To best understand how a progestin may be classified, it is helpful to clarify the types of effects a progestin may have on the female body in terms of progestational, estrogenic, and androgenic activity. Also, progestins are categorized by generation.
2. Norethindrone Acetate
3. Ethynodiol Diacetate
Levonorgestrel is a second-generation progestin and is the most widely prescribed contraceptive progestin worldwide. It has high progestational and androgenic effects. Levonorgestrel negatively affects serum lipoproteins. Several low-dose estrogen brands containing this progestin are available. Levonorgestrel birth control has also been FDA approved for emergency contraception (such as Plan B One-Step and Next Choice). The FDA has stated that all combination pills with this progestin are safe and effective for emergency contraception under the Yuzpe method. The FDA has also approved three extended cycle pill brands that use this progestin -- Seasonale, Seasonique, and Lybrel.
Desogestrel is a third-generation progestin with high progestational selectivity, minimizing androgenic effects and estrogenic activity. It shows less negative impact on metabolism, weight gain, acne, and other side effects typical of older progestins. It shows positive effects on lipoproteins as seen by a slight rise of HDL cholesterol. Clinical trials show a possibly higher risk of non-fatal venous thrombosis with desogestrel pills versus those with levonorgestrel. Mircette (a low-dose estrogen/desogestrel pill) provides a shorter placebo interval, which may be helpful for women who have migraines, dysmenorrhea, or other negative issues during that week. A low estrogen/varying desogestrel triphasic pill, Cyclessa, is also available.
Norgestimate, a third-generation progestin, has high progestational activity while showing slight estrogenic effects and tends to be less androgenic. It also has minimal effect on serum lipoproteins as well as on carbohydrate metabolism. The low androgenic effects of norgestimate have resulted in successful treatment of acne. In fact, birth control pills that contain norgestimate are the only ones FDA approved to help reduce acne. Ortho Tri-Cyclen Lo is a brand that provides norgestimate and a mid-level dose of estrogen. So this pill may be helpful in lowering side effects such as nausea and vomiting while not causing an increased incidence of spotting (typically associated with low-estrogen pills).
Drospirenone is the only progestin derived from 17a-spirolactoneis. It helps suppress the secretion of the hormones that regulate the body's water and electrolytes. It also has low androgenic activity. Drospirenone and estrogen seem to lessen symptoms associated with mild PMS (increased appetite, negative mood, and water retention). Drospirenone may cause higher potassium levels, so women with kidney, liver, or adrenal disease should not use it. The brands YAZ and Beyaz Beyaz have 24 days of active pills and 4 days of placebo pills. This combination may cause fewer hormone fluctuations than typical pill packs. YAZ has also been FDA approved to help treat premenstrual dysphoric disorder as well as treat moderate acne in females aged 14 years and up.