title: Drug absorption: a practical method to estimate the absorption rate constant.
abstract: A simple equation is proposed to estimate the apparent absorption rate constant (Ka). In order to test this equation, experimental data were obtained following the oral administration of 10 mg/kg of sulfamethazine (SMZ) to ten normal volunteers. The Ka was estimated in three ways (by the proposed equation, by the method of residuals and by the method of the percent unabsorbed versus time plots), and then compared to the value obtained using a NONLIN computer program. The validity of the calculated Ka was further tested by performing computer simulations and estimating the quality of the fit by comparing the coefficient of regression. It was concluded that with the proposed relationship, the estimated values of Ka are closer to the results obtained with the NONLIN method than are the Ka values calculated with graphical methods. Moreover, the calculated method has the advantage that the accuracy of the estimated Ka is not affected by fast absorption, as long as a plasma concentration prior to the peak is known and that the relationship is easy and practical to handle. The one limitation to the proposed method is that it can only be applied to drugs distributed into a single compartment.
mesh_terms: D000328:Adult; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D013418:Sulfamethazine / Q000378:metabolism
chemical_list: D004364:Pharmaceutical Preparations; D013418:Sulfamethazine