Antifertility Drugs, Antibiotics, Antacids, Antihistamines

1. DRUGS :- Drugs are chemical of low molecular masses, which interact with macro molecular targets and produce a biological response.

2. CHEMOTHERAPY :- The use of chemicals for therapeutic effect is called chemotherapy.

3. CLASSIFICATION OF DRUGS :- 
(a) ON THE BASIS OF PHARMACOLOGICAL EFFECT- drugs for a particular type of problem as analgesics for pain relieving.
(b) ON THE BASIS OF DRUG ACTION-Action of drug on a particular biochemical process.
(c) ON THE BASIS OF CHEMICAL ACTION-Drugs having similar structure .eg - sulpha drugs.
(d) ON THE BASIS OF MOLECULAR TARGETS- Drugs interacting with bio molecules as lipids, proteins.

4. ENZYMES AS DRUG TARGETS:-
(i) CATALYTIC ACTION OF ENZYMES:-
(a) Enzymes have active sites which hold the substrate molecule .it can be attracted by reacting molecules.
(b) Substrate is bonded to active sites through hydrogen bonds, ionic bonds, Vander Waal or dipole –dipole interactions.
(ii) DRUG- ENZYME INTERACTIONS:-
(a)Drug compete with natural substrate for their attachments on the active sites of enzymes .They are called competitive inhibitors. (b)Some drugs binds to a different site of the enzyme called allosteric sites which changes the shape of active sites.

5. ANTAGONISTS:- The drugs that bind to the receptor site and inhibit its natural function.

6. AGONISTS:- Drugs mimic the natural messenger by switching on the receptor.

7. ANTACIDS:- These are compounds which neutralize excess acid of stomach. eg - Aluminum hydroxide, Magnesium hydroxide.

8. ANTI HISTAMINES:-The drugs which interfere with the natural action of histamines and prevent the allergic reaction. eg - ranitidine, tegarnet, avil.

9. ANTI FERTILITY DRUGS:- These are the chemical substances used to control the pregnancy. They are also called oral contraceptives or birth control pills.
Eg - Mifepristone, norethindrone.