Glossary
Plain-English definitions for terms used across PepStack. No jargon without explanation.
Amino Acid
The building blocks of proteins and peptides. There are 20 standard amino acids that combine in different sequences to form peptides and proteins.
Bioavailability
The percentage of a substance that enters your bloodstream and is available to have an active effect. Different administration routes affect bioavailability.
Clinical Trial
A research study that tests how well new medical approaches work in people. Trials go through phases (I-IV) with increasing numbers of participants.
Compounding Pharmacy
A pharmacy that creates customized medications by mixing ingredients. Some peptides are available through compounding pharmacies with a prescription.
Contraindication
A condition or factor that makes a particular treatment or procedure inadvisable. For example, pregnancy is a contraindication for most peptides.
Evidence Tier
PepStack's rating system (1-5) indicating the strength and quality of scientific evidence supporting a peptide's effects. Tier 1 = FDA approved, Tier 5 = preclinical only.
FDA Approval
Formal authorization by the U.S. Food and Drug Administration for a drug to be marketed and sold for a specific medical use, based on clinical trial evidence.
Half-Life
The time it takes for half of a substance to be eliminated from your body. A longer half-life means the substance stays active longer.
Intramuscular (IM)
An injection administered directly into a muscle. Some peptides are given via intramuscular injection for faster absorption.
Mechanism of Action
How a substance produces its effects in the body --- the specific biochemical interaction through which a drug or peptide works.
Peptide
A short chain of amino acids (typically 2-50). Peptides are smaller than proteins and can act as signaling molecules in the body, triggering specific biological responses.
Phase I Trial
The first stage of clinical testing, focused on safety and dosing in a small group (20-80 people). Tests whether a treatment is safe, not whether it works.
Phase II Trial
Tests whether a treatment works for a specific condition in a larger group (100-300 people). Also continues to evaluate safety.
Phase III Trial
Large-scale trials (1,000-3,000+ people) that confirm effectiveness, monitor side effects, and compare to existing treatments. Required for FDA approval.
PMID
PubMed Identifier --- a unique number assigned to each article in the PubMed database. Used to find and verify specific research papers.
Preclinical
Research conducted before human testing, including laboratory (in-vitro) and animal studies. Preclinical results do not guarantee the same effects in humans.
Protocol / Studied Dosage
A dosing context including amount, frequency, route of administration, and duration as described in a cited study or source. Listed for reference, not as treatment guidance.
Randomized Controlled Trial (RCT)
A study where participants are randomly assigned to receive either the treatment or a placebo. Considered the gold standard for clinical evidence.
Reconstitution
The process of mixing a freeze-dried (lyophilized) peptide powder with sterile water or bacteriostatic water to create an injectable solution.
Subcutaneous (SubQ)
An injection given into the fatty tissue just beneath the skin. The most common administration route for peptides used outside clinical settings.
503A Pharmacy
A traditional compounding pharmacy that creates custom medications based on individual prescriptions from a licensed prescriber. Regulated under Section 503A of the Federal Food, Drug, and Cosmetic Act.
503B Outsourcing Facility
A compounding facility that can produce larger batches of medications without individual prescriptions. Subject to FDA oversight and current good manufacturing practice (cGMP) requirements.
Accelerated Approval
An FDA pathway that allows earlier approval of drugs for serious conditions based on a surrogate endpoint (like a lab measurement) rather than a clinical outcome. May require post-approval confirmatory trials.
Biosimilar
A biologic product that is highly similar to an already-approved biologic (the reference product) with no clinically meaningful differences in safety or effectiveness.
Category 1 / Category 2 (FDA Compounding)
FDA classifications for bulk drug substances used in compounding under Section 503A. Category 1: Substances under FDA evaluation that fall within a specific interim enforcement policy allowing their use in compounding while review continues. Category 2: Substances the FDA has evaluated and determined present significant safety risks; FDA does not intend to apply the Category 1 interim policy to these substances.
GLP-1 (Glucagon-Like Peptide-1)
A hormone produced in the gut that stimulates insulin release, suppresses glucagon, slows gastric emptying, and promotes satiety. GLP-1 receptor agonists (like semaglutide and liraglutide) are FDA-approved for diabetes and weight management.
GnRH (Gonadotropin-Releasing Hormone)
A hormone produced in the hypothalamus that controls the release of reproductive hormones (LH and FSH). GnRH agonists and antagonists are used in fertility treatment and hormone-sensitive cancers.
Immunogenicity
The ability of a substance to provoke an immune response. For peptide therapeutics, immunogenicity can lead to the body producing antibodies against the drug, potentially reducing its effectiveness or causing allergic reactions.
Orphan Drug
A drug developed for a rare disease (affecting fewer than 200,000 people in the US). Orphan Drug designation provides incentives including tax credits, reduced fees, and 7 years of market exclusivity.
WADA (World Anti-Doping Agency)
The international organization that maintains the list of prohibited substances in sport. Many peptides, including growth hormone secretagogues and certain research peptides, are on the WADA prohibited list.