Phosphocreatine
The phosphorylated form of creatine that serves as the muscle's rapid-turnover energy reserve, regenerating ATP during short bursts of intense effort. As an intravenous drug (exogenous phosphocreatine) it is used in some countries for cardiac protection; as a supplement, ordinary creatine monohydrate is the practical way to raise muscle phosphocreatine.
01 Overview
Phosphocreatine (creatine phosphate) donates its high-energy phosphate to ADP via creatine kinase, rapidly regenerating ATP during the first seconds of maximal exercise and buffering cellular energy in the heart and brain. Muscle phosphocreatine stores are the primary reason oral creatine supplementation improves high-intensity performance.
Exogenous phosphocreatine is given intravenously as a cardioprotective agent in some countries (notably Russia, China and parts of Europe) during cardiac ischaemia and surgery, with regional evidence for reduced arrhythmia and myocardial injury. It is not approved in the US or UK. For athletes, raising intramuscular phosphocreatine is achieved practically through oral creatine rather than by taking phosphocreatine itself.
02 Mechanism
Acts as an immediate phosphate donor to regenerate ATP from ADP via creatine kinase, buffering energy supply during high-intensity effort and ischaemia in muscle, heart and brain.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Cardioprotection | 1–2 g/day | IV | IV dosing used regionally in cardiac ischaemia; not approved in US/UK. |
| Via creatine monohydrate | 3–5 g/day | Oral | Practical route to raise muscle phosphocreatine is oral creatine, not PCr itself. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Rapid ATP regenerationBuffers ATP during short, maximal efforts; the basis of creatine's ergogenic effect. | Clinical | ||
| Myocardial protection (regional use)IV phosphocreatine reduced arrhythmia and injury markers in regional cardiac studies. | modest | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site / infusion reactionsLocal reactions or hypotension with rapid IV infusion. | Mild | Uncommon | Observational | |
| Water retention (oral creatine route)Intramuscular water retention and small weight gain when loading via oral creatine. | Mild | Common | Clinical |