The present invention is concerned with deuterium-enriched pyrimidine compounds of formula I, their derivatives and pharmaceutically acceptable salts and methods of use thereof, The compounds of formula I are useful for the prevention and treatment of liver fibrosis and cirrhosis, hepatocellular carcinoma, neuroendrcrine neoplasia including metastasis and fibrosis fibrotic processes associated with neuroendocrine cell dysregulation for example Crohn's disease, pulmonary arterial hypertension, pulmonary hypertension associated with chronic obstructive pulmonary disease (COPD), right ventricular hypertrophy, pulmonary vascular remodeling, asthma, cystic fibrosis, hypertension, ischemic stroke, angina pectoris, congestive heart failure, arrhythmia, arterial fibrillation, gastrointestinal disorders, anxiety, depression, stress disorders, post-traumatic stress disorder, obsessive compulsive disorders, demyelinating diseases, acute or chronic cerebrovascular damage, cerebral infarction, subarachanoid hemorrhage, and cerebral edema, neuropathological diseases and cardiovascular system regulation.