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Biomedical subjects

S Kushinsky

Publications and source records attributed to S Kushinsky.

At least 19 recordsLinked to original sources
PubMed1989

Pharmacokinetics of norethindrone: effect of particle size.

In 24 healthy women between the ages of 19 and 35 years who had not used oral contraceptive preparations for at least 60 days, it was found that the smaller the particle size of norethindrone (NET) administered, the higher was the plasma NET level obtained. Three different preparations having particle sizes of NET smaller than 250 microns, 44 microns or 10 microns were tested in a crossover pattern. The time required to reach maximum plasma concentration (Tmax) became shorter with decreasing particle size, 1.69 hr, 1.52 hr and 1.06 hr, respectively. As particle size was reduced, the maximum NET plasma concentration (Cmax) increased for the 3 different 1 mg NET preparations, i.e. 8.66 ng/ml, 10.53 ng/ml and 15.73 ng/ml. A trial with a 2 mg NET preparation made with NET utilizing the 44 microns same material displayed a Tmax similar to the 1 mg NET preparation having the same particle size while the Cmax reached a level of 17.56 ng/ml. The area under the plasma concentration versus time curve from 0-24 hrs and the extrapolated total area under the curve, increased with decreasing particle size. The use of a smaller particle size allows for more rapid dissolution or oral contraceptive tablets when measured in vitro; however, there is no evidence that such faster dissolution leads to a significant difference in efficacy. Oral contraceptive tablets have, since their inception, utilized both large and small NET particle size material in various preparations.

Administration, Oral↗
PubMed1989

Bioequivalence of two oral contraceptive drugs containing norethindrone and ethinyl estradiol.

Two oral contraceptive drugs, Formulation A and Formulation B, both of similar hormonal content, were compared with each other to determine if they were bioequivalent. Both drugs contain 1 mg of norethindrone (NET) and 0.035 mg of ethinyl estradiol (EE). Application of an interval test for the ratio of the computed parameter means demonstrated equivalence for the two formulations with respect to the 0-24 hour area under the plasma level versus time curve (AUC24), the total area under the curve (AUCtot) and for the maximum plasma concentration (Cmax) for both ethinyl estradiol and norethindrone. The data support the hypothesis for bioequivalence of the two formulations with respect to total absorption.

Adult↗
PubMed1988

Radioimmunoassay of detirelix ([ N-Ac-D-Nal(2)1,D-p-Cl-Phe2,D-Trp3, D-hArg(Et)6(2),D-Ala10]-luteinizing hormone-releasing hormone) in plasma or serum.

A procedure for the radioimmunoassay (RIA) of detirelix in plasma or serum at concentrations as low as 0.15 ng/ml is described. Antiserum was produced by deacetylation of the N-terminus amino groups of detirelix and coupling this analog to bovine serum albumin with a carbodiimide and immunizing rabbits with the resultant conjugate. For RIA, 125I-labeled detirelix was used as the tracer and a double antibody procedure was used to separate the free and bound fractions. No purification of samples was required prior to RIA. Accuracy of the method was assessed by adding known quantities of detirelix to detirelix-free plasma and determining the ratio of measured to added analyte. Linear regression analysis for the concentration range 0.15-150.0 ng/ml yielded a regression equation of y = 0.88 X +1.46 and a correlation coefficient of 0.996. Additional validation was obtained from an in vivo study in which [14C]detirelix was administered to monkeys and plasma clearance profiles were determined by RIA and an HPLC-radiochemical method. The RIA results were in good agreement with those obtained by the HPLC method.

Animals↗
PubMed1987

Capillary column gas chromatographic method using electron-capture detection for the simultaneous determination of nicardipine and its pyridine metabolite II in plasma.

A rapid, specific and direct method based on capillary column gas chromatography with electron-capture detection is described for the simultaneous determination of nicardipine, a new calcium antagonist, and its pyridine metabolite II in human plasma. In this method, the nicardipine, its pyridine metabolite II and internal standard are extracted from the plasma and then partially purified by acid-base partitioning prior to the final injection onto the capillary column gas chromatograph for quantification by means of an electron-capture detector. The quantification limit of the method is 1 ng/ml of plasma for both nicardipine and its pyridine metabolite II. The coefficients of variation for nicardipine and the pyridine metabolite II at concentrations of 1-50 ng/ml are less than 7% and less than 9% (n = 4), respectively. The method has been validated against a previously developed high-performance liquid chromatographic method (sensitivity 5 ng/ml).

Chromatography, Gas↗
PubMed1986

Bioequivalence of norethindrone and ethinyl estradiol for two different weight tablets with the same hormonal content.

Two tablets of differing weights, 100 mg (A) and 50 mg (B), of an oral contraceptive drug (OC) were compared with each other and to a solution (C) of the same components. The composition of the OC consisted of 1 mg of norethindrone (NET) and 0.035 mg of ethinyl estradiol (EE2). Both tablets were shown to differ from the solution, which was more rapidly absorbed, but were not significantly different from each other. Formulation means for NET and EE2, for each of the two products, were similar. Application of an interval test for the ratio of computed parameters demonstrated equivalence of the two formulations with respect to 0-24 hr area under the curve (AUC24) and total area under the curve (AUC+o+) for both NET and EE2 and with respect to concentration maximum (Cmax) for EE2. The data support the hypothesis for bioequivalence of the two formulations with respect to total absorption.

Absorption↗
PubMed1977

A non-chromatographic radioimmunoassay of testosterone in serum.

Convenient methodology based on separation of testosterone from non-alcoholic neutral steroids by means of a sulfation procedure has been developed for the radioimmunoassay (RIA) of testosterone in male and in female serum. When coordinated with our previously published non-chromatographic procedure (1) for the RIA of estrone and 17 beta-estradiol in serum all 3 steroids can be determined in the same specimen. With only minor modification (14) progesterone also can be determined. Validation of the procedure was based on: 1. agreement between results obtained using TLC and sulfation to fractionate testosterone (r=0.99; b=1.03), 2. accurate recovery of different quatities of testosterone added to serum, 3. independence of the concentration of testosterone and volume of serum used for assay, 4. low procedural blanks (1.1+/-0.7 pg), 5. low intra-assay (4.7-4.8%) and interassay (4.8-8.8%) variability and 6. correspondence of observed values for testosterone in male serum (7.00+/-2.03 ng/ml) and in femal serum (420+/-115 pg/ml) with those reported previously by others.

Animals↗
PubMed1976

A non-chromatographic radioimmunoassay of progesterone in serum.

Convenient methodology based on separation of progesterone from alcoholic neutral steroids by means of a sulfation-procedure has been developed for the radioimmunoassay (RIA) of progesterone in male and female serum. When coordinated with our previously published non-chromatographic procedure for the RIA of estrone and estradiol in serum, all 3 seteroids can be determined in the same specimen. Validation of the procedure was based on: 1. Agreement between results obtained using ILC and sulfation to fractionate progesterone (r=0.98; b=0.86), 2. accurate recovery of different quantities of progesterone added to serum, 3. independence of the concentration of progesterone and volume of serum used for assay, 4. low procedural blanks (3.6 +/- 1.3 pg), 5. low intraassay (9.7 - 10.3%) and interassay (11.0 - 11.6%) variability and 6. correspondence of observed values for progesterone in male serum (108 +/- 20 pg/ml) and in female serum (follicular, 285 +/- 149 pg/ml; luteal, 3.46 +/- 1.45 ng/ml) with those reported previously by others.

Chromatography, Thin Layer↗
PubMed1975

Comparison of dextran-coated charcoal and ammonium sulfate in the radioimmunoassay of estrogens.

A comparison was made between the use of ammonium sulfate (AS) and Dextran coated charcoal (DCC) to separate free and antibody-bound estrogens in the RIA of estrone and estradiol in serum. Under the conditions tested, AS yielded values which were approximately twice those obtained using DCC. This difference was found for both estrogens, using male and female serum and regardless of whether the estrogens were separated from one another by means of the Girard reagent or TLC. There was no significant difference in the sensitivity, accuracy or usable range of the standard curve or in the water-blank for the two procedures.

Ammonium Sulfate↗