In oral contraceptives, if the estrogen dose is constant for 21 days and progestin is lower in the first half and higher in the second half, it is called:

• A. Monophasic
• B. Biphasic
• C. Triphasic
• D. Quadriphasic

Answer: (B)

The correct answer is biphasic because this type of oral contraceptive contains two different doses of progestin over the course of the cycle, while the estrogen dose remains constant. In a biphasic regimen, the first half of the cycle typically features a lower dose of progestin, and the second half increases to a higher dose. This design aims to mimic the natural hormonal changes that occur during a woman’s menstrual cycle, while still providing effective contraceptive coverage.

The distinction made by this two-phase approach allows for a more tailored hormonal response, potentially leading to different side effects and therapeutic outcomes compared to monophasic formulations, which deliver a single consistent dose of both hormones throughout the entire 21 days. Similarly, triphasic and quadriphasic regimens include three and four varying doses of hormones, respectively, which complicates the dosing schedule further and is not applicable in this case. Therefore, the biphasic structure is significant for its design intended to balance both efficacy and side effect profiles, making it suitable for women who may benefit from such variations in hormone levels throughout their cycle.