A comparative study of free plasma choline levels following intramuscular administration of L-alpha-glycerylphosphorylcholine and citicoline in normal volunteers.

L-alpha-glycerylphosphorylcholine (alpha-GPC) is a recently developed cognitive enhancer whose mode of action is considered to involve the release of free choline, which is then utilized for acetylcholine and phosphatidylcholine biosynthesis in the brain. The purpose of this study was to evaluate the profile of free plasma choline levels following a single i. m. dose of alpha-GPC in 12 normal volunteers. Citicoline (CTC), which also acts as a choline precursor, was included for comparison purposes. Each subject was studied on three randomized occasions, (i) in a control day in the absence of drug administration (to evaluate the plasma level profile of endogenous choline), (ii) after i. m. alpha-GPC (1,000 mg) and (iii) after i. m. CTC (1,000 mg) respectively, with a wash-out period of at least 1-week between sessions. Blood samples for plasma choline HPLC determinations were collected at regular intervals over a 6 h period. In the control session, plasma choline levels remained stable during the sampling period. The administration of alpha-GPC was associated with a rapid rise in plasma choline, peak levels being usually observed at the first (0.25 h) or second (0.5 h) sampling time after the injection. Thereafter, the concentration of choline declined gradually and returned to near baseline values at the end of the observation period. After the administration of CTC, plasma choline levels showed a similar time course but were considerably lower than those observed after the administration of alpha-GPC. Pharmacokinetic parameters calculated after subtracting the zero time concentration from all post-drug values indicated that exogenously derived choline declined in plasma with a half-life of 0.5 to 6.2 h, without any significant difference between alpha-GPC or CTC. Choline AUC values after alpha-GPC were significantly higher than those observed after CTC, but the difference was no longer significant when AUCs were corrected for the different choline content of the two preparations (405 mg for alpha-GPC vs 213 mg for CTC). It is concluded that the i. m. administration of alpha-GPC provides an effective means of increasing plasma choline levels.