In humans, the end product of purine metabolism is uric acid. End product of purine metabolism in non-primate mammals is:
Uric acid
Ammonia
Urea
Allantoin
Humans conve adenosine and guanosine to uric acid. Adenosine is first conveed to inosine by adenosine deaminase. In mammals other than higher primates, uricase conves uric acid to the water-soluble product allantoin. However, since humans lack uricase, the end product of purine catabolism in humans is uric acid. Ref: Rodwell V.W. (2011). Chapter 33. Metabolism of Purine & Pyrimidine Nucleotides. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.