N-Acetyl-DL-penicillamine and acetaminophen toxicity in mice

N-Acetyl-DL-penicillamine (IIIb), a structural analog of N-acetyl-L-cysteine (IIIa), did not protect mice from lethal doses of acetaminophen (I), whereas IIIa offered protection. This lack of efficacy of IIIb probably is due to the decreased nucleophilicity of its sulfhydryl group compared to that of IIIa, the probable involvement of cysteine in and conjugate addition to the reactive intermediates of I, and the absence of metabolic conversion of IIIb to inorganic sulfate.