Rapid absorption from the urinary bladder of a series of n-alkyl carbamates: a route for the recirculation of drugs.

1 The rate of loss of a series of n-alkyl carbamates from the lumen of the urinary bladders of female rats has been studied. 2 The rate of loss obeys first order kinetics and was not affected by water flux across the bladder wall nor by binding of the carbamates to it. 3 The rate of loss of octyl carbamate was reduced by about 76% by the presence of 5% Tween 80. Histological evidence indicates that this may be due to the formation of a thin luminal lining which may be adsorbed Tween 80 or mucopolysaccharide material. 4 The absorption rate of the carbamates was limited by their hydrophilicity but reached a plateau for the more lipophilic homologues with a half life for loss of approximately 10 min. 5 The implications of these results with regard to the recirculation of unmetabolized drugs and hydrolysed conjugates of drugs, the systemic absorption of intravesically applied cancer chemotherapeutic agents and bladder wall permeability to carcinogens are discussed.