Understanding Peptide Half-Life and Dosing Frequency
How long a peptide remains active in the body determines how often it needs to be administered. Understanding half-life is essential for effective research protocols.
Half-life is one of the most important concepts in peptide research. It determines dosing frequency, influences protocol design, and affects the consistency of research outcomes. This guide explains peptide half-life in practical terms.
What is Half-Life?
Half-life (t½) is the time required for the concentration of a substance in the body to decrease by 50%. After one half-life, 50% of the original amount remains. After two half-lives, 25% remains. After three half-lives, 12.5% remains, and so on.
Half-Life Decay Example
Starting with 100 units of a peptide with 4-hour half-life:
| Time | Half-Lives | Amount Remaining |
|---|---|---|
| 0 hours | 0 | 100 units (100%) |
| 4 hours | 1 | 50 units (50%) |
| 8 hours | 2 | 25 units (25%) |
| 12 hours | 3 | 12.5 units (12.5%) |
| 16 hours | 4 | 6.25 units (6.25%) |
Common Peptide Half-Lives
Peptide half-lives vary dramatically—from minutes to over a week:
| Peptide | Half-Life | Typical Dosing |
|---|---|---|
| CJC-1295 (no DAC) | ~30 minutes | 1-3x daily |
| Ipamorelin | ~2 hours | 1-3x daily |
| BPC-157 | ~4 hours | 1-2x daily |
| TB-500 | ~24 hours | 2x weekly |
| CJC-1295 (with DAC) | ~8 days | 1-2x weekly |
| GLP1-S | ~7 days | 1x weekly |
Factors Affecting Half-Life
Molecular Size
Larger peptides generally have longer half-lives due to slower renal clearance.
Modifications
Chemical modifications (PEGylation, lipidation, DAC) can dramatically extend half-life.
Protein Binding
Peptides that bind to plasma proteins are protected from rapid degradation.
Administration Route
Subcutaneous injection provides slower absorption than IV, affecting apparent half-life.
Dosing Frequency Guidelines
The goal of dosing frequency is typically to maintain relatively stable levels. General guidelines:
- Short half-life (<4 hours): Multiple daily doses, or accept fluctuating levels
- Medium half-life (4-24 hours): Once or twice daily dosing
- Long half-life (>24 hours): Weekly or twice-weekly dosing
Important Consideration
Steady-state concentrations are typically reached after 4-5 half-lives of consistent dosing. This is important for research protocols requiring stable peptide levels.
Practical Implications
Understanding half-life helps you:
- Design consistent, reproducible research protocols
- Calculate appropriate washout periods between experiments
- Determine optimal timing for blood sampling or measurements
- Predict accumulation with repeated dosing