reason a compound's route of administration (oral versus injected versus topical) changes how much of it actually has an effect — and why studies conducted with one route can't be assumed to apply to another.
- Therapeutic index
- A measure of the gap between an amount of a drug that produces a beneficial effect and an amount that produces toxicity. A narrow therapeutic index means the margin for error is small — which is exactly the kind of thing that has to be established through formal veterinary safety studies for a specific species before any drug should be used, and exactly what's missing for peptides with no published veterinary safety data.
- Receptor agonist
- A molecule that binds to a specific biological receptor and activates it, triggering the receptor's normal downstream effect. Ipamorelin, for example, is described in the founding 1998 research literature as a receptor agonist selective for the ghrelin/growth hormone secretagogue receptor — meaning it activates that specific receptor pathway without significantly activating others nearby.
- Ghrelin / growth hormone secretagogue receptor (GHSR)
- The receptor that, when activated, stimulates the release of growth hormone from the pituitary gland. Several research peptides, including ipamorelin, are studied specifically for how selectively they activate this receptor versus other, unrelated hormone pathways nearby.
- Growth hormone-releasing hormone (GHRH)
- A naturally occurring hormone that signals the pituitary gland to release growth hormone. Some research peptides, such as CJC-1295, are synthetic analogs designed to mimic or extend GHRH's signaling effect — studied in humans and in animal models, but not established for veterinary use.
- Peptide bond
- The chemical bond that links amino acids together into a chain, forming a peptide or protein. It's the basic structural feature that defines what a "peptide" is in the first place — a short chain of amino acids joined by these bonds, as distinct from a small-molecule drug.
- Amino acid sequence
- The specific order of amino acids that makes up a peptide or protein. Even a single amino acid change can alter how a peptide behaves — which is part of why a "similar" peptide isn't necessarily interchangeable with the one that was actually studied.
- Feline drug metabolism deficiency (UGT1A6 pseudogene)
- Domestic cats lack a functional copy of UGT1A6, the liver enzyme most mammals use to clear certain compounds through glucuronidation. Research into the genetics of this defect, published in PLOS ONE, traces it to a mutation shared across all members of the cat family, likely because a highly carnivorous diet made the enzyme unnecessary over evolutionary time. It's the reason cats are so much more sensitive to acetaminophen and aspirin toxicity than dogs or humans — and it means clearance data from another species can't simply be assumed to apply to cats.
- P-glycoprotein (P-gp)
- A transport protein, encoded in dogs by the MDR1/ABCB1 gene, that normally pumps certain drugs out of sensitive tissue like the brain. Dogs with the MDR1 mutation have reduced P-glycoprotein function, which is why they can react much more severely than other dogs to certain medications that rely on this transport system to stay out of the brain.
- Herding-breed drug sensitivity
- The practical name for the clinical pattern seen in breeds with a high prevalence of the MDR1 mutation. According to Washington State University's veterinary diagnostic laboratory, roughly 70% of Collies and about half of Australian Shepherds carry the mutation — meaning breed identity alone is a clinically relevant factor a veterinarian needs to know before prescribing certain drugs, peptide or otherwise.
- Murine model
- A study conducted in mice or rats. Much of the foundational research behind peptides discussed on this site — including the peer-reviewed KPV inflammatory bowel disease research — is murine, meaning it establishes biological plausibility in a lab-rodent species, not evidence about dogs, cats, or horses.
- Angiogenesis
- The formation of new blood vessels from existing ones. It's a biological process central to wound healing and tissue repair, and one of the mechanisms most frequently cited in preclinical research on regenerative peptides such as BPC-157 and GHK-Cu.
- In vitro
- Research conducted outside a living organism — typically in a lab dish or cell culture. It's an important first step in understanding a compound's mechanism, but findings from in vitro research don't automatically hold true in a living animal, which is why it sits at the bottom of the evidence hierarchy compared to in vivo and clinical studies.
- In vivo
- Research conducted within a living organism, as opposed to in a lab dish (in vitro). In vivo animal studies are a step closer to real-world relevance than in vitro work, but a rodent in vivo study still isn't the same as evidence in the specific species — dog, cat, or horse — a pet owner actually cares about.
- Preclinical study
- Research conducted before any human (or veterinary clinical) trials — typically in vitro and animal in vivo work used to establish whether a compound is worth studying further. Nearly all of the research behind the peptides discussed on this site is preclinical; very few have progressed to controlled clinical trials in any species, human or animal.
- Translational research
- Research aimed at moving a finding from the lab (cell cultures, animal models) toward real-world clinical use. A compound can have strong preclinical translational potential and still have no approved clinical application — the gap between "promising mechanism" and "proven treatment" is often where translational research stalls out, sometimes for years or indefinitely.
- Systematic review
- A research summary that follows a defined, reproducible method to gather and evaluate all the available studies on a topic, as opposed to a general narrative summary. Systematic reviews are generally considered stronger evidence than any single study, though a systematic review of weak underlying studies still produces a weak overall conclusion.
- New Animal Drug Application (NADA)
- The formal FDA approval pathway a drug must go through to become an FDA-approved veterinary drug — demonstrating safety and effectiveness for a specific species and condition. Very few peptide-based products currently hold NADA approval for companion-animal use.
- 503A pharmacy
- A state-licensed compounding pharmacy that prepares patient-specific compounded medications based on an individual prescription from a licensed veterinarian or physician, operating under state pharmacy board oversight rather than full FDA drug-manufacturing regulation.
- 503B outsourcing facility
- A compounding facility registered with the FDA that can produce compounded drugs in larger batches, without a patient-specific prescription for each unit, under FDA current good manufacturing practice (cGMP) oversight — a different regulatory tier than a standard 503A compounding pharmacy.
- Current Good Manufacturing Practice (cGMP)
- A set of FDA-enforced quality and manufacturing standards intended to ensure a drug is consistently produced and controlled to appropriate quality standards. FDA guidance on compounding animal drugs from bulk substances (CVM GFI #256) specifically ties its enforcement-discretion policy to compliance with cGMP-related conditions.
- Enforcement discretion
- An FDA policy stance where the agency acknowledges an activity technically falls outside approved regulatory status, but states it does not currently intend to pursue enforcement action against it, provided certain conditions are met. This is the actual legal mechanism behind most veterinary compounding today — not a formal exemption, but a conditional choice not to enforce, which can change with new guidance.
- Compounding from bulk drug substances
- Preparing a compounded drug starting from a raw (bulk) active pharmaceutical ingredient, rather than from an already-FDA-approved finished drug product. This is the specific practice addressed by the FDA's CVM GFI #256 guidance, and it carries a different, more closely scrutinized regulatory status than compounding that starts from an approved product.
- Withdrawal period
- The mandated waiting time after a drug is given to a food-producing animal (such as a horse that could enter the food supply) before that animal's meat or milk can legally be used, to ensure drug residues have cleared to a safe level. AMDUCA requires substantially extended withdrawal periods whenever a drug is used extralabel in a food-producing species.
- Investigational New Animal Drug (INAD)
- A designation that allows a drug still working through the FDA approval process to be studied in animals under a formal investigational protocol, distinct from both an approved drug and an unregulated research-use-only product sold with no oversight at all.
