โ Scribed by Riegelman, Sidney ;Crowell, Wilfred
No coin nor oath required. For personal study only.
The rectal absorption rates of sodium iodide and the sodium salt of 2,4,6-triiodophenol in suppository bases at various pH values and in the presence of surfaceactive agents and polyethylene glycol additives were determined by continuous external detection at the site of insertion. The rate of sodium iodide absorption is accelerated in the presence of surfactants and appears to be roportional to the surface tension lowering and the peptizing action of their s d a c e active components. The rate of abso tion of the phenolate is retarded by the presence of surfactants. Hydrolysis and szsequent solubilization of the free phenol is postulated to explain this effect.
N THE FIRST PAPER of this series (I), a method (using a female rat) was reported for the direct and continuous external detection of the rate of rectal absorption of drugs from suppository vehicles. The rate of absorption of sodium iodide, iodoform, and 2,4,6-triiodophenol tagged with iodine-131 could be followed by virtue of the gamma emission from the radioactive source which was detected by a scintillation counter in conjunction with an autoscaler. The absorption data appeared to follow a pseudo-kst order rate process when corrected for the effect of two concomitant events. The drug is continuously returning to the environments of the absorption site and is detected there by the counter. Also within the confined rectal segment to which the suppository was limited, the rate limiting step in the overall absorption process is assumed to be the diffusion of the drug within the vehicle. An equation was presented which rectified the data for analysis to conform to a pseudo-first order rate process. An alternative to the use of the corrected data is the analysis of the initial portion of the uncorrected data where each of the factors causing deviation would be at a minimum. Analysis of the initial data probably results in an absorption half-life which is slightly too long, due to the small amount of curvature present even in the earliest points. While the absolute values of the specific rate constants may differ with each method of analysis, the relative comparison of the data by either method results in identical conclusions. For this reason, the simpler method of analysis using the initial data has been adopted in this report.
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