??Miyamoto et al.57 studied the effects of surfactants and bile salts on the gastrointestinal absorption of antibiotics using an in situ rat-gut perfusion technique.Some surfactants increase the rate of intestinal absorption, whereas others decrease it. Some of these effects may result from alteration of the membrane by the surfactant.in the effective concentration] Quaternary ammonium compounds are examples of surface-active agents that in them-se ies posses antibacterial activity." This may depend in par tant. The agents are adsorbed on the cell surface and suppos ody bring about destruction by increasing the permeabili or "eakiness" of the lipid cell memorase Death then occus irough a loss of essential mambrant the el. Boin to the negative and gram-postite rigs rems are suspink.?A surfactant may affect the activity of a drug or may itself exert drug action As an example of the first case, the penetration of hexylresorcinol into the pinworm
?Ascaris,
?is increased by the presence of a low concentration of sur-factant.to the action of the cation quaive any compound, nand anionic agents attack grin quaterine organisms more

?than gram-negative bacteria.