Biological availability of sulfamethoxypyridazine and sulfisomidine polymers.

Dissolution rates and apparent solubilities of forms I, II and III of Sulfamethoxypyridazine (1) and forms I and II of sulfisomidine (2) were determined in water at 37 degrees C. The ratios of apparent solubilities of I:II:III for 1 forms and I:II for 2 forms were 1:1.18:1.25 and 1:1.32 respectively. Upon long contact of 2 with water the ratio of II:I decreased. This has been attributed to gradual transformation of 2 from form II to I. Gastrointestinal absorption of form III of 1, in human volunteers, was studied in comparison with the more stable form I. The same study was carried out on forms I and II of 2. Data were correlated and expressed in availability rate constants (K1), applying the one compartment open: model. This and other parameters show that form III of 1 is 1.4 times as much absorbed as form I, and that the availability of the metastable form II of 2 is 1.2 times as much absorbed as the stable form I.

Rapid and sensitive colorimetric determination of cobalt(II).

A highly selective and sensitive spectrophotometric determination of cobalt (II) was developed. 7-Nitroso-8-hydroxyquinoline-5-sulfonic acid sodium salt was used as the chromogenic reagent for color development. Although other metals form colored chelates with the ligand, it was possible to develop a selective method using McIlvaine's pH 8 citric acid-phosphate buffer. Under these conditions, iron(II), iron (III), copper (II), zinc (II), and manganese (II), minerals likely to be compounded with cobalt (II) in geriatric formulations, do not interfere with the precision of the method or the color development. Calcium (II) and magnesium (II) do not form colored chelates with the used ligand. Hormones, vitamins, and additives likely to be present along with the cobalt ion in pharmaceutical formulations do not interfere. The sensitivity is 0.37 mug of cobalt (II)/ml of sample solution.

Rapid, sensitive colorimetric method for determination of ethinyl estradiol.

A colorimetric procedure, based on the formation of an azo dye by condensation of diazotized 5-chloro-2,4-dinitroaniline with ethinyl estradiol, was developed. An alkaline solution of ethinyl estradiol is reacted with the reagent, and the resulting color is measured at 450 nm. Absorbance versus concentration is linear up to 10 mug/ml; the lower limit of detection is 1 mug/ml under the conditions studied. Replicate analysis showed good agreement, and an average recovery of 99.6 +/- 0.3% was obtained for analyses of synthetic mixtures. Vitamins and minerals likely to be present along with ethinyl estradiol in certain geriatric formulations, as well as ordinary tablet excipients and coating materials, do not interfere with the precision of the method or development of the color. The method is applicable to progestin-estrogen preparations. Assay results on various single-component as well as contraceptive commercial samples are reported.