Abstract
Probiotics or biotherapeutic agents can influence physiology through direct or indirect effects occurring in the gastrointestinal tract. Knowledge on their pharmacokinetics is needed 1) to answer the questions how much probiotic should be consumed?, how often?, how long?; 2) to correlate the effects with the concentration of the probiotic at the target site; 3) to validate hypotheses such as “a probiotic should be of human origin, … have a high survival capacity, … adhere to the intestinal epithelium” …; 4) to anticipate the effects of other probiotics; 5) to establish what concentrations should be present in the commercial preparations; 6) for safety. Some in vitro models have been developed to predict the survival of probiotics in vivo or their adherence to the intestinal epithelium, however, the best way to establish the pharmacokinetics of a probiotic is to measure it in vivo. Three techniques can be used: collection of feces, pixigraphy, and intestinal intubation. The use of transit markers such as spores of Bacillus stearothermophilus is necessary to study the potential for probiotics to colonize (i.e. to persist for longer period than the inert marker). Knowledge on the pharmacokinetics of probiotics is reviewed. Some strains can adhere to cell lines such as CaCo2 or HT29. The survival of ingested probiotics differs greatly between genus and strains. Some strains are rapidly destroyed in the stomach while others such as some Bifidobacterium sp. or Lactobacillus sp. survive till feces.
