The efficacy of some of the newer creatine formulations is a real concern for many athletes; with good reason. One of the most popular creatine serums currently on the market has recently come under harsh criticism by the scientific community. We analyzed the validity of these allegations in a recent issue of the Creatine Newsletter . Read the first part of a two-part newsletter series discussing a scientific study that compared the ergogenic effects of ordinary creatine monohydrate powder with that of a popular creatine serum; part two compares the ability of the same brand of creatine serum to raise serum creatine levels with reference to the elevation observed with creatine monohydrate powder.
The structure of cyclocreatine is fairly flat (planar), which aids in passive diffusion across membranes. It has been used with success in an animal study, where mice suffered from a SLC6A8 (creatine transporter at the blood brain barrier) deficiency, which is not responsive to standard creatine supplementation.  This study failed to report increases in creatine stores in the brain, but noted a reduction of mental retardation associated with increased cyclocreatine and phosphorylated cyclocreatine storages.  As demonstrated by this animal study and previous ones, cyclocreatine is bioactive after oral ingestion   and may merely be a creatine mimetic, able to phosphorylate ADP via the creatine kinase system. 
Creatine has once been implicated in increasing DHT , a more potent androgen that is implicated in power output (good) but also hair loss in susceptible men and prostate cancer (bad). While the increase in DHT and hair loss is not a concern if you have a robust head of hair, those with a receding hairline may experience an acceleration of their rate of hairline receding when using any androgenic supplement that can increase DHT. Despite the concerns with creatine supplementation and hair loss, no trials have been conducted on the topic. Although DHT itself is a negative stressor, creatine accumulation in hair cells is protective of them secondary to increasing energy production; the ultimate effect of creatine supplementation in men with a receding hairline has not been investigated.