Plasma concentrations of ethynyl oestradiol and norethindrone after oral administration to women

Pasqualini, Jörge R.; Castellet, R; Portois, M. C.; Hill, J. L.; Kincl, Fred A.

doi:10.1530/jrf.0.0490189

Cited by 39 publications

(6 citation statements)

References 10 publications

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“…Such a correlation after oral administration of NET was reported by Nygren et al (1974) for three subjects. lnterindividual variations of the plasma concentrations after oral administration of gestagens have been reported by other investigators (Weiner et al, 1976;Pasqualini et al, 1977;Stanczyk ef al., 1975). This probably reflects differences in drug absorption, distribution and metabolism among individuals.…”

Section: Discussionsupporting

confidence: 55%

Plasma Levels of Norethindrone After Single Oral Dose Administration of Norethindrone and Lynestrenol

Odlind¹,

Weiner²,

Victor³

et al. 1979

Clinical Endocrinology

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Single oral doses of 0.3 mg, 0.5 mg and 5 mg Norethindrone (NET) and 0.5 mg and 5 mg Lynestrenol (lyn) were given to five women. Lynestrenol is probably metabolized through NET and exerts its main biological activity as NET. Plasma concentrations of NET were determined by a radioimmunoassay at different intervals after administration of the tablets. Peak concentrations of NET were found within two hours after intake of each table. The plasma half life of Net after NET and lyn administration for the period 8-24 h was 8-11 h. No significant difference was found between the half life of NET and the NET tablets and after the lyn tablets. When 5 mg NET was given the plasma half life of NET for the period 24-72 h was around 10 h and this was significantly shorter than the half-life of NET after 5 mg lyn, which was 16 1/2 h. The systemic availability of the drugs was estimated by calculating and comparing the areas under the plasma concentration versus time curve (AUC). 0-24 H. The AUC 0.24 after 0.3 MG NET was almost identical to the AUC 0.24 after 0.5 mg lyn. The AUC 0-24 after 0.5 mg NET was significantly larger than after 0.5 lyn. No difference was found between the AUC 0-24 after 5 mg lyn and 5 mg NET. This study supports the concept of a conversion from lyn to NET. It also shows that there were only minor pharmacokinetic differences between the drugs when all samples were measured as NET.

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Section: Discussionsupporting

confidence: 55%

Plasma Levels of Norethindrone After Single Oral Dose Administration of Norethindrone and Lynestrenol

Odlind¹,

Weiner²,

Victor³

et al. 1979

Clinical Endocrinology

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“…Plasma levels of 300-500 pg ml-' oestradiol have been reported following this regime (Henderson et al, 1977), which compare favourably with the peak plasma levels of 435 ± 144 pg ml-' found in women 1 h after ingestion of 50 pg ethynyl oestradiol (Pasqualini et al, 1977). In the rat, these levels are sufficient to inhibit ovulation and remain fairly constant throughout the treatment period.…”

Section: Administration Of Steroidssupporting

confidence: 55%

Sex and hormonal influences on platelet sensitivity and coagulation in the rat

Emms

Lewis

1985

British J Pharmacology

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Platelet sensitivity to adenosine di‐phosphate (ADP), thrombin, collagen, arachidonic acid and prostaglandin I2 (PGI2) and the activity of the coagulation system as measured by the activated partial thromboplastin time, prothrombin time, Russell's viper venom time and plasma fibrinogen have been examined in male and female rats, female rats during the oestrous cycle and female rats treated with oestrogen and a progestogen. Male rat platelets were less sensitive to thrombin and more sensitive to inhibition by PGI2 than those from females and fibrinogen levels in male rat plasma were approximately twice those seen in females. During the oestrous cycle, platelets were more sensitive to ADP and less sensitive to thrombin at dioestrus. Following 6 weeks treatment with 17 β‐oestradiol or ethynyl oestradiol, both platelet aggregation and release of granular ATP induced by collagen were significantly reduced. Platelet sensitivity to other agents, ADP, arachidonic acid, thrombin and PGI2 was, however, unchanged following oestrogen treatment. Activation of factor X by Russell's viper venom was accelerated in rats treated with ethynyl oestradiol, although this enhancement was not reflected in the overall clotting times.

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“…These figures for the terminal phase tl/2 are in the range reported by other workers. 4,6,7,9,11 Ethinylestradiol did not alter the plasma tV2, plasma clearance, or apparent volume of distribution of norethindrone when the data following administration of We have also shown that the bioavailability of norethindrone is significantly less than 100% when given orally, with a mean bioavailability of 64% (range, 47% to 73%) compared with the intravenous formulation. This reduced bioavailability might be due to incomplete absorption but norethindrone is reported to be well absorbed after oral administration.…”

Section: Discussionmentioning

confidence: 69%

Kinetics of norethindrone in women; II. Single‐dose kinetics

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Breckenridge

Crawford

et al. 1978

Clin Pharma and Therapeutics

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In order to study the kinetics of norethindrone in women, we have administered single doses of 4 preparations of norethindrone (N) to Liverpool, England Department of Pharmacology and Therapeutics, University of LiverpoolNorethindrone ( 17a -ethinyl-I7 (3 -hydroxyestr-4-en-3-one) is a synthetic progestogen which is widely used both on its own and as a component of many combined contraceptive steroid preparations. Despite its widespread use, little is known of the relationship of blood concentrations of norethindrone to efficacy or toxicity. The plasma half-life (tV2) of norethindrone has been variously estimated as between 3 and 5 hrll and about 6 hr 9 , or as a biexponential decay with a terminal tV2 ranging between 3 and 12 hr. 6 We have developed a sensitive radioimmunoassay method for the measurement of norethindrone concentrations in plasma. 2During our initial studies in women taking the combined form of oral contraceptive, we found

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Plasma concentrations of ethynyl oestradiol and norethindrone after oral administration to women

Cited by 39 publications

References 10 publications

Plasma Levels of Norethindrone After Single Oral Dose Administration of Norethindrone and Lynestrenol

Plasma Levels of Norethindrone After Single Oral Dose Administration of Norethindrone and Lynestrenol

Sex and hormonal influences on platelet sensitivity and coagulation in the rat

Kinetics of norethindrone in women; II. Single‐dose kinetics

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