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P21 Cycling: Dosage Comparison
P21 cycling protocols vary in dose, frequency, and washout structure depending on research objectives. This table compares the most widely adopted approaches in preclinical neuroplasticity research and their observed tolerance profiles. Continuous Daily (No Cy
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- P21 cycling protocols vary in dose, frequency, and washout structure depending on research objectives. This table compares the most widely adopted approaches in preclinical neuroplasticity research and their observed tolerance profiles.
- Continuous Daily (No Cycling)
- 1–5 mg/kg SC
- None
- Attenuation begins week 5–6; plateau by week 8
- Short-term cognitive studies ≤4 weeks
- Standard in early research but not optimal for long-term protocols; tolerance predictable and measurable
- 5-On-2-Off Standard Cycle
- 0.5–5 mg/kg SC
- 2.5:1
- Minimal attenuation through week 12+
- General neuroplasticity research, extended timelines
- Most balanced approach; maintains response across longest timelines with practical dosing schedule
- 7-On-3-Off Extended Cycle
- 2.3:1
- Minimal attenuation through week 10–12
- Research requiring fewer interruptions (e.g., behavioral enrichment studies)
- Slightly higher tolerance risk than 5-on-2-off but acceptable for protocols where twice-weekly washout is impractful
- 3-On-4-Off High-Intensity Burst
- 5–10 mg/kg SC
- 0.75:1
- No measurable tolerance; limited by cumulative dose
- High-dose trials, receptor saturation studies
- Prevents tolerance but reduces total exposure; used when maximizing peak effect matters more than sustained elevation
- 6-On-2-Off (Over-Extended)
- 2–5 mg/kg SC
- 3:1
- Attenuation begins week 6–8
- Not recommended for >8-week protocols
- Ratio too high; tolerance develops nearly as fast as continuous dosing despite washout presence