Precipitate formation of some sulfonated tetrazolthiomethyl cephalosporins with basic chemicals.

Cephalosporins containing a thiomethyltetrazole-sulfomethyl or sulfoaminoethyl substituent at the three-position react in aqueous solution with protamine or quinine to form a precipitate. This phenomenon may provide some insight into their pharmacokinetics and modes of action especially as it relates to the high and prolonged serum levels and high degree of serum protein-binding.