Please provide examples of progestin-only contraceptives and describe their pharmacological effects.

1. Progestin-only pill (mini-pill): This contraceptive contains only progestin hormone and works by thickening the cervical mucus, making it difficult for sperm to reach the egg. It also thins the lining of the uterus, making it less likely for a fertilized egg to implant.

2. Progestin-only implant (Nexplanon): This contraceptive is a small rod inserted under the skin of the upper arm that releases progestin hormone slowly over time. It works by inhibiting ovulation, thickening cervical mucus, and thinning the uterine lining.

3. Progestin-only injection (Depo-Provera): This contraceptive is administered as an injection every three months and contains a synthetic form of progestin. It works by suppressing ovulation, thickening cervical mucus, and thinning the uterine lining.

4. Progestin-only intrauterine device (IUD): This contraceptive is a small T-shaped device inserted into the uterus that releases progestin hormone locally. It works by thickening cervical mucus, inhibiting sperm movement, and thinning the uterine lining.

Overall, progestin-only contraceptives primarily work by preventing ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation of a fertilized egg. They are highly effective in preventing pregnancy when used correctly.