Provide examples of combined oral contraceptives and their pharmacological effects.

1. Ortho Tri-Cyclen: This combined oral contraceptive contains ethinyl estradiol and norgestimate. Ethinyl estradiol is a synthetic form of estrogen, which helps to prevent ovulation and thicken cervical mucus to prevent sperm from reaching the egg. Norgestimate is a synthetic form of progesterone, which also helps to prevent ovulation and thicken cervical mucus.

2. Yasmin: This combined oral contraceptive contains ethinyl estradiol and drospirenone. Drospirenone is a synthetic form of progesterone that has anti-androgenic effects, meaning it can help reduce acne and excess hair growth. It also helps to prevent ovulation and thicken cervical mucus.

3. Lo Loestrin Fe: This combined oral contraceptive contains ethinyl estradiol and norethindrone acetate. Norethindrone acetate is a synthetic form of progesterone that helps to prevent ovulation and thicken cervical mucus.

4. Seasonique: This combined oral contraceptive contains ethinyl estradiol and levonorgestrel. Levonorgestrel is a synthetic form of progesterone that helps to prevent ovulation and thicken cervical mucus.

Overall, combined oral contraceptives work by preventing ovulation, thickening cervical mucus to prevent sperm from reaching the egg, and thinning the lining of the uterus to prevent implantation of a fertilized egg.