Table 1 Low dose progestin-only oral contraceptive

Mechanisms of conceptive protection

 Suppresses ovulation [in approximately half of users],

 Thickening the cervical mucus to inhibit sperm penetration

 Lowering the midcycle LH and FSH peaks

 Slowing the movement of the ovum through the fallopian tubes

 Altering the endometrium

Action of norethindrone

 Peak levels of norethindrone occur 24 h after oral dose followed by a rapid distribution and elimination. Efficacy is dependent upon compliance of an every 22–24 h dosage regiment