(ii) The anti-fertility drugs are mostly hormonal contraceptive and are available for the female only. These are gonadal steroids i.e., vestrogens and progestogens.

(a) Synthetic oestrogens. Two synthetic oestrogens are used as oral contraceptives. These are ethinyl oestradial and mestranol.

(b) Synthetic progestogens: These are of three types i.e., pregonames, vestranes and gonames.
Classification of homonal contraceptives:

(a) Oral pills: A numbr of oral pills are available. A few popular out of these are: combined pill, progestogen only pill (POP), post-coital pill, once-a-month (long acting) pill and male pill.

(b) Depot (slow release formulations). They are available in injection form, as subctuaneous implants and also as vaginal rings.
Mode of action of Hormonal contraceptive : The mechanism of action of a combined oral pill is to prevent the release of the ovum from the ovary. This is achieved by blocking the pituitary secretion of gonadotropin which is necessary for the ovulation to occur.
Progestogen only preparations render the cervical mucous thick and scanty and thereby inhibit sperm penetration. They also inhibit tubal mortality and delay the transport of the sperm and the ovum of the uterine cavity.


(iii) Antihistamines are defined as the drugs which combat the effects of histamine a chemical released by certain cells of the body (mast cells) during an allergic reaction.
The commonly used antihistamines are:
(a) Diphenyl hydramine (Benadryl)
(b) Chlophe niramine (chlortrimeton)
(c) Fexo fenidine (Allegra)
(d) Cetrizine (Zrytect).