In vitro uptake of oral contraceptive steroids by magnesium trisilicate

✍ Scribed by Saleh A. H. Khalil; M. Iwuagwu

• Publisher: John Wiley and Sons
• Year: 1978
• Tongue: English
• Weight: 342 KB
• Volume: 67
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600670250

✦ Synopsis

Some steroids used in oral contraceptives were adsorbed significantly by magnesium trisilicate. The adsorption affinity followed the sequence: ethindrone greater than mestranol greater than norethindrone greater than ethinyl estradiol. Adsorption data obtained at relatively low initial concentrations fitted a Langmuir plot; the values for monolayer adsorption ranged between 0.24 and 0.32 mg/g. At higher concentrations of the steroids, multilayer adsorption occurred. The results of desorption experiments made at 37 degrees in water and 0.05 N HCl suggested that desorption was incomplete and depended on the amount of steroid adsorbed. During the dissolution testing of a brand of contraceptive tablets containing norethindrone acetate, the presence of 0.5% (w/v) magnesium trisilicate in the medium resulted in almost complete reduction in the amount of the steroid remaining in solution after 1 hr.