Drugs, Pesticides and Everyday Chemistry

5.1 Classification of Drugs

By therapeutic use:

Category	Function	Examples
Analgesics	Pain relief (no loss of consciousness)	Aspirin, Paracetamol, Ibuprofen, Morphine
Antipyretics	Reduce fever	Paracetamol, Aspirin
Antibiotics	Kill/inhibit bacteria	Penicillin (Fleming 1928), Streptomycin, Tetracycline, Amoxicillin
Antiseptics	Prevent infection on living tissue	Iodine tincture (2%), Savlon, Dettol (chloroxylenol), H₂O₂ (3%)
Disinfectants	Kill microbes on non-living surfaces	Phenol (carbolic acid), bleaching powder, formalin, chlorine
Antihistamines	Block histamine (allergy/cold)	Cetirizine, Diphenhydramine
Tranquillizers	Reduce anxiety, CNS depression	Diazepam (Valium), Alprazolam
Antacids	Neutralise stomach acid	Milk of magnesia Mg(OH)₂, ENO (NaHCO₃ + citric acid)

Drug Dependence and Antibiotic Resistance

Drug dependence: Narcotics (heroin, morphine) cause physical addiction. Steroids (anabolic) are banned in sports.

Antibiotic resistance is a global health crisis:

• Overuse of antibiotics leads to resistant bacteria (MRSA, XDR-TB)
• WHO lists AMR (Antimicrobial Resistance) as one of the top 10 global public health threats

5.2 Pesticides

Classification by chemical structure:

Class	Examples	Status
Organochlorines	DDT (dichloro-diphenyl-trichloroethane), BHC (lindane, benzene hexachloride), Aldrin, Dieldrin	Most banned under Stockholm Convention 2004 (POPs)
Organophosphates	Malathion, Parathion, Chlorpyrifos	Still used; less persistent than OCs
Carbamates	Carbaryl, Methomyl	Used in garden/agricultural pest control
Pyrethroids	Permethrin, Cypermethrin	Lower mammalian toxicity; widely used
Neonicotinoids	Imidacloprid, Clothianidin	Systemic; controversial for bee colony collapse

DDT — History and Biomagnification

DDT was synthesised by Paul Hermann Müller, who won the Nobel Prize in Physiology or Medicine in 1948 for discovering DDT's insecticidal properties.

• Banned in India for agricultural use in 1989 (still permitted for malaria vector control)
• Biomagnification: DDT concentrates up the food chain — 0.000003 ppm in water → 25 ppm in carnivorous fish → 75 ppm in eagles
• Causes eggshell thinning in birds (eagles, ospreys)

Stockholm Convention on Persistent Organic Pollutants (POPs), 2004: International treaty banning/restricting 12 initial "dirty dozen" chemicals including DDT, PCBs, dioxins. India ratified in 2006.

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