Mast cells. Mast cells and basophils are generally thought to be the major sources of histamine and can themselves be modulated by histamine as they express H 1, H 2 and H 4 receptors, although how this varies between different mast-cell types is not yet clear.
3. The pill is to be taken soon after unprotected sex. It should be taken preferably within 24 hours and before 72 hours or else the pill may turn useless. 4. I-pill checks pregnancy by preventing ovulation or fertilisation or implantation of the fertilised egg. 5. I-pill is 95 per cent effective if taken in time.
Even though emergency contraception is often called the âmorning after pillâ or âday after pill,â it may be effective for up to 5 days (120 hours) after unprotected sex. In the United States, there are two different kinds of emergency contraceptive pills available: ulipristal acetate and progestin-only (like Plan B One-Step, Next Choice One Dose, My Way).