Citicoline (cytidine 5'-diphosphocholine, CDP-choline) is an endogenous intermediate in the biosynthesis of phosphatidylcholine, a major membrane phospholipid. In the body it is understood to be rapidly hydrolysed and dephosphorylated to cytidine and choline, which enter the brain separately and are used to resynthesise CDP-choline inside brain cells. Preclinical studies have examined citicoline in models of cerebral ischaemia, retinal ganglion cell injury and aminoglycoside damage to auditory hair cells. A 2014 review concluded that there was at that time no adequate description of the mechanism or mechanisms behind its pharmacological actions.