Progestins are classified according to their structure in C19 and C21 progestagens. The C19 ones are derived from testosterone, the C21 ones from progesterone. C21 progestagens include cyproterone acetate, dydrogesterone, medroxyprogesterone acetate, chlormadinone acetate, megestrol and promegestone. Of these, dydrogesterone is structurally most similar to progesterone. C19 progestagens include norethisterone, (levo)norgestrel, lynestrenol, desogestrel, norgestimate, gestodene and tibolone.

Different progestins have different combinations of androgen (testosterone-like) and progesterone activity. If the activity of 1 mg of norethindrone is taken as the baseline, 1 mg of the other progestins have activities as follows:

Norethindrone was synthetized for the first time in 1951 by the Mexican chemist Luis E. Miramontes. This substance became the basis for the contraceptive pill.

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Monophasic OCs said to ease menstrual migraines
From OB/GYN News, 2/15/05 by Nancy A. Melville

SCOTTSDALE, ARIZ. -- Because fluctuating hormones are believed to be the key culprit behind menstrual migraines, low-dose monophasic oral contraceptives are generally the best alternative to help such patients, Christine Lay, M.D., said at a symposium sponsored by the American Headache Society.

Ob.gyns. often turn to biphasic contraception instead of monophasic pills in the belief that varying the hormone dosage will help alleviate menstrual migraines, but the dosage schedule can make the problem worse, said Dr. Lay, a neurologist with the Headache Institute at Roosevelt Hospital. New York.

Dr. Lay gave the example of Mircette, which contains 21 days of 0.15-mg desogestrel/0.02-mg ethinyl estradiol, followed by 2 days of placebo pills and 5 days of 0.01-mg ethinyl estradiol. "I have numerous ob.gyns. who put patients on Mircette because they think it might help menstrually-related migraines," she said.

Instead, the method introduces another level of fluctuation of estrogen, and it is that fluctuation that is believed to trigger the migraines in the first place, said Dr. Lay

Even worse for menstrual migraines are triphasic pills, which cause greater fluctuation in hormone levels and often are high-dose pills, said Dr. Lay.

"The triphasic pills are the worst for migraine patients," she said. "Invariably, you will have a patient track her calendar and over a month's period of time she will report that within a day or two of switching to a new dose of pill, the woman will experience a migraine attack."

Migraine patients generally fare much better when using monophasic low-dose (20-mcg) birth control pills, which offer a more uniform hormone level, Dr. Lay said, adding that the estrogen patch is another effective way of providing a more steady level of estrogen. Newer noncycling methods such as Seasonale (ethinyl estradiol and levonorgestrel) are also good alternatives for migraineurs, she said in an interview

Estrogen use in patients who suffered from migraines was frowned upon for many years, but the International Headache Society Task Force on Combined Oral Contraceptives and HRT determined more recently that it was safe for migraineurs, provided that there are no other risk factors for coronary heart disease or vascular disease.

In addition, the migraine should be without aura and patients should be given the lowest effective hormone dose.

In the ebb and flow of hormone levels, it is the withdrawal of estrogen, specifically, that experts believe contributes to menstrual migraines. The withdrawal is believed not only to affect trigeminal pain pathways and have vasculature effects, but it may modulate neurotransmitters and magnesium, Dr. Lay said at the meeting.

The release of prostaglandin also plays a role in migraines, sensitizing peripheral nociceptors to pain and mediating hyperalgesia, and prostaglandin is known to increase during migraine attacks.

A key approach to treatment is having patients maintain a diary in which they track their menses and headache days, Dr. Lay said. The journal can help guide treatment options and determine the role of oral contraceptive use.

Since menstrual migraines can occur in young, otherwise healthy women, Dr. Lay strongly recommended using caution in approaching contraceptive issues.

"This is a critical time to discuss with patients pregnancy planning and medication contraindications in pregnancy because, invariably, some of these patients could wind up getting pregnant" unintentionally. 'We recommend taking a patient off the pill when efforts to prevent migraines are unsuccessful," Dr. Lay added.

"Physicians may have the patient go off the pill in order to observe the migraine pattern over time. However, the migraine pattern may not improve for at least 3-6 months. In such cases, it's essential to talk about pregnancy issues if the patient is on the pill for contraceptive purposes."

Short-term prophylaxis approaches recommended to prevent the onset of menstrual migraines range from NSAIDs to triptans, and for a more long-term prevention, Dr. Lay suggested considering standard preventive medications, including tricyclic antidepressant, antiepileptic drugs, [beta]-blockers, and selective serotonin reuptake inhibitors.

BY NANCY A. MELVILLE

Contributing Writer

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