Nitrogenous waste is excreted primarily as urea. Nucleotides contain either a purine or a pyrimidine nitrogenous base. Urea and creatinine are nitrogenous end products of metabolism. They excrete nitrogen as the complex nitrogenous waste compound uric acid, and related derivatives. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. They have a urinary bladder and nitrogenous waste products are excreted primarily as urea. The bladder is small as nitrogenous waste is excreted as uric acid. The primary nitrogenous waste product in arachnids is guanine. Ammonia (NH) is a common byproduct of the metabolism of nitrogenous compounds. The main nitrogenous waste product is ammonia. The inhibitor hinders the oxidation of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). Tropane is a nitrogenous bicyclic organic compound. Animals must excrete this in the form of nitrogenous compounds. They consist of a nitrogenous base attached to a sugar-phosphate backbone. Guanidine can be thought of as a nitrogenous analogue of carbonic acid.