A method for assaying activity of the enzyme spermidine/spermine N1-acetyltransferase (SSAT) uses SSAT substrates by detecting their acetylated forms. SSAT substrates may include rimantadine and tocainide wherein their metabolism occurs in part by the action of the inducible enzyme SSAT to produce the acetylated metabolites N-acetylrimantadine and N-acetyltocainide respectively. SSAT activity may be correlated to pathologic conditions.