Sequential oral contraceptives

Sequential oral contraceptives (see also Oestrogens, progestins and eombinations)... 

Dimethisterone (see also Progestins Sequential oral contraceptives... 

Oral contraceptives, investigational (see Combined oral contraceptives) Oral contraceptives, sequential (see Sequential oral contraceptives) Orange I... 

The hostility of the thickened cervical mucus to sperm penetration has been used as a means to achieve contraception, and low-dose oral contraceptives depend largely on this condition for their effectiveness in fertility controlJ Sequential oral contraceptives do not affect mucus and like estrogen, may even increase sperm penetration. 

Further evidence that oral contraceptives of the sequential type may carry a risk of inducing endometrial carcinoma is presented by Vanderick et al. (159 ). They examined 1348 endometrial biopsies taken from 748 patients on a sequential regimen. A tendency towards hyperplasia or an outspoken cystic hyperplasia appeared in 25—48% of the cases. Few cases of adenomatous hyperplasia were found. They concluded that long-term treatment with these sequential formulations has to be administrated with caution taking into account the possibility of premalignant transformation. More comparative data are needed before one can draw the conclusion that combined and sequential oral contraceptives carry different risks with regard to the developement of endometrial carcinoma. 

Lyon, F. A. (1975) Adenocarcinoma during long-term sequential oral contraception. y4mc/-. J. Obstet. Gynec., 123, 299. 

NB There is also conclusive evidence that these agents have a protective effect against cancers of the ovary and endometrium) Oral contraceptives, sequential (Suppl. 7 1987)... 

Conflicting data concerning the effects of oral contraceptives on carbohydrate metabolism have been presented the effects are probably clinically insignificant. However, estrogen hormone replacement therapy with a sequential-type product containing mestranol and norethisterone caused significantly impaired glucose tolerance (30). 

Both sequential and non-sequential types of oral contraceptives impair the absorption of polyglutamic folate but not that of monoglutamic folate the change can result in megaloblastic anemia in predisposed subjects, for example those with celiac disease or having a deficient diet (182). 

While numerous studies have evaluated the effect of oral contraceptives and postmenopausal hormone replacement on drug clearance, many were flawed by poor study design. Table 21.1 lists studies that were of crossover or sequential design such that each subject was evaluated in the contraceptive phase and placebo phase. These study designs minimize the effect of interindividual variability. In most studies there was no effect of hormonal therapy on drug metabolism, but in some there were interactions that inhibited or increased the metabolism of concurrently administered drugs. 

Oestrogens seem to have an inhibiting effect upon bone resorption but do not stimulate new bone formation. There is consequently presumptive evidence that sequential type preparations may be of value in slowing down the osteoporotic process in the perimenopausal woman on oral contraceptive medication [344]. 

The oral contraceptives are of two main types the combined hormonal contraceptives containing both an oestrogen and a progestogen (monophasic, biphasie, triphasie, or sequential), available as tablets or a patch, and the progestogen-only contraceptives, which are available as tablets (sometimes ealled mini pills), parenteral preparations (implants, depot injections) and intrauterine devices. 

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