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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Ethinyl estradiol/drospirenone : a newer oral contraceptive
From American Family Physician, 5/15/04 by Melissa A. Somma

Synopsis: Ethinyl estradiol/drospirenone (Yasmin) is a monophasic oral contraceptive containing 30 mcg of ethinyl estradiol and 3 mg of a unique progestin, drospirenone, a spironolactone analog with antimineralocorticoid activity.

Safety: Ethinyl estradiol/drospirenone shares the same safety concerns of thrombosis, embolism, gallbladder disease, hypertension and liver disease with other oral contraceptives. Drospirenone, a spironolactone analog, has the theoretic potential to elevate potassium levels. However, in an eight-month study of 80 women taking ethinyl estradiol/ drospirenone, no changes in serum potassium levels were noted. (1) The manufacturer recommends that a test for potassium levels be performed during the first treatment cycle for patients taking any other drug capable of increasing serum potassium levels with ethinyl estradiol/drospirenone. (2) As with other oral contraceptives, this product is contraindicated in women who have renal or hepatic insufficiency. The ethinyl estradiol/ drospirenone product is unique in that it is contraindicated in patients who have adrenal insufficiency.

Tolerability: The incidence of the expected side effects of headache, breast pain, nausea, abdominal pain, and migraine is similar with ethinyl estradiol/drospirenone as with traditional oral contraceptives. When compared with ethinyl estradiol/desogestrel, both products had similar low rates of spotting and breakthrough bleeding, which progressively lessened with duration of product use. (3) Because of the drospirenone component, diuresis-induced weight loss (0.46 kg versus 0.19 kg with desogestrel) may occur. (3)

Effectiveness: In a year-long study of 326 women (3,201 cycles), one pregnancy occurred, 4 which compares with the efficacy of other oral contraceptives in clinical studies. Long-term studies have not been performed to determine the effectiveness of this oral contraceptive in typical use, though it should be similar to other products.

In a randomized study comparing ethinyl estradiol/drospirenone with 30 mcg ethinyl estradiol/0.15 mg desogestrel, both products produced a comparable decrease in the incidence and severity of acne.2,3 Ethinyl estradiol/ drospirenone is not currently labeled for the treatment of acne.

In an original dose-ranging study comparing ethinyl estradiol/drospirenone with 30 mcg ethinyl estradiol/0.15 mcg levonorgestrel, systolic and diastolic blood pressures decreased by a range of 1 to 4 mm Hg while increasing by 1 to 2 mm Hg in the control group.1 The difference in blood pressure may have been attributed to the drospirenone component of the product.Additional clinical trials are needed to support the theoretical benefit of drospirenone in the treatment of bloating, weight gain, and blood pressure reduction.

Price: One-cycle pack (one-month supply) of ethinyl estradiol/drospirenone costs $33. The price range for other brand and generic monophasic oral contraceptives is $24 to $49, making ethinyl estradiol/drospirenone a moderately priced option. For patients who have prescription coverage for oral contraceptives, ethinyl estradiol/drospirenone is often covered.

Simplicity: Ethinyl estradiol/drospirenone is available in a 28-day dose-pack that contains 21 active yellow tablets comprised of 30 mcg ethinyl estradiol and 3 mg drospirenone, and 7 placebo white tablets.

Bottom line: An effective oral contraceptive, ethinyl estradiol/drospirenone can elevate potassium levels when given in combination with other potassium-elevating agents and offers no advantage over traditional oral contraceptives.

REFERENCES

(1.) Oelkers W, Foidart JM, Dombrovicz N, Heithecker R. Effcts of a new oral contraceptive containing an antimineralocorticoid progestogen, drospirenone, on the renin-aldosterone system, body weight, blood pressure, glucose tolerance, and lipid metabolism. J Clin Endocrinol Metab 1995;80:1816-21.

(2.) Anonymous. Yasmin--an oral contraceptive with a new progestin. Med Letter 2002;44(1133):55-7.

(3.) Huber J, Foidart JM, Wuttke W, Merki-Feld GS, The HS, et al. Efficacy and tolerability of a monophasic oral contraceptive containing ethinylestradiol and drospirenone. Eur J Contracept Reprod Health Care 2000;14:25-34.

(4.) Parsey KS, Pong A. An open-label, multicenter study to evaluate Yasmin, a low-dose combination oral contraceptive containing drospirenone, a new progestogen. Contraception 2000;61:105-11.

Melissa A. Somma, Pharm.D., CDE, is assistant professor in the department of pharmacy and therapeutics, University of Pittsburgh School of Pharmacy, Pittsburgh, Pa., and is the director of outpatient pharmacologic education, University of Pittsburgh Medical Center, St. Margaret Family Practice Residency Program, Pittsburgh, Pa.

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