In vitro adsorption study of fluoxetine onto activated charcoal at gastric and intestinal pH using high performance liquid chromatography with fluorescence detector.

BACKGROUND: This in vitro investigation was performed to study the adsorption characteristics of fluoxetine to activated charcoal and its commercial formulation Carbomix powder in simulated gastric (pH = 1.2) and intestinal (pH = 7.2) fluid environments.

METHODS: Solutions containing fluoxetine and charcoal were incubated at 37 degrees C for one hour. Reversed phase high performance liquid chromatography was used for the determination of free fluoxetine concentrations (range 0.2-8 micrograms/mL) in the diluted filtrate.

RESULTS: The maximum adsorption capacities at pH 1.2 for activated charcoal and Carbomix were 223 and 333 mg/g, respectively; at pH 7.2 they were 301 and 453 mg/g, respectively. The affinity constant values at pH 1.2 of activated charcoal and Carbomix were 441 and 122 L/g, respectively, while at pH 7.2 they were 482 and 589 L/g, respectively, indicating a strong binding of fluoxetine onto charcoals.

CONCLUSIONS: Relative to the toxic and lethal doses in cases of fluoxetine intoxications, both types of charcoals tested were found effective for adsorption at gastric and intestinal pH. Adsorbed fluoxetine was significantly increased at intestinal pH, consistent with predominant adsorption of the undissociated form of the drug. We conclude that activated charcoal and Carbomix have adsorptive properties appropriate to medical treatment in cases of fluoxetine overdose.