See 24 h. urine collection instruction:
3 days before collection, avoid the following foods : cocoa, coffee, tea, chocolate, nuts, citrus fruits, products containing vanilla. No nicotine consumption. Avoid psychological and physical stress. If possible, no use of: Nitroglycerin, alpha-methyldopa, MAO inhibitors, tricyclic antidepressants, L-dopa, no acute administration of calcium antagonists, theophylline, nasal drops, bronchodilators, appetite suppressants, cough drops