Is it better to take progesterone as a pill, a shot, a vaginal suppository or a cream?
All of the above forms of progesterone and progestogens have been used.
The method of administration is best determined by availability, convenience of use and price.
Absorption and duration of action will vary by the form of progesterone used:
- pills - peak absorption is about 1-4 hours and is cleared by 24 hours. Taking the pills with food enhances absorption.
- shots - usually given in the form of progesterone in oil, doses peak at about 12 hours after administration and take at least 48 hours or more to clear. There are depot forms of medroxyprogesterone acetate (Depo-Provera®) that last at least 12 weeks which gives it its contraceptive effect.
- vaginal suppositories, cream - absorbed to peak in 4 hours and cleared by 24 hours. Sometimes mixed in cocoa butter or propylene glycol as the carrying agent. A cream is also commercially available (Crinone®).
- skin creams - creams tend not to absorb through the skin very well but alcohol-based gels are effective with a once a day application. A 10% alcohol and propylene glycol base also seems to be quite effective and clears by 24 hours.
What are the effects of too little or too much progesterone?
Progesterone acts to stabilize the tissue lining of the uterus (endometrium) so if it is absent, such as with ovarian anovulation, irregular and heavy menstrual bleeding often occurs after a period without any menstrual bleeding.
Thus progesterone is used to prevent this irregularity of bleeding if it is given continuously. If, on the other hand, a one time bolus of progesterone is given such as with a shot or with only 5 days of oral pills, then the falling progesterone levels will actually cause an estrogen-primed endometrium to slough and therefore start a menses.
Too much progesterone often causes tiredness and even sedation. This side effect can be beneficial in a women who has epilepsy or even uterine irritability causing preterm labor because progesterone in high doses can decrease seizure activity and uterine contractions.
Progesterone tends to promote vaginal dryness by counteracting the effect on lubrication of estrogens and it can also decrease the amount of menstruation or block it entirely by reversing estrogen effect on the growth of the uterine lining.
If a woman has stopped having menses on a birth control pill, the progestogen component needs to be decreased if menstrual bleeding is desirable.