Contraceptives, progestogen-only

Clinical studies with Norplant attest to its high contraceptive efficacy and safety. The main reason patients request the removal of Norplant is unpredictable vaginal bleeding episodes followed by amenorrhea. The bleeding problem is an unavoidable sequela of progestogen-only contraception. 

Combined oral contraceptives are less likely to be associated with irregular vaginal bleeding than progestogen-only contraceptives. However, they are... 

Levonorgestrel is a progestogen derivative. It is found either in combined oral contraceptives coupled with an oestrogen derivative or alone in progestogen-only contraceptives. 

In contrast, progestogen-only contraceptives cause reduced SHBG concentrations and modest falls in progestogen concentrations over time. 

Most studies of carbohydrate metabolism have shown little effect of progestogen-only contraceptives, but there is a suggestion of slight deterioration in glucose tolerance and raised plasma insulin concentrations. Women with diabetes mellitus can generally take pro-gestogen-only contraceptives without a change in insulin requirements. 

There does not appear to be any clinically significant delay in return of fertility after discontinuation of progestogen-only contraceptives. Although there have been no large studies, data from several small studies suggest no effect. Furthermore, because progestogen-only contraceptives prevent ovulation in only about half of cycles, and because the pregnancy prevention effects fall rapidly if a tablet is taken late, the normal reproductive physiol-ogy presumably returns quickly after tablet discontinuation. 

Up to 10% of pregnancies among users of progestogen-only contraceptives implant outside the uterus this is not greatly different to the ectopic pregnancy rate in unprotected women, but it is much higher than among users of adequate combined oral contraception (292). The reasons... 

There is much evidence that progestogen-only contraceptives (including tablets, injectables, and implants)... 

Fraser IS. Menstrual changes associated with progestogen-only contraception. Acta Obstet Gynecol Scand Suppl 1986 134 21-7. 

Progestogen-only contraceptives during lactation I. Infant growth. Contraception 1994 50(l) 35-53. 

Medroxyprogesterone acetate is given in a relatively high dose for hormonal contraception and acts primarily by inhibiting ovulation. However, as with the other progestogen-only contraceptives, other mechanisms probably play a very significant role. It is extremely effective, with less than one pregnancy per 100 woman-years. 

The reduced penetrability of cervical mucus, which contributes to the contraceptive effect, may well provide some small degree of protection against pelvic inflammatory disease. However, this effect is likely to be less than that exerted by combined oral contraceptives, since the expanded cervical ectropion found among combined oral contraceptive users is not present in users of progestogen-only contraceptives. 

Hormonal contraceptives, which use oral oestrogen and/or progesterone, such as combined hormonal contraceptives and progestogen-only contraceptives. 

The progestogen-only contraceptive pill contains progestogen alone. 

Adverse effects include CNS symptoms (reversible blurring of vision, diplopia, dizziness and ataxia) and depression of cardiac AV conduction. Alimentary symptoms, skin rashes, blood disorders and liver and kidney dysfunction also occur. Osteomalacia by enhanced metabolism of vitamin D (enzyme induction) occurs over years so also does folate deficiency. Enzyme induction reduces the efficacy of combined and progestogen-only contraceptives. Carbamazepine impairs cognitive function less than phenytoin. 

Sex hormones and hormone antagonists. Oestrogens increase the synthesis of some vitamin K dependent clotting factors and progestogen-only contraceptives are preferred. The hormone antagonists danazol, flutamide and tamoxifen enhance the effect of warfarin. 

The oral formulation ( mini-pill ) is taken every day it must be taken at the same time each day (to within 3 hours). Oral progestogen-only contraception is less effective but safer (no effect on blood coagulation) than combined formulations. 

Progestogen-only contraception is particularly appropriate to women having an absolute contraindication for oestrogen, e.g. history of thromboembolism, smokers over 35 years (who refuse to give it up), and for diabetics. Hypertension is not an absolute contraindication to the more effective combined pill since only a proportion of women have oestrogen dependent hypertension (and often such women are normotensive until exposed to increased levels of oestrogen). It is used by lactating women as it interferes with the milk less than the combined pill. 

Changes in hpid metabolism among users of progestogen-only contraceptives are minimal. Some studies have shown very small falls in HDL and HDL2 cholesterol, but no effect on other parameters of lipid... 

---