Which OC would you choose? Test your skills with these 3 cases

TABLE 1
Contraindications to oral contraceptives^1,2

Which OCP? A look at the choices

In determining which OCP to prescribe for a particular patient, there are a number of issues to consider:

• What estrogen dosage and progestin formulation should be used for this patient?
• Should the patient be placed on a mono-phasic, biphasic, triphasic, or quadra-phasic pill?
• How frequently does she want to menstruate?
• Has she taken OCPs before, either for primary contraception or for another condition that the pill is frequently prescribed for, such as dysmenorrhea or premenstrual syndrome? If she has taken OCPs, did she experience any significant adverse effects?

Most commonly prescribed OCPs are a combination of an estrogen and progesterone. Progestin-only OCPs are also available, but are used less frequently than combination pills because they must be taken within a smaller window of time each day to maintain their effectiveness.

Pill formulations
Combination OCPs typically contain the estrogen ethinyl estradiol (EE) or its precursor, mestranol, which is metabolized into EE, and one of the 9 progestins available in the United States.^6,7 (An OC approved in May 2010 contains a new estrogen, estradiol valerate [EV], and dienogest, a novel progestin.⁷)

Categorized according to when they were approved or introduced, progestins include:

• norethindrone, norethindrone acetate (first generation)
• norgestrel, levonorgestrel, ethynodiol diacetate (second generation)
• norgestimate, desogestrel (third generation)
• drospirenone, dienogest (other).^6,7

Each progestin differs in its affinity to progesterone, estrogen, and androgen receptors and, therefore, each has a slightly different physiologic effect. The first-generation progestins norethindrone and norethindrone acetate have a shorter half-life compared with those introduced later. While some studies have shown that third-generation progestins have a greater risk of VTE compared with first- and second-generation formulations, others have not found that to be the case. Two recent studies, conducted in the Netherlands and Denmark, did find an increased risk of VTE associated with the third-generation progestin desogestrel.^8,9

Drospirenone, one of the more recently approved progestins, should be used with caution in any patient who may be at increased risk of hyperkalemia because of its spironolac-tone-like effects.¹⁰ Overall, however, there is little evidence to help guide initial OCP selection based on patient characteristics.

Dosing considerations
Estrogen dosages range from 10 to 50 mcg EE (and from 1 to 3 mg EV); progesterone dosage is ≤1 mg, with the exception of dienogest (2-3 mg). (Pills with higher doses of estrogen were available in the 1960s and 1970s, but were phased out because they carried a greater risk of vascular complications.) Your goal should be to select the lowest effective dosage of estrogen to minimize the risk of adverse effects.

There is a tradeoff, however: The lowest dose pills (10-20 mcg EE) have an increased risk of irregular bleeding, although they also have a reduced risk of minor adverse effects (eg, breast tenderness and headache, among other premenstrual symptoms).¹¹ And, for women who are not meticulously compliant, low-dose pills are associated with a greater failure rate compared with OCPs with higher doses of EE.¹⁰

Other than the reduction of premenopausal symptoms, the advantages of pills with a lower dose of estrogen remain largely theoretical. The most serious adverse effects associated with estrogen—deep vein thrombosis (DVT) and pulmonary embolism—may not be significantly different between the lower or higher dose pills, although 2 recent studies found a reduced risk of VTE with lower estrogen doses.^8,9

The original OCPs were monophasic, with each active pill having the same amount of estrogen and progesterone. Biphasic pills generally increase in progesterone dose, typically containing one dose for the first 10 days of the pill pack and an increased dose for the next 11 days.

Triphasic pills, designed to mimic the endogenous fluctuation of estrogen and progesterone during the menstrual cycle, have 3 levels of hormones in the active pills. Typically, the progesterone dose is lowest for the first 7 days and then increases on Day 8 and again on Day 15, while the estrogen dose remains constant. In some triphasic formulations, however, the estrogen dose increases and then is reduced in the last 7 days of active pills. (Natazia, the EV/dienogest OCP approved last year, is quadraphasic, featuring 2 different dosages of EV-only pills and 2 different dosages of estrogen/progestin pills.⁷)