In humans, the end product of purine metabolism is uric acid. End product of purine metabolism in non-primate mammals is:

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.