Narcotic drugs: [Opioids]
(i) These are narcotic analgesics. These relieve pain and produce sleep. These drugs are addictive. In poisonous dose, these produces coma and ultimately death.
(ii) They are used for either short-term or long term relief of severe pains. They are mainly used for post operative pain, pain of terminal cancer.
(iii) Eg: Morphine, Codeine
Non-narcotic drugs:
(i) These are non- narcotic analgesics. These reduce the pain without causing impairment of consciousness.
(ii) They alleviate pain by reducing local inflammatory responses.
(iii) These are used for short-term pain relief and for modest pain like headache, muscle strain, bruising or arthritis.
(iv) These drugs have many other effects such as reducing fever (antipyretic) and preventing platelet coagulation (eg. aspirin).
(v) These reduce fever by causing the hypothalamus to over ride a prostaglandin - induced increase in temperature.
(vi) Eg. Aspirin, Paracetamol, Ibuprofen. There are two types in it.
a) Anti inflammatory: eg: Aspirin, Paracetamol
b) Non steroidal anti -inflammatory drugs: (NSAIDs) eg: Ibuprofen

A drug is a substance that is used to modify or explore physiological systems or pathological states for the benefit of the recipient. It is used for the purpose of diagnosis, prevention, cure/relief of a disease.
a) Classification of drugs:
Drugs are classified based on their properties such as chemical structure, pharmacological effect, target system, site of action etc.
b) Classification based on the chemical structure:
In this classification, drugs with a common chemical skeleton are classified into a single group. For example, ampicillin, amoxicillin, methicillin etc.. all have similar structure and are classified into a single group called penicillin. Similarly, we have other group of drugs such as opiates, steroids, catecholamines etc. Compounds having similar chemical structure are expected to have similar chemical properties. However, their biological actions are not always similar. For example, all drugs belonging to penicillin group have same biological action, while groups such as barbiturates, steroids etc.. have different biological action.
Penicillins

Classification based on Pharmacological effect:
In this classification, the drugs are grouped based on their biological effect that they produce on the recipient. For example, the medicines that have the ability to kill the pathogenic bacteria are grouped as antibiotics. This kind of grouping will provide the full range of drugs that can be used for a particular condition (disease). The physician has to carefully choose a suitable medicine from the available drugs based on the clinical condition of the recipient.
Examples:
Antibiotic drugs: amoxicillin, ampicillin, cefixime, cefpodoxime, erythromycin, tetracycline etc.. Antihypertensive drugs: propranolol, atenolol, metoprolol succinate, amlodipine etc...
Classification based on the target system (drug action):
In this classification, the drugs are grouped based on the biological system/process, that they target in the recipient. This classification is more specific than the pharmacological classification. For example, the antibiotics streptomycin and erythromycin inhibit the protein synthesis (target process) in bacteria and are classified in a same group. However, their mode of action is different. Streptomycin inhibits the initiation of protein synthesis, while erythromycin prevents the incorporation of new amino acids to the protein.
Classification based on the site of action (molecular target):
The drug molecule interacts with biomolecules such as enzymes, receptors etc, which are referred as drug targets. We can classify the drug based on the drug target with which it binds. This classification is highly specific compared to the others. These compounds often have a common mechanism of action, as the target is the same.

a) Bakelite - Cross linked polymer
b) Nylon - Linear polymer
c) polythene (HDPE) - Linear polymer
d) polythene (LDPE) - Branched polyner

(i) Natural rubber is mixed with 3-5% sulphur and heated at 100-150°C causes cross-linking of the cis-1,4-polyisoprene chains through disulphide (-S-S-) bonds.
(ii) The physical properties of rubber can be altered by controlling the amount of sulphur that is used for vulcanization.
(iii) In sulphur rubber, made with about 1 to 3% sulphur is soft and stretchy.When 3 to 10% sulphur is used the resultant rubber is somewhat harder but flexible.

(i) A polymer containing two or more different kinds of monomer units is called a copolymer.
(ii) For example, SBR rubber(Buna-S) contains styrene and butadiene monomer units.
(iii) Copolymers have properties quite different from the homopolymers.
(iv) Mixture of styrene and 1,3 butadiene to form a copolymer (Buna -S)
Preparation of Buna-S:
It is a co-polymer. It is obtained by the polymerisation of buta -1,3 - diene and styrene in the ratio 3: 1 in the presence of sodium.

Anti fertility drugs are synthetic hormones that suppresses ovulation and fertilisation. They are used in birth control pills.
eg: Synthetic Oestrogen : Ethynylestradiol, Menstranol,
Synthetic Progestrone : Norethindrone, Norethynodrel etc.