Medicines and Drugs

Medicines are small molecular weight chemicals. They are used for diagnosis, prevention and treatment of diseases. Medicines used as drugs can be classified in four ways.

(i) Based on pharmacological properties - This is a classification that is useful for doctors to prescribe medicines for a specific type of disease.

Example - Analgesics, Antiseptics

(ii) Based on the action of medicines - Classification based on the action of a medicine on a specific biochemical process.

Example - Antihistamine medicines are used to block the action of a compound called histamine that causes inflammation in the body.

(iii) Based on chemical structure - Medicines with common structural features will perform similar pharmacological actions.

(iv) Based on molecular targets - The most useful classification for pharmacologists

Therapeutic actions of different classes of drugs

1. Antacids

Overproduction of stomach acid causes ulcers. Antacids are medicines used to reduce high stomach acidity. Example - Ranitidine, Cimetidine

2. Antihistamine

It is a drug used to relieve the symptoms of hay fever and other allergies. It counteracts some of the effects of histamine a substance found in the body of a person. Excess amount of histamine may cause various disorders. Antihistamines have side effects, including drowsiness. Therefore it is dangerous to people who operate heavy machinery or drive. Example - Brompheniramine, Terfenadine

3. Neuroactive Drugs

i. Tranquilizers - Tranquilizer is a drug that calms a person by acting on the nervous system. Tranquilizers belong to a group of drugs called antianxiety and hypnotic drugs. Such drugs were formerly referred to as depressants. They do not cause depression, but will reduce a person's nervous activity. There are two types of tranquilizers - antipsychotic drugs and antianxiety drugs. Antipsychotic drugs are used to treat patients with psychoses. Antianxiety drugs are used to treat various emotional problems, particularly anxiety. Example - Iproniazid, Phenelzine, Meprobamate

ii. Analgesics - A class of drugs that relieve pain. Narcotic Analgesics such as morphine are powerful pain killers that act directly on the brain. Some anesthetics also have analgesic properties. Aspirin and paracetamol are examples of antipyretic analgesics which also reduce fever. These drugs are not addictive but are less potent than narcotics.

4. Antimicrobials 

Antimicrobials are drugs that can kill or inhibit the growth of microorganisms such as bacteria and fungi. Example - Antibiotic, Antiseptic, Disinfectant

i. Antibiotic - Antibiotics are used to treat infections in humans and animals. They can inhibit the growth of microorganisms at low concentrations or kill them by interfering with their metabolism. There are two types of antibiotics - Bactericidal (cidal effect) and Bacteriostatic (static effect).

1. Bactericidal - those that kill microorganisms. Example - Penicillin, Aminoglycosides, Ofloxacin

2. Bacteriostatic - resists microorganisms. Example - Erythromycin, Tetracycline, Chloramphenicol

ii. Antiseptic - It is a substance that destroys or stops the growth of germs on living tissue. They are applied to skin to help prevent infection. Doctors use special antiseptic to scrub their hands and to wash the patients skin before surgery. They also spray serious wounds with antiseptics in order to keep them from becoming infected. Example - Dettol, Furacin, Soframycin

iii. Disinfectant - Disinfectants are used on floors, drainage systems, and equipment. The same substance can be used as both antiseptics and disinfectants by varying its concentration. Example - Phenol, Vesphene, Viscodyne

Various Types of Medicines

A drug or medicine is a chemical substance or preparation taken to treat or prevent disease. Drugs can be given to the body in the form of injections, tablets, creams, sprays, or drops. Most drugs are made from natural products. The different types of drugs are listed below.

1. Antivenom

Antivenom is a medication taken/used to reduce the potency of venom from living organisms. It is mainly used to reduce the potency of snake venom.

2. Antacid

Antacids are medicines that are taken to reduce acidity. HCl is the acid in the human digestive system. Acidity is a condition in which the amount of HCl acid in the stomach is increased. The ingredients in antacids are Sodium Bicarbonate, Calcium Carbonate, Aluminum Hydroxide, and Magnesium Hydroxide.

3. Analgesics

Analgesics are drugs that reduce or eliminate pain without causing drowsiness, mental confusion, incoordination, paralysis, or any other neurological disturbances. They are known as painkillers. The part of the brain where analgesics act is the thalamus. The neurotransmitter where analgesics act is the GABA. Aspirin and Morphine are examples of Analgesics.

4. Antipyretics

Antipyretics are medicines taken to reduce fever. They help reduce body temperature. For example - Paracetamol.

5. Antibiotics

Antibiotics are medicines used to kill germs inside the body. In 1928, Alexander Fleming discovered the first effective antibiotic 'penicillin' from a fungus called Penicillium Notatum. Examples of Antibiotics are Penicillin, Ampicillin, Tetracycline and Amoxicillin.

6. Antiseptic

Antiseptics are drugs used to kill germs outside the body. The first antiseptic discovered in the world was Phenol.

7. Tranquilizer

Tranquilizers are drugs used to treat depression and anxiety. Tranquilizers are now used not only in psychiatric treatment but also to calm patients after certain surgeries.

8. Contraceptives

Birth control drugs are mainly mixtures of synthetic estrogens and progesterone or their derivatives. An example of a synthetic progesterone derivative that is most commonly used as an anti-fertility drug is Norethindrone. The estrogen derivative used in combination with a progesterone derivative is Ethynyl. 

9. Anthelmintics

Anthelmintics are medicines used to treat infections caused by a broad range of parasites in agriculture, aquaculture, and in some cases for human infections. For example - Albendazole

10. Antihistamine

Antihistamines are drugs used to treat allergies. Histamine is the cause of common cold and pollen allergies. Excess amount of histamine may cause various disorders. Antihistamines counteract some of the effects of histamine. Example for Antihistamine is Terfenadine.

11. Sedative

Sedative is a drug that decreases the activity of the central nervous system. Sedatives are prescribed mainly to ease anxiety or to produce sleep. Their effect depends on the dosage. When taken in small amounts, the drugs calm a person. Slightly larger doses cause sleep. When used to produce sleep, the drugs are generally called hypnotics.