Single and multiple administration of a new triphasic oral contraceptive to women: Pharmacokinetics of ethinyl estradiol and free and total testosterone levels in serum Wilhelm Kuhnz, PhD, Durda Sostarek, Christiane Gansau, Tom Louton, PhD, and Marianne Mahler, MD
Berlin, Germany Ethinyl estradiol is part of almost every combined oral contraceptive, and its pharmacokinetic characteristics have been thoroughly investigated in numerous studies. However, little is known about its pharmacokinetics during long-term administration, as compared with single-dose administration. In this study 10 women received a triphasic formulation that contained ethinyl estradiol together with the progestin gestodene over one treatment cycle. Mean area under the curve values of ethinyl estradiol were significantly higher on the last treatment day, as compared with the corresponding values obtained from the same women after Single-dose administration. However, the observed increase in area under the curve was within the range of pharmacokinetic accumulation, to be expected on the basis of dosing interval and terminal half-life. Another point of interest was the effect of the triphasic preparation on testosterone concentrations in serum. Both total and free testosterone levels were suppressed by about 60% as compared with pretreatment values, and there was no correlation with corresponding sex hormonebinding globulin levels in the serum. (AM J OBSTET GYNECOL 1991 ;165:596-602.)
Key words: Pharmacokinetics, ethinyl estradiol, chronic administration, testosterone
Gestodene is a new synthetic progestin that, in combination with ethinyl estradiol, is part of a monophasic and a triphasic oral contraceptive. The pharmacokinetics of gestodene after single and multiple administration of the monophasic formulation has been investigated in several clinical studies. \·3 The pharmacokinetics after single and multiple administration of the triphasic formulation has been reported previously." In this communication the pharmacokinetics of ethinyl estradiol is presented. It was the aim of this study to compare basic pharmacokinetic parameters of ethinyl estradiol in individual su~jects after single-dose administration with the corresponding parameters obtained during a complete treatment cycle. In particular, it was of interest to see whether there was an accumulation of ethinyl estradiol in the serum during long-term treatment. In addition, effects of the triphasic formulation on total and free testosterone concentrations were investigated. Since testosterone binds to sex hormonebinding globulin with a high affinity, another aim of this study was to assess any effect of changes in sex hormone-binding globulin concentrations during treatment on total and free testosterone levels in the From the Research Laboratories, Schering AG. Received for publication September 10, 1990; revised March 1, 1991; accepted March 15,1991. Reprint requests: Wilhelm Kuhnz, PhD, Department of Pharmacokinetics, Schering AG, Miillerstra{3e 170-178, D-JOOO Berlin 65, Federal Republic of Germany. 611 /29546
596
serum. This could be of interest because reduced free testosterone concentrations could be responsible for a reduction of androgen-dependent side effects.
Material and methods Study design. The study was designed as an open investigation on 10 healthy women, whose demographic data are presented in Table I. The women had normal biphasic cycles and had not used oral contraceptives for at least 2 months before they participated in the study. All women underwent a thorough physical and gynecologic examination, and informed consent was obtained before their participation. The women received a single, coated tablet of the triphasic formulation, which contained 0.1 mg gestodene together with 0.03 mg ethinyl estradiol, on day 21 of a pretreatment cycle. Blood samples (5 ml) were taken after an overnight fast, before drug administration, and 0.5, 1, 1.5, 2, 4, 6, 8, 10, 12,24,48, and 72 hours after drug intake. A standardized breakfast was served 2 hours after treatment. After a washout period of 7 days, in a second part of the study, the same women received the following triphasic formulation during a whole cycle: days 1 to 6, 0.05 mg gestodene together with 0.03 mg ethinyl estradiol; days 7 to 11, 0.07 mg gestodene together with 0.04 mg ethinyl estradiol; days 12 to 21, 0.1 mg gestodene together with 0.03 mg ethinyl estradiol. Blood samples (5 ml) were taken after an overnight
Pharmacokinetics of ethinyl estradiol
Volume 165 Number 3
597
Table I. Demographic data of 10 women who participated in the study Patient No.
Weight (kg)
Height (em)
Age (yr)
1 2 3 4 5 6 7 8 9 10
62 53 57 55 69 64 60 59 60 60
163 157 160 165 172 170 179 156 160 174
28 38 31 25 23 26 33 39 38 36
Mean ± SD
59.9 ± 4.5
165.6 ± 7.8
31.7 ± 6.0
fast on days 2 and 7 before and 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours after drug administration and on day 21 before and 0.5, 1, 1.5,2,4,6,8, 12,24,48,72, and 96 hours after drug intake. A standardized breakfast was served 2 hours after treatment on days 2, 7, and 21. Additional blood samples were obtained on days 5, 10,12,14,16,18, and 20 in the morning, before drug administration. All blood samples were kept at 4° C until coagulation; the serum was separated and stored at - 20° C until analysis. Analytic determinations Determination of ethinyl estradiol. Ethinyl estradiol was measured by a specific radioimmunoassay in all serum samples in duplicate, after an extraction of 0.3 ml serum with diethyl ether. The recovery of the extraction was >90%. Ethinyl estradiol-6, 7_3H (specific activity, 2.2 TBq/mmol; New England Nuclear) was used as tracer; radiochemical purity was >98%. The antiserum (Schering) was obtained by immunization of rabbits with the immunogen ethinyl estradiol-6f3-carboxymethyloximebovine serum albumin; the final dilution was 1: 400,000 in the assay. Details on the specificity of the antiserum are described elsewhere." Extracts from serum samples were dissolved in buffer, antiserum and tracer (5000 counts/min) were added, and the mixture was incubated at 4° C for 16 hours. Bound and free steroids were separated by charcoal treatment, analogous with published procedures. 6 The sensitivity of the standard curve was about 3 to 4 pg ethinyl estradiol per tube, and the lower limit of quantitation was 15 pg/ml. Interassay precision (n = 5) was determined with three different control samples, containing ethinyl estradiol 50, 100, and 200 pg/ml plasma, respectively. Experimentally measured concentration values were 56.6 ± 6.0,120.6 ± 9.1, and 217.6 ± 19.4pg/ml,respectively. The coefficients of variation of interassay precision were 10.6%,7.5%, and 8.9%, respectively. Deviations of measured from nomimal values were 13.2%,20.6%, and 8.8%, respectively. Other parameters. Total and free concentrations of tes-
tosterone and sex hormone-binding globulin and transcortin concentrations in the serum were determined radioimmunologically with commerically available assay kits: total and free testosterone, by solidphase radioimmunoassays (Coat-A-Count, Diagnostic Products Corporation, Los Angeles), sex hormonebinding globulin, by an immunoradiometric assay (SHBG-IRMA-Count, Diagnostic Products Corporation, Los Angeles); and transcortin, by a radioimmunoassay (IRE Medgenix, Fleurus, Belgium). Two quality control samples, representing low and high concentrations of the analyte, respectively, were included in each assay and measured in duplicate. Deviation of experimentally measured concentrations from nominal values was :0;16% for all analytes and interassay precision was
Berlin, Germany Ethinyl estradiol is part of almost every combined oral contraceptive, and its pharmacokinetic characteristics have been thoroughly investigated in numerous studies. However, little is known about its pharmacokinetics during long-term administration, as compared with single-dose administration. In this study 10 women received a triphasic formulation that contained ethinyl estradiol together with the progestin gestodene over one treatment cycle. Mean area under the curve values of ethinyl estradiol were significantly higher on the last treatment day, as compared with the corresponding values obtained from the same women after Single-dose administration. However, the observed increase in area under the curve was within the range of pharmacokinetic accumulation, to be expected on the basis of dosing interval and terminal half-life. Another point of interest was the effect of the triphasic preparation on testosterone concentrations in serum. Both total and free testosterone levels were suppressed by about 60% as compared with pretreatment values, and there was no correlation with corresponding sex hormonebinding globulin levels in the serum. (AM J OBSTET GYNECOL 1991 ;165:596-602.)
Key words: Pharmacokinetics, ethinyl estradiol, chronic administration, testosterone
Gestodene is a new synthetic progestin that, in combination with ethinyl estradiol, is part of a monophasic and a triphasic oral contraceptive. The pharmacokinetics of gestodene after single and multiple administration of the monophasic formulation has been investigated in several clinical studies. \·3 The pharmacokinetics after single and multiple administration of the triphasic formulation has been reported previously." In this communication the pharmacokinetics of ethinyl estradiol is presented. It was the aim of this study to compare basic pharmacokinetic parameters of ethinyl estradiol in individual su~jects after single-dose administration with the corresponding parameters obtained during a complete treatment cycle. In particular, it was of interest to see whether there was an accumulation of ethinyl estradiol in the serum during long-term treatment. In addition, effects of the triphasic formulation on total and free testosterone concentrations were investigated. Since testosterone binds to sex hormonebinding globulin with a high affinity, another aim of this study was to assess any effect of changes in sex hormone-binding globulin concentrations during treatment on total and free testosterone levels in the From the Research Laboratories, Schering AG. Received for publication September 10, 1990; revised March 1, 1991; accepted March 15,1991. Reprint requests: Wilhelm Kuhnz, PhD, Department of Pharmacokinetics, Schering AG, Miillerstra{3e 170-178, D-JOOO Berlin 65, Federal Republic of Germany. 611 /29546
596
serum. This could be of interest because reduced free testosterone concentrations could be responsible for a reduction of androgen-dependent side effects.
Material and methods Study design. The study was designed as an open investigation on 10 healthy women, whose demographic data are presented in Table I. The women had normal biphasic cycles and had not used oral contraceptives for at least 2 months before they participated in the study. All women underwent a thorough physical and gynecologic examination, and informed consent was obtained before their participation. The women received a single, coated tablet of the triphasic formulation, which contained 0.1 mg gestodene together with 0.03 mg ethinyl estradiol, on day 21 of a pretreatment cycle. Blood samples (5 ml) were taken after an overnight fast, before drug administration, and 0.5, 1, 1.5, 2, 4, 6, 8, 10, 12,24,48, and 72 hours after drug intake. A standardized breakfast was served 2 hours after treatment. After a washout period of 7 days, in a second part of the study, the same women received the following triphasic formulation during a whole cycle: days 1 to 6, 0.05 mg gestodene together with 0.03 mg ethinyl estradiol; days 7 to 11, 0.07 mg gestodene together with 0.04 mg ethinyl estradiol; days 12 to 21, 0.1 mg gestodene together with 0.03 mg ethinyl estradiol. Blood samples (5 ml) were taken after an overnight
Pharmacokinetics of ethinyl estradiol
Volume 165 Number 3
597
Table I. Demographic data of 10 women who participated in the study Patient No.
Weight (kg)
Height (em)
Age (yr)
1 2 3 4 5 6 7 8 9 10
62 53 57 55 69 64 60 59 60 60
163 157 160 165 172 170 179 156 160 174
28 38 31 25 23 26 33 39 38 36
Mean ± SD
59.9 ± 4.5
165.6 ± 7.8
31.7 ± 6.0
fast on days 2 and 7 before and 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours after drug administration and on day 21 before and 0.5, 1, 1.5,2,4,6,8, 12,24,48,72, and 96 hours after drug intake. A standardized breakfast was served 2 hours after treatment on days 2, 7, and 21. Additional blood samples were obtained on days 5, 10,12,14,16,18, and 20 in the morning, before drug administration. All blood samples were kept at 4° C until coagulation; the serum was separated and stored at - 20° C until analysis. Analytic determinations Determination of ethinyl estradiol. Ethinyl estradiol was measured by a specific radioimmunoassay in all serum samples in duplicate, after an extraction of 0.3 ml serum with diethyl ether. The recovery of the extraction was >90%. Ethinyl estradiol-6, 7_3H (specific activity, 2.2 TBq/mmol; New England Nuclear) was used as tracer; radiochemical purity was >98%. The antiserum (Schering) was obtained by immunization of rabbits with the immunogen ethinyl estradiol-6f3-carboxymethyloximebovine serum albumin; the final dilution was 1: 400,000 in the assay. Details on the specificity of the antiserum are described elsewhere." Extracts from serum samples were dissolved in buffer, antiserum and tracer (5000 counts/min) were added, and the mixture was incubated at 4° C for 16 hours. Bound and free steroids were separated by charcoal treatment, analogous with published procedures. 6 The sensitivity of the standard curve was about 3 to 4 pg ethinyl estradiol per tube, and the lower limit of quantitation was 15 pg/ml. Interassay precision (n = 5) was determined with three different control samples, containing ethinyl estradiol 50, 100, and 200 pg/ml plasma, respectively. Experimentally measured concentration values were 56.6 ± 6.0,120.6 ± 9.1, and 217.6 ± 19.4pg/ml,respectively. The coefficients of variation of interassay precision were 10.6%,7.5%, and 8.9%, respectively. Deviations of measured from nomimal values were 13.2%,20.6%, and 8.8%, respectively. Other parameters. Total and free concentrations of tes-
tosterone and sex hormone-binding globulin and transcortin concentrations in the serum were determined radioimmunologically with commerically available assay kits: total and free testosterone, by solidphase radioimmunoassays (Coat-A-Count, Diagnostic Products Corporation, Los Angeles), sex hormonebinding globulin, by an immunoradiometric assay (SHBG-IRMA-Count, Diagnostic Products Corporation, Los Angeles); and transcortin, by a radioimmunoassay (IRE Medgenix, Fleurus, Belgium). Two quality control samples, representing low and high concentrations of the analyte, respectively, were included in each assay and measured in duplicate. Deviation of experimentally measured concentrations from nominal values was :0;16% for all analytes and interassay precision was
