P-21 — Clinical Reference

**⚠ Educational reference only — not medical advice.** This article is for research and educational reference. Always consult your own physician before considering any peptide protocol. See the full Disclaimer at the end of this article. ## Introduction P-21 is an IGF-1-derived peptide investigated in preclinical neuroscience, developed in the laboratory of Pedersen and colleagues. Structurally inspired by a portion of IGF-1 with modifications intended to retain neurogenic and cognitive-supportive activity while reducing the systemic anabolic and proliferative effects of full IGF-1. Strictly investigational; no approved clinical indication. ## Mechanism of Action Reported to enhance hippocampal neurogenesis, reduce neuroinflammatory markers, and improve performance on memory-dependent behavioral tasks in rodent models. Designed to lack the canonical IGF-1-receptor binding profile that drives the hypoglycemic and mitogenic effects of full IGF-1, though human receptor-level characterization is incomplete. ## Research Indications Preclinical: cognitive aging, Alzheimer's-disease models, traumatic brain injury recovery. No human efficacy data of clinical-grade rigor. ## Reconstitution Typical 5 mg lyophilized vial: add **2.5 mL of bacteriostatic water**, swirl gently. Final concentration **2000 mcg/mL (2 mg/mL)** — each 0.05 mL (5 units on a U-100 insulin syringe) delivers 100 mcg. ## Dosing Protocol (research literature) Human dosing is not well characterized. Research protocols extrapolated from preclinical work typically use **100–250 mcg subcutaneously once daily** for **8–16 weeks** before reassessment. Some protocols cycle 5 days on / 2 days off. ## Administration Subcutaneous into abdominal fat, rotating sites. AM dosing aligns with cognitive-endpoint study designs. ## Storage & Handling Lyophilized: refrigerate (2–8°C). Reconstituted: refrigerate; stable approximately **14–21 days**. Protect from light. ## Side Effects Human safety data are limited. Theoretical concerns include any unintended IGF-1-receptor-mediated effects (hypoglycemia, mitogenic stimulation) and CNS effects not systematically characterized. ## Contraindications Pregnancy, lactation, active malignancy, poorly controlled diabetes. ## Monitoring Baseline cognitive instruments (MoCA or domain-specific tasks appropriate to the protocol), fasting glucose, HbA1c. Re-measure at 8 and 16 weeks. ## Disclaimer **This article is for informational and research-reference purposes only.** Nothing in this document constitutes medical advice, a prescription, or a recommendation from a physician. The reconstitution, dosing, and protocol information above reflects ranges commonly cited in published research and clinician-directed protocols — it is provided as reference material only, not as instructions, an endorsement of off-label use, or a substitute for individualized medical evaluation. **Customers should do their own research and consult their own physician** before considering any peptide protocol. Whether a given compound is appropriate for an individual — and at what dose, for what duration, and alongside what monitoring — is a decision that only a licensed clinician with knowledge of that individual's medical history, current medications, and conditions can make. The platform and the author make no claim that any compound described here is safe, effective, or appropriate for any particular person or purpose, and accept no responsibility for outcomes arising from self-directed use of the information.