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  • Title: New progestogens in oral contraception.
    Author: Fotherby K, Caldwell AD.
    Journal: Contraception; 1994 Jan; 49(1):1-32. PubMed ID: 8137623.
    Abstract:
    The major developments in combined oral contraceptives (COCs) have been a reduction in the total dose of both the oestrogen and progestogen administered per cycle and the introduction of new progestogens which are claimed to be more 'selective' than the older ones. This review examines in detail the clinical efficacy of the new COCs, where possible in comparison with those containing levonorgestrel or norethisterone, and their pharmacological effect on carbohydrate and lipid metabolism, haematological factors, pituitary-ovarian function and serum protein and androgen concentrations. Based mainly on the pharmacological evidence, the newer COCs are an improvement over the older low-dose formulations and are clearly preferable to the high-dose ones. However, the older low-dose COCs, despite many years of use, have not resulted in a high incidence of adverse effects. The increasing use of the new COCs, as evidenced by their increasing market share throughout Europe, does indicate that they have been well accepted in clinical practice. European researchers have conducted most of the clinical tests of the 3 new progestogens used in low-dose, combined oral contraceptive (OC) formulations: desogestrel (DSG), gestodene (GSD), and norgestimate (NGM). Enough clinical trial data for GSD and DSG OCs exist to compare with those of other low-dose OCs. The newer OCs are at least as effective and have at least as good cycle control as other low-dose OCs. Minor side effects of the newer OCs correspond to those of other OCs. Various flaws in studies make it hard to compare major adverse side effects of the different OCs. To compare OCs, parameters must be accurately measured. Continuation rates, measurement of blood pressure, and incidence of specific side effects can be accurately measured, but only in large comparative trials using standardized assessment methods. Other possible comparative parameters are metabolic parameters, but trials must be well-designed and adequately controlled. Almost all studies show that the new OCs do not affect fasting levels of glucose and insulin. More research is needed on the validity of a glucose tolerance test to stimulate any changes in carbohydrate metabolism, however. Recent data show that lipid metabolism may vary among the new OCs, but the research is largely limited to assessing the serum levels of various lipids. Yet, assessment of various ratios or an assay of the apoproteins are better indicators of the risk of cardiovascular disease. An assay of just high density lipoprotein-cholesterol allows researchers to distinguish between OCs. Hematologic factors are not a good basis for comparison, due to a variety of problems with measurement. Accurate measurements of serum proteins (e.g., sex hormone binding globulin) can be made, however. New OC use has increased 2-fold in 4 years in some European countries, attesting to their popularity and acceptability.
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